diff options
| author | Yuan Chen <chenyuan@kylinos.cn> | 2025-08-29 07:11:07 +0100 |
|---|---|---|
| committer | Daniel Borkmann <daniel@iogearbox.net> | 2025-09-02 17:20:54 +0200 |
| commit | 6417ca85305ecaffef13cf9063ac35da8fba8500 (patch) | |
| tree | 1a30a895a5db6d3498f0e810b84d74274c23fb20 /tools/bpf/bpftool/link.c | |
| parent | 70f32a10ad423fd19e22e71d05d0968e61316278 (diff) | |
bpftool: Add CET-aware symbol matching for x86_64 architectures
Adjust symbol matching logic to account for Control-flow Enforcement
Technology (CET) on x86_64 systems. CET prefixes functions with
a 4-byte 'endbr' instruction, shifting the actual hook entry point to
symbol + 4.
Signed-off-by: Yuan Chen <chenyuan@kylinos.cn>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Quentin Monnet <qmo@kernel.org>
Acked-by: Yonghong Song <yonghong.song@linux.dev>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Link: https://lore.kernel.org/bpf/20250829061107.23905-3-chenyuan_fl@163.com
Diffstat (limited to 'tools/bpf/bpftool/link.c')
| -rw-r--r-- | tools/bpf/bpftool/link.c | 54 |
1 files changed, 50 insertions, 4 deletions
diff --git a/tools/bpf/bpftool/link.c b/tools/bpf/bpftool/link.c index a773e05d5ade..bdcd717b0348 100644 --- a/tools/bpf/bpftool/link.c +++ b/tools/bpf/bpftool/link.c @@ -282,11 +282,52 @@ get_addr_cookie_array(__u64 *addrs, __u64 *cookies, __u32 count) return data; } +static bool is_x86_ibt_enabled(void) +{ +#if defined(__x86_64__) + struct kernel_config_option options[] = { + { "CONFIG_X86_KERNEL_IBT", }, + }; + char *values[ARRAY_SIZE(options)] = { }; + bool ret; + + if (read_kernel_config(options, ARRAY_SIZE(options), values, NULL)) + return false; + + ret = !!values[0]; + free(values[0]); + return ret; +#else + return false; +#endif +} + +static bool +symbol_matches_target(__u64 sym_addr, __u64 target_addr, bool is_ibt_enabled) +{ + if (sym_addr == target_addr) + return true; + + /* + * On x86_64 architectures with CET (Control-flow Enforcement Technology), + * function entry points have a 4-byte 'endbr' instruction prefix. + * This causes kprobe hooks to target the address *after* 'endbr' + * (symbol address + 4), preserving the CET instruction. + * Here we check if the symbol address matches the hook target address + * minus 4, indicating a CET-enabled function entry point. + */ + if (is_ibt_enabled && sym_addr == target_addr - 4) + return true; + + return false; +} + static void show_kprobe_multi_json(struct bpf_link_info *info, json_writer_t *wtr) { struct addr_cookie *data; __u32 i, j = 0; + bool is_ibt_enabled; jsonw_bool_field(json_wtr, "retprobe", info->kprobe_multi.flags & BPF_F_KPROBE_MULTI_RETURN); @@ -306,11 +347,13 @@ show_kprobe_multi_json(struct bpf_link_info *info, json_writer_t *wtr) if (!dd.sym_count) goto error; + is_ibt_enabled = is_x86_ibt_enabled(); for (i = 0; i < dd.sym_count; i++) { - if (dd.sym_mapping[i].address != data[j].addr) + if (!symbol_matches_target(dd.sym_mapping[i].address, + data[j].addr, is_ibt_enabled)) continue; jsonw_start_object(json_wtr); - jsonw_uint_field(json_wtr, "addr", dd.sym_mapping[i].address); + jsonw_uint_field(json_wtr, "addr", (unsigned long)data[j].addr); jsonw_string_field(json_wtr, "func", dd.sym_mapping[i].name); /* Print null if it is vmlinux */ if (dd.sym_mapping[i].module[0] == '\0') { @@ -719,6 +762,7 @@ static void show_kprobe_multi_plain(struct bpf_link_info *info) { struct addr_cookie *data; __u32 i, j = 0; + bool is_ibt_enabled; if (!info->kprobe_multi.count) return; @@ -742,12 +786,14 @@ static void show_kprobe_multi_plain(struct bpf_link_info *info) if (!dd.sym_count) goto error; + is_ibt_enabled = is_x86_ibt_enabled(); printf("\n\t%-16s %-16s %s", "addr", "cookie", "func [module]"); for (i = 0; i < dd.sym_count; i++) { - if (dd.sym_mapping[i].address != data[j].addr) + if (!symbol_matches_target(dd.sym_mapping[i].address, + data[j].addr, is_ibt_enabled)) continue; printf("\n\t%016lx %-16llx %s", - dd.sym_mapping[i].address, data[j].cookie, dd.sym_mapping[i].name); + (unsigned long)data[j].addr, data[j].cookie, dd.sym_mapping[i].name); if (dd.sym_mapping[i].module[0] != '\0') printf(" [%s] ", dd.sym_mapping[i].module); else |