[PATCH -tip 0/4] perf-probe updates: string support, etc.

[PATCH -tip 0/4] perf-probe updates: string support, etc.

[Masami Hiramatsu]

Hi,

Here is a series of patches which improves perf probe to
add below features. I cleared some coding style issues.

- String support, which enables dynamic events to trace string
  variables instead of its address.

- Fixed-index array entry support, which allows user to trace
  an array entry with digit index, e.g. array[0].

- Global/static variable support, which allows user to trace
  global or static variables, as same as local one.


TODOs (possible features):
  - Support dynamic array-indexing (var[var2])
  - Support force type-casting ((type)var)
  - Show what deta-structure member is assigned to each argument.
  - Better support for probes on modules
  - More debugger like enhancements(%next, --disasm, etc.)

Thank you,

---

Masami Hiramatsu (4):
      perf probe: Support static and global variables
      perf probe: Support tracing an entry of array
      perf probe: Support "string" type
      tracing/kprobes: Support "string" type


 Documentation/trace/kprobetrace.txt     |    2 
 kernel/trace/trace_kprobe.c             |  370 ++++++++++++++++++++++++-------
 tools/perf/Documentation/perf-probe.txt |    4 
 tools/perf/util/probe-event.c           |   71 ++++--
 tools/perf/util/probe-event.h           |    1 
 tools/perf/util/probe-finder.c          |  192 +++++++++++++---
 6 files changed, 498 insertions(+), 142 deletions(-)

-- 
Masami Hiramatsu
e-mail: mhiramat@redhat.com

[PATCH -tip 1/4] tracing/kprobes: Support "string" type

[Masami Hiramatsu]

Support string type tracing and printing in kprobe-tracer.
This allows user to trace string data in kernel including
__user data. Note that sometimes __user data may not be
accessed if it is paged-out (sorry, but kprobes operation
should be done in atomic, we can not wait for page-in).

Signed-off-by: Masami Hiramatsu <mhiramat@redhat.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
---

 Documentation/trace/kprobetrace.txt |    2 
 kernel/trace/trace_kprobe.c         |  370 ++++++++++++++++++++++++++++-------
 2 files changed, 293 insertions(+), 79 deletions(-)

diff --git a/Documentation/trace/kprobetrace.txt b/Documentation/trace/kprobetrace.txt
index ec94748..5f77d94 100644
--- a/Documentation/trace/kprobetrace.txt
+++ b/Documentation/trace/kprobetrace.txt
@@ -42,7 +42,7 @@ Synopsis of kprobe_events
   +|-offs(FETCHARG) : Fetch memory at FETCHARG +|- offs address.(**)
   NAME=FETCHARG : Set NAME as the argument name of FETCHARG.
   FETCHARG:TYPE : Set TYPE as the type of FETCHARG. Currently, basic types
-		  (u8/u16/u32/u64/s8/s16/s32/s64) are supported.
+		  (u8/u16/u32/u64/s8/s16/s32/s64) and string are supported.
 
   (*) only for return probe.
   (**) this is useful for fetching a field of data structures.
diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
index 2d7bf41..10fcc4e 100644
--- a/kernel/trace/trace_kprobe.c
+++ b/kernel/trace/trace_kprobe.c
@@ -30,6 +30,8 @@
 #include <linux/ptrace.h>
 #include <linux/perf_event.h>
 #include <linux/stringify.h>
+#include <linux/limits.h>
+#include <linux/uaccess.h>
 #include <asm/bitsperlong.h>
 
 #include "trace.h"
@@ -38,6 +40,7 @@
 #define MAX_TRACE_ARGS 128
 #define MAX_ARGSTR_LEN 63
 #define MAX_EVENT_NAME_LEN 64
+#define MAX_STRING_SIZE PATH_MAX
 #define KPROBE_EVENT_SYSTEM "kprobes"
 
 /* Reserved field names */
@@ -58,14 +61,16 @@ const char *reserved_field_names[] = {
 };
 
 /* Printing function type */
-typedef int (*print_type_func_t)(struct trace_seq *, const char *, void *);
+typedef int (*print_type_func_t)(struct trace_seq *, const char *, void *,
+				 void *);
 #define PRINT_TYPE_FUNC_NAME(type)	print_type_##type
 #define PRINT_TYPE_FMT_NAME(type)	print_type_format_##type
 
 /* Printing  in basic type function template */
 #define DEFINE_BASIC_PRINT_TYPE_FUNC(type, fmt, cast)			\
 static __kprobes int PRINT_TYPE_FUNC_NAME(type)(struct trace_seq *s,	\
-						const char *name, void *data)\
+						const char *name,	\
+						void *data, void *ent)\
 {									\
 	return trace_seq_printf(s, " %s=" fmt, name, (cast)*(type *)data);\
 }									\
@@ -80,6 +85,49 @@ DEFINE_BASIC_PRINT_TYPE_FUNC(s16, "%d", int)
 DEFINE_BASIC_PRINT_TYPE_FUNC(s32, "%ld", long)
 DEFINE_BASIC_PRINT_TYPE_FUNC(s64, "%lld", long long)
 
+/* data_rloc: data relative location, compatible with u32 */
+#define make_data_rloc(len, roffs)	\
+	(((u32)(len) << 16) | ((u32)(roffs) & 0xffff))
+#define get_rloc_len(dl)	((u32)(dl) >> 16)
+#define get_rloc_offs(dl)	((u32)(dl) & 0xffff)
+
+static inline void *get_rloc_data(u32 *dl)
+{
+	return (u8 *)dl + get_rloc_offs(*dl);
+}
+
+/* For data_loc conversion */
+static inline void *get_loc_data(u32 *dl, void *ent)
+{
+	return (u8 *)ent + get_rloc_offs(*dl);
+}
+
+/*
+ * Convert data_rloc to data_loc:
+ *  data_rloc stores the offset from data_rloc itself, but data_loc
+ *  stores the offset from event entry.
+ */
+#define convert_rloc_to_loc(dl, offs)	((u32)(dl) + (offs))
+
+/* For defining macros, define string/string_size types */
+typedef u32 string;
+typedef u32 string_size;
+
+/* Print type function for string type */
+static __kprobes int PRINT_TYPE_FUNC_NAME(string)(struct trace_seq *s,
+						  const char *name,
+						  void *data, void *ent)
+{
+	int len = *(u32 *)data >> 16;
+
+	if (!len)
+		return trace_seq_printf(s, " %s=(fault)", name);
+	else
+		return trace_seq_printf(s, " %s=\"%s\"", name,
+					(const char *)get_loc_data(data, ent));
+}
+static const char PRINT_TYPE_FMT_NAME(string)[] = "\\\"%s\\\"";
+
 /* Data fetch function type */
 typedef	void (*fetch_func_t)(struct pt_regs *, void *, void *);
 
@@ -94,32 +142,38 @@ static __kprobes void call_fetch(struct fetch_param *fprm,
 	return fprm->fn(regs, fprm->data, dest);
 }
 
-#define FETCH_FUNC_NAME(kind, type)	fetch_##kind##_##type
+#define FETCH_FUNC_NAME(method, type)	fetch_##method##_##type
 /*
  * Define macro for basic types - we don't need to define s* types, because
  * we have to care only about bitwidth at recording time.
  */
-#define DEFINE_BASIC_FETCH_FUNCS(kind)  \
-DEFINE_FETCH_##kind(u8)			\
-DEFINE_FETCH_##kind(u16)		\
-DEFINE_FETCH_##kind(u32)		\
-DEFINE_FETCH_##kind(u64)
-
-#define CHECK_BASIC_FETCH_FUNCS(kind, fn)	\
-	((FETCH_FUNC_NAME(kind, u8) == fn) ||	\
-	 (FETCH_FUNC_NAME(kind, u16) == fn) ||	\
-	 (FETCH_FUNC_NAME(kind, u32) == fn) ||	\
-	 (FETCH_FUNC_NAME(kind, u64) == fn))
+#define DEFINE_BASIC_FETCH_FUNCS(method) \
+DEFINE_FETCH_##method(u8)		\
+DEFINE_FETCH_##method(u16)		\
+DEFINE_FETCH_##method(u32)		\
+DEFINE_FETCH_##method(u64)
+
+#define CHECK_FETCH_FUNCS(method, fn)			\
+	(((FETCH_FUNC_NAME(method, u8) == fn) ||	\
+	  (FETCH_FUNC_NAME(method, u16) == fn) ||	\
+	  (FETCH_FUNC_NAME(method, u32) == fn) ||	\
+	  (FETCH_FUNC_NAME(method, u64) == fn) ||	\
+	  (FETCH_FUNC_NAME(method, string) == fn) ||	\
+	  (FETCH_FUNC_NAME(method, string_size) == fn)) \
+	 && (fn != NULL))
 
