From: Feng Yang <yangfeng@kylinos.cn>
When the binary path is excessively long, the generated probe_name in libbpf
exceeds the kernel's MAX_EVENT_NAME_LEN limit (64 bytes).
This causes legacy uprobe event attachment to fail with error code -22.
The fix reorders the fields to place the unique ID before the name.
This ensures that even if truncation occurs via snprintf, the unique ID
remains intact, preserving event name uniqueness. Additionally, explicit
checks with MAX_EVENT_NAME_LEN are added to enforce length constraints.
Before Fix:
./test_progs -t attach_probe/kprobe-long_name
......
libbpf: failed to add legacy kprobe event for 'bpf_testmod_looooooooooooooooooooooooooooooong_name+0x0': -EINVAL
libbpf: prog 'handle_kprobe': failed to create kprobe 'bpf_testmod_looooooooooooooooooooooooooooooong_name+0x0' perf event: -EINVAL
test_attach_kprobe_long_event_name:FAIL:attach_kprobe_long_event_name unexpected error: -22
test_attach_probe:PASS:uprobe_ref_ctr_cleanup 0 nsec
#13/11 attach_probe/kprobe-long_name:FAIL
#13 attach_probe:FAIL
./test_progs -t attach_probe/uprobe-long_name
......
libbpf: failed to add legacy uprobe event for /root/linux-bpf/bpf-next/tools/testing/selftests/bpf/test_progs:0x13efd9: -EINVAL
libbpf: prog 'handle_uprobe': failed to create uprobe '/root/linux-bpf/bpf-next/tools/testing/selftests/bpf/test_progs:0x13efd9' perf event: -EINVAL
test_attach_uprobe_long_event_name:FAIL:attach_uprobe_long_event_name unexpected error: -22
#13/10 attach_probe/uprobe-long_name:FAIL
#13 attach_probe:FAIL
After Fix:
./test_progs -t attach_probe/uprobe-long_name
#13/10 attach_probe/uprobe-long_name:OK
#13 attach_probe:OK
Summary: 1/1 PASSED, 0 SKIPPED, 0 FAILED
./test_progs -t attach_probe/kprobe-long_name
#13/11 attach_probe/kprobe-long_name:OK
#13 attach_probe:OK
Summary: 1/1 PASSED, 0 SKIPPED, 0 FAILED
Fixes: 46ed5fc33db9 ("libbpf: Refactor and simplify legacy kprobe code")
Fixes: cc10623c6810 ("libbpf: Add legacy uprobe attaching support")
Signed-off-by: Hengqi Chen <hengqi.chen@gmail.com>
Signed-off-by: Feng Yang <yangfeng@kylinos.cn>
---
tools/lib/bpf/libbpf.c | 41 +++++++++++++++--------------------------
1 file changed, 15 insertions(+), 26 deletions(-)
diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index b2591f5cab65..b7fc57ac16a6 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -60,6 +60,8 @@
#define BPF_FS_MAGIC 0xcafe4a11
#endif
+#define MAX_EVENT_NAME_LEN 64
+
#define BPF_FS_DEFAULT_PATH "/sys/fs/bpf"
#define BPF_INSN_SZ (sizeof(struct bpf_insn))
@@ -11136,16 +11138,16 @@ static const char *tracefs_available_filter_functions_addrs(void)
: TRACEFS"/available_filter_functions_addrs";
}
-static void gen_kprobe_legacy_event_name(char *buf, size_t buf_sz,
- const char *kfunc_name, size_t offset)
+static void gen_probe_legacy_event_name(char *buf, size_t buf_sz,
+ const char *name, size_t offset)
{
static int index = 0;
int i;
- snprintf(buf, buf_sz, "libbpf_%u_%s_0x%zx_%d", getpid(), kfunc_name, offset,
- __sync_fetch_and_add(&index, 1));
+ snprintf(buf, buf_sz, "libbpf_%u_%d_%s_0x%zx", getpid(),
+ __sync_fetch_and_add(&index, 1), name, offset);
- /* sanitize binary_path in the probe name */
+ /* sanitize name in the probe name */
for (i = 0; buf[i]; i++) {
