[PATCH -tip tracing/kprobes] Powerpc port of the kprobe-based event tracer.

[PATCH -tip tracing/kprobes] Powerpc port of the kprobe-based event tracer.

[Mahesh J Salgaonkar]

[-- Attachment #1: kprobes.ppc.patch --]
[-- Type: text/plain, Size: 8887 bytes --]

This patch ports the kprobe-based event tracer to powerpc. This patch
is based on x86 port.

Port the following API's to ppc for accessing registers and stack entries
from pt_regs.

- regs_query_register_offset(const char *name)
   Query the offset of "name" register.

- regs_query_register_name(unsigned int offset)
   Query the name of register by its offset.

- regs_get_register(struct pt_regs *regs, unsigned int offset)
   Get the value of a register by its offset.

- regs_within_kernel_stack(struct pt_regs *regs, unsigned long addr)
   Check the address is in the kernel stack.

- regs_get_kernel_stack_nth(struct pt_regs *reg, unsigned int nth)
   Get Nth entry of the kernel stack. (N >= 0)

- regs_get_argument_nth(struct pt_regs *reg, unsigned int nth)
   Get Nth argument at function call. (N >= 0)

Signed-off-by: Mahesh Salgaonkar <mahesh@linux.vnet.ibm.com>
---
 arch/powerpc/include/asm/ptrace.h |   65 +++++++++++++++++
 arch/powerpc/kernel/ptrace.c      |  141 ++++++++++++++++++++++++++++++++++++++
 kernel/trace/Kconfig              |    2 
 3 files changed, 207 insertions(+), 1 deletion(-)

Index: linux-2.6-tip/arch/powerpc/include/asm/ptrace.h
===================================================================
--- linux-2.6-tip.orig/arch/powerpc/include/asm/ptrace.h
+++ linux-2.6-tip/arch/powerpc/include/asm/ptrace.h
@@ -131,6 +131,71 @@ do {									      \
 } while (0)
 #endif /* __powerpc64__ */
 
+/* Query offset/name of register from its name/offset */
+#include <linux/stddef.h>
+#include <linux/thread_info.h>
+extern int regs_query_register_offset(const char *name);
+extern const char *regs_query_register_name(unsigned int offset);
+#define MAX_REG_OFFSET (offsetof(struct pt_regs, result))
+#define kernel_stack_pointer(regs) ((regs)->gpr[1])
+
+/**
+ * regs_get_register() - get register value from its offset
+ * @regs:	   pt_regs from which register value is gotten
+ * @offset:    offset number of the register.
+ *
+ * regs_get_register returns the value of a register whose offset from @regs
+ * is @offset. The @offset is the offset of the register in struct pt_regs.
+ * If @offset is bigger than MAX_REG_OFFSET, this returns 0.
+ */
+static inline unsigned long regs_get_register(struct pt_regs *regs,
+						unsigned int offset)
+{
+	if (unlikely(offset > MAX_REG_OFFSET))
+		return 0;
+	return *(unsigned long *)((unsigned long)regs + offset);
+}
+
+/**
+ * regs_within_kernel_stack() - check the address in the stack
+ * @regs:      pt_regs which contains kernel stack pointer.
+ * @addr:      address which is checked.
+ *
+ * regs_within_kenel_stack() checks @addr is within the kernel stack page(s).
+ * If @addr is within the kernel stack, it returns true. If not, returns false.
+ */
+
+static inline int regs_within_kernel_stack(struct pt_regs *regs,
+						unsigned long addr)
+{
+	return ((addr & ~(THREAD_SIZE - 1))  ==
+		(kernel_stack_pointer(regs) & ~(THREAD_SIZE - 1)));
+}
+
+/**
+ * regs_get_kernel_stack_nth() - get Nth entry of the stack
+ * @regs:	pt_regs which contains kernel stack pointer.
+ * @n:		stack entry number.
+ *
+ * regs_get_kernel_stack_nth() returns @n th entry of the kernel stack which
+ * is specifined by @regs. If the @n th entry is NOT in the kernel stack,
+ * this returns 0.
+ */
+static inline unsigned long regs_get_kernel_stack_nth(struct pt_regs *regs,
+						      unsigned int n)
+{
+	unsigned long *addr = (unsigned long *)kernel_stack_pointer(regs);
+	addr += n;
+	if (regs_within_kernel_stack(regs, (unsigned long)addr))
+		return *addr;
+	else
+		return 0;
+}
+
+/* Get Nth argument at function call */
+extern unsigned long regs_get_argument_nth(struct pt_regs *regs,
+						unsigned int n);
+
 /*
  * These are defined as per linux/ptrace.h, which see.
  */
Index: linux-2.6-tip/kernel/trace/Kconfig
===================================================================
--- linux-2.6-tip.orig/kernel/trace/Kconfig
+++ linux-2.6-tip/kernel/trace/Kconfig
@@ -430,7 +430,7 @@ config BLK_DEV_IO_TRACE
 
 config KPROBE_TRACER
 	depends on KPROBES
-	depends on X86
+	depends on x86 || PPC
 	bool "Trace kprobes"
 	select TRACING
 	select GENERIC_TRACER
Index: linux-2.6-tip/arch/powerpc/kernel/ptrace.c
===================================================================
--- linux-2.6-tip.orig/arch/powerpc/kernel/ptrace.c
+++ linux-2.6-tip/arch/powerpc/kernel/ptrace.c
@@ -39,6 +39,147 @@
 #include <asm/system.h>
 