 /* Data fetch function templates */
 #define DEFINE_FETCH_reg(type)						\
 static __kprobes void FETCH_FUNC_NAME(reg, type)(struct pt_regs *regs,	\
-					  void *offset, void *dest)	\
+					void *offset, void *dest)	\
 {									\
 	*(type *)dest = (type)regs_get_register(regs,			\
 				(unsigned int)((unsigned long)offset));	\
 }
 DEFINE_BASIC_FETCH_FUNCS(reg)
+/* No string on the register */
+#define fetch_reg_string NULL
+#define fetch_reg_string_size NULL
 
 #define DEFINE_FETCH_stack(type)					\
 static __kprobes void FETCH_FUNC_NAME(stack, type)(struct pt_regs *regs,\
@@ -129,6 +183,9 @@ static __kprobes void FETCH_FUNC_NAME(stack, type)(struct pt_regs *regs,\
 				(unsigned int)((unsigned long)offset));	\
 }
 DEFINE_BASIC_FETCH_FUNCS(stack)
+/* No string on the stack entry */
+#define fetch_stack_string NULL
+#define fetch_stack_string_size NULL
 
 #define DEFINE_FETCH_retval(type)					\
 static __kprobes void FETCH_FUNC_NAME(retval, type)(struct pt_regs *regs,\
@@ -137,6 +194,9 @@ static __kprobes void FETCH_FUNC_NAME(retval, type)(struct pt_regs *regs,\
 	*(type *)dest = (type)regs_return_value(regs);			\
 }
 DEFINE_BASIC_FETCH_FUNCS(retval)
+/* No string on the retval */
+#define fetch_retval_string NULL
+#define fetch_retval_string_size NULL
 
 #define DEFINE_FETCH_memory(type)					\
 static __kprobes void FETCH_FUNC_NAME(memory, type)(struct pt_regs *regs,\
@@ -149,6 +209,62 @@ static __kprobes void FETCH_FUNC_NAME(memory, type)(struct pt_regs *regs,\
 		*(type *)dest = retval;					\
 }
 DEFINE_BASIC_FETCH_FUNCS(memory)
+/*
+ * Fetch a null-terminated string. Caller MUST set *(u32 *)dest with max
+ * length and relative data location.
+ */
+static __kprobes void FETCH_FUNC_NAME(memory, string)(struct pt_regs *regs,
+						      void *addr, void *dest)
+{
+	long ret;
+	int maxlen = get_rloc_len(*(u32 *)dest);
+	u8 *dst = get_rloc_data(dest);
+	u8 *src = addr;
+	mm_segment_t old_fs = get_fs();
+	if (!maxlen)
+		return;
+	/*
+	 * Try to get string again, since the string can be changed while
+	 * probing.
+	 */
+	set_fs(KERNEL_DS);
+	pagefault_disable();
+	do
+		ret = __copy_from_user_inatomic(dst++, src++, 1);
+	while (dst[-1] && ret == 0 && src - (u8 *)addr < maxlen);
+	dst[-1] = '\0';
+	pagefault_enable();
+	set_fs(old_fs);
+
+	if (ret < 0) {	/* Failed to fetch string */
+		((u8 *)get_rloc_data(dest))[0] = '\0';
+		*(u32 *)dest = make_data_rloc(0, get_rloc_offs(*(u32 *)dest));
+	} else
+		*(u32 *)dest = make_data_rloc(src - (u8 *)addr,
+					      get_rloc_offs(*(u32 *)dest));
+}
+/* Return the length of string -- including null terminal byte */
+static __kprobes void FETCH_FUNC_NAME(memory, string_size)(struct pt_regs *regs,
+							void *addr, void *dest)
+{
+	int ret, len = 0;
+	u8 c;
+	mm_segment_t old_fs = get_fs();
+
+	set_fs(KERNEL_DS);
+	pagefault_disable();
+	do {
+		ret = __copy_from_user_inatomic(&c, (u8 *)addr + len, 1);
+		len++;
+	} while (c && ret == 0 && len < MAX_STRING_SIZE);
+	pagefault_enable();
+	set_fs(old_fs);
+
+	if (ret < 0)	/* Failed to check the length */
+		*(u32 *)dest = 0;
+	else
+		*(u32 *)dest = len;
+}
 
 /* Memory fetching by symbol */
 struct symbol_cache {
@@ -203,6 +319,8 @@ static __kprobes void FETCH_FUNC_NAME(symbol, type)(struct pt_regs *regs,\
 		*(type *)dest = 0;					\
 }
 DEFINE_BASIC_FETCH_FUNCS(symbol)
+DEFINE_FETCH_symbol(string)
+DEFINE_FETCH_symbol(string_size)
 
 /* Dereference memory access function */
 struct deref_fetch_param {
@@ -224,12 +342,14 @@ static __kprobes void FETCH_FUNC_NAME(deref, type)(struct pt_regs *regs,\
 		*(type *)dest = 0;					\
 }
 DEFINE_BASIC_FETCH_FUNCS(deref)
+DEFINE_FETCH_deref(string)
+DEFINE_FETCH_deref(string_size)
 
 static __kprobes void free_deref_fetch_param(struct deref_fetch_param *data)
 {
-	if (CHECK_BASIC_FETCH_FUNCS(deref, data->orig.fn))
+	if (CHECK_FETCH_FUNCS(deref, data->orig.fn))
 		free_deref_fetch_param(data->orig.data);
-	else if (CHECK_BASIC_FETCH_FUNCS(symbol, data->orig.fn))
+	else if (CHECK_FETCH_FUNCS(symbol, data->orig.fn))
 		free_symbol_cache(data->orig.data);
 	kfree(data);
 }
@@ -240,23 +360,43 @@ static __kprobes void free_deref_fetch_param(struct deref_fetch_param *data)
 #define DEFAULT_FETCH_TYPE _DEFAULT_FETCH_TYPE(BITS_PER_LONG)
 #define DEFAULT_FETCH_TYPE_STR __stringify(DEFAULT_FETCH_TYPE)
 
-#define ASSIGN_FETCH_FUNC(kind, type)	\
-	.kind = FETCH_FUNC_NAME(kind, type)
-
-#define ASSIGN_FETCH_TYPE(ptype, ftype, sign)	\
-	{.name = #ptype,			\
-	 .size = sizeof(ftype),			\
-	 .is_signed = sign,			\
-	 .print = PRINT_TYPE_FUNC_NAME(ptype),	\
-	 .fmt = PRINT_TYPE_FMT_NAME(ptype),	\
-ASSIGN_FETCH_FUNC(reg, ftype),			\
-ASSIGN_FETCH_FUNC(stack, ftype),		\
-ASSIGN_FETCH_FUNC(retval, ftype),		\
-ASSIGN_FETCH_FUNC(memory, ftype),		\
-ASSIGN_FETCH_FUNC(symbol, ftype),		\
-ASSIGN_FETCH_FUNC(deref, ftype),		\
+/* Fetch types */
+enum {
+	FETCH_MTD_reg = 0,
+	FETCH_MTD_stack,
+	FETCH_MTD_retval,
+	FETCH_MTD_memory,
+	FETCH_MTD_symbol,
+	FETCH_MTD_deref,
+	FETCH_MTD_END,
+};
+
+#define ASSIGN_FETCH_FUNC(method, type)	\
+	[FETCH_MTD_##method] = FETCH_FUNC_NAME(method, type)
+
+#define __ASSIGN_FETCH_TYPE(_name, ptype, ftype, _size, sign, _fmttype)	\
+	{.name = _name,				\
+	 .size = _size,					\
+	 .is_signed = sign,				\
+	 .print = PRINT_TYPE_FUNC_NAME(ptype),		\
+	 .fmt = PRINT_TYPE_FMT_NAME(ptype),		\
+	 .fmttype = _fmttype,				\
+	 .fetch = {					\
+ASSIGN_FETCH_FUNC(reg, ftype),				\
+ASSIGN_FETCH_FUNC(stack, ftype),			\
+ASSIGN_FETCH_FUNC(retval, ftype),			\
+ASSIGN_FETCH_FUNC(memory, ftype),			\
+ASSIGN_FETCH_FUNC(symbol, ftype),			\
+ASSIGN_FETCH_FUNC(deref, ftype),			\
+	  }						\
 	}
 
