[PATCHv2 04/11] libbpf: Change has_nop_combo to work on top of nop10

[Jiri Olsa]

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")
Reviewed-by: Jakub Sitnicki <ja...@cloudflare.com>
Signed-off-by: Jiri Olsa <jo...@kernel.org>
---
 tools/lib/bpf/usdt.c | 16 ++++++++--------
 1 file changed, 8 insertions(+), 8 deletions(-)

diff --git a/tools/lib/bpf/usdt.c b/tools/lib/bpf/usdt.c
index e3710933fd52..7e62e4d5bedd 100644
--- a/tools/lib/bpf/usdt.c
+++ b/tools/lib/bpf/usdt.c
@@ -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
-        * 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")
         */
        man->has_uprobe_syscall = kernel_supports(obj, FEAT_UPROBE_SYSCALL);
@@ -596,14 +596,14 @@ static int parse_usdt_spec(struct usdt_spec *spec, const 
struct usdt_note *note,
 #if defined(__x86_64__)
 static bool has_nop_combo(int fd, long off)
 {
-       unsigned char nop_combo[6] = {
-               0x90, 0x0f, 0x1f, 0x44, 0x00, 0x00 /* nop,nop5 */
+       unsigned char nop_combo[11] = {
+               0x90, 0x66, 0x66, 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 memcmp(buf, nop_combo, 6) == 0;
+       return memcmp(buf, nop_combo, 11) == 0;
 }
 #else
 static bool has_nop_combo(int fd, long off)
@@ -814,8 +814,8 @@ static int collect_usdt_targets(struct usdt_manager *man, 
struct elf_fd *elf_fd,
                memset(target, 0, sizeof(*target));
 
                /*
-                * We have uprobe syscall and usdt with nop,nop5 instructions 
combo,
-                * so we can place the uprobe directly on nop5 (+1) and get 
this probe
+                * We have uprobe syscall and usdt with nop,nop10 instructions 
combo,
+                * so we can place the uprobe directly on nop10 (+1) and get 
this probe
                 * optimized.
                 */
                if (man->has_uprobe_syscall && has_nop_combo(elf_fd->fd, 
usdt_rel_ip)) {
-- 
2.53.0