 /*
+ * The parameter save area on the stack is used to store arguments being passed
+ * to callee function and is located at fixed offset from stack pointer.
+ */
+#ifdef CONFIG_PPC32
+#define PARAMETER_SAVE_AREA_OFFSET	24  /* bytes */
+#else /* CONFIG_PPC32 */
+#define PARAMETER_SAVE_AREA_OFFSET	48  /* bytes */
+#endif
+
+struct pt_regs_offset {
+	const char *name;
+	int offset;
+};
+
+#define REG_OFFSET_NAME(r) {.name = #r, .offset = offsetof(struct pt_regs, r)}
+#define REG_OFFSET_END {.name = NULL, .offset = 0}
+
+static const struct pt_regs_offset regoffset_table[] = {
+	REG_OFFSET_NAME(gpr[0]),
+	REG_OFFSET_NAME(gpr[1]),
+	REG_OFFSET_NAME(gpr[2]),
+	REG_OFFSET_NAME(gpr[3]),
+	REG_OFFSET_NAME(gpr[4]),
+	REG_OFFSET_NAME(gpr[5]),
+	REG_OFFSET_NAME(gpr[6]),
+	REG_OFFSET_NAME(gpr[7]),
+	REG_OFFSET_NAME(gpr[8]),
+	REG_OFFSET_NAME(gpr[9]),
+	REG_OFFSET_NAME(gpr[10]),
+	REG_OFFSET_NAME(gpr[11]),
+	REG_OFFSET_NAME(gpr[12]),
+	REG_OFFSET_NAME(gpr[13]),
+	REG_OFFSET_NAME(gpr[14]),
+	REG_OFFSET_NAME(gpr[15]),
+	REG_OFFSET_NAME(gpr[16]),
+	REG_OFFSET_NAME(gpr[17]),
+	REG_OFFSET_NAME(gpr[18]),
+	REG_OFFSET_NAME(gpr[19]),
+	REG_OFFSET_NAME(gpr[20]),
+	REG_OFFSET_NAME(gpr[21]),
+	REG_OFFSET_NAME(gpr[22]),
+	REG_OFFSET_NAME(gpr[23]),
+	REG_OFFSET_NAME(gpr[24]),
+	REG_OFFSET_NAME(gpr[25]),
+	REG_OFFSET_NAME(gpr[26]),
+	REG_OFFSET_NAME(gpr[27]),
+	REG_OFFSET_NAME(gpr[28]),
+	REG_OFFSET_NAME(gpr[29]),
+	REG_OFFSET_NAME(gpr[30]),
+	REG_OFFSET_NAME(gpr[31]),
+	REG_OFFSET_NAME(nip),
+	REG_OFFSET_NAME(msr),
+	REG_OFFSET_NAME(orig_gpr3),
+	REG_OFFSET_NAME(ctr),
+	REG_OFFSET_NAME(link),
+	REG_OFFSET_NAME(xer),
+	REG_OFFSET_NAME(ccr),
+#ifdef CONFIG_PPC64
+	REG_OFFSET_NAME(softe),
+#else
+	REG_OFFSET_NAME(mq),
+#endif
+	REG_OFFSET_NAME(trap),
+	REG_OFFSET_NAME(dar),
+	REG_OFFSET_NAME(dsisr),
+	REG_OFFSET_NAME(result),
+	REG_OFFSET_END,
+};
+
+/**
+ * regs_query_register_offset() - query register offset from its name
+ * @name:	the name of a register
+ *
+ * regs_query_register_offset() returns the offset of a register in struct
+ * pt_regs from its name. If the name is invalid, this returns -EINVAL;
+ */
+int regs_query_register_offset(const char *name)
+{
+	const struct pt_regs_offset *roff;
+	for (roff = regoffset_table; roff->name != NULL; roff++)
+		if (!strcmp(roff->name, name))
+			return roff->offset;
+	return -EINVAL;
+}
+
+/**
+ * regs_query_register_name() - query register name from its offset
+ * @offset:	the offset of a register in struct pt_regs.
+ *
+ * regs_query_register_name() returns the name of a register from its
+ * offset in struct pt_regs. If the @offset is invalid, this returns NULL;
+ */
+const char *regs_query_register_name(unsigned int offset)
+{
+	const struct pt_regs_offset *roff;
+	for (roff = regoffset_table; roff->name != NULL; roff++)
+		if (roff->offset == offset)
+			return roff->name;
+	return NULL;
+}
+
+static const int arg_offs_table[] = {
+	[0] = offsetof(struct pt_regs, gpr[3]),
+	[1] = offsetof(struct pt_regs, gpr[4]),
+	[2] = offsetof(struct pt_regs, gpr[5]),
+	[3] = offsetof(struct pt_regs, gpr[6]),
+	[4] = offsetof(struct pt_regs, gpr[7]),
+	[5] = offsetof(struct pt_regs, gpr[8]),
+	[6] = offsetof(struct pt_regs, gpr[9]),
+	[7] = offsetof(struct pt_regs, gpr[10])
+};
+
+/**
+ * regs_get_argument_nth() - get Nth argument at function call
+ * @regs:	pt_regs which contains registers at function entry.
+ * @n:		argument number.
+ *
+ * regs_get_argument_nth() returns @n th argument of a function call.
+ * Since usually the kernel stack will be changed right after function entry,
+ * you must use this at function entry. If the @n th entry is NOT in the
+ * kernel stack or pt_regs, this returns 0.
+ */
+unsigned long regs_get_argument_nth(struct pt_regs *regs, unsigned int n)
+{
+	if (n < ARRAY_SIZE(arg_offs_table))
+		return *(unsigned long *)((char *)regs + arg_offs_table[n]);
+	else {
+		/*
+		 * If more arguments are passed that can be stored in
+		 * registers, the remaining arguments are stored in the
+		 * parameter save area located at fixed offset from stack
+		 * pointer.
+		 * Following the PowerPC ABI, the first few arguments are
+		 * actually passed in registers (r3-r10), with equivalent space
+		 * left unused in the parameter save area.
+		 */
+		n += (PARAMETER_SAVE_AREA_OFFSET / sizeof(unsigned long));
+		return regs_get_kernel_stack_nth(regs, n);
+	}
+}
+/*
  * does not yet catch signals sent when the child dies.
  * in exit.c or in signal.c.
  */

Re: [PATCH -tip tracing/kprobes] Powerpc port of the kprobe-based event tracer.

[Masami Hiramatsu]

Hi Mahesh,


Mahesh J Salgaonkar wrote:
> This patch ports the kprobe-based event tracer to powerpc. This patch
> is based on x86 port.
>
> Port the following API's to ppc for accessing registers and stack entries
> from pt_regs.
>
> - regs_query_register_offset(const char *name)
>     Query the offset of "name" register.
>
> - regs_query_register_name(unsigned int offset)
>     Query the name of register by its offset.
>
> - regs_get_register(struct pt_regs *regs, unsigned int offset)
>     Get the value of a register by its offset.
>
> - regs_within_kernel_stack(struct pt_regs *regs, unsigned long addr)
>     Check the address is in the kernel stack.
>
> - regs_get_kernel_stack_nth(struct pt_regs *reg, unsigned int nth)
>     Get Nth entry of the kernel stack. (N>= 0)
>
> - regs_get_argument_nth(struct pt_regs *reg, unsigned int nth)
>     Get Nth argument at function call. (N>= 0)
>
> Signed-off-by: Mahesh Salgaonkar<mahesh@linux.vnet.ibm.com>

Thank you for porting!


> ---
>   arch/powerpc/include/asm/ptrace.h |   65 +++++++++++++++++
>   arch/powerpc/kernel/ptrace.c      |  141 ++++++++++++++++++++++++++++++++++++++
>   kernel/trace/Kconfig              |    2
>   3 files changed, 207 insertions(+), 1 deletion(-)
>
> Index: linux-2.6-tip/arch/powerpc/include/asm/ptrace.h
> ===================================================================
> --- linux-2.6-tip.orig/arch/powerpc/include/asm/ptrace.h
> +++ linux-2.6-tip/arch/powerpc/include/asm/ptrace.h
> @@ -131,6 +131,71 @@ do {									      \
>   } while (0)
>   #endif /* __powerpc64__ */
>
> +/* Query offset/name of register from its name/offset */
> +#include<linux/stddef.h>
> +#include<linux/thread_info.h>
> +extern int regs_query_register_offset(const char *name);
> +extern const char *regs_query_register_name(unsigned int offset);
> +#define MAX_REG_OFFSET (offsetof(struct pt_regs, result))
> +#define kernel_stack_pointer(regs) ((regs)->gpr[1])

Hmm, kernel_stack_pointer() would better be defined just after
user_stack_pointer().