+#define ASSIGN_FETCH_TYPE(ptype, ftype, sign)			\
+	__ASSIGN_FETCH_TYPE(#ptype, ptype, ftype, sizeof(ftype), sign, #ptype)
+
+#define FETCH_TYPE_STRING 0
+#define FETCH_TYPE_STRSIZE 1
+
 /* Fetch type information table */
 static const struct fetch_type {
 	const char	*name;		/* Name of type */
@@ -264,14 +404,16 @@ static const struct fetch_type {
 	int		is_signed;	/* Signed flag */
 	print_type_func_t	print;	/* Print functions */
 	const char	*fmt;		/* Fromat string */
+	const char	*fmttype;	/* Name in format file */
 	/* Fetch functions */
-	fetch_func_t	reg;
-	fetch_func_t	stack;
-	fetch_func_t	retval;
-	fetch_func_t	memory;
-	fetch_func_t	symbol;
-	fetch_func_t	deref;
+	fetch_func_t	fetch[FETCH_MTD_END];
 } fetch_type_table[] = {
+	/* Special types */
+	[FETCH_TYPE_STRING] = __ASSIGN_FETCH_TYPE("string", string, string,
+					sizeof(u32), 1, "__data_loc char[]"),
+	[FETCH_TYPE_STRSIZE] = __ASSIGN_FETCH_TYPE("string_size", u32,
+					string_size, sizeof(u32), 0, "u32"),
+	/* Basic types */
 	ASSIGN_FETCH_TYPE(u8,  u8,  0),
 	ASSIGN_FETCH_TYPE(u16, u16, 0),
 	ASSIGN_FETCH_TYPE(u32, u32, 0),
@@ -302,12 +444,28 @@ static __kprobes void fetch_stack_address(struct pt_regs *regs,
 	*(unsigned long *)dest = kernel_stack_pointer(regs);
 }
 
+static fetch_func_t get_fetch_size_function(const struct fetch_type *type,
+					    fetch_func_t orig_fn)
+{
+	int i;
+
+	if (type != &fetch_type_table[FETCH_TYPE_STRING])
+		return NULL;	/* Only string type needs size function */
+	for (i = 0; i < FETCH_MTD_END; i++)
+		if (type->fetch[i] == orig_fn)
+			return fetch_type_table[FETCH_TYPE_STRSIZE].fetch[i];
+
+	WARN_ON(1);	/* This should not happen */
+	return NULL;
+}
+
 /**
  * Kprobe event core functions
  */
 
 struct probe_arg {
 	struct fetch_param	fetch;
+	struct fetch_param	fetch_size;
 	unsigned int		offset;	/* Offset from argument entry */
 	const char		*name;	/* Name of this argument */
 	const char		*comm;	/* Command of this argument */
@@ -428,9 +586,9 @@ error:
 
 static void free_probe_arg(struct probe_arg *arg)
 {
-	if (CHECK_BASIC_FETCH_FUNCS(deref, arg->fetch.fn))
+	if (CHECK_FETCH_FUNCS(deref, arg->fetch.fn))
 		free_deref_fetch_param(arg->fetch.data);
-	else if (CHECK_BASIC_FETCH_FUNCS(symbol, arg->fetch.fn))
+	else if (CHECK_FETCH_FUNCS(symbol, arg->fetch.fn))
 		free_symbol_cache(arg->fetch.data);
 	kfree(arg->name);
 	kfree(arg->comm);
@@ -547,7 +705,7 @@ static int parse_probe_vars(char *arg, const struct fetch_type *t,
 
 	if (strcmp(arg, "retval") == 0) {
 		if (is_return)
-			f->fn = t->retval;
+			f->fn = t->fetch[FETCH_MTD_retval];
 		else
 			ret = -EINVAL;
 	} else if (strncmp(arg, "stack", 5) == 0) {
@@ -561,7 +719,7 @@ static int parse_probe_vars(char *arg, const struct fetch_type *t,
 			if (ret || param > PARAM_MAX_STACK)
 				ret = -EINVAL;
 			else {
-				f->fn = t->stack;
+				f->fn = t->fetch[FETCH_MTD_stack];
 				f->data = (void *)param;
 			}
 		} else
@@ -587,7 +745,7 @@ static int __parse_probe_arg(char *arg, const struct fetch_type *t,
 	case '%':	/* named register */
 		ret = regs_query_register_offset(arg + 1);
 		if (ret >= 0) {
-			f->fn = t->reg;
+			f->fn = t->fetch[FETCH_MTD_reg];
 			f->data = (void *)(unsigned long)ret;
 			ret = 0;
 		}
@@ -597,7 +755,7 @@ static int __parse_probe_arg(char *arg, const struct fetch_type *t,
 			ret = strict_strtoul(arg + 1, 0, &param);
 			if (ret)
 				break;
-			f->fn = t->memory;
+			f->fn = t->fetch[FETCH_MTD_memory];
 			f->data = (void *)param;
 		} else {
 			ret = split_symbol_offset(arg + 1, &offset);
@@ -605,7 +763,7 @@ static int __parse_probe_arg(char *arg, const struct fetch_type *t,
 				break;
 			f->data = alloc_symbol_cache(arg + 1, offset);
 			if (f->data)
-				f->fn = t->symbol;
+				f->fn = t->fetch[FETCH_MTD_symbol];
 		}
 		break;
 	case '+':	/* deref memory */
@@ -635,14 +793,17 @@ static int __parse_probe_arg(char *arg, const struct fetch_type *t,
 			if (ret)
 				kfree(dprm);
 			else {
-				f->fn = t->deref;
+				f->fn = t->fetch[FETCH_MTD_deref];
 				f->data = (void *)dprm;
 			}
 		}
 		break;
 	}
-	if (!ret && !f->fn)
+	if (!ret && !f->fn) {	/* Parsed, but do not find fetch method */
+		pr_info("%s type has no corresponding fetch method.\n",
+			t->name);
 		ret = -EINVAL;
+	}
 	return ret;
 }
 
@@ -651,6 +812,7 @@ static int parse_probe_arg(char *arg, struct trace_probe *tp,
 			   struct probe_arg *parg, int is_return)
 {
 	const char *t;
+	int ret;
 
 	if (strlen(arg) > MAX_ARGSTR_LEN) {
 		pr_info("Argument is too long.: %s\n",  arg);
@@ -673,7 +835,13 @@ static int parse_probe_arg(char *arg, struct trace_probe *tp,
 	}
 	parg->offset = tp->size;
 	tp->size += parg->type->size;
-	return __parse_probe_arg(arg, parg->type, &parg->fetch, is_return);
+	ret = __parse_probe_arg(arg, parg->type, &parg->fetch, is_return);
+	if (ret >= 0) {
+		parg->fetch_size.fn = get_fetch_size_function(parg->type,
+							      parg->fetch.fn);
+		parg->fetch_size.data = parg->fetch.data;
+	}
+	return ret;
 }
 
 /* Return 1 if name is reserved or already used by another argument */
@@ -1042,6 +1210,54 @@ static const struct file_operations kprobe_profile_ops = {
 	.release        = seq_release,
 };
 
