[PATCH 3/3] bpf: add line_info support to BTF.ext section.

[Cupertino Miranda <cupertino.miranda@oracle.com>]

This patch adds line_info debug information support to .BTF.ext
sections.
Line info information is used by the BPF verifier to improve error
reporting and give more precise source core referenced errors.

gcc/Changelog:
	* config/bpf/bpf-protos.h (bpf_output_call): Change prototype.
	* config/bpf/bpf.cc (bpf_output_call): Change to adapt operands
	and return
	the instruction template instead of emmidiatelly emit asm and
	not allow proper final expected execution flow.
	(bpf_output_line_info): Add function to introduce line info
	entries in respective structures
	(bpf_asm_out_unwind_emit): Add function as hook to
	TARGET_ASM_UNWIND_EMIT. This hook is called before any
	instruction is emitted.
	* config/bpf/bpf.md: Change calls to bpf_output_call.
	* config/bpf/btfext-out.cc (struct btf_ext_lineinfo): Add fields
	to struct.
	(bpf_create_lineinfo, btf_add_line_info_for): Add support
	function to insert line_info data in respective structures.
	(output_btfext_line_info): Function to emit line_info data in
	.BTF.ext section.
	(btf_ext_output): Call output_btfext_line_info.
	* config/bpf/btfext-out.h: Add prototype for
	btf_add_line_info_for.
---
 gcc/config/bpf/bpf-protos.h                   |   2 +-
 gcc/config/bpf/bpf.cc                         | 103 ++++++++++++++---
 gcc/config/bpf/bpf.md                         |   4 +-
 gcc/config/bpf/btfext-out.cc                  | 108 +++++++++++++++++-
 gcc/config/bpf/btfext-out.h                   |   4 +
 .../gcc.target/bpf/btfext-funcinfo.c          |   3 +-
 6 files changed, 203 insertions(+), 21 deletions(-)

diff --git a/gcc/config/bpf/bpf-protos.h b/gcc/config/bpf/bpf-protos.h
index b4866d34209..ddaca50af69 100644
--- a/gcc/config/bpf/bpf-protos.h
+++ b/gcc/config/bpf/bpf-protos.h
@@ -23,7 +23,7 @@ along with GCC; see the file COPYING3.  If not see
 /* Routines implemented in bpf.cc.  */
 
 extern HOST_WIDE_INT bpf_initial_elimination_offset (int, int);
-extern const char *bpf_output_call (rtx);
+extern const char *bpf_output_call (const char *templ, rtx *, int target_index);
 extern void bpf_target_macros (cpp_reader *);
 extern void bpf_print_operand (FILE *, rtx, int);
 extern void bpf_print_operand_address (FILE *, rtx);
diff --git a/gcc/config/bpf/bpf.cc b/gcc/config/bpf/bpf.cc
index d9141dd625a..f1a8eb8d62c 100644
--- a/gcc/config/bpf/bpf.cc
+++ b/gcc/config/bpf/bpf.cc
@@ -754,14 +754,12 @@ bpf_output_destructor (rtx symbol, int priority ATTRIBUTE_UNUSED)
    bpf.md.  */
 
 const char *
-bpf_output_call (rtx target)
+bpf_output_call (const char *templ, rtx *operands, int target_index)
 {
-  rtx xops[1];
-
+  rtx target = operands[target_index];
   switch (GET_CODE (target))
     {
     case CONST_INT:
-      output_asm_insn ("call\t%0", &target);
       break;
     case SYMBOL_REF:
       {
@@ -774,26 +772,20 @@ bpf_output_call (rtx target)
 	  {
 	    tree attr_args = TREE_VALUE (attr);
 
-	    xops[0] = GEN_INT (TREE_INT_CST_LOW (TREE_VALUE (attr_args)));
-	    output_asm_insn ("call\t%0", xops);
-	  }
-	else
-	  output_asm_insn ("call\t%0", &target);
+	    operands[target_index] = GEN_INT (TREE_INT_CST_LOW (TREE_VALUE (attr_args)));
 
