[PATCH 1/2] libbpf: Use probe_name for legacy kprobe

Fix a bug in commit 46ed5fc33db9, which wrongly used the
func_name instead of probe_name to register legacy kprobe.

Fixes: 46ed5fc33db9 ("libbpf: Refactor and simplify legacy kprobe code")
Co-developed-by: Chengming Zhou <redacted>
Signed-off-by: Qiang Wang <redacted>
Signed-off-by: Chengming Zhou <redacted>
---
 tools/lib/bpf/libbpf.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 7c74342bb668..b7d6c951fa09 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c

@@ -9735,7 +9735,7 @@ bpf_program__attach_kprobe_opts(const struct bpf_program *prog,
 		gen_kprobe_legacy_event_name(probe_name, sizeof(probe_name),
 					     func_name, offset);
 
-		legacy_probe = strdup(func_name);
+		legacy_probe = strdup(probe_name);
 		if (!legacy_probe)
 			return libbpf_err_ptr(-ENOMEM);
 

-- 
2.20.1

If repeated legacy kprobes on same function in one process,
libbpf will register using the same probe name and got -EBUSY
error. So append index to the probe name format to fix this
problem.

Co-developed-by: Chengming Zhou <redacted>
Signed-off-by: Qiang Wang <redacted>
Signed-off-by: Chengming Zhou <redacted>
---
 tools/lib/bpf/libbpf.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index b7d6c951fa09..0c41a45ffd54 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c

@@ -9634,7 +9634,9 @@ static int append_to_file(const char *file, const char *fmt, ...)
 static void gen_kprobe_legacy_event_name(char *buf, size_t buf_sz,
 					 const char *kfunc_name, size_t offset)
 {
-	snprintf(buf, buf_sz, "libbpf_%u_%s_0x%zx", getpid(), kfunc_name, offset);
+	static int index = 0;
+	snprintf(buf, buf_sz, "libbpf_%u_%s_0x%zx_%d", getpid(), kfunc_name, offset
+		 __sync_fetch_and_add(&index, 1));
 }
 
 static int add_kprobe_event_legacy(const char *probe_name, bool retprobe,

-- 
2.20.1

On 2021/12/25 4:32 PM, Qiang Wang wrote:

Add empty line after variable declaration.

+	snprintf(buf, buf_sz, "libbpf_%u_%s_0x%zx_%d", getpid(), kfunc_name, offset

Missing a comma after offset.

On 2021/12/25 4:32 PM, Qiang Wang wrote:

Reviewed-by: Hengqi Chen <hengqi.chen@gmail.com>
Tested-by: Hengqi Chen <hengqi.chen@gmail.com>

Hi Qiang,

Thank you for the patch! Yet something to improve:

[auto build test ERROR on bpf-next/master]
[also build test ERROR on bpf/master horms-ipvs/master linus/master v5.16-rc7 next-20211224]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch]

url:    https://github.com/0day-ci/linux/commits/Qiang-Wang/libbpf-Use-probe_name-for-legacy-kprobe/20211225-163349
base:   https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next.git master
config: i386-randconfig-c001-20211227 (https://download.01.org/0day-ci/archive/20211227/202112272030.W0PW9fN7-lkp@intel.com/config)
compiler: clang version 14.0.0 (https://github.com/llvm/llvm-project 511726c64d3b6cca66f7c54d457d586aa3129f67)
reproduce (this is a W=1 build):
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # https://github.com/0day-ci/linux/commit/4a70a6c46086b85c64cae0b5c67980bd7f73cfeb
        git remote add linux-review https://github.com/0day-ci/linux
        git fetch --no-tags linux-review Qiang-Wang/libbpf-Use-probe_name-for-legacy-kprobe/20211225-163349
        git checkout 4a70a6c46086b85c64cae0b5c67980bd7f73cfeb
        # save the config file to linux build tree
        mkdir build_dir
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 O=build_dir ARCH=i386 SHELL=/bin/bash

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <redacted>

All errors (new ones prefixed by >>):

quoted

libbpf.c:9896:4: error: expected ')'

                    __sync_fetch_and_add(&index, 1));
                    ^
   libbpf.c:9895:10: note: to match this '('
           snprintf(buf, buf_sz, "libbpf_%u_%s_0x%zx_%d", getpid(), kfunc_name, offset
                   ^
   1 error generated.
   make[6]: *** [tools/build/Makefile.build:97: kernel/bpf/preload/libbpf/staticobjs/libbpf.o] Error 1
   make[6]: Target '__build' not remade because of errors.

---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org