+/* Sum up total data length for dynamic arraies (strings) */
+static __kprobes int __get_data_size(struct trace_probe *tp,
+				     struct pt_regs *regs)
+{
+	int i, ret = 0;
+	u32 len;
+
+	for (i = 0; i < tp->nr_args; i++)
+		if (unlikely(tp->args[i].fetch_size.fn)) {
+			call_fetch(&tp->args[i].fetch_size, regs, &len);
+			ret += len;
+		}
+
+	return ret;
+}
+
+/* Store the value of each argument */
+static __kprobes void store_trace_args(int ent_size, struct trace_probe *tp,
+				       struct pt_regs *regs,
+				       u8 *data, int maxlen)
+{
+	int i;
+	u32 end = tp->size;
+	u32 *dl;	/* Data (relative) location */
+
+	for (i = 0; i < tp->nr_args; i++) {
+		if (unlikely(tp->args[i].fetch_size.fn)) {
+			/*
+			 * First, we set the relative location and
+			 * maximum data length to *dl
+			 */
+			dl = (u32 *)(data + tp->args[i].offset);
+			*dl = make_data_rloc(maxlen, end - tp->args[i].offset);
+			/* Then try to fetch string or dynamic array data */
+			call_fetch(&tp->args[i].fetch, regs, dl);
+			/* Reduce maximum length */
+			end += get_rloc_len(*dl);
+			maxlen -= get_rloc_len(*dl);
+			/* Trick here, convert data_rloc to data_loc */
+			*dl = convert_rloc_to_loc(*dl,
+				 ent_size + tp->args[i].offset);
+		} else
+			/* Just fetching data normally */
+			call_fetch(&tp->args[i].fetch, regs,
+				   data + tp->args[i].offset);
+	}
+}
+
 /* Kprobe handler */
 static __kprobes void kprobe_trace_func(struct kprobe *kp, struct pt_regs *regs)
 {
@@ -1049,8 +1265,7 @@ static __kprobes void kprobe_trace_func(struct kprobe *kp, struct pt_regs *regs)
 	struct kprobe_trace_entry_head *entry;
 	struct ring_buffer_event *event;
 	struct ring_buffer *buffer;
-	u8 *data;
-	int size, i, pc;
+	int size, dsize, pc;
 	unsigned long irq_flags;
 	struct ftrace_event_call *call = &tp->call;
 
@@ -1059,7 +1274,8 @@ static __kprobes void kprobe_trace_func(struct kprobe *kp, struct pt_regs *regs)
 	local_save_flags(irq_flags);
 	pc = preempt_count();
 
-	size = sizeof(*entry) + tp->size;
+	dsize = __get_data_size(tp, regs);
+	size = sizeof(*entry) + tp->size + dsize;
 
 	event = trace_current_buffer_lock_reserve(&buffer, call->id, size,
 						  irq_flags, pc);
@@ -1068,9 +1284,7 @@ static __kprobes void kprobe_trace_func(struct kprobe *kp, struct pt_regs *regs)
 
 	entry = ring_buffer_event_data(event);
 	entry->ip = (unsigned long)kp->addr;
-	data = (u8 *)&entry[1];
-	for (i = 0; i < tp->nr_args; i++)
-		call_fetch(&tp->args[i].fetch, regs, data + tp->args[i].offset);
+	store_trace_args(sizeof(*entry), tp, regs, (u8 *)&entry[1], dsize);
 
 	if (!filter_current_check_discard(buffer, call, entry, event))
 		trace_nowake_buffer_unlock_commit(buffer, event, irq_flags, pc);
@@ -1084,15 +1298,15 @@ static __kprobes void kretprobe_trace_func(struct kretprobe_instance *ri,
 	struct kretprobe_trace_entry_head *entry;
 	struct ring_buffer_event *event;
 	struct ring_buffer *buffer;
-	u8 *data;
-	int size, i, pc;
+	int size, pc, dsize;
 	unsigned long irq_flags;
 	struct ftrace_event_call *call = &tp->call;
 
 	local_save_flags(irq_flags);
 	pc = preempt_count();
 
-	size = sizeof(*entry) + tp->size;
+	dsize = __get_data_size(tp, regs);
+	size = sizeof(*entry) + tp->size + dsize;
 
 	event = trace_current_buffer_lock_reserve(&buffer, call->id, size,
 						  irq_flags, pc);
@@ -1102,9 +1316,7 @@ static __kprobes void kretprobe_trace_func(struct kretprobe_instance *ri,
 	entry = ring_buffer_event_data(event);
 	entry->func = (unsigned long)tp->rp.kp.addr;
 	entry->ret_ip = (unsigned long)ri->ret_addr;
-	data = (u8 *)&entry[1];
-	for (i = 0; i < tp->nr_args; i++)
-		call_fetch(&tp->args[i].fetch, regs, data + tp->args[i].offset);
+	store_trace_args(sizeof(*entry), tp, regs, (u8 *)&entry[1], dsize);
 
 	if (!filter_current_check_discard(buffer, call, entry, event))
 		trace_nowake_buffer_unlock_commit(buffer, event, irq_flags, pc);
@@ -1137,7 +1349,7 @@ print_kprobe_event(struct trace_iterator *iter, int flags)
 	data = (u8 *)&field[1];
 	for (i = 0; i < tp->nr_args; i++)
 		if (!tp->args[i].type->print(s, tp->args[i].name,
-					     data + tp->args[i].offset))
+					     data + tp->args[i].offset, field))
 			goto partial;
 
 	if (!trace_seq_puts(s, "\n"))
@@ -1180,7 +1392,7 @@ print_kretprobe_event(struct trace_iterator *iter, int flags)
 	data = (u8 *)&field[1];
 	for (i = 0; i < tp->nr_args; i++)
 		if (!tp->args[i].type->print(s, tp->args[i].name,
-					     data + tp->args[i].offset))
+					     data + tp->args[i].offset, field))
 			goto partial;
 
 	if (!trace_seq_puts(s, "\n"))
@@ -1242,7 +1454,7 @@ static int kprobe_event_define_fields(struct ftrace_event_call *event_call)
 	DEFINE_FIELD(unsigned long, ip, FIELD_STRING_IP, 0);
 	/* Set argument names as fields */
 	for (i = 0; i < tp->nr_args; i++) {
-		ret = trace_define_field(event_call, tp->args[i].type->name,
+		ret = trace_define_field(event_call, tp->args[i].type->fmttype,
 					 tp->args[i].name,
 					 sizeof(field) + tp->args[i].offset,
 					 tp->args[i].type->size,
@@ -1264,7 +1476,7 @@ static int kretprobe_event_define_fields(struct ftrace_event_call *event_call)
 	DEFINE_FIELD(unsigned long, ret_ip, FIELD_STRING_RETIP, 0);
 	/* Set argument names as fields */
 	for (i = 0; i < tp->nr_args; i++) {
-		ret = trace_define_field(event_call, tp->args[i].type->name,
+		ret = trace_define_field(event_call, tp->args[i].type->fmttype,
 					 tp->args[i].name,
 					 sizeof(field) + tp->args[i].offset,
 					 tp->args[i].type->size,
@@ -1304,8 +1516,13 @@ static int __set_print_fmt(struct trace_probe *tp, char *buf, int len)
 	pos += snprintf(buf + pos, LEN_OR_ZERO, "\", %s", arg);
 
 	for (i = 0; i < tp->nr_args; i++) {
-		pos += snprintf(buf + pos, LEN_OR_ZERO, ", REC->%s",
-				tp->args[i].name);
+		if (strcmp(tp->args[i].type->name, "string") == 0)
+			pos += snprintf(buf + pos, LEN_OR_ZERO,
+					", __get_str(%s)",
+					tp->args[i].name);
+		else
+			pos += snprintf(buf + pos, LEN_OR_ZERO, ", REC->%s",
+					tp->args[i].name);
 	}
 
 #undef LEN_OR_ZERO
@@ -1341,12 +1558,12 @@ static __kprobes void kprobe_perf_func(struct kprobe *kp,
 	struct trace_probe *tp = container_of(kp, struct trace_probe, rp.kp);
 	struct ftrace_event_call *call = &tp->call;
 	struct kprobe_trace_entry_head *entry;
-	u8 *data;
-	int size, __size, i;
+	int size, __size, dsize;
 	unsigned long irq_flags;
 	int rctx;
 