if (!isalnum(buf[i]))
buf[i] = '_';
@@ -11270,9 +11272,9 @@ int probe_kern_syscall_wrapper(int token_fd)
return pfd >= 0 ? 1 : 0;
} else { /* legacy mode */
- char probe_name[128];
+ char probe_name[MAX_EVENT_NAME_LEN];
- gen_kprobe_legacy_event_name(probe_name, sizeof(probe_name), syscall_name, 0);
+ gen_probe_legacy_event_name(probe_name, sizeof(probe_name), syscall_name, 0);
if (add_kprobe_event_legacy(probe_name, false, syscall_name, 0) < 0)
return 0;
@@ -11328,9 +11330,9 @@ bpf_program__attach_kprobe_opts(const struct bpf_program *prog,
func_name, offset,
-1 /* pid */, 0 /* ref_ctr_off */);
} else {
- char probe_name[256];
+ char probe_name[MAX_EVENT_NAME_LEN];
- gen_kprobe_legacy_event_name(probe_name, sizeof(probe_name),
+ gen_probe_legacy_event_name(probe_name, sizeof(probe_name),
func_name, offset);
legacy_probe = strdup(probe_name);
@@ -11875,20 +11877,6 @@ static int attach_uprobe_multi(const struct bpf_program *prog, long cookie, stru
return ret;
}
-static void gen_uprobe_legacy_event_name(char *buf, size_t buf_sz,
- const char *binary_path, uint64_t offset)
-{
- int i;
-
- snprintf(buf, buf_sz, "libbpf_%u_%s_0x%zx", getpid(), binary_path, (size_t)offset);
-
- /* sanitize binary_path in the probe name */
- for (i = 0; buf[i]; i++) {
- if (!isalnum(buf[i]))
- buf[i] = '_';
- }
-}
-
static inline int add_uprobe_event_legacy(const char *probe_name, bool retprobe,
const char *binary_path, size_t offset)
{
@@ -12312,13 +12300,14 @@ bpf_program__attach_uprobe_opts(const struct bpf_program *prog, pid_t pid,
pfd = perf_event_open_probe(true /* uprobe */, retprobe, binary_path,
func_offset, pid, ref_ctr_off);
} else {
- char probe_name[PATH_MAX + 64];
+ char probe_name[MAX_EVENT_NAME_LEN];
if (ref_ctr_off)
return libbpf_err_ptr(-EINVAL);
- gen_uprobe_legacy_event_name(probe_name, sizeof(probe_name),
- binary_path, func_offset);
+ gen_probe_legacy_event_name(probe_name, sizeof(probe_name),
+ basename((void *)binary_path),
+ func_offset);
legacy_probe = strdup(probe_name);
if (!legacy_probe)
--
2.43.0On Tue, Apr 15, 2025 at 2:40 AM Feng Yang <yangfeng59949@163.com> wrote:
>
> From: Feng Yang <yangfeng@kylinos.cn>
>
> When the binary path is excessively long, the generated probe_name in libbpf
> exceeds the kernel's MAX_EVENT_NAME_LEN limit (64 bytes).
> This causes legacy uprobe event attachment to fail with error code -22.
>
> The fix reorders the fields to place the unique ID before the name.
> This ensures that even if truncation occurs via snprintf, the unique ID
> remains intact, preserving event name uniqueness. Additionally, explicit
> checks with MAX_EVENT_NAME_LEN are added to enforce length constraints.
>
> Before Fix:
> ./test_progs -t attach_probe/kprobe-long_name
> ......
> libbpf: failed to add legacy kprobe event for 'bpf_testmod_looooooooooooooooooooooooooooooong_name+0x0': -EINVAL
> libbpf: prog 'handle_kprobe': failed to create kprobe 'bpf_testmod_looooooooooooooooooooooooooooooong_name+0x0' perf event: -EINVAL
> test_attach_kprobe_long_event_name:FAIL:attach_kprobe_long_event_name unexpected error: -22
> test_attach_probe:PASS:uprobe_ref_ctr_cleanup 0 nsec
> #13/11 attach_probe/kprobe-long_name:FAIL
> #13 attach_probe:FAIL
>
> ./test_progs -t attach_probe/uprobe-long_name
> ......
