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bpf: Add function to extract program source info

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Prepare a function for use in future patches that can extract the file
info, line info, and the source line number for a given BPF program
provided it's program counter.

Only the basename of the file path is provided, given it can be
excessively long in some cases.

This will be used in later patches to print source info to the BPF
stream.

Reviewed-by: Emil Tsalapatis <emil@etsalapatis.com>
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Link: https://lore.kernel.org/r/20250703204818.925464-4-memxor@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Kumar Kartikeya Dwivedi 2025-07-03 13:48:09 -07:00 committed by Alexei Starovoitov
parent 5ab154f146
commit 0e521efaf3
2 changed files with 50 additions and 0 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

3
include/linux/bpf.h
View file

@ -3661,4 +3661,7 @@ static inline bool bpf_is_subprog(const struct bpf_prog *prog)
return prog->aux->func_idx != 0;
}
int bpf_prog_get_file_line(struct bpf_prog *prog, unsigned long ip, const char **filep,
const char **linep, int *nump);
#endif /* _LINUX_BPF_H */

47
kernel/bpf/core.c
View file

@ -3213,3 +3213,50 @@ EXPORT_SYMBOL(bpf_stats_enabled_key);
EXPORT_TRACEPOINT_SYMBOL_GPL(xdp_exception);
EXPORT_TRACEPOINT_SYMBOL_GPL(xdp_bulk_tx);
#ifdef CONFIG_BPF_SYSCALL
int bpf_prog_get_file_line(struct bpf_prog *prog, unsigned long ip, const char **filep,
const char **linep, int *nump)
{
int idx = -1, insn_start, insn_end, len;
struct bpf_line_info *linfo;
void **jited_linfo;
struct btf *btf;
btf = prog->aux->btf;
linfo = prog->aux->linfo;
jited_linfo = prog->aux->jited_linfo;
if (!btf || !linfo || !jited_linfo)
return -EINVAL;
len = prog->aux->func ? prog->aux->func[prog->aux->func_idx]->len : prog->len;
linfo = &prog->aux->linfo[prog->aux->linfo_idx];
jited_linfo = &prog->aux->jited_linfo[prog->aux->linfo_idx];
insn_start = linfo[0].insn_off;
insn_end = insn_start + len;
for (int i = 0; i < prog->aux->nr_linfo &&
linfo[i].insn_off >= insn_start && linfo[i].insn_off < insn_end; i++) {
if (jited_linfo[i] >= (void *)ip)
break;
idx = i;
}
if (idx == -1)
return -ENOENT;
/* Get base component of the file path. */
*filep = btf_name_by_offset(btf, linfo[idx].file_name_off);
*filep = kbasename(*filep);
/* Obtain the source line, and strip whitespace in prefix. */
*linep = btf_name_by_offset(btf, linfo[idx].line_off);
while (isspace(**linep))
*linep += 1;
*nump = BPF_LINE_INFO_LINE_NUM(linfo[idx].line_col);
return 0;
}
#endif