[...]


> Index: linux-2.6-tip/arch/powerpc/kernel/ptrace.c
> ===================================================================
> --- linux-2.6-tip.orig/arch/powerpc/kernel/ptrace.c
> +++ linux-2.6-tip/arch/powerpc/kernel/ptrace.c
> @@ -39,6 +39,147 @@
>   #include<asm/system.h>
>
>   /*
> + * The parameter save area on the stack is used to store arguments being passed
> + * to callee function and is located at fixed offset from stack pointer.
> + */
> +#ifdef CONFIG_PPC32
> +#define PARAMETER_SAVE_AREA_OFFSET	24  /* bytes */
> +#else /* CONFIG_PPC32 */
> +#define PARAMETER_SAVE_AREA_OFFSET	48  /* bytes */
> +#endif
> +
> +struct pt_regs_offset {
> +	const char *name;
> +	int offset;
> +};
> +
> +#define REG_OFFSET_NAME(r) {.name = #r, .offset = offsetof(struct pt_regs, r)}
> +#define REG_OFFSET_END {.name = NULL, .offset = 0}
> +
> +static const struct pt_regs_offset regoffset_table[] = {
> +	REG_OFFSET_NAME(gpr[0]),
> +	REG_OFFSET_NAME(gpr[1]),
> +	REG_OFFSET_NAME(gpr[2]),
> +	REG_OFFSET_NAME(gpr[3]),
> +	REG_OFFSET_NAME(gpr[4]),
> +	REG_OFFSET_NAME(gpr[5]),
> +	REG_OFFSET_NAME(gpr[6]),
> +	REG_OFFSET_NAME(gpr[7]),
> +	REG_OFFSET_NAME(gpr[8]),
> +	REG_OFFSET_NAME(gpr[9]),
> +	REG_OFFSET_NAME(gpr[10]),
> +	REG_OFFSET_NAME(gpr[11]),
> +	REG_OFFSET_NAME(gpr[12]),
> +	REG_OFFSET_NAME(gpr[13]),
> +	REG_OFFSET_NAME(gpr[14]),
> +	REG_OFFSET_NAME(gpr[15]),
> +	REG_OFFSET_NAME(gpr[16]),
> +	REG_OFFSET_NAME(gpr[17]),
> +	REG_OFFSET_NAME(gpr[18]),
> +	REG_OFFSET_NAME(gpr[19]),
> +	REG_OFFSET_NAME(gpr[20]),
> +	REG_OFFSET_NAME(gpr[21]),
> +	REG_OFFSET_NAME(gpr[22]),
> +	REG_OFFSET_NAME(gpr[23]),
> +	REG_OFFSET_NAME(gpr[24]),
> +	REG_OFFSET_NAME(gpr[25]),
> +	REG_OFFSET_NAME(gpr[26]),
> +	REG_OFFSET_NAME(gpr[27]),
> +	REG_OFFSET_NAME(gpr[28]),
> +	REG_OFFSET_NAME(gpr[29]),
> +	REG_OFFSET_NAME(gpr[30]),
> +	REG_OFFSET_NAME(gpr[31]),
> +	REG_OFFSET_NAME(nip),
> +	REG_OFFSET_NAME(msr),
> +	REG_OFFSET_NAME(orig_gpr3),
> +	REG_OFFSET_NAME(ctr),
> +	REG_OFFSET_NAME(link),
> +	REG_OFFSET_NAME(xer),
> +	REG_OFFSET_NAME(ccr),
> +#ifdef CONFIG_PPC64
> +	REG_OFFSET_NAME(softe),
> +#else
> +	REG_OFFSET_NAME(mq),
> +#endif
> +	REG_OFFSET_NAME(trap),
> +	REG_OFFSET_NAME(dar),
> +	REG_OFFSET_NAME(dsisr),
> +	REG_OFFSET_NAME(result),
> +	REG_OFFSET_END,
> +};
> +
> +/**
> + * regs_query_register_offset() - query register offset from its name
> + * @name:	the name of a register
> + *
> + * regs_query_register_offset() returns the offset of a register in struct
> + * pt_regs from its name. If the name is invalid, this returns -EINVAL;
> + */
> +int regs_query_register_offset(const char *name)
> +{
> +	const struct pt_regs_offset *roff;
> +	for (roff = regoffset_table; roff->name != NULL; roff++)
> +		if (!strcmp(roff->name, name))
> +			return roff->offset;
> +	return -EINVAL;
> +}
> +
> +/**
> + * regs_query_register_name() - query register name from its offset
> + * @offset:	the offset of a register in struct pt_regs.
> + *
> + * regs_query_register_name() returns the name of a register from its
> + * offset in struct pt_regs. If the @offset is invalid, this returns NULL;
> + */
> +const char *regs_query_register_name(unsigned int offset)
> +{
> +	const struct pt_regs_offset *roff;
> +	for (roff = regoffset_table; roff->name != NULL; roff++)
> +		if (roff->offset == offset)
> +			return roff->name;
> +	return NULL;
> +}
> +
> +static const int arg_offs_table[] = {
> +	[0] = offsetof(struct pt_regs, gpr[3]),
> +	[1] = offsetof(struct pt_regs, gpr[4]),
> +	[2] = offsetof(struct pt_regs, gpr[5]),
> +	[3] = offsetof(struct pt_regs, gpr[6]),
> +	[4] = offsetof(struct pt_regs, gpr[7]),
> +	[5] = offsetof(struct pt_regs, gpr[8]),
> +	[6] = offsetof(struct pt_regs, gpr[9]),
> +	[7] = offsetof(struct pt_regs, gpr[10])
> +};
> +
> +/**
> + * regs_get_argument_nth() - get Nth argument at function call
> + * @regs:	pt_regs which contains registers at function entry.
> + * @n:		argument number.
> + *
> + * regs_get_argument_nth() returns @n th argument of a function call.
> + * Since usually the kernel stack will be changed right after function entry,
> + * you must use this at function entry. If the @n th entry is NOT in the
> + * kernel stack or pt_regs, this returns 0.
> + */
> +unsigned long regs_get_argument_nth(struct pt_regs *regs, unsigned int n)
> +{
> +	if (n<  ARRAY_SIZE(arg_offs_table))
              ^ here, we needs a space.