> libbpf: failed to add legacy uprobe event for /root/linux-bpf/bpf-next/tools/testing/selftests/bpf/test_progs:0x13efd9: -EINVAL
> libbpf: prog 'handle_uprobe': failed to create uprobe '/root/linux-bpf/bpf-next/tools/testing/selftests/bpf/test_progs:0x13efd9' perf event: -EINVAL
> test_attach_uprobe_long_event_name:FAIL:attach_uprobe_long_event_name unexpected error: -22
> #13/10 attach_probe/uprobe-long_name:FAIL
> #13 attach_probe:FAIL
> After Fix:
> ./test_progs -t attach_probe/uprobe-long_name
> #13/10 attach_probe/uprobe-long_name:OK
> #13 attach_probe:OK
> Summary: 1/1 PASSED, 0 SKIPPED, 0 FAILED
>
> ./test_progs -t attach_probe/kprobe-long_name
> #13/11 attach_probe/kprobe-long_name:OK
> #13 attach_probe:OK
> Summary: 1/1 PASSED, 0 SKIPPED, 0 FAILED
>
> Fixes: 46ed5fc33db9 ("libbpf: Refactor and simplify legacy kprobe code")
> Fixes: cc10623c6810 ("libbpf: Add legacy uprobe attaching support")
> Signed-off-by: Hengqi Chen <hengqi.chen@gmail.com>
> Signed-off-by: Feng Yang <yangfeng@kylinos.cn>
> ---
> tools/lib/bpf/libbpf.c | 41 +++++++++++++++--------------------------
> 1 file changed, 15 insertions(+), 26 deletions(-)
>
> diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
> index b2591f5cab65..b7fc57ac16a6 100644
> --- a/tools/lib/bpf/libbpf.c
> +++ b/tools/lib/bpf/libbpf.c
> @@ -60,6 +60,8 @@
> #define BPF_FS_MAGIC 0xcafe4a11
> #endif
>
> +#define MAX_EVENT_NAME_LEN 64
> +
> #define BPF_FS_DEFAULT_PATH "/sys/fs/bpf"
>
> #define BPF_INSN_SZ (sizeof(struct bpf_insn))
> @@ -11136,16 +11138,16 @@ static const char *tracefs_available_filter_functions_addrs(void)
> : TRACEFS"/available_filter_functions_addrs";
> }
>
> -static void gen_kprobe_legacy_event_name(char *buf, size_t buf_sz,
> - const char *kfunc_name, size_t offset)
> +static void gen_probe_legacy_event_name(char *buf, size_t buf_sz,
> + const char *name, size_t offset)
> {
> static int index = 0;
> int i;
>
> - snprintf(buf, buf_sz, "libbpf_%u_%s_0x%zx_%d", getpid(), kfunc_name, offset,
> - __sync_fetch_and_add(&index, 1));
> + snprintf(buf, buf_sz, "libbpf_%u_%d_%s_0x%zx", getpid(),
> + __sync_fetch_and_add(&index, 1), name, offset);
>
> - /* sanitize binary_path in the probe name */
> + /* sanitize name in the probe name */
> for (i = 0; buf[i]; i++) {
> if (!isalnum(buf[i]))
> buf[i] = '_';
> @@ -11270,9 +11272,9 @@ int probe_kern_syscall_wrapper(int token_fd)
>
> return pfd >= 0 ? 1 : 0;
> } else { /* legacy mode */
> - char probe_name[128];
> + char probe_name[MAX_EVENT_NAME_LEN];
>
> - gen_kprobe_legacy_event_name(probe_name, sizeof(probe_name), syscall_name, 0);
> + gen_probe_legacy_event_name(probe_name, sizeof(probe_name), syscall_name, 0);
> if (add_kprobe_event_legacy(probe_name, false, syscall_name, 0) < 0)
> return 0;
>
> @@ -11328,9 +11330,9 @@ bpf_program__attach_kprobe_opts(const struct bpf_program *prog,
> func_name, offset,
> -1 /* pid */, 0 /* ref_ctr_off */);
> } else {
> - char probe_name[256];
> + char probe_name[MAX_EVENT_NAME_LEN];
>
> - gen_kprobe_legacy_event_name(probe_name, sizeof(probe_name),