-	__size = sizeof(*entry) + tp->size;
+	dsize = __get_data_size(tp, regs);
+	__size = sizeof(*entry) + tp->size + dsize;
 	size = ALIGN(__size + sizeof(u32), sizeof(u64));
 	size -= sizeof(u32);
 	if (WARN_ONCE(size > PERF_MAX_TRACE_SIZE,
@@ -1358,9 +1575,8 @@ static __kprobes void kprobe_perf_func(struct kprobe *kp,
 		return;
 
 	entry->ip = (unsigned long)kp->addr;
-	data = (u8 *)&entry[1];
-	for (i = 0; i < tp->nr_args; i++)
-		call_fetch(&tp->args[i].fetch, regs, data + tp->args[i].offset);
+	memset(&entry[1], 0, dsize);
+	store_trace_args(sizeof(*entry), tp, regs, (u8 *)&entry[1], dsize);
 
 	perf_trace_buf_submit(entry, size, rctx, entry->ip, 1, irq_flags, regs, call->perf_data);
 }
@@ -1372,12 +1588,12 @@ static __kprobes void kretprobe_perf_func(struct kretprobe_instance *ri,
 	struct trace_probe *tp = container_of(ri->rp, struct trace_probe, rp);
 	struct ftrace_event_call *call = &tp->call;
 	struct kretprobe_trace_entry_head *entry;
-	u8 *data;
-	int size, __size, i;
+	int size, __size, dsize;
 	unsigned long irq_flags;
 	int rctx;
 
-	__size = sizeof(*entry) + tp->size;
+	dsize = __get_data_size(tp, regs);
+	__size = sizeof(*entry) + tp->size + dsize;
 	size = ALIGN(__size + sizeof(u32), sizeof(u64));
 	size -= sizeof(u32);
 	if (WARN_ONCE(size > PERF_MAX_TRACE_SIZE,
@@ -1390,9 +1606,7 @@ static __kprobes void kretprobe_perf_func(struct kretprobe_instance *ri,
 
 	entry->func = (unsigned long)tp->rp.kp.addr;
 	entry->ret_ip = (unsigned long)ri->ret_addr;
-	data = (u8 *)&entry[1];
-	for (i = 0; i < tp->nr_args; i++)
-		call_fetch(&tp->args[i].fetch, regs, data + tp->args[i].offset);
+	store_trace_args(sizeof(*entry), tp, regs, (u8 *)&entry[1], dsize);
 
 	perf_trace_buf_submit(entry, size, rctx, entry->ret_ip, 1,
 			       irq_flags, regs, call->perf_data);


-- 
Masami Hiramatsu
e-mail: mhiramat@redhat.com

[PATCH -tip 2/4] perf probe: Support "string" type

[Masami Hiramatsu]

Support string type casting to event argument. If perf-probe
finds an argument casted as string, it ensures the target
variable is "(unsigned/signed) char *(or []). perf-probe also
adds dereference if the target is a pointer.
So, both of 'char buf[10];' and 'char *buf;' can be accessed
by 'buf:string'

Signed-off-by: Masami Hiramatsu <mhiramat@redhat.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
---

 tools/perf/Documentation/perf-probe.txt |    2 +
 tools/perf/util/probe-finder.c          |   59 +++++++++++++++++++++++++------
 2 files changed, 49 insertions(+), 12 deletions(-)

diff --git a/tools/perf/Documentation/perf-probe.txt b/tools/perf/Documentation/perf-probe.txt
index 94a258c..e5cf3ff 100644
--- a/tools/perf/Documentation/perf-probe.txt
+++ b/tools/perf/Documentation/perf-probe.txt
@@ -91,7 +91,7 @@ Each probe argument follows below syntax.
  [NAME=]LOCALVAR|$retval|%REG|@SYMBOL[:TYPE]
 
 'NAME' specifies the name of this argument (optional). You can use the name of local variable, local data structure member (e.g. var->field, var.field2), or kprobe-tracer argument format (e.g. $retval, %ax, etc). Note that the name of this argument will be set as the last member name if you specify a local data structure member (e.g. field2 for 'var->field1.field2'.)
-'TYPE' casts the type of this argument (optional). If omitted, perf probe automatically set the type based on debuginfo.
+'TYPE' casts the type of this argument (optional). If omitted, perf probe automatically set the type based on debuginfo. You can specify 'string' type only for the local variable or structure member which is an array of or a pointer to 'char' or 'unsigned char' type.
 
 LINE SYNTAX
 -----------
diff --git a/tools/perf/util/probe-finder.c b/tools/perf/util/probe-finder.c
index d964cb1..af3868b 100644
--- a/tools/perf/util/probe-finder.c
+++ b/tools/perf/util/probe-finder.c
@@ -414,18 +414,61 @@ static int convert_location(Dwarf_Op *op, struct probe_finder *pf)
 }
 
 static int convert_variable_type(Dwarf_Die *vr_die,
-				 struct kprobe_trace_arg *targ)
+				 struct kprobe_trace_arg *tvar,
+				 const char *cast)
 {
+	struct kprobe_trace_arg_ref **ref_ptr = &tvar->ref;
 	Dwarf_Die type;
 	char buf[16];
 	int ret;
 
+	/* TODO: check all types */
+	if (cast && strcmp(cast, "string") != 0) {
+		/* Non string type is OK */
+		tvar->type = strdup(cast);
+		return (tvar->type == NULL) ? -ENOMEM : 0;
+	}
+
 	if (die_get_real_type(vr_die, &type) == NULL) {
 		pr_warning("Failed to get a type information of %s.\n",
 			   dwarf_diename(vr_die));
 		return -ENOENT;
 	}
 
+	if (cast && strcmp(cast, "string") == 0) {	/* String type */
+		ret = dwarf_tag(&type);
+		if (ret != DW_TAG_pointer_type &&
+		    ret != DW_TAG_array_type) {
+			pr_warning("Failed to cast into string: "
+				   "%s(%s) is not a pointer nor array.",
+				   dwarf_diename(vr_die), dwarf_diename(&type));
+			return -EINVAL;
+		}
+		if (ret == DW_TAG_pointer_type) {
+			if (die_get_real_type(&type, &type) == NULL) {
+				pr_warning("Failed to get a type information.");
+				return -ENOENT;
+			}
+			while (*ref_ptr)
+				ref_ptr = &(*ref_ptr)->next;
+			/* Add new reference with offset +0 */
+			*ref_ptr = zalloc(sizeof(struct kprobe_trace_arg_ref));
+			if (*ref_ptr == NULL) {
+				pr_warning("Out of memory error\n");
+				return -ENOMEM;
+			}
+		}
+		if (die_compare_name(&type, "char") != 0 &&
+		    die_compare_name(&type, "unsigned char") != 0) {
+			pr_warning("Failed to cast into string: "
+				   "%s is not (unsigned) char *.",
+				   dwarf_diename(vr_die));
+			return -EINVAL;
+		}
+		tvar->type = strdup(cast);
+		return (tvar->type == NULL) ? -ENOMEM : 0;
+	}
+
 	ret = die_get_byte_size(&type) * 8;
 	if (ret) {
 		/* Check the bitwidth */
@@ -445,8 +488,8 @@ static int convert_variable_type(Dwarf_Die *vr_die,
 				   strerror(-ret));
 			return ret;
 		}
-		targ->type = strdup(buf);
-		if (targ->type == NULL)
+		tvar->type = strdup(buf);
+		if (tvar->type == NULL)
 			return -ENOMEM;
 	}
 	return 0;
@@ -556,14 +599,8 @@ static int convert_variable(Dwarf_Die *vr_die, struct probe_finder *pf)
 					      &die_mem);
 		vr_die = &die_mem;
 	}
-	if (ret == 0) {
-		if (pf->pvar->type) {
-			pf->tvar->type = strdup(pf->pvar->type);
-			if (pf->tvar->type == NULL)
-				ret = -ENOMEM;
-		} else
-			ret = convert_variable_type(vr_die, pf->tvar);
-	}
+	if (ret == 0)
+		ret = convert_variable_type(vr_die, pf->tvar, pf->pvar->type);
 	/* *expr will be cached in libdw. Don't free it. */
 	return ret;
 error:


-- 
Masami Hiramatsu
e-mail: mhiramat@redhat.com

[PATCH -tip 3/4] perf probe: Support tracing an entry of array

[Masami Hiramatsu]

Add array-entry tracing support to perf probe. This enables to trace
an entry of array which is indexed by constant value, e.g. array[0].

