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libbpf: Change has_nop_combo to work on top of nop10

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We now expect nop combo with 10 bytes nop instead of 5 bytes nop,
fixing has_nop_combo to reflect that.

Fixes: 41a5c7df4466 ("libbpf: Add support to detect nop,nop5 instructions combo for usdt probe")
Fixes: 554ba38456da ("uprobes/x86: Move optimized uprobe from nop5 to nop10")
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Jakub Sitnicki <jakub@cloudflare.com>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://patch.msgid.link/20260703114917.238144-7-jolsa@kernel.org
This commit is contained in:
Jiri Olsa authored and Andrii Nakryiko committed 2026-10-02 05:41:50 -07:00
1 parent d8b7bfc9f6
commit 30d076b7e2
1 file changed
+8 -8
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src/usdt.c
+8 -8
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@@ -305,7 +305,7 @@ struct usdt_manager *usdt_manager_new(struct bpf_object *obj)
/* /*
* Detect kernel support for uprobe() syscall, it's presence means we can * Detect kernel support for uprobe() syscall, it's presence means we can
* take advantage of faster nop5 uprobe handling. * take advantage of faster nop10 uprobe handling.
* Added in: 56101b69c919 ("uprobes/x86: Add uprobe syscall to speed up uprobe") * Added in: 56101b69c919 ("uprobes/x86: Add uprobe syscall to speed up uprobe")
*/ */
man->has_uprobe_syscall = kernel_supports(obj, FEAT_UPROBE_SYSCALL); man->has_uprobe_syscall = kernel_supports(obj, FEAT_UPROBE_SYSCALL);
@@ -605,14 +605,14 @@ static int parse_usdt_spec(struct usdt_spec *spec, const struct usdt_note *note,
#if defined(__x86_64__) #if defined(__x86_64__)
static bool has_nop_combo(int fd, long off) static bool has_nop_combo(int fd, long off)
{ {
unsigned char nop_combo[6] = { unsigned char nop_combo[11] = {
0x90, 0x0f, 0x1f, 0x44, 0x00, 0x00 /* nop,nop5 */ 0x90, 0x66, 0x2e, 0x0f, 0x1f, 0x84, 0x00, 0x00, 0x00, 0x00, 0x00,
}; };
unsigned char buf[6]; unsigned char buf[11];
if (pread(fd, buf, 6, off) != 6) if (pread(fd, buf, 11, off) != 11)
return false; return false;
return memcmp(buf, nop_combo, 6) == 0; return memcmp(buf, nop_combo, 11) == 0;
} }
#else #else
static bool has_nop_combo(int fd, long off) static bool has_nop_combo(int fd, long off)
@@ -825,8 +825,8 @@ static int collect_usdt_targets(struct usdt_manager *man, struct elf_fd *elf_fd,
memset(target, 0, sizeof(*target)); memset(target, 0, sizeof(*target));
/* /*
* We have uprobe syscall and usdt with nop,nop5 instructions combo, * We have uprobe syscall and usdt with nop,nop10 instructions combo,
* so we can place the uprobe directly on nop5 (+1) and get this probe * so we can place the uprobe directly on nop10 (+1) and get this probe
* optimized. * optimized.
*/ */
if (man->has_uprobe_syscall && has_nop_combo(elf_fd->fd, usdt_rel_ip)) { if (man->has_uprobe_syscall && has_nop_combo(elf_fd->fd, usdt_rel_ip)) {