> + gen_probe_legacy_event_name(probe_name, sizeof(probe_name),
> func_name, offset);
>
> legacy_probe = strdup(probe_name);
> @@ -11875,20 +11877,6 @@ static int attach_uprobe_multi(const struct bpf_program *prog, long cookie, stru
> return ret;
> }
>
> -static void gen_uprobe_legacy_event_name(char *buf, size_t buf_sz,
> - const char *binary_path, uint64_t offset)
> -{
> - int i;
> -
> - snprintf(buf, buf_sz, "libbpf_%u_%s_0x%zx", getpid(), binary_path, (size_t)offset);
> -
> - /* sanitize binary_path in the probe name */
> - for (i = 0; buf[i]; i++) {
> - if (!isalnum(buf[i]))
> - buf[i] = '_';
> - }
> -}
> -
> static inline int add_uprobe_event_legacy(const char *probe_name, bool retprobe,
> const char *binary_path, size_t offset)
> {
> @@ -12312,13 +12300,14 @@ bpf_program__attach_uprobe_opts(const struct bpf_program *prog, pid_t pid,
> pfd = perf_event_open_probe(true /* uprobe */, retprobe, binary_path,
> func_offset, pid, ref_ctr_off);
> } else {
> - char probe_name[PATH_MAX + 64];
> + char probe_name[MAX_EVENT_NAME_LEN];
>
> if (ref_ctr_off)
> return libbpf_err_ptr(-EINVAL);
>
> - gen_uprobe_legacy_event_name(probe_name, sizeof(probe_name),
> - binary_path, func_offset);
> + gen_probe_legacy_event_name(probe_name, sizeof(probe_name),
> + basename((void *)binary_path),
This patch is a nice refactoring overall and I like it. But this (void
*) cast on binary_path I'm not so fond of. Yes, if you read
smallprint, you'll see that with _GNU_SOURCE basename won't *really*
modify input argument, but meh.
Let's instead do a simple `strrchr(binary_path, '/') ?: binary_path`?
pw-bot: cr
> + func_offset);
>
> legacy_probe = strdup(probe_name);
> if (!legacy_probe)
> --
> 2.43.0
>
Hi Andrii,
On Wed, Apr 16, 2025 at 7:05 AM Andrii Nakryiko
<andrii.nakryiko@gmail.com> wrote:
>
> On Tue, Apr 15, 2025 at 2:40 AM Feng Yang <yangfeng59949@163.com> wrote:
> >
> > From: Feng Yang <yangfeng@kylinos.cn>
> >
> > When the binary path is excessively long, the generated probe_name in libbpf
> > exceeds the kernel's MAX_EVENT_NAME_LEN limit (64 bytes).
> > This causes legacy uprobe event attachment to fail with error code -22.
> >
> > The fix reorders the fields to place the unique ID before the name.
> > This ensures that even if truncation occurs via snprintf, the unique ID
> > remains intact, preserving event name uniqueness. Additionally, explicit
> > checks with MAX_EVENT_NAME_LEN are added to enforce length constraints.
> >
> > Before Fix:
> > ./test_progs -t attach_probe/kprobe-long_name
> > ......
> > libbpf: failed to add legacy kprobe event for 'bpf_testmod_looooooooooooooooooooooooooooooong_name+0x0': -EINVAL
> > libbpf: prog 'handle_kprobe': failed to create kprobe 'bpf_testmod_looooooooooooooooooooooooooooooong_name+0x0' perf event: -EINVAL
> > test_attach_kprobe_long_event_name:FAIL:attach_kprobe_long_event_name unexpected error: -22
> > test_attach_probe:PASS:uprobe_ref_ctr_cleanup 0 nsec
> > #13/11 attach_probe/kprobe-long_name:FAIL
> > #13 attach_probe:FAIL
> >
> > ./test_progs -t attach_probe/uprobe-long_name
> > ......