For example:

  $ perf probe -a 'bio_split bi->bi_io_vec[0]'

Signed-off-by: Masami Hiramatsu <mhiramat@redhat.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
---

 tools/perf/Documentation/perf-probe.txt |    2 +
 tools/perf/util/probe-event.c           |   56 ++++++++++++++++++++++---------
 tools/perf/util/probe-event.h           |    1 +
 tools/perf/util/probe-finder.c          |   48 +++++++++++++++++++++++----
 4 files changed, 83 insertions(+), 24 deletions(-)

diff --git a/tools/perf/Documentation/perf-probe.txt b/tools/perf/Documentation/perf-probe.txt
index e5cf3ff..ddc3999 100644
--- a/tools/perf/Documentation/perf-probe.txt
+++ b/tools/perf/Documentation/perf-probe.txt
@@ -90,7 +90,7 @@ Each probe argument follows below syntax.
 
  [NAME=]LOCALVAR|$retval|%REG|@SYMBOL[:TYPE]
 
-'NAME' specifies the name of this argument (optional). You can use the name of local variable, local data structure member (e.g. var->field, var.field2), or kprobe-tracer argument format (e.g. $retval, %ax, etc). Note that the name of this argument will be set as the last member name if you specify a local data structure member (e.g. field2 for 'var->field1.field2'.)
+'NAME' specifies the name of this argument (optional). You can use the name of local variable, local data structure member (e.g. var->field, var.field2), local array with fixed index (e.g. array[1], var->array[0], var->pointer[2]), or kprobe-tracer argument format (e.g. $retval, %ax, etc). Note that the name of this argument will be set as the last member name if you specify a local data structure member (e.g. field2 for 'var->field1.field2'.)
 'TYPE' casts the type of this argument (optional). If omitted, perf probe automatically set the type based on debuginfo. You can specify 'string' type only for the local variable or structure member which is an array of or a pointer to 'char' or 'unsigned char' type.
 
 LINE SYNTAX
diff --git a/tools/perf/util/probe-event.c b/tools/perf/util/probe-event.c
index 914c670..351baa9 100644
--- a/tools/perf/util/probe-event.c
+++ b/tools/perf/util/probe-event.c
@@ -557,7 +557,7 @@ static int parse_perf_probe_point(char *arg, struct perf_probe_event *pev)
 /* Parse perf-probe event argument */
 static int parse_perf_probe_arg(char *str, struct perf_probe_arg *arg)
 {
-	char *tmp;
+	char *tmp, *goodname;
 	struct perf_probe_arg_field **fieldp;
 
 	pr_debug("parsing arg: %s into ", str);
@@ -580,7 +580,7 @@ static int parse_perf_probe_arg(char *str, struct perf_probe_arg *arg)
 		pr_debug("type:%s ", arg->type);
 	}
 
-	tmp = strpbrk(str, "-.");
+	tmp = strpbrk(str, "-.[");
 	if (!is_c_varname(str) || !tmp) {
 		/* A variable, register, symbol or special value */
 		arg->var = strdup(str);
@@ -590,10 +590,11 @@ static int parse_perf_probe_arg(char *str, struct perf_probe_arg *arg)
 		return 0;
 	}
 
-	/* Structure fields */
+	/* Structure fields or array element */
 	arg->var = strndup(str, tmp - str);
 	if (arg->var == NULL)
 		return -ENOMEM;
+	goodname = arg->var;
 	pr_debug("%s, ", arg->var);
 	fieldp = &arg->field;
 
@@ -601,22 +602,38 @@ static int parse_perf_probe_arg(char *str, struct perf_probe_arg *arg)
 		*fieldp = zalloc(sizeof(struct perf_probe_arg_field));
 		if (*fieldp == NULL)
 			return -ENOMEM;
-		if (*tmp == '.') {
-			str = tmp + 1;
-			(*fieldp)->ref = false;
-		} else if (tmp[1] == '>') {
-			str = tmp + 2;
+		if (*tmp == '[') {	/* Array */
+			str = tmp;
+			(*fieldp)->index = strtol(str + 1, &tmp, 0);
 			(*fieldp)->ref = true;
-		} else {
-			semantic_error("Argument parse error: %s\n", str);
-			return -EINVAL;
+			if (*tmp != ']' || tmp == str + 1) {
+				semantic_error("Array index must be a"
+						" number.\n");
+				return -EINVAL;
+			}
+			tmp++;
+			if (*tmp == '\0')
+				tmp = NULL;
+		} else {		/* Structure */
+			if (*tmp == '.') {
+				str = tmp + 1;
+				(*fieldp)->ref = false;
+			} else if (tmp[1] == '>') {
+				str = tmp + 2;
+				(*fieldp)->ref = true;
+			} else {
+				semantic_error("Argument parse error: %s\n",
+					       str);
+				return -EINVAL;
+			}
+			tmp = strpbrk(str, "-.[");
 		}
-
-		tmp = strpbrk(str, "-.");
 		if (tmp) {
 			(*fieldp)->name = strndup(str, tmp - str);
 			if ((*fieldp)->name == NULL)
 				return -ENOMEM;
+			if (*str != '[')
+				goodname = (*fieldp)->name;
 			pr_debug("%s(%d), ", (*fieldp)->name, (*fieldp)->ref);
 			fieldp = &(*fieldp)->next;
 		}
@@ -624,11 +641,13 @@ static int parse_perf_probe_arg(char *str, struct perf_probe_arg *arg)
 	(*fieldp)->name = strdup(str);
 	if ((*fieldp)->name == NULL)
 		return -ENOMEM;
+	if (*str != '[')
+		goodname = (*fieldp)->name;
 	pr_debug("%s(%d)\n", (*fieldp)->name, (*fieldp)->ref);
 
-	/* If no name is specified, set the last field name */
+	/* If no name is specified, set the last field name (not array index)*/
 	if (!arg->name) {
-		arg->name = strdup((*fieldp)->name);
+		arg->name = strdup(goodname);
 		if (arg->name == NULL)
 			return -ENOMEM;
 	}
@@ -776,8 +795,11 @@ int synthesize_perf_probe_arg(struct perf_probe_arg *pa, char *buf, size_t len)
 	len -= ret;
 
 	while (field) {
-		ret = e_snprintf(tmp, len, "%s%s", field->ref ? "->" : ".",
-				 field->name);
+		if (field->name[0] == '[')
+			ret = e_snprintf(tmp, len, "%s", field->name);
+		else
+			ret = e_snprintf(tmp, len, "%s%s",
+					 field->ref ? "->" : ".", field->name);
 		if (ret <= 0)
 			goto error;
 		tmp += ret;
diff --git a/tools/perf/util/probe-event.h b/tools/perf/util/probe-event.h
index e9db1a2..bc06d3e 100644
--- a/tools/perf/util/probe-event.h
+++ b/tools/perf/util/probe-event.h
@@ -50,6 +50,7 @@ struct perf_probe_point {
 struct perf_probe_arg_field {
 	struct perf_probe_arg_field	*next;	/* Next field */
 	char				*name;	/* Name of the field */
+	long				index;	/* Array index number */
 	bool				ref;	/* Referencing flag */
 };
 
diff --git a/tools/perf/util/probe-finder.c b/tools/perf/util/probe-finder.c
index af3868b..75d6e6c 100644
--- a/tools/perf/util/probe-finder.c
+++ b/tools/perf/util/probe-finder.c
@@ -435,6 +435,9 @@ static int convert_variable_type(Dwarf_Die *vr_die,
 		return -ENOENT;
 	}
 