> +		return *(unsigned long *)((char *)regs + arg_offs_table[n]);
> +	else {
> +		/*
> +		 * If more arguments are passed that can be stored in
> +		 * registers, the remaining arguments are stored in the
> +		 * parameter save area located at fixed offset from stack
> +		 * pointer.
> +		 * Following the PowerPC ABI, the first few arguments are
> +		 * actually passed in registers (r3-r10), with equivalent space
> +		 * left unused in the parameter save area.
> +		 */
> +		n += (PARAMETER_SAVE_AREA_OFFSET / sizeof(unsigned long));
> +		return regs_get_kernel_stack_nth(regs, n);
> +	}
> +}
> +/*
>    * does not yet catch signals sent when the child dies.
>    * in exit.c or in signal.c.
>    */
>

others seems good!

Thank you!

-- 
Masami Hiramatsu

Software Engineer
Hitachi Computer Products (America), Inc.
Software Solutions Division

e-mail: mhiramat@redhat.com

[PATCH -tip tracing/kprobes] Powerpc port of the kprobe-based event tracer.

[Wenji Huang]

Hi,

> +#define kernel_stack_pointer(regs) ((regs)->gpr[1])
> +
> +/**
> + * regs_get_register() - get register value from its offset
> + * @regs:	   pt_regs from which register value is gotten
> + * @offset:    offset number of the register.
> + *
> + * regs_get_register returns the value of a register whose offset from @regs
> + * is @offset. The @offset is the offset of the register in struct pt_regs.

"is @offset." seems be redundant.
> + * If @offset is bigger than MAX_REG_OFFSET, this returns 0.
> + */
> +static inline unsigned long regs_get_register(struct pt_regs *regs,

[...]
> + * regs_within_kernel_stack() - check the address in the stack
> + * @regs:      pt_regs which contains kernel stack pointer.
> + * @addr:      address which is checked.
> + *
> + * regs_within_kenel_stack() checks @addr is within the kernel stack page(s).
> + * If @addr is within the kernel stack, it returns true. If not, returns false.

s/regs_within_kenel_stack/regs_within_kernel_stack/
The return type function is declared as int.
> + */
> +
> +static inline int regs_within_kernel_stack(struct pt_regs *regs,
> +						unsigned long addr)
> +{
> +	return ((addr & ~(THREAD_SIZE - 1))  ==
> +		(kernel_stack_pointer(regs) & ~(THREAD_SIZE - 1)));
> +}
> +
> +/**
> + * regs_get_kernel_stack_nth() - get Nth entry of the stack
> + * @regs:	pt_regs which contains kernel stack pointer.
> + * @n:		stack entry number.
> + *
> + * regs_get_kernel_stack_nth() returns @n th entry of the kernel stack which
> + * is specifined by @regs. If the @n th entry is NOT in the kernel stack,
> + * this returns 0.

s/specifined/specified/
> + */
> +static inline unsigned long regs_get_kernel_stack_nth(struct pt_regs *regs,
> +						      unsigned int n)
> +{
> +	unsigned long *addr = (unsigned long *)kernel_stack_pointer(regs);
> +	addr += n;
> +	if (regs_within_kernel_stack(regs, (unsigned long)addr))
> +		return *addr;
> +	else
> +		return 0;
> +}
> +
> +
> +/* Get Nth argument at function call */
> +extern unsigned long regs_get_argument_nth(struct pt_regs *regs,
> +						unsigned int n);
> +

Maybe to put extern declaration at the very beginning is better.
>  /*
>   * These are defined as per linux/ptrace.h, which see.
>   */
[...]

Regards,
Wenji

Re: [PATCH -tip tracing/kprobes] Powerpc port of the kprobe-based event tracer.

[Mahesh J Salgaonkar]

[-- Attachment #1: Type: text/plain, Size: 312 bytes --]

On Mon, Oct 26, 2009 at 06:06:10PM -0400, Masami Hiramatsu wrote:
> Hi Mahesh,
> 
> 
> >Signed-off-by: Mahesh Salgaonkar<mahesh@linux.vnet.ibm.com>
> 
> Thank you for porting!
> 
Thanks Masami for reviewing. I made the changes as per your suggestions.
Please find the modified patch attached.

Thanks,
-Mahesh.


[-- Attachment #2: kprobes.ppc.patch --]
[-- Type: text/plain, Size: 9142 bytes --]

Powerpc port of the kprobe-based event tracer

This patch ports the kprobe-based event tracer to powerpc. This patch
is based in x86 port.

Port the following API's to ppc for accessing registers and stack entries
from pt_regs.

- regs_query_register_offset(const char *name)
   Query the offset of "name" register.

- regs_query_register_name(unsigned int offset)
   Query the name of register by its offset.

- regs_get_register(struct pt_regs *regs, unsigned int offset)
   Get the value of a register by its offset.

- regs_within_kernel_stack(struct pt_regs *regs, unsigned long addr)
   Check the address is in the kernel stack.

- regs_get_kernel_stack_nth(struct pt_regs *reg, unsigned int nth)
   Get Nth entry of the kernel stack. (N >= 0)

- regs_get_argument_nth(struct pt_regs *reg, unsigned int nth)
   Get Nth argument at function call. (N >= 0)

Signed-off-by: Mahesh Salgaonkar <mahesh@linux.vnet.ibm.com>
---
 arch/powerpc/include/asm/ptrace.h |   65 +++++++++++++++++
 arch/powerpc/kernel/ptrace.c      |  141 ++++++++++++++++++++++++++++++++++++++
 kernel/trace/Kconfig              |    2 
 3 files changed, 207 insertions(+), 1 deletion(-)

Index: linux-2.6-tip/arch/powerpc/include/asm/ptrace.h
===================================================================
--- linux-2.6-tip.orig/arch/powerpc/include/asm/ptrace.h
+++ linux-2.6-tip/arch/powerpc/include/asm/ptrace.h
@@ -83,6 +83,7 @@ struct pt_regs {
 
 #define instruction_pointer(regs) ((regs)->nip)
 #define user_stack_pointer(regs) ((regs)->gpr[1])
+#define kernel_stack_pointer(regs) ((regs)->gpr[1])
 #define regs_return_value(regs) ((regs)->gpr[3])
 
 #ifdef CONFIG_SMP
@@ -131,6 +132,70 @@ do {									      \
 } while (0)
 #endif /* __powerpc64__ */
 