> > libbpf: failed to add legacy uprobe event for /root/linux-bpf/bpf-next/tools/testing/selftests/bpf/test_progs:0x13efd9: -EINVAL
> > libbpf: prog 'handle_uprobe': failed to create uprobe '/root/linux-bpf/bpf-next/tools/testing/selftests/bpf/test_progs:0x13efd9' perf event: -EINVAL
> > test_attach_uprobe_long_event_name:FAIL:attach_uprobe_long_event_name unexpected error: -22
> > #13/10 attach_probe/uprobe-long_name:FAIL
> > #13 attach_probe:FAIL
> > After Fix:
> > ./test_progs -t attach_probe/uprobe-long_name
> > #13/10 attach_probe/uprobe-long_name:OK
> > #13 attach_probe:OK
> > Summary: 1/1 PASSED, 0 SKIPPED, 0 FAILED
> >
> > ./test_progs -t attach_probe/kprobe-long_name
> > #13/11 attach_probe/kprobe-long_name:OK
> > #13 attach_probe:OK
> > Summary: 1/1 PASSED, 0 SKIPPED, 0 FAILED
> >
> > Fixes: 46ed5fc33db9 ("libbpf: Refactor and simplify legacy kprobe code")
> > Fixes: cc10623c6810 ("libbpf: Add legacy uprobe attaching support")
> > Signed-off-by: Hengqi Chen <hengqi.chen@gmail.com>
> > Signed-off-by: Feng Yang <yangfeng@kylinos.cn>
> > ---
> > tools/lib/bpf/libbpf.c | 41 +++++++++++++++--------------------------
> > 1 file changed, 15 insertions(+), 26 deletions(-)
> >
> > diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
> > index b2591f5cab65..b7fc57ac16a6 100644
> > --- a/tools/lib/bpf/libbpf.c
> > +++ b/tools/lib/bpf/libbpf.c
> > @@ -60,6 +60,8 @@
> > #define BPF_FS_MAGIC 0xcafe4a11
> > #endif
> >
> > +#define MAX_EVENT_NAME_LEN 64
> > +
> > #define BPF_FS_DEFAULT_PATH "/sys/fs/bpf"
> >
> > #define BPF_INSN_SZ (sizeof(struct bpf_insn))
> > @@ -11136,16 +11138,16 @@ static const char *tracefs_available_filter_functions_addrs(void)
> > : TRACEFS"/available_filter_functions_addrs";
> > }
> >
> > -static void gen_kprobe_legacy_event_name(char *buf, size_t buf_sz,
> > - const char *kfunc_name, size_t offset)
> > +static void gen_probe_legacy_event_name(char *buf, size_t buf_sz,
> > + const char *name, size_t offset)
> > {
> > static int index = 0;
> > int i;
> >
> > - snprintf(buf, buf_sz, "libbpf_%u_%s_0x%zx_%d", getpid(), kfunc_name, offset,
> > - __sync_fetch_and_add(&index, 1));
> > + snprintf(buf, buf_sz, "libbpf_%u_%d_%s_0x%zx", getpid(),
> > + __sync_fetch_and_add(&index, 1), name, offset);
> >
> > - /* sanitize binary_path in the probe name */
> > + /* sanitize name in the probe name */
> > for (i = 0; buf[i]; i++) {
> > if (!isalnum(buf[i]))
> > buf[i] = '_';
> > @@ -11270,9 +11272,9 @@ int probe_kern_syscall_wrapper(int token_fd)
> >
> > return pfd >= 0 ? 1 : 0;
> > } else { /* legacy mode */
> > - char probe_name[128];
> > + char probe_name[MAX_EVENT_NAME_LEN];
> >
> > - gen_kprobe_legacy_event_name(probe_name, sizeof(probe_name), syscall_name, 0);
> > + gen_probe_legacy_event_name(probe_name, sizeof(probe_name), syscall_name, 0);
> > if (add_kprobe_event_legacy(probe_name, false, syscall_name, 0) < 0)
> > return 0;
> >
> > @@ -11328,9 +11330,9 @@ bpf_program__attach_kprobe_opts(const struct bpf_program *prog,
> > func_name, offset,
> > -1 /* pid */, 0 /* ref_ctr_off */);
> > } else {