+	  }
 	break;
       }
     default:
-      if (TARGET_XBPF)
-	output_asm_insn ("call\t%0", &target);
-      else
+      if (!TARGET_XBPF)
 	{
 	  error ("indirect call in function, which are not supported by eBPF");
-	  output_asm_insn ("call 0", NULL);
+	  operands[target_index] = GEN_INT (0);
 	}
       break;
     }
-
-  return "";
+  return templ;
 }
 
 const char *
@@ -1144,6 +1136,87 @@ bpf_debug_unwind_info ()
 #undef TARGET_DEBUG_UNWIND_INFO
 #define TARGET_DEBUG_UNWIND_INFO bpf_debug_unwind_info
 
+/* Create a BTF.ext line_info entry.  */
+
+static void
+bpf_output_line_info (FILE *asm_out_file, rtx_insn *insn)
+{
+  static unsigned int line_info_label = 1;
+  static tree cfun_decl = NULL_TREE;
+  static bool func_start_added = false;
+  const char *label = NULL;
+  unsigned int loc = 0;
+  const char *filename = NULL;
+  unsigned int line = 0;
+  unsigned int column = 0;
+
+  if(!btf_debuginfo_p ())
+    return;
+
+  gcc_assert (insn != NULL_RTX);
+
+  if (current_function_decl != cfun_decl
+      && GET_CODE (insn) == NOTE)
+    {
+      label = current_function_func_begin_label;
+      loc = DECL_SOURCE_LOCATION (current_function_decl);
+      filename = LOCATION_FILE (loc);
+      line = LOCATION_LINE (loc);
+      column = LOCATION_COLUMN (loc);
+      func_start_added = true;
+    }
+  else
+    {
+      if (GET_CODE (insn) == NOTE)
+	return;
+
+      /* Already added a label for this location. This might not be fully
+	 acurate but it is better then adding 2 entries on the same location,
+	 which is imcompatible with the verifier expectations.  */
+      if (func_start_added == true)
+	{
+	  func_start_added = false;
+	  return;
+	}
+
+      loc = INSN_LOCATION (insn);
+      filename = LOCATION_FILE (loc);
+      line = LOCATION_LINE (loc);
+      column = LOCATION_COLUMN (loc);
+
+      if (filename == NULL || line == 0)
+	return;
+
+      char tmp_label[25];
+      sprintf(tmp_label, "LI%u", line_info_label);
+      ASM_OUTPUT_LABEL (asm_out_file, tmp_label);
+      line_info_label += 1;
+      label = CONST_CAST (char *, ggc_strdup (tmp_label));
+    }
+
+  cfun_decl = current_function_decl;
+
+  if (filename != NULL && line != 0)
+    btf_add_line_info_for (label, filename, line, column);
+}
+
+
+/* This hook is defined as a way for BPF target to create a label before each
+ * emitted instruction and emit line_info information. This data is later output
+ * in .BTF.ext section.
+ * This approach expects TARGET_EMIT_BEFORE_INSN to be returing TRUE as
+ * this function needs to be called before the instruction is emitted.  Current
+ * default behaviour returns TRUE and the hook is left undefined.  */
+
+static void
+bpf_asm_out_unwind_emit (FILE *asm_out_file, rtx_insn *insn)
+{
+  bpf_output_line_info (asm_out_file, insn);
+}
+
+#undef TARGET_ASM_UNWIND_EMIT
+#define TARGET_ASM_UNWIND_EMIT bpf_asm_out_unwind_emit
+
 /* Output assembly directives to assemble data of various sized and
    alignments.  */
 
diff --git a/gcc/config/bpf/bpf.md b/gcc/config/bpf/bpf.md
index 95859328d25..3fdf81b86a6 100644
--- a/gcc/config/bpf/bpf.md
+++ b/gcc/config/bpf/bpf.md
@@ -546,7 +546,7 @@
   ;; operands[2] is next_arg_register
   ;; operands[3] is struct_value_size_rtx.
   ""
-  { return bpf_output_call (operands[0]); }
+  { return bpf_output_call ("call\t%0", operands, 0); }
   [(set_attr "type" "jmp")])
 