+/* Query offset/name of register from its name/offset */
+#include <linux/stddef.h>
+#include <linux/thread_info.h>
+extern int regs_query_register_offset(const char *name);
+extern const char *regs_query_register_name(unsigned int offset);
+#define MAX_REG_OFFSET (offsetof(struct pt_regs, result))
+
+/**
+ * regs_get_register() - get register value from its offset
+ * @regs:	   pt_regs from which register value is gotten
+ * @offset:    offset number of the register.
+ *
+ * regs_get_register returns the value of a register whose offset from @regs
+ * is @offset. The @offset is the offset of the register in struct pt_regs.
+ * If @offset is bigger than MAX_REG_OFFSET, this returns 0.
+ */
+static inline unsigned long regs_get_register(struct pt_regs *regs,
+						unsigned int offset)
+{
+	if (unlikely(offset > MAX_REG_OFFSET))
+		return 0;
+	return *(unsigned long *)((unsigned long)regs + offset);
+}
+
+/**
+ * regs_within_kernel_stack() - check the address in the stack
+ * @regs:      pt_regs which contains kernel stack pointer.
+ * @addr:      address which is checked.
+ *
+ * regs_within_kenel_stack() checks @addr is within the kernel stack page(s).
+ * If @addr is within the kernel stack, it returns true. If not, returns false.
+ */
+
+static inline int regs_within_kernel_stack(struct pt_regs *regs,
+						unsigned long addr)
+{
+	return ((addr & ~(THREAD_SIZE - 1))  ==
+		(kernel_stack_pointer(regs) & ~(THREAD_SIZE - 1)));
+}
+
+/**
+ * regs_get_kernel_stack_nth() - get Nth entry of the stack
+ * @regs:	pt_regs which contains kernel stack pointer.
+ * @n:		stack entry number.
+ *
+ * regs_get_kernel_stack_nth() returns @n th entry of the kernel stack which
+ * is specifined by @regs. If the @n th entry is NOT in the kernel stack,
+ * this returns 0.
+ */
+static inline unsigned long regs_get_kernel_stack_nth(struct pt_regs *regs,
+						      unsigned int n)
+{
+	unsigned long *addr = (unsigned long *)kernel_stack_pointer(regs);
+	addr += n;
+	if (regs_within_kernel_stack(regs, (unsigned long)addr))
+		return *addr;
+	else
+		return 0;
+}
+
+/* Get Nth argument at function call */
+extern unsigned long regs_get_argument_nth(struct pt_regs *regs,
+						unsigned int n);
+
 /*
  * These are defined as per linux/ptrace.h, which see.
  */
Index: linux-2.6-tip/kernel/trace/Kconfig
===================================================================
--- linux-2.6-tip.orig/kernel/trace/Kconfig
+++ linux-2.6-tip/kernel/trace/Kconfig
@@ -430,7 +430,7 @@ config BLK_DEV_IO_TRACE
 
 config KPROBE_TRACER
 	depends on KPROBES
-	depends on X86
+	depends on x86 || PPC
 	bool "Trace kprobes"
 	select TRACING
 	select GENERIC_TRACER
Index: linux-2.6-tip/arch/powerpc/kernel/ptrace.c
===================================================================
--- linux-2.6-tip.orig/arch/powerpc/kernel/ptrace.c
+++ linux-2.6-tip/arch/powerpc/kernel/ptrace.c
@@ -39,6 +39,147 @@
 #include <asm/system.h>
 
 /*
+ * The parameter save area on the stack is used to store arguments being passed
+ * to callee function and is located at fixed offset from stack pointer.
+ */
+#ifdef CONFIG_PPC32
+#define PARAMETER_SAVE_AREA_OFFSET	24  /* bytes */
+#else /* CONFIG_PPC32 */
+#define PARAMETER_SAVE_AREA_OFFSET	48  /* bytes */
+#endif
+
+struct pt_regs_offset {
+	const char *name;
+	int offset;
+};
+
+#define REG_OFFSET_NAME(r) {.name = #r, .offset = offsetof(struct pt_regs, r)}
+#define REG_OFFSET_END {.name = NULL, .offset = 0}
+
+static const struct pt_regs_offset regoffset_table[] = {
+	REG_OFFSET_NAME(gpr[0]),
+	REG_OFFSET_NAME(gpr[1]),
+	REG_OFFSET_NAME(gpr[2]),
+	REG_OFFSET_NAME(gpr[3]),
+	REG_OFFSET_NAME(gpr[4]),
+	REG_OFFSET_NAME(gpr[5]),
+	REG_OFFSET_NAME(gpr[6]),
+	REG_OFFSET_NAME(gpr[7]),
+	REG_OFFSET_NAME(gpr[8]),
+	REG_OFFSET_NAME(gpr[9]),
+	REG_OFFSET_NAME(gpr[10]),
+	REG_OFFSET_NAME(gpr[11]),
+	REG_OFFSET_NAME(gpr[12]),
+	REG_OFFSET_NAME(gpr[13]),
+	REG_OFFSET_NAME(gpr[14]),
+	REG_OFFSET_NAME(gpr[15]),
+	REG_OFFSET_NAME(gpr[16]),
+	REG_OFFSET_NAME(gpr[17]),
+	REG_OFFSET_NAME(gpr[18]),
+	REG_OFFSET_NAME(gpr[19]),
+	REG_OFFSET_NAME(gpr[20]),
+	REG_OFFSET_NAME(gpr[21]),
+	REG_OFFSET_NAME(gpr[22]),
+	REG_OFFSET_NAME(gpr[23]),
+	REG_OFFSET_NAME(gpr[24]),
+	REG_OFFSET_NAME(gpr[25]),
+	REG_OFFSET_NAME(gpr[26]),
+	REG_OFFSET_NAME(gpr[27]),
+	REG_OFFSET_NAME(gpr[28]),
+	REG_OFFSET_NAME(gpr[29]),
+	REG_OFFSET_NAME(gpr[30]),
+	REG_OFFSET_NAME(gpr[31]),
+	REG_OFFSET_NAME(nip),
+	REG_OFFSET_NAME(msr),
+	REG_OFFSET_NAME(orig_gpr3),
+	REG_OFFSET_NAME(ctr),
+	REG_OFFSET_NAME(link),
+	REG_OFFSET_NAME(xer),
+	REG_OFFSET_NAME(ccr),
+#ifdef CONFIG_PPC64
+	REG_OFFSET_NAME(softe),
+#else
+	REG_OFFSET_NAME(mq),
+#endif
+	REG_OFFSET_NAME(trap),
+	REG_OFFSET_NAME(dar),
+	REG_OFFSET_NAME(dsisr),
+	REG_OFFSET_NAME(result),
+	REG_OFFSET_END,
+};
+
+/**
+ * regs_query_register_offset() - query register offset from its name
+ * @name:	the name of a register
+ *
+ * regs_query_register_offset() returns the offset of a register in struct
+ * pt_regs from its name. If the name is invalid, this returns -EINVAL;
+ */
+int regs_query_register_offset(const char *name)
+{
+	const struct pt_regs_offset *roff;
+	for (roff = regoffset_table; roff->name != NULL; roff++)
+		if (!strcmp(roff->name, name))
+			return roff->offset;
+	return -EINVAL;
+}
+
+/**
+ * regs_query_register_name() - query register name from its offset
+ * @offset:	the offset of a register in struct pt_regs.
+ *
+ * regs_query_register_name() returns the name of a register from its
+ * offset in struct pt_regs. If the @offset is invalid, this returns NULL;
+ */
+const char *regs_query_register_name(unsigned int offset)
+{
+	const struct pt_regs_offset *roff;
+	for (roff = regoffset_table; roff->name != NULL; roff++)
+		if (roff->offset == offset)
+			return roff->name;
+	return NULL;
+}
+
+static const int arg_offs_table[] = {
+	[0] = offsetof(struct pt_regs, gpr[3]),
+	[1] = offsetof(struct pt_regs, gpr[4]),
+	[2] = offsetof(struct pt_regs, gpr[5]),
+	[3] = offsetof(struct pt_regs, gpr[6]),
+	[4] = offsetof(struct pt_regs, gpr[7]),
+	[5] = offsetof(struct pt_regs, gpr[8]),
+	[6] = offsetof(struct pt_regs, gpr[9]),
+	[7] = offsetof(struct pt_regs, gpr[10])
+};
+
+/**
+ * regs_get_argument_nth() - get Nth argument at function call
+ * @regs:	pt_regs which contains registers at function entry.
+ * @n:		argument number.
+ *
+ * regs_get_argument_nth() returns @n th argument of a function call.
+ * Since usually the kernel stack will be changed right after function entry,
+ * you must use this at function entry. If the @n th entry is NOT in the
+ * kernel stack or pt_regs, this returns 0.
+ */
+unsigned long regs_get_argument_nth(struct pt_regs *regs, unsigned int n)
+{
+	if (n < ARRAY_SIZE(arg_offs_table))
+		return *(unsigned long *)((char *)regs + arg_offs_table[n]);
+	else {
+		/*
+		 * If more arguments are passed that can be stored in
+		 * registers, the remaining arguments are stored in the
+		 * parameter save area located at fixed offset from stack
+		 * pointer.
+		 * Following the PowerPC ABI, the first few arguments are
+		 * actually passed in registers (r3-r10), with equivalent space
+		 * left unused in the parameter save area.
+		 */
+		n += (PARAMETER_SAVE_AREA_OFFSET / sizeof(unsigned long));
+		return regs_get_kernel_stack_nth(regs, n);
+	}
+}
+/*
  * does not yet catch signals sent when the child dies.
  * in exit.c or in signal.c.
  */

