On 6/26/25 12:49 AM, Yuan Chen wrote:
From: Yuan Chen <chenyuan@xxxxxxxxxx>
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 entry point to symbol + 4.
Signed-off-by: Yuan Chen <chenyuan@xxxxxxxxxx>
---
tools/bpf/bpftool/link.c | 30 ++++++++++++++++++++++++++++--
1 file changed, 28 insertions(+), 2 deletions(-)
diff --git a/tools/bpf/bpftool/link.c b/tools/bpf/bpftool/link.c
index 03513ffffb79..dfd192b4c5ad 100644
--- a/tools/bpf/bpftool/link.c
+++ b/tools/bpf/bpftool/link.c
@@ -307,8 +307,21 @@ show_kprobe_multi_json(struct bpf_link_info *info, json_writer_t *wtr)
goto error;
for (i = 0; i < dd.sym_count; i++) {
- if (dd.sym_mapping[i].address != data[j].addr)
+ if (dd.sym_mapping[i].address != data[j].addr) {
+#if defined(__x86_64__) || defined(__amd64__)
+ /*
+ * On x86_64 architectures with CET (Control-flow Enforcement Technology),
+ * function entry points have a 4-byte 'endbr' instruction prefix.
+ * This causes the actual function address = symbol address + 4.
+ * Here we check if this symbol matches the target address minus 4,
+ * indicating we've found a CET-enabled function entry point.
+ */
+ if (dd.sym_mapping[i].address == data[j].addr - 4)
+ goto found;
+#endif
In kernel/trace/bpf_trace.c, I see
static inline unsigned long get_entry_ip(unsigned long fentry_ip)
{
#ifdef CONFIG_X86_KERNEL_IBT
if (is_endbr((void *)(fentry_ip - ENDBR_INSN_SIZE)))
fentry_ip -= ENDBR_INSN_SIZE;
#endif
return fentry_ip;
}
Could you explain why arm64 also need to do checking
if (dd.sym_mapping[i].address == data[j].addr - 4)
like x86_64?
continue;
+ }
+found:
jsonw_start_object(json_wtr);
jsonw_uint_field(json_wtr, "addr", dd.sym_mapping[i].address);
jsonw_string_field(json_wtr, "func", dd.sym_mapping[i].name);
@@ -744,8 +757,21 @@ static void show_kprobe_multi_plain(struct bpf_link_info *info)
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 (dd.sym_mapping[i].address != data[j].addr) {
+#if defined(__x86_64__) || defined(__amd64__)
+ /*
+ * On x86_64 architectures with CET (Control-flow Enforcement Technology),
+ * function entry points have a 4-byte 'endbr' instruction prefix.
+ * This causes the actual function address = symbol address + 4.
+ * Here we check if this symbol matches the target address minus 4,
+ * indicating we've found a CET-enabled function entry point.
+ */
+ if (dd.sym_mapping[i].address == data[j].addr - 4)
+ goto found;
+#endif
continue;
+ }
+found:
printf("\n\t%016lx %-16llx %s",
dd.sym_mapping[i].address, data[j].cookie, dd.sym_mapping[i].name);
if (dd.sym_mapping[i].module[0] != '\0')