 (define_expand "call_value"
@@ -569,7 +569,7 @@
   ;; operands[3] is next_arg_register
   ;; operands[4] is struct_value_size_rtx.
   ""
-  { return bpf_output_call (operands[1]); }
+  { return bpf_output_call ("call\t%1", operands, 1); }
   [(set_attr "type" "jmp")])
 
 (define_insn "sibcall"
diff --git a/gcc/config/bpf/btfext-out.cc b/gcc/config/bpf/btfext-out.cc
index ff1fd0739f1..42ec48e394e 100644
--- a/gcc/config/bpf/btfext-out.cc
+++ b/gcc/config/bpf/btfext-out.cc
@@ -32,6 +32,7 @@
 #include "rtl.h"
 #include "tree-pretty-print.h"
 #include "cgraph.h"
+#include "toplev.h"  /* get_src_pwd */
 
 #include "btfext-out.h"
 
@@ -124,7 +125,8 @@ struct GTY ((chain_next ("%h.next"))) btf_ext_funcinfo
 /* A lineinfo record, in the .BTF.ext lineinfo section.  */
 struct GTY ((chain_next ("%h.next"))) btf_ext_lineinfo
 {
-  uint32_t insn_off;      /* Offset of the instruction.  */
+  const char *insn_label; /* Instruction label.  */
+  const char *file_name;  /* Source-code file name.  */
   uint32_t file_name_off; /* Offset of file name in BTF string table.  */
   uint32_t line_off;      /* Offset of source line in BTF string table.  */
   uint32_t line_col;      /* Line number (bits 31-11) and column (11-0).  */
@@ -235,6 +237,26 @@ bpf_create_or_find_funcinfo (const char *fnname, const char *sec_name,
   return *head;
 }
 
+/* Function to create a lineinfo node in info.  */
+
+static struct btf_ext_lineinfo *
+bpf_create_lineinfo (const char *sec_name, btf_ext_info_sec **in_sec = NULL)
+{
+  struct btf_ext_info_sec *sec_elem =
+    btfext_info_sec_find_or_add (sec_name, true);
+
+  if (in_sec != NULL)
+    *in_sec = sec_elem;
+
+  struct btf_ext_lineinfo **head =
+    SEARCH_NODE_AND_RETURN(struct btf_ext_lineinfo,
+			   sec_elem->line_info.head,
+			   false);
+  *head = ggc_cleared_alloc<struct btf_ext_lineinfo> ();
+
+  return *head;
+}
+
 /* Function to create a core_reloc node in info.  */
 
 static struct btf_ext_core_reloc *
@@ -429,6 +451,47 @@ btf_validate_funcinfo (btf_ext_info_sec *sec)
     }
 }
 
+struct btf_ext_lineinfo *
+btf_add_line_info_for (const char *label, const char *filename,
+		       unsigned int line, unsigned int column)
+{
+  const char *sec_name = decl_section_name (current_function_decl);
+
+  if (sec_name == NULL)
+    sec_name = ".text";
+
+  struct btf_ext_info_sec *sec = NULL;
+  struct btf_ext_lineinfo *info =
+    bpf_create_lineinfo (sec_name, &sec);
+
+  unsigned int line_column = ((0x000fffff & line) << 12)
+			     | (0x00000fff & column);
+
+  info->insn_label = label;
+
+  if (!IS_DIR_SEPARATOR (filename[0]))
+    {
+      char full_filename[256];
+
+      /* Filename is a relative path.  */
+      const char * cu_pwd = get_src_pwd ();
+      gcc_assert (strlen (cu_pwd) + strlen (filename) + 2 < 256);
+
+      sprintf(full_filename, "%s%c%s", cu_pwd, DIR_SEPARATOR, filename);
+      info->file_name = ggc_strdup (full_filename);
+    }
+  else
+    /* Filename is an absolute path.  */
+    info->file_name = ggc_strdup (filename);
+
+  info->file_name_off = btf_ext_add_string (info->file_name);
+  info->line_off = 0;
+  info->line_col = line_column;
+
+  sec->line_info.num_info += 1;
+  return info;
+}
+
 /* Compute the section size in section for func_info, line_info and core_info
    regions of .BTF.ext.  */
 
