> Hi Cupertino,
>
> On 2/27/26 08:08, Cupertino Miranda wrote:
>> Hi everyone, David
>>
>> This is v2 for line_info support.
>> Looking forward to your review.
>
> Very nice.
> I tried it with a couple of tests locally and it works well, now
> we get accurate source line info from verifier errors :)
>
> I have one small comment below, but otherwise LGTM.
> OK with that addressed.
>
> Thanks!
>
>>
>> Cheers,
>> Cupertino
>>
>> Changes from v1:
>> - Corrected typos.
>> - Fixed line_col encoding and created macros.
>> - Added a test case for line_info.
>> - Improved line and column info repetition detection.
>> Previous patch was generating multiple entries for the same line and
>> column data for consecutive labels.
>>
>>
>> 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 code referenced errors.
>>
>> gcc/ChangeLog:
>> PR target/113453
>> * 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 immediately 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/testsuite/ChangeLog:
>> PR target/113453
>> * gcc.target/bpf/btfext-funcinfo.c: Adapt test.
>> * gcc.target/bpf/btfext-lineinfo.c: New test.
>> ---
>> gcc/config/bpf/bpf-protos.h | 2 +-
>> gcc/config/bpf/bpf.cc | 105 +++++++++++++---
>> gcc/config/bpf/bpf.md | 4 +-
>> gcc/config/bpf/btfext-out.cc | 114 +++++++++++++++++-
>> gcc/config/bpf/btfext-out.h | 4 +
>> .../gcc.target/bpf/btfext-funcinfo.c | 3 +-
>> .../gcc.target/bpf/btfext-lineinfo.c | 51 ++++++++
>> 7 files changed, 262 insertions(+), 21 deletions(-)
>> create mode 100644 gcc/testsuite/gcc.target/bpf/btfext-lineinfo.c
>>
>> diff --git a/gcc/config/bpf/bpf-protos.h b/gcc/config/bpf/bpf-protos.h
>> index 4a4799e9bf22..1113cc3e6d17 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 d91013ad140b..4773d789d8e3 100644
>> --- a/gcc/config/bpf/bpf.cc
>> +++ b/gcc/config/bpf/bpf.cc
>> @@ -745,14 +745,12 @@ 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:
>> {
>> @@ -765,26 +763,21 @@ 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);
>> + operands[target_index] =
>> + GEN_INT (TREE_INT_CST_LOW (TREE_VALUE (attr_args)));
>> }
>> - else
>> - output_asm_insn ("call\t%0", &target);
>> -
>> 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 *
>> @@ -1145,6 +1138,90 @@ 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;
>> + expanded_location exploc = {NULL, 0, 0, NULL, false};
>> + static expanded_location prev_exploc = {NULL, 0, 0, NULL, false};
>> +
>> + if(!btf_debuginfo_p () || flag_building_libgcc)
>> + 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);
>> + exploc = expand_location (loc);
>> + func_start_added = true;
>> + prev_exploc = exploc;
>> + }
>> + else
>> + {
>> + if (GET_CODE (insn) == NOTE)
>> + return;
>> +
>> + /* Already added a label for this location. This might not be fully
>> + accurate but it is better then adding 2 entries on the same location,
>> + which is incompatible with the verifier expectations. */
>> + if (func_start_added == true)
>> + {
>> + func_start_added = false;
>> + return;
>> + }
>> +
>> +
>> + if (!INSN_HAS_LOCATION (insn))
>> + return;
>> +
>> + exploc = insn_location (insn);
>> +
>> + if (exploc.file == NULL || exploc.line == 0
>> + || (exploc.line == prev_exploc.line
>> + && exploc.column == prev_exploc.column))
>> + return;
>> +
>> + prev_exploc = exploc;
>> +
>> + 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 (exploc.file != NULL && exploc.line != 0)
>> + btf_add_line_info_for (label, exploc.file, exploc.line, exploc.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 returning 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 0eec006d3cfe..bc739f2746c0 100644
>> --- a/gcc/config/bpf/bpf.md
>> +++ b/gcc/config/bpf/bpf.md
>> @@ -545,7 +545,7 @@
>> ;; 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"
>> @@ -568,7 +568,7 @@
>> ;; 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 04bc60d69b0e..9a7e34aeb634 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"
>>
>> @@ -124,14 +125,19 @@ 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). */
>> + uint32_t line_col; /* Line number (bits 31-10) and column (9-0). */
>>
>> struct btf_ext_lineinfo *next; /* Linked list to collect line_info elems.