> > - char probe_name[256];
> > + char probe_name[MAX_EVENT_NAME_LEN];
> >
> > - gen_kprobe_legacy_event_name(probe_name, sizeof(probe_name),
> > + gen_probe_legacy_event_name(probe_name, sizeof(probe_name),
> > func_name, offset);
> >
> > legacy_probe = strdup(probe_name);
> > @@ -11875,20 +11877,6 @@ static int attach_uprobe_multi(const struct bpf_program *prog, long cookie, stru
> > return ret;
> > }
> >
> > -static void gen_uprobe_legacy_event_name(char *buf, size_t buf_sz,
> > - const char *binary_path, uint64_t offset)
> > -{
> > - int i;
> > -
> > - snprintf(buf, buf_sz, "libbpf_%u_%s_0x%zx", getpid(), binary_path, (size_t)offset);
> > -
> > - /* sanitize binary_path in the probe name */
> > - for (i = 0; buf[i]; i++) {
> > - if (!isalnum(buf[i]))
> > - buf[i] = '_';
> > - }
> > -}
> > -
> > static inline int add_uprobe_event_legacy(const char *probe_name, bool retprobe,
> > const char *binary_path, size_t offset)
> > {
> > @@ -12312,13 +12300,14 @@ bpf_program__attach_uprobe_opts(const struct bpf_program *prog, pid_t pid,
> > pfd = perf_event_open_probe(true /* uprobe */, retprobe, binary_path,
> > func_offset, pid, ref_ctr_off);
> > } else {
> > - char probe_name[PATH_MAX + 64];
> > + char probe_name[MAX_EVENT_NAME_LEN];
> >
> > if (ref_ctr_off)
> > return libbpf_err_ptr(-EINVAL);
> >
> > - gen_uprobe_legacy_event_name(probe_name, sizeof(probe_name),
> > - binary_path, func_offset);
> > + gen_probe_legacy_event_name(probe_name, sizeof(probe_name),
> > + basename((void *)binary_path),
>
> This patch is a nice refactoring overall and I like it. But this (void
> *) cast on binary_path I'm not so fond of. Yes, if you read
> smallprint, you'll see that with _GNU_SOURCE basename won't *really*
> modify input argument, but meh.
>
This has been used in bpf_object__new() like:
/* Using basename() GNU version which doesn't modify arg. */
libbpf_strlcpy(obj->name, basename((void *)path), sizeof(obj->name));
> Let's instead do a simple `strrchr(binary_path, '/') ?: binary_path`?
>
> pw-bot: cr
>
>
> > + func_offset);
> >
> > legacy_probe = strdup(probe_name);
> > if (!legacy_probe)
> > --
> > 2.43.0
> >
On Tue, Apr 15, 2025 at 6:44 PM Hengqi Chen <hengqi.chen@gmail.com> wrote:
>
> Hi Andrii,
>
> On Wed, Apr 16, 2025 at 7:05 AM Andrii Nakryiko
> <andrii.nakryiko@gmail.com> wrote:
> >
> > On Tue, Apr 15, 2025 at 2:40 AM Feng Yang <yangfeng59949@163.com> wrote:
> > >
> > > From: Feng Yang <yangfeng@kylinos.cn>
> > >
> > > When the binary path is excessively long, the generated probe_name in libbpf
> > > exceeds the kernel's MAX_EVENT_NAME_LEN limit (64 bytes).
> > > This causes legacy uprobe event attachment to fail with error code -22.
> > >
> > > The fix reorders the fields to place the unique ID before the name.
> > > This ensures that even if truncation occurs via snprintf, the unique ID
> > > remains intact, preserving event name uniqueness. Additionally, explicit
> > > checks with MAX_EVENT_NAME_LEN are added to enforce length constraints.
> > >
> > > Before Fix:
> > > ./test_progs -t attach_probe/kprobe-long_name
> > > ......