+	pr_debug("%s type is %s.\n",
+		 dwarf_diename(vr_die), dwarf_diename(&type));
+
 	if (cast && strcmp(cast, "string") == 0) {	/* String type */
 		ret = dwarf_tag(&type);
 		if (ret != DW_TAG_pointer_type &&
@@ -503,16 +506,44 @@ static int convert_variable_fields(Dwarf_Die *vr_die, const char *varname,
 	struct kprobe_trace_arg_ref *ref = *ref_ptr;
 	Dwarf_Die type;
 	Dwarf_Word offs;
-	int ret;
+	int ret, tag;
 
 	pr_debug("converting %s in %s\n", field->name, varname);
 	if (die_get_real_type(vr_die, &type) == NULL) {
 		pr_warning("Failed to get the type of %s.\n", varname);
 		return -ENOENT;
 	}
-
-	/* Check the pointer and dereference */
-	if (dwarf_tag(&type) == DW_TAG_pointer_type) {
+	pr_debug2("Var real type: (%x)\n", (unsigned)dwarf_dieoffset(&type));
+	tag = dwarf_tag(&type);
+
+	if (field->name[0] == '[' &&
+	    (tag == DW_TAG_array_type || tag == DW_TAG_pointer_type)) {
+		if (field->next)
+			/* Save original type for next field */
+			memcpy(die_mem, &type, sizeof(*die_mem));
+		/* Get the type of this array */
+		if (die_get_real_type(&type, &type) == NULL) {
+			pr_warning("Failed to get the type of %s.\n", varname);
+			return -ENOENT;
+		}
+		pr_debug2("Array real type: (%x)\n",
+			 (unsigned)dwarf_dieoffset(&type));
+		if (tag == DW_TAG_pointer_type) {
+			ref = zalloc(sizeof(struct kprobe_trace_arg_ref));
+			if (ref == NULL)
+				return -ENOMEM;
+			if (*ref_ptr)
+				(*ref_ptr)->next = ref;
+			else
+				*ref_ptr = ref;
+		}
+		ref->offset += die_get_byte_size(&type) * field->index;
+		if (!field->next)
+			/* Save vr_die for converting types */
+			memcpy(die_mem, vr_die, sizeof(*die_mem));
+		goto next;
+	} else if (tag == DW_TAG_pointer_type) {
+		/* Check the pointer and dereference */
 		if (!field->ref) {
 			pr_err("Semantic error: %s must be referred by '->'\n",
 			       field->name);
@@ -538,10 +569,15 @@ static int convert_variable_fields(Dwarf_Die *vr_die, const char *varname,
 			*ref_ptr = ref;
 	} else {
 		/* Verify it is a data structure  */
-		if (dwarf_tag(&type) != DW_TAG_structure_type) {
+		if (tag != DW_TAG_structure_type) {
 			pr_warning("%s is not a data structure.\n", varname);
 			return -EINVAL;
 		}
+		if (field->name[0] == '[') {
+			pr_err("Semantic error: %s is not a pointor nor array.",
+			       varname);
+			return -EINVAL;
+		}
 		if (field->ref) {
 			pr_err("Semantic error: %s must be referred by '.'\n",
 			       field->name);
@@ -568,6 +604,7 @@ static int convert_variable_fields(Dwarf_Die *vr_die, const char *varname,
 	}
 	ref->offset += (long)offs;
 
+next:
 	/* Converting next field */
 	if (field->next)
 		return convert_variable_fields(die_mem, field->name,
@@ -617,7 +654,6 @@ static int find_variable(Dwarf_Die *sp_die, struct probe_finder *pf)
 	char buf[32], *ptr;
 	int ret;
 
-	/* TODO: Support arrays */
 	if (pf->pvar->name)
 		pf->tvar->name = strdup(pf->pvar->name);
 	else {


-- 
Masami Hiramatsu
e-mail: mhiramat@redhat.com

[PATCH -tip 4/4] perf probe: Support static and global variables

[Masami Hiramatsu]

Add static and global variables support to perf probe.
This allows user to trace non-local variables (and
structure members) at probe points.

Signed-off-by: Masami Hiramatsu <mhiramat@redhat.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
---

 tools/perf/util/probe-event.c  |   15 ++++++-
 tools/perf/util/probe-finder.c |   85 +++++++++++++++++++++++++++++-----------
 2 files changed, 73 insertions(+), 27 deletions(-)

diff --git a/tools/perf/util/probe-event.c b/tools/perf/util/probe-event.c
index 351baa9..09cf546 100644
--- a/tools/perf/util/probe-event.c
+++ b/tools/perf/util/probe-event.c
@@ -926,6 +926,7 @@ out:
 static int synthesize_kprobe_trace_arg(struct kprobe_trace_arg *arg,
 				       char *buf, size_t buflen)
 {
+	struct kprobe_trace_arg_ref *ref = arg->ref;
 	int ret, depth = 0;
 	char *tmp = buf;
 
@@ -939,16 +940,24 @@ static int synthesize_kprobe_trace_arg(struct kprobe_trace_arg *arg,
 	buf += ret;
 	buflen -= ret;
 
+	/* Special case: @XXX */
+	if (arg->value[0] == '@' && arg->ref)
+			ref = ref->next;
+
 	/* Dereferencing arguments */
-	if (arg->ref) {
-		depth = __synthesize_kprobe_trace_arg_ref(arg->ref, &buf,
+	if (ref) {
+		depth = __synthesize_kprobe_trace_arg_ref(ref, &buf,
 							  &buflen, 1);
 		if (depth < 0)
 			return depth;
 	}
 
 	/* Print argument value */
-	ret = e_snprintf(buf, buflen, "%s", arg->value);
+	if (arg->value[0] == '@' && arg->ref)
+		ret = e_snprintf(buf, buflen, "%s%+ld", arg->value,
+				 arg->ref->offset);
+	else
+		ret = e_snprintf(buf, buflen, "%s", arg->value);
 	if (ret < 0)
 		return ret;
 	buf += ret;
diff --git a/tools/perf/util/probe-finder.c b/tools/perf/util/probe-finder.c
index 75d6e6c..294a437 100644
--- a/tools/perf/util/probe-finder.c
+++ b/tools/perf/util/probe-finder.c
@@ -356,14 +356,50 @@ static Dwarf_Die *die_find_member(Dwarf_Die *st_die, const char *name,
  * Probe finder related functions
  */
 
+static struct kprobe_trace_arg_ref *alloc_trace_arg_ref(long offs)
+{
+	struct kprobe_trace_arg_ref *ref;
+	ref = zalloc(sizeof(struct kprobe_trace_arg_ref));
+	if (ref != NULL)
+		ref->offset = offs;
+	return ref;
+}
+
 /* Show a location */
-static int convert_location(Dwarf_Op *op, struct probe_finder *pf)
+static int convert_variable_location(Dwarf_Die *vr_die, struct probe_finder *pf)
 {
+	Dwarf_Attribute attr;
+	Dwarf_Op *op;
+	size_t nops;
 	unsigned int regn;
 	Dwarf_Word offs = 0;
 	bool ref = false;
 	const char *regs;
 	struct kprobe_trace_arg *tvar = pf->tvar;
+	int ret;
+
+	/* TODO: handle more than 1 exprs */
+	if (dwarf_attr(vr_die, DW_AT_location, &attr) == NULL ||
+	    dwarf_getlocation_addr(&attr, pf->addr, &op, &nops, 1) <= 0 ||
+	    nops == 0) {
+		/* TODO: Support const_value */
+		pr_err("Failed to find the location of %s at this address.\n"
+		       " Perhaps, it has been optimized out.\n", pf->pvar->var);
+		return -ENOENT;
+	}
+
+	if (op->atom == DW_OP_addr) {
+		/* Static variables on memory (not stack), make @varname */
+		ret = strlen(dwarf_diename(vr_die));
+		tvar->value = zalloc(ret + 2);
+		if (tvar->value == NULL)
+			return -ENOMEM;
+		snprintf(tvar->value, ret + 2, "@%s", dwarf_diename(vr_die));
+		tvar->ref = alloc_trace_arg_ref((long)offs);
+		if (tvar->ref == NULL)
+			return -ENOMEM;
+		return 0;
+	}
 
 	/* If this is based on frame buffer, set the offset */
 	if (op->atom == DW_OP_fbreg) {
@@ -405,10 +441,9 @@ static int convert_location(Dwarf_Op *op, struct probe_finder *pf)
 		return -ENOMEM;
 
 	if (ref) {
-		tvar->ref = zalloc(sizeof(struct kprobe_trace_arg_ref));
+		tvar->ref = alloc_trace_arg_ref((long)offs);
 		if (tvar->ref == NULL)
 			return -ENOMEM;
-		tvar->ref->offset = (long)offs;
 	}
 	return 0;
 }
@@ -616,20 +651,13 @@ next:
 /* Show a variables in kprobe event format */
 static int convert_variable(Dwarf_Die *vr_die, struct probe_finder *pf)
 {
-	Dwarf_Attribute attr;
 	Dwarf_Die die_mem;
-	Dwarf_Op *expr;
-	size_t nexpr;
 	int ret;
 
