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Subject[PATCH net-next] selftests: bpf: modify urandom_read and link it non-statically
Date
After some experiences I found that urandom_read does not need to be
linked statically. When the 'read' syscall call is moved to separate
non-inlined function then bpf_get_stackid() is able to find
the executable in stack trace and extract its build_id from it.

Signed-off-by: Ivan Vecera <ivecera@redhat.com>
---
tools/testing/selftests/bpf/Makefile | 2 +-
tools/testing/selftests/bpf/urandom_read.c | 15 +++++++++++----
2 files changed, 12 insertions(+), 5 deletions(-)

diff --git a/tools/testing/selftests/bpf/Makefile b/tools/testing/selftests/bpf/Makefile
index 2aed37ea61a4..c33900a8fec0 100644
--- a/tools/testing/selftests/bpf/Makefile
+++ b/tools/testing/selftests/bpf/Makefile
@@ -69,7 +69,7 @@ TEST_CUSTOM_PROGS = $(OUTPUT)/urandom_read
all: $(TEST_CUSTOM_PROGS)

$(OUTPUT)/urandom_read: $(OUTPUT)/%: %.c
- $(CC) -o $@ -static $< -Wl,--build-id
+ $(CC) -o $@ $< -Wl,--build-id

BPFOBJ := $(OUTPUT)/libbpf.a

diff --git a/tools/testing/selftests/bpf/urandom_read.c b/tools/testing/selftests/bpf/urandom_read.c
index 9de8b7cb4e6d..db781052758d 100644
--- a/tools/testing/selftests/bpf/urandom_read.c
+++ b/tools/testing/selftests/bpf/urandom_read.c
@@ -7,11 +7,19 @@

#define BUF_SIZE 256

+static __attribute__((noinline))
+void urandom_read(int fd, int count)
+{
+ char buf[BUF_SIZE];
+ int i;
+
+ for (i = 0; i < count; ++i)
+ read(fd, buf, BUF_SIZE);
+}
+
int main(int argc, char *argv[])
{
int fd = open("/dev/urandom", O_RDONLY);
- int i;
- char buf[BUF_SIZE];
int count = 4;

if (fd < 0)
@@ -20,8 +28,7 @@ int main(int argc, char *argv[])
if (argc == 2)
count = atoi(argv[1]);

- for (i = 0; i < count; ++i)
- read(fd, buf, BUF_SIZE);
+ urandom_read(fd, count);

close(fd);
return 0;
--
2.19.2
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