> > > libbpf: failed to add legacy kprobe event for 'bpf_testmod_looooooooooooooooooooooooooooooong_name+0x0': -EINVAL
> > > libbpf: prog 'handle_kprobe': failed to create kprobe 'bpf_testmod_looooooooooooooooooooooooooooooong_name+0x0' perf event: -EINVAL
> > > test_attach_kprobe_long_event_name:FAIL:attach_kprobe_long_event_name unexpected error: -22
> > > test_attach_probe:PASS:uprobe_ref_ctr_cleanup 0 nsec
> > > #13/11 attach_probe/kprobe-long_name:FAIL
> > > #13 attach_probe:FAIL
> > >
> > > ./test_progs -t attach_probe/uprobe-long_name
> > > ......
> > > libbpf: failed to add legacy uprobe event for /root/linux-bpf/bpf-next/tools/testing/selftests/bpf/test_progs:0x13efd9: -EINVAL
> > > libbpf: prog 'handle_uprobe': failed to create uprobe '/root/linux-bpf/bpf-next/tools/testing/selftests/bpf/test_progs:0x13efd9' perf event: -EINVAL
> > > test_attach_uprobe_long_event_name:FAIL:attach_uprobe_long_event_name unexpected error: -22
> > > #13/10 attach_probe/uprobe-long_name:FAIL
> > > #13 attach_probe:FAIL
> > > After Fix:
> > > ./test_progs -t attach_probe/uprobe-long_name
> > > #13/10 attach_probe/uprobe-long_name:OK
> > > #13 attach_probe:OK
> > > Summary: 1/1 PASSED, 0 SKIPPED, 0 FAILED
> > >
> > > ./test_progs -t attach_probe/kprobe-long_name
> > > #13/11 attach_probe/kprobe-long_name:OK
> > > #13 attach_probe:OK
> > > Summary: 1/1 PASSED, 0 SKIPPED, 0 FAILED
> > >
> > > Fixes: 46ed5fc33db9 ("libbpf: Refactor and simplify legacy kprobe code")
> > > Fixes: cc10623c6810 ("libbpf: Add legacy uprobe attaching support")
> > > Signed-off-by: Hengqi Chen <hengqi.chen@gmail.com>
> > > Signed-off-by: Feng Yang <yangfeng@kylinos.cn>
> > > ---
> > > tools/lib/bpf/libbpf.c | 41 +++++++++++++++--------------------------
> > > 1 file changed, 15 insertions(+), 26 deletions(-)
> > >
> > > diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
> > > index b2591f5cab65..b7fc57ac16a6 100644
> > > --- a/tools/lib/bpf/libbpf.c
> > > +++ b/tools/lib/bpf/libbpf.c
> > > @@ -60,6 +60,8 @@
> > > #define BPF_FS_MAGIC 0xcafe4a11
> > > #endif
> > >
> > > +#define MAX_EVENT_NAME_LEN 64
> > > +
> > > #define BPF_FS_DEFAULT_PATH "/sys/fs/bpf"
> > >
> > > #define BPF_INSN_SZ (sizeof(struct bpf_insn))
> > > @@ -11136,16 +11138,16 @@ static const char *tracefs_available_filter_functions_addrs(void)
> > > : TRACEFS"/available_filter_functions_addrs";
> > > }
> > >
> > > -static void gen_kprobe_legacy_event_name(char *buf, size_t buf_sz,
> > > - const char *kfunc_name, size_t offset)
> > > +static void gen_probe_legacy_event_name(char *buf, size_t buf_sz,
> > > + const char *name, size_t offset)
> > > {
> > > static int index = 0;
> > > int i;
> > >
> > > - snprintf(buf, buf_sz, "libbpf_%u_%s_0x%zx_%d", getpid(), kfunc_name, offset,
> > > - __sync_fetch_and_add(&index, 1));
> > > + snprintf(buf, buf_sz, "libbpf_%u_%d_%s_0x%zx", getpid(),
> > > + __sync_fetch_and_add(&index, 1), name, offset);
> > >
> > > - /* sanitize binary_path in the probe name */
> > > + /* sanitize name in the probe name */
> > > for (i = 0; buf[i]; i++) {
> > > if (!isalnum(buf[i]))
> > > buf[i] = '_';