-	if (dwarf_attr(vr_die, DW_AT_location, &attr) == NULL)
-		goto error;
-	/* TODO: handle more than 1 exprs */
-	ret = dwarf_getlocation_addr(&attr, pf->addr, &expr, &nexpr, 1);
-	if (ret <= 0 || nexpr == 0)
-		goto error;
+	pr_debug("Converting variable %s into trace event.\n",
+		 dwarf_diename(vr_die));
 
-	ret = convert_location(expr, pf);
+	ret = convert_variable_location(vr_die, pf);
 	if (ret == 0 && pf->pvar->field) {
 		ret = convert_variable_fields(vr_die, pf->pvar->var,
 					      pf->pvar->field, &pf->tvar->ref,
@@ -640,19 +668,14 @@ static int convert_variable(Dwarf_Die *vr_die, struct probe_finder *pf)
 		ret = convert_variable_type(vr_die, pf->tvar, pf->pvar->type);
 	/* *expr will be cached in libdw. Don't free it. */
 	return ret;
-error:
-	/* TODO: Support const_value */
-	pr_err("Failed to find the location of %s at this address.\n"
-	       " Perhaps, it has been optimized out.\n", pf->pvar->var);
-	return -ENOENT;
 }
 
 /* Find a variable in a subprogram die */
 static int find_variable(Dwarf_Die *sp_die, struct probe_finder *pf)
 {
-	Dwarf_Die vr_die;
+	Dwarf_Die vr_die, *scopes;
 	char buf[32], *ptr;
-	int ret;
+	int ret, nscopes;
 
 	if (pf->pvar->name)
 		pf->tvar->name = strdup(pf->pvar->name);
@@ -680,12 +703,26 @@ static int find_variable(Dwarf_Die *sp_die, struct probe_finder *pf)
 	pr_debug("Searching '%s' variable in context.\n",
 		 pf->pvar->var);
 	/* Search child die for local variables and parameters. */
-	if (!die_find_variable(sp_die, pf->pvar->var, &vr_die)) {
+	if (die_find_variable(sp_die, pf->pvar->var, &vr_die))
+		ret = convert_variable(&vr_die, pf);
+	else {
+		/* Search upper class */
+		nscopes = dwarf_getscopes_die(sp_die, &scopes);
+		if (nscopes > 0) {
+			ret = dwarf_getscopevar(scopes, nscopes, pf->pvar->var,
+						0, NULL, 0, 0, &vr_die);
+			if (ret >= 0)
+				ret = convert_variable(&vr_die, pf);
+			else
+				ret = -ENOENT;
+			free(scopes);
+		} else
+			ret = -ENOENT;
+	}
+	if (ret < 0)
 		pr_warning("Failed to find '%s' in this function.\n",
 			   pf->pvar->var);
-		return -ENOENT;
-	}
-	return convert_variable(&vr_die, pf);
+	return ret;
 }
 
 /* Show a probe point to output buffer */


-- 
Masami Hiramatsu
e-mail: mhiramat@redhat.com

Re: [PATCH -tip 0/4] perf-probe updates: string support, etc.

[Chase Douglas]

On May 19, 2010, at 3:57 PM, Masami Hiramatsu wrote:
> Hi,
> 
> Here is a series of patches which improves perf probe to
> add below features. I cleared some coding style issues.
> 
> - String support, which enables dynamic events to trace string
>  variables instead of its address.
> 
> - Fixed-index array entry support, which allows user to trace
>  an array entry with digit index, e.g. array[0].
> 
> - Global/static variable support, which allows user to trace
>  global or static variables, as same as local one.
> 
> 
> TODOs (possible features):
>  - Support dynamic array-indexing (var[var2])
>  - Support force type-casting ((type)var)
>  - Show what deta-structure member is assigned to each argument.
>  - Better support for probes on modules
>  - More debugger like enhancements(%next, --disasm, etc.)
> 
> Thank you,
> 
> ---
> 
> Masami Hiramatsu (4):
>      perf probe: Support static and global variables
>      perf probe: Support tracing an entry of array
>      perf probe: Support "string" type
>      tracing/kprobes: Support "string" type

What's the status of these patches? They seem very useful to me, but I
don't see them in Arnaldo's tree at git.kernel.org.

Thanks,

-- Chase

Re: [PATCH -tip 0/4] perf-probe updates: string support, etc.

[Arnaldo Carvalho de Melo]

Em Mon, Jul 05, 2010 at 10:30:47AM -0400, Chase Douglas escreveu:
> On May 19, 2010, at 3:57 PM, Masami Hiramatsu wrote:
> > Hi,
> > 
> > Here is a series of patches which improves perf probe to
> > add below features. I cleared some coding style issues.
> > 
> > - String support, which enables dynamic events to trace string
> >  variables instead of its address.
> > 
> > - Fixed-index array entry support, which allows user to trace
> >  an array entry with digit index, e.g. array[0].
> > 
> > - Global/static variable support, which allows user to trace
> >  global or static variables, as same as local one.
> > 
> > 
> > TODOs (possible features):
> >  - Support dynamic array-indexing (var[var2])
> >  - Support force type-casting ((type)var)
> >  - Show what deta-structure member is assigned to each argument.
> >  - Better support for probes on modules
> >  - More debugger like enhancements(%next, --disasm, etc.)
> > 
> > Thank you,
> > 
> > ---
> > 
> > Masami Hiramatsu (4):
> >      perf probe: Support static and global variables
> >      perf probe: Support tracing an entry of array
> >      perf probe: Support "string" type
> >      tracing/kprobes: Support "string" type
> 
> What's the status of these patches? They seem very useful to me, but I
> don't see them in Arnaldo's tree at git.kernel.org.

Thanks for reminding me about these ones, will look at them to get them
in perf/core.

- Arnaldo

Re: [PATCH -tip 0/4] perf-probe updates: string support, etc.

[Arnaldo Carvalho de Melo]

Em Mon, Jul 05, 2010 at 02:44:50PM -0300, Arnaldo Carvalho de Melo escreveu:
> Em Mon, Jul 05, 2010 at 10:30:47AM -0400, Chase Douglas escreveu:
> > On May 19, 2010, at 3:57 PM, Masami Hiramatsu wrote:
> > > Here is a series of patches which improves perf probe to
> > > add below features. I cleared some coding style issues.

> > > - String support, which enables dynamic events to trace string
> > >  variables instead of its address.

> > > - Fixed-index array entry support, which allows user to trace
> > >  an array entry with digit index, e.g. array[0].

> > > - Global/static variable support, which allows user to trace
> > >  global or static variables, as same as local one.

> > What's the status of these patches? They seem very useful to me, but I
> > don't see them in Arnaldo's tree at git.kernel.org.

> Thanks for reminding me about these ones, will look at them to get them
> in perf/core.

Masami, I fixed up a minor conflict and while trying it this happened:

[root@emilia ~]# perf probe -a 'bio_split bi->bi_io_vec[0]'
kprobe_events file does not exist - please rebuild kernel with CONFIG_KPROBE_EVENT.
  Error: Failed to add events. (-1)

But on a second try:

[root@emilia ~]# l /sys/kernel/debug/tracing/kprobe_events 
-rw-r--r-- 1 root root 0 Jul  5 18:37 /sys/kernel/debug/tracing/kprobe_events
[root@emilia ~]# cat /sys/kernel/debug/tracing/kprobe_events 
[root@emilia ~]#
[root@emilia ~]# perf probe -a 'bio_split bi->bi_io_vec[0]'
Add new event:
  probe:bio_split      (on bio_split with bi_io_vec=bi->bi_io_vec[0])

You can now use it on all perf tools, such as:

	perf record -e probe:bio_split -aR sleep 1

[root@emilia ~]# cat /sys/kernel/debug/tracing/kprobe_events 
p:probe/bio_split bio_split bi_io_vec=+0(+72(%di)):u64
[root@emilia ~]# 

I'll push it as is, posting the pull request with the patches today,
please check if everything is ok and send fixups if needed,

Thanks,

- Arnaldo