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Subject[tip:perf/core] perf bpf: Don't warn about unavailability of builtin clang, just fallback
Commit-ID:  872523233d640c21ce13ea51269c5c031ebb2f78
Gitweb: https://git.kernel.org/tip/872523233d640c21ce13ea51269c5c031ebb2f78
Author: Arnaldo Carvalho de Melo <acme@redhat.com>
AuthorDate: Thu, 18 Jan 2018 13:07:00 -0300
Committer: Arnaldo Carvalho de Melo <acme@redhat.com>
CommitDate: Thu, 18 Jan 2018 13:07:00 -0300

perf bpf: Don't warn about unavailability of builtin clang, just fallback

When clang is not linked with 'perf' we should just add a debug message
about that before doing the fallback to calling the external compiler.

I.e. just the "-95" warning below gets turned into a debug message:

# cat sys_enter_open.c
#include "bpf.h"

SEC("syscalls:sys_enter_open")
int func(void *ctx)
{
struct {
char *ptr;
char path[256];
} filename = {
.ptr = *((char **)(ctx + 16)),
};
int len = bpf_probe_read_str(filename.path, sizeof(filename.path), filename.ptr);
if (len > 0) {
if (len == 1)
perf_event_output(ctx, &__bpf_stdout__, BPF_F_CURRENT_CPU, &filename, len + sizeof(filename.ptr));
else if (len < 256)
perf_event_output(ctx, &__bpf_stdout__, BPF_F_CURRENT_CPU, &filename, len + sizeof(filename.ptr));
}
return 0;
}
# trace -e open,sys_enter_open.c
bpf: builtin compilation failed: -95, try external compiler
0.000 ( ): __bpf_stdout__:@......./proc/self/task/11160/comm..)
0.014 ( 0.116 ms): qemu-system-x8/6721 open(filename: /proc/self/task/11160/comm, flags: RDWR) = 91
2335.411 ( ): __bpf_stdout__:FB..~.../etc/resolv.conf....)
2335.421 ( 0.030 ms): chronyd/883 open(filename: /etc/resolv.conf, flags: CLOEXEC) = 5
^C#

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Wang Nan <wangnan0@huawei.com>
Link: https://lkml.kernel.org/n/tip-z5aak9oay448ffj37giz94yr@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
tools/perf/util/bpf-loader.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/perf/util/bpf-loader.c b/tools/perf/util/bpf-loader.c
index 72c107f..ab2598a 100644
--- a/tools/perf/util/bpf-loader.c
+++ b/tools/perf/util/bpf-loader.c
@@ -94,7 +94,7 @@ struct bpf_object *bpf__prepare_load(const char *filename, bool source)
err = perf_clang__compile_bpf(filename, &obj_buf, &obj_buf_sz);
perf_clang__cleanup();
if (err) {
- pr_warning("bpf: builtin compilation failed: %d, try external compiler\n", err);
+ pr_debug("bpf: builtin compilation failed: %d, try external compiler\n", err);
err = llvm__compile_bpf(filename, &obj_buf, &obj_buf_sz);
if (err)
return ERR_PTR(-BPF_LOADER_ERRNO__COMPILE);
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