>> */
>> };
>>
>> +#define BTF_LINE_INFO_LINE(line_col) ((line_col) >> 10)
>> +#define BTF_LINE_INFO_COLUMN(line_col) ((line_col) & 0x3ff)
>> +#define BTF_LINE_INFO_LINE_COL(line, column) (line << 10 | (column &
>> 0x3ff))
>> +
>> /* Internal representation of a BPF CO-RE relocation record. */
>> struct GTY ((chain_next ("%h.next"))) btf_ext_core_reloc {
>> ctf_dtdef_ref bpfcr_type; /* BTF type involved in relocation. */
>> @@ -235,6 +241,26 @@ 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 *
>> @@ -438,6 +464,47 @@ btf_validate_funcinfo (btf_ext_info_sec *sec)
>> }
>> }
>>
>> +#define STR_BUFF_SIZE 256
>> +
>> +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);
>> +
>> + info->insn_label = label;
>> +
>> + if (!IS_DIR_SEPARATOR (filename[0]))
>> + {
>> + char full_filename[STR_BUFF_SIZE];
>> +
>> + /* Filename is a relative path. */
>> + const char * cu_pwd = get_src_pwd ();
>> + gcc_assert (strlen (cu_pwd) + strlen (filename) + 2 < STR_BUFF_SIZE);
>> +
>> + sprintf (full_filename, "%s%c%s", cu_pwd, DIR_SEPARATOR, filename);
>
> On second look I don't like using gcc_assert here; this will result in an
> ICE simply if the input filename is very long...
>
> While I doubt that will occur much in practice, we should still deal with
> it gracefully. IMO just truncating via e.g. snprintf would be fine and
> much better than causing an ICE.
There is no need to truncate.
Just use xasprintf.
>
>> + 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 = BTF_LINE_INFO_LINE_COL (line, column);
>> +
>> + sec->line_info.num_info += 1;
>> + return info;
>> +}
>> +#undef STR_BUFF_SIZE
>> +
>> /* Compute the section size in section for func_info, line_info and
>> core_info
>> regions of .BTF.ext. */
>>
>> @@ -545,6 +612,48 @@ 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)",
>> + BTF_LINE_INFO_LINE (elem->line_col),
>> + BTF_LINE_INFO_COLUMN (elem->line_col));
>> + elem = elem->next;
>> + }
>> + }
>> +
>> + gcc_assert (count == sec->line_info.num_info);
>> + sec = sec->next;
>> + }
>> +}
>> +
>> /* Output all CO-RE relocation sections. */
>>
>> static void
>> @@ -622,6 +731,7 @@ 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 a4c87ffd1f02..fe9b3768643e 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 fbbefeae68f0..f7f5b44b1ff4 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 } } */
>> diff --git a/gcc/testsuite/gcc.target/bpf/btfext-lineinfo.c
>> b/gcc/testsuite/gcc.target/bpf/btfext-lineinfo.c
>> new file mode 100644
>> index 000000000000..dc1c297d663e
>> --- /dev/null
>> +++ b/gcc/testsuite/gcc.target/bpf/btfext-lineinfo.c
>> @@ -0,0 +1,51 @@
>> +/* { dg-do compile } */
>> +/* { dg-options "-O2 -dA -gbtf -masm=normal" } */
>> +
>> +struct T {
>> + int a;
>> + int b;
>> + struct U {
>> + int c;
>> + struct V {
>> + int d;
>> + int e[4];
>> + int f;
>> + } v;
>> + } u;
>> +} __attribute__((preserve_access_index));
>> +
>> +__attribute__((section("foo_sec"), used))
>> +int foo_func (struct T *t)
>> +{
>> + t->u.c = 5;
>> + return t->u.v.e[3];
>> +}
>> +
>> +__attribute__((section("bar_sec"), used))
>> +int bar_func (struct T *t)
>> +{
>> + int *x = &(t->u.v.f);
>> + int old = *x;
>> + *x = 4;
>> + return old;
>> +}
>> +
>> +/* { dg-final { scan-assembler-times "LineInfo section string for foo_sec"
>> 1 } } */
>> +/* { dg-final { scan-assembler-times "LineInfo section string for bar_sec"
>> 1 } } */
>> +/* { dg-final { scan-assembler-times "label for function foo_func" 1 } } */
>> +/* { dg-final { scan-assembler-times "label for function bar_func" 1 } } */
>> +
>> +
>> +/* { dg-final { scan-assembler-times "btfext-lineinfo\.c.0\"\[\t
>> \]+\[^\n\]*btf_aux_string" 1 } } */
>> +/* { dg-final { scan-assembler-times "4byte\[\t \]+\.LFB.\[\t \]+#
>> insn_label" 2 } } */
>> +/* { dg-final { scan-assembler-times "4byte\[\t \]+LI.\[\t \]+# insn_label"
>> 6 } } */
>> +
>> +/* { dg-final { scan-assembler-times "# \\(line, col\\)" 8 } } */
>> +/* { dg-final { scan-assembler-times "# \\(line, col\\) \\(18, 5\\)" 1 } }
>> */
>> +/* { dg-final { scan-assembler-times "# \\(line, col\\) \\(20, 10\\)" 1 } }
>> */
>> +/* { dg-final { scan-assembler-times "# \\(line, col\\) \\(21, 18\\)" 1 } }
>> */
>> +/* { dg-final { scan-assembler-times "# \\(line, col\\) \\(22, 1\\)" 1 } }
>> */
>> +/* { dg-final { scan-assembler-times "# \\(line, col\\) \\(25, 5\\)" 1 } }
>> */
>> +/* { dg-final { scan-assembler-times "# \\(line, col\\) \\(28, 7\\)" 1 } }
>> */
>> +/* { dg-final { scan-assembler-times "# \\(line, col\\) \\(29, 6\\)" 1 } }
>> */
>> +/* { dg-final { scan-assembler-times "# \\(line, col\\) \\(31, 1\\)" 1 } }
>> */