Re: [PATCH -tip tracing/kprobes] Powerpc port of the kprobe-based event tracer.

[Masami Hiramatsu]

Hi Wenji,

Thank you for reviewing, it seems that same issues are in x86 version too...

Wenji Huang wrote:
> Hi,
>
>> +#define kernel_stack_pointer(regs) ((regs)->gpr[1])
>> +
>> +/**
>> + * regs_get_register() - get register value from its offset
>> + * @regs:	   pt_regs from which register value is gotten
>> + * @offset:    offset number of the register.
>> + *
>> + * regs_get_register returns the value of a register whose offset from @regs
>> + * is @offset. The @offset is the offset of the register in struct pt_regs.
>
> "is @offset." seems be redundant.
>> + * If @offset is bigger than MAX_REG_OFFSET, this returns 0.
>> + */
>> +static inline unsigned long regs_get_register(struct pt_regs *regs,
>
> [...]
>> + * regs_within_kernel_stack() - check the address in the stack
>> + * @regs:      pt_regs which contains kernel stack pointer.
>> + * @addr:      address which is checked.
>> + *
>> + * regs_within_kenel_stack() checks @addr is within the kernel stack page(s).
>> + * If @addr is within the kernel stack, it returns true. If not, returns false.
>
> s/regs_within_kenel_stack/regs_within_kernel_stack/
> The return type function is declared as int.
>> + */
>> +
>> +static inline int regs_within_kernel_stack(struct pt_regs *regs,
>> +						unsigned long addr)
>> +{
>> +	return ((addr&  ~(THREAD_SIZE - 1))  ==
>> +		(kernel_stack_pointer(regs)&  ~(THREAD_SIZE - 1)));
>> +}
>> +
>> +/**
>> + * regs_get_kernel_stack_nth() - get Nth entry of the stack
>> + * @regs:	pt_regs which contains kernel stack pointer.
>> + * @n:		stack entry number.
>> + *
>> + * regs_get_kernel_stack_nth() returns @n th entry of the kernel stack which
>> + * is specifined by @regs. If the @n th entry is NOT in the kernel stack,
>> + * this returns 0.
>
> s/specifined/specified/
>> + */
>> +static inline unsigned long regs_get_kernel_stack_nth(struct pt_regs *regs,
>> +						      unsigned int n)
>> +{
>> +	unsigned long *addr = (unsigned long *)kernel_stack_pointer(regs);
>> +	addr += n;
>> +	if (regs_within_kernel_stack(regs, (unsigned long)addr))
>> +		return *addr;
>> +	else
>> +		return 0;
>> +}
>> +
>> +
>> +/* Get Nth argument at function call */
>> +extern unsigned long regs_get_argument_nth(struct pt_regs *regs,
>> +						unsigned int n);
>> +
>
> Maybe to put extern declaration at the very beginning is better.
>>   /*
>>    * These are defined as per linux/ptrace.h, which see.
>>    */
> [...]
>
> Regards,
> Wenji

-- 
Masami Hiramatsu

Software Engineer
Hitachi Computer Products (America), Inc.
Software Solutions Division

e-mail: mhiramat@redhat.com

Re: [PATCH -tip tracing/kprobes] Powerpc port of the kprobe-based event tracer.

[Mahesh J Salgaonkar]

[-- Attachment #1: Type: text/plain, Size: 1060 bytes --]

On Tue, Oct 27, 2009 at 10:47:48AM +0800, Wenji Huang wrote:
> Hi,
> 

Thanks for reviewing changes. I have addressed all your suggestions.

> [...]
> >+ * regs_within_kernel_stack() - check the address in the stack
> >+ * @regs:      pt_regs which contains kernel stack pointer.
> >+ * @addr:      address which is checked.
> >+ *
> >+ * regs_within_kenel_stack() checks @addr is within the kernel stack page(s).
> >+ * If @addr is within the kernel stack, it returns true. If not, returns false.
> 
> s/regs_within_kenel_stack/regs_within_kernel_stack/
> The return type function is declared as int.

Changed it to bool. This code has been taken from x86 port. We may have
to fix this there too.

> >+ */
> >+
> >+static inline int regs_within_kernel_stack(struct pt_regs *regs,
> >+						unsigned long addr)
> >+{
> >+	return ((addr & ~(THREAD_SIZE - 1))  ==
> >+		(kernel_stack_pointer(regs) & ~(THREAD_SIZE - 1)));
> >+}
> >+
> 
> Regards,
> Wenji

Please find the modified patch atached.