@@ -537,6 +600,48 @@ output_btfext_func_info (struct btf_ext_info_sec *sec)
     }
 }
 
+/* Outputs line_info region on .BTF.ext.  */
+
+static void
+output_btfext_line_info (struct btf_ext_info_sec *sec)
+{
+  unsigned int str_aux_off = ctfc_get_strtab_len (ctf_get_tu_ctfc (),
+						  CTF_STRTAB);
+  bool executed = false;
+  while (sec != NULL)
+    {
+      uint32_t count = 0;
+      if (sec->line_info.num_info > 0)
+	{
+	  if (executed == false && (executed = true))
+	    dw2_asm_output_data (4, 16, "LineInfo entry size");
+	  dw2_asm_output_data (4, sec->sec_name_off + str_aux_off,
+			       "LineInfo section string for %s",
+			       sec->sec_name);
+	  dw2_asm_output_data (4, sec->line_info.num_info, "Number of entries");
+
+	  struct btf_ext_lineinfo *elem = sec->line_info.head;
+	  while (elem != NULL)
+	    {
+	      count += 1;
+	      dw2_asm_output_offset (4, elem->insn_label, NULL, "insn_label");
+
+	      unsigned int file_name_off = btf_ext_add_string (elem->file_name);
+	      dw2_asm_output_data (4, file_name_off + str_aux_off,
+				   "file_name_off");
+	      dw2_asm_output_data (4, elem->line_off, "line_off");
+	      dw2_asm_output_data (4, elem->line_col, "(line, col) (%u, %u)",
+				   elem->line_col >> 12,
+				   elem->line_col & 0x00000fff);
+	      elem = elem->next;
+	    }
+	}
+
+      gcc_assert (count == sec->line_info.num_info);
+      sec = sec->next;
+    }
+}
+
 /* Output all CO-RE relocation sections.  */
 
 static void
@@ -609,6 +714,7 @@ btf_ext_output (void)
 {
   output_btfext_header ();
   output_btfext_func_info (btf_ext);
+  output_btfext_line_info (btf_ext);
   if (TARGET_BPF_CORE)
     output_btfext_core_sections ();
 
diff --git a/gcc/config/bpf/btfext-out.h b/gcc/config/bpf/btfext-out.h
index b36309475c9..9c6848324e7 100644
--- a/gcc/config/bpf/btfext-out.h
+++ b/gcc/config/bpf/btfext-out.h
@@ -99,6 +99,10 @@ extern int bpf_core_get_sou_member_index (ctf_container_ref, const tree);
 
 struct btf_ext_funcinfo *btf_add_func_info_for (tree decl,
 						const char *label);
+struct btf_ext_lineinfo *
+btf_add_line_info_for (const char *label, const char *filename,
+		       unsigned int line, unsigned int column);
+
 unsigned int btf_ext_add_string (const char *str);
 
 #ifdef	__cplusplus
diff --git a/gcc/testsuite/gcc.target/bpf/btfext-funcinfo.c b/gcc/testsuite/gcc.target/bpf/btfext-funcinfo.c
index 6fdd14574ec..0f1e0ad1e89 100644
--- a/gcc/testsuite/gcc.target/bpf/btfext-funcinfo.c
+++ b/gcc/testsuite/gcc.target/bpf/btfext-funcinfo.c
@@ -39,6 +39,5 @@ int bar_func (struct T *t)
 /* { dg-final { scan-assembler-times "ascii \"bar_sec.0\"\[\t \]+\[^\n\]*btf_aux_string" 1 } } */
 /* { dg-final { scan-assembler-times "FuncInfo entry size" 1 } } */
 
-/* { dg-final { scan-assembler-times ".4byte\t0x1\t# Number of entries" 3 } } */
-/* { dg-final { scan-assembler-times ".4byte\t0x2\t# Number of entries" 1 } } */
+/* { dg-final { scan-assembler-times "FuncInfo section\[^\n\]*\n\[^0\]*0x1\t# Number of entries" 2 } } */
 /* { dg-final { scan-assembler-times "Required padding" 1 } } */
-- 
2.30.2