> > > @@ -11270,9 +11272,9 @@ int probe_kern_syscall_wrapper(int token_fd)
> > >
> > > return pfd >= 0 ? 1 : 0;
> > > } else { /* legacy mode */
> > > - char probe_name[128];
> > > + char probe_name[MAX_EVENT_NAME_LEN];
> > >
> > > - gen_kprobe_legacy_event_name(probe_name, sizeof(probe_name), syscall_name, 0);
> > > + gen_probe_legacy_event_name(probe_name, sizeof(probe_name), syscall_name, 0);
> > > if (add_kprobe_event_legacy(probe_name, false, syscall_name, 0) < 0)
> > > return 0;
> > >
> > > @@ -11328,9 +11330,9 @@ bpf_program__attach_kprobe_opts(const struct bpf_program *prog,
> > > func_name, offset,
> > > -1 /* pid */, 0 /* ref_ctr_off */);
> > > } else {
> > > - char probe_name[256];
> > > + char probe_name[MAX_EVENT_NAME_LEN];
> > >
> > > - gen_kprobe_legacy_event_name(probe_name, sizeof(probe_name),
> > > + gen_probe_legacy_event_name(probe_name, sizeof(probe_name),
> > > func_name, offset);
> > >
> > > legacy_probe = strdup(probe_name);
> > > @@ -11875,20 +11877,6 @@ static int attach_uprobe_multi(const struct bpf_program *prog, long cookie, stru
> > > return ret;
> > > }
> > >
> > > -static void gen_uprobe_legacy_event_name(char *buf, size_t buf_sz,
> > > - const char *binary_path, uint64_t offset)
> > > -{
> > > - int i;
> > > -
> > > - snprintf(buf, buf_sz, "libbpf_%u_%s_0x%zx", getpid(), binary_path, (size_t)offset);
> > > -
> > > - /* sanitize binary_path in the probe name */
> > > - for (i = 0; buf[i]; i++) {
> > > - if (!isalnum(buf[i]))
> > > - buf[i] = '_';
> > > - }
> > > -}
> > > -
> > > static inline int add_uprobe_event_legacy(const char *probe_name, bool retprobe,
> > > const char *binary_path, size_t offset)
> > > {
> > > @@ -12312,13 +12300,14 @@ bpf_program__attach_uprobe_opts(const struct bpf_program *prog, pid_t pid,
> > > pfd = perf_event_open_probe(true /* uprobe */, retprobe, binary_path,
> > > func_offset, pid, ref_ctr_off);
> > > } else {
> > > - char probe_name[PATH_MAX + 64];
> > > + char probe_name[MAX_EVENT_NAME_LEN];
> > >
> > > if (ref_ctr_off)
> > > return libbpf_err_ptr(-EINVAL);
> > >
> > > - gen_uprobe_legacy_event_name(probe_name, sizeof(probe_name),
> > > - binary_path, func_offset);
> > > + gen_probe_legacy_event_name(probe_name, sizeof(probe_name),
> > > + basename((void *)binary_path),
> >
> > This patch is a nice refactoring overall and I like it. But this (void
> > *) cast on binary_path I'm not so fond of. Yes, if you read
> > smallprint, you'll see that with _GNU_SOURCE basename won't *really*
> > modify input argument, but meh.
> >
>
> This has been used in bpf_object__new() like:
>
> /* Using basename() GNU version which doesn't modify arg. */
> libbpf_strlcpy(obj->name, basename((void *)path), sizeof(obj->name));
yeah, I know, which is why I remembered this semantical quirk. Still,
in this case we are just adding a hint, so some simple strrchr() seems
adequate
>
> > Let's instead do a simple `strrchr(binary_path, '/') ?: binary_path`?
> >
> > pw-bot: cr
> >
> >
> > > + func_offset);
> > >
> > > legacy_probe = strdup(probe_name);
> > > if (!legacy_probe)
> > > --
> > > 2.43.0
> > >
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