-- 
Signed-off-by: Mahesh Salgaonkar <mahesh@linux.vnet.ibm.com>

[-- Attachment #2: kprobes.ppc.patch --]
[-- Type: text/plain, Size: 9130 bytes --]

Powerpc port of the kprobe-based event tracer

This patch ports the kprobe-based event tracer to powerpc. This patch
is based in x86 port.

Port the following API's to ppc for accessing registers and stack entries
from pt_regs.

- regs_query_register_offset(const char *name)
   Query the offset of "name" register.

- regs_query_register_name(unsigned int offset)
   Query the name of register by its offset.

- regs_get_register(struct pt_regs *regs, unsigned int offset)
   Get the value of a register by its offset.

- regs_within_kernel_stack(struct pt_regs *regs, unsigned long addr)
   Check the address is in the kernel stack.

- regs_get_kernel_stack_nth(struct pt_regs *reg, unsigned int nth)
   Get Nth entry of the kernel stack. (N >= 0)

- regs_get_argument_nth(struct pt_regs *reg, unsigned int nth)
   Get Nth argument at function call. (N >= 0)

Signed-off-by: Mahesh Salgaonkar <mahesh@linux.vnet.ibm.com>
---
 arch/powerpc/include/asm/ptrace.h |   64 +++++++++++++++++
 arch/powerpc/kernel/ptrace.c      |  141 ++++++++++++++++++++++++++++++++++++++
 kernel/trace/Kconfig              |    2 
 3 files changed, 206 insertions(+), 1 deletion(-)

Index: linux-2.6-tip/arch/powerpc/include/asm/ptrace.h
===================================================================
--- linux-2.6-tip.orig/arch/powerpc/include/asm/ptrace.h
+++ linux-2.6-tip/arch/powerpc/include/asm/ptrace.h
@@ -83,6 +83,7 @@ struct pt_regs {
 
 #define instruction_pointer(regs) ((regs)->nip)
 #define user_stack_pointer(regs) ((regs)->gpr[1])
+#define kernel_stack_pointer(regs) ((regs)->gpr[1])
 #define regs_return_value(regs) ((regs)->gpr[3])
 
 #ifdef CONFIG_SMP
@@ -131,6 +132,69 @@ do {									      \
 } while (0)
 #endif /* __powerpc64__ */
 
+/* Query offset/name of register from its name/offset */
+#include <linux/stddef.h>
+#include <linux/thread_info.h>
+extern int regs_query_register_offset(const char *name);
+extern const char *regs_query_register_name(unsigned int offset);
+/* Get Nth argument at function call */
+extern unsigned long regs_get_argument_nth(struct pt_regs *regs,
+						unsigned int n);
+#define MAX_REG_OFFSET (offsetof(struct pt_regs, result))
+
+/**
+ * regs_get_register() - get register value from its offset
+ * @regs:	   pt_regs from which register value is gotten
+ * @offset:    offset number of the register.
+ *
+ * regs_get_register returns the value of a register whose offset from @regs.
+ * The @offset is the offset of the register in struct pt_regs.
+ * If @offset is bigger than MAX_REG_OFFSET, this returns 0.
+ */
+static inline unsigned long regs_get_register(struct pt_regs *regs,
+						unsigned int offset)
+{
+	if (unlikely(offset > MAX_REG_OFFSET))
+		return 0;
+	return *(unsigned long *)((unsigned long)regs + offset);
+}
+
+/**
+ * regs_within_kernel_stack() - check the address in the stack
+ * @regs:      pt_regs which contains kernel stack pointer.
+ * @addr:      address which is checked.
+ *
+ * regs_within_kernel_stack() checks @addr is within the kernel stack page(s).
+ * If @addr is within the kernel stack, it returns true. If not, returns false.
+ */
+
+static inline bool regs_within_kernel_stack(struct pt_regs *regs,
+						unsigned long addr)
+{
+	return ((addr & ~(THREAD_SIZE - 1))  ==
+		(kernel_stack_pointer(regs) & ~(THREAD_SIZE - 1)));
+}
+
+/**
+ * regs_get_kernel_stack_nth() - get Nth entry of the stack
+ * @regs:	pt_regs which contains kernel stack pointer.
+ * @n:		stack entry number.
+ *
+ * regs_get_kernel_stack_nth() returns @n th entry of the kernel stack which
+ * is specified by @regs. If the @n th entry is NOT in the kernel stack,
+ * this returns 0.
+ */
+static inline unsigned long regs_get_kernel_stack_nth(struct pt_regs *regs,
+						      unsigned int n)
+{
+	unsigned long *addr = (unsigned long *)kernel_stack_pointer(regs);
+	addr += n;
+	if (regs_within_kernel_stack(regs, (unsigned long)addr))
+		return *addr;
+	else
+		return 0;
+}
+
 /*
  * These are defined as per linux/ptrace.h, which see.
  */
Index: linux-2.6-tip/kernel/trace/Kconfig
===================================================================
--- linux-2.6-tip.orig/kernel/trace/Kconfig
+++ linux-2.6-tip/kernel/trace/Kconfig
@@ -430,7 +430,7 @@ config BLK_DEV_IO_TRACE
 
 config KPROBE_TRACER
 	depends on KPROBES
-	depends on X86
+	depends on x86 || PPC
 	bool "Trace kprobes"
 	select TRACING
 	select GENERIC_TRACER
Index: linux-2.6-tip/arch/powerpc/kernel/ptrace.c
===================================================================
--- linux-2.6-tip.orig/arch/powerpc/kernel/ptrace.c
+++ linux-2.6-tip/arch/powerpc/kernel/ptrace.c
@@ -39,6 +39,147 @@
 #include <asm/system.h>
 
 /*
+ * The parameter save area on the stack is used to store arguments being passed
+ * to callee function and is located at fixed offset from stack pointer.
+ */
+#ifdef CONFIG_PPC32
+#define PARAMETER_SAVE_AREA_OFFSET	24  /* bytes */
+#else /* CONFIG_PPC32 */
+#define PARAMETER_SAVE_AREA_OFFSET	48  /* bytes */
+#endif
+
+struct pt_regs_offset {
+	const char *name;
+	int offset;
+};
+
+#define REG_OFFSET_NAME(r) {.name = #r, .offset = offsetof(struct pt_regs, r)}
+#define REG_OFFSET_END {.name = NULL, .offset = 0}
+
+static const struct pt_regs_offset regoffset_table[] = {
+	REG_OFFSET_NAME(gpr[0]),
+	REG_OFFSET_NAME(gpr[1]),
+	REG_OFFSET_NAME(gpr[2]),
+	REG_OFFSET_NAME(gpr[3]),
+	REG_OFFSET_NAME(gpr[4]),
+	REG_OFFSET_NAME(gpr[5]),
+	REG_OFFSET_NAME(gpr[6]),
+	REG_OFFSET_NAME(gpr[7]),
+	REG_OFFSET_NAME(gpr[8]),
+	REG_OFFSET_NAME(gpr[9]),
+	REG_OFFSET_NAME(gpr[10]),
+	REG_OFFSET_NAME(gpr[11]),
+	REG_OFFSET_NAME(gpr[12]),
+	REG_OFFSET_NAME(gpr[13]),
+	REG_OFFSET_NAME(gpr[14]),
+	REG_OFFSET_NAME(gpr[15]),
+	REG_OFFSET_NAME(gpr[16]),
+	REG_OFFSET_NAME(gpr[17]),
+	REG_OFFSET_NAME(gpr[18]),
+	REG_OFFSET_NAME(gpr[19]),
+	REG_OFFSET_NAME(gpr[20]),
+	REG_OFFSET_NAME(gpr[21]),
+	REG_OFFSET_NAME(gpr[22]),
+	REG_OFFSET_NAME(gpr[23]),
+	REG_OFFSET_NAME(gpr[24]),
+	REG_OFFSET_NAME(gpr[25]),
+	REG_OFFSET_NAME(gpr[26]),
+	REG_OFFSET_NAME(gpr[27]),
+	REG_OFFSET_NAME(gpr[28]),
+	REG_OFFSET_NAME(gpr[29]),
+	REG_OFFSET_NAME(gpr[30]),
+	REG_OFFSET_NAME(gpr[31]),
+	REG_OFFSET_NAME(nip),
+	REG_OFFSET_NAME(msr),
+	REG_OFFSET_NAME(orig_gpr3),
+	REG_OFFSET_NAME(ctr),
+	REG_OFFSET_NAME(link),
+	REG_OFFSET_NAME(xer),
+	REG_OFFSET_NAME(ccr),
+#ifdef CONFIG_PPC64
+	REG_OFFSET_NAME(softe),
+#else
+	REG_OFFSET_NAME(mq),
+#endif
+	REG_OFFSET_NAME(trap),
+	REG_OFFSET_NAME(dar),
+	REG_OFFSET_NAME(dsisr),
+	REG_OFFSET_NAME(result),
+	REG_OFFSET_END,
+};
+
+/**
+ * regs_query_register_offset() - query register offset from its name
+ * @name:	the name of a register
+ *
+ * regs_query_register_offset() returns the offset of a register in struct
+ * pt_regs from its name. If the name is invalid, this returns -EINVAL;
+ */
+int regs_query_register_offset(const char *name)
+{
+	const struct pt_regs_offset *roff;
+	for (roff = regoffset_table; roff->name != NULL; roff++)
+		if (!strcmp(roff->name, name))
+			return roff->offset;
+	return -EINVAL;
+}
+
+/**
+ * regs_query_register_name() - query register name from its offset
+ * @offset:	the offset of a register in struct pt_regs.
+ *
+ * regs_query_register_name() returns the name of a register from its
+ * offset in struct pt_regs. If the @offset is invalid, this returns NULL;
+ */
+const char *regs_query_register_name(unsigned int offset)
+{
+	const struct pt_regs_offset *roff;
+	for (roff = regoffset_table; roff->name != NULL; roff++)
+		if (roff->offset == offset)
+			return roff->name;
+	return NULL;
+}
+
+static const int arg_offs_table[] = {
+	[0] = offsetof(struct pt_regs, gpr[3]),
+	[1] = offsetof(struct pt_regs, gpr[4]),
+	[2] = offsetof(struct pt_regs, gpr[5]),
+	[3] = offsetof(struct pt_regs, gpr[6]),
+	[4] = offsetof(struct pt_regs, gpr[7]),
+	[5] = offsetof(struct pt_regs, gpr[8]),
+	[6] = offsetof(struct pt_regs, gpr[9]),
+	[7] = offsetof(struct pt_regs, gpr[10])
+};
+
+/**
+ * regs_get_argument_nth() - get Nth argument at function call
+ * @regs:	pt_regs which contains registers at function entry.
+ * @n:		argument number.
+ *
+ * regs_get_argument_nth() returns @n th argument of a function call.
+ * Since usually the kernel stack will be changed right after function entry,
+ * you must use this at function entry. If the @n th entry is NOT in the
+ * kernel stack or pt_regs, this returns 0.
+ */
+unsigned long regs_get_argument_nth(struct pt_regs *regs, unsigned int n)
+{
+	if (n < ARRAY_SIZE(arg_offs_table))
+		return *(unsigned long *)((char *)regs + arg_offs_table[n]);
+	else {
+		/*
+		 * If more arguments are passed that can be stored in
+		 * registers, the remaining arguments are stored in the
+		 * parameter save area located at fixed offset from stack
+		 * pointer.
+		 * Following the PowerPC ABI, the first few arguments are
+		 * actually passed in registers (r3-r10), with equivalent space
+		 * left unused in the parameter save area.
+		 */
+		n += (PARAMETER_SAVE_AREA_OFFSET / sizeof(unsigned long));
+		return regs_get_kernel_stack_nth(regs, n);
+	}
+}
+/*
  * does not yet catch signals sent when the child dies.
  * in exit.c or in signal.c.
  */

Re: [PATCH -tip tracing/kprobes] Powerpc port of the kprobe-based event tracer.

[Masami Hiramatsu]

Mahesh J Salgaonkar wrote:
> On Tue, Oct 27, 2009 at 10:47:48AM +0800, Wenji Huang wrote:
>> Hi,
>>
> 
> Thanks for reviewing changes. I have addressed all your suggestions.
> 
>> [...]
>>> + * regs_within_kernel_stack() - check the address in the stack
>>> + * @regs:      pt_regs which contains kernel stack pointer.
>>> + * @addr:      address which is checked.
>>> + *
>>> + * regs_within_kenel_stack() checks @addr is within the kernel stack page(s).
>>> + * If @addr is within the kernel stack, it returns true. If not, returns false.
>>
>> s/regs_within_kenel_stack/regs_within_kernel_stack/
>> The return type function is declared as int.
> 
> Changed it to bool. This code has been taken from x86 port. We may have
> to fix this there too.

Thanks Mahesh and Wenji!

Please feel free to post the x86 fix patch too :-)

> 
>>> + */
>>> +
>>> +static inline int regs_within_kernel_stack(struct pt_regs *regs,
>>> +						unsigned long addr)
>>> +{
>>> +	return ((addr&  ~(THREAD_SIZE - 1))  ==
>>> +		(kernel_stack_pointer(regs)&  ~(THREAD_SIZE - 1)));
>>> +}
>>> +
>>
>> Regards,
>> Wenji
> 
> Please find the modified patch atached.

Acked-by: Masami Hiramatsu <mhiramat@redhat.com>


Thanks!

-- 
Masami Hiramatsu

Software Engineer
Hitachi Computer Products (America), Inc.
Software Solutions Division

e-mail: mhiramat@redhat.com