On 8/9/24 10:24 AM, Christophe Leroy wrote:
Le 09/08/2024 à 06:25, Madhavan Srinivasan a écrit :
On 8/6/24 12:24 PM, Christophe Leroy wrote:
Le 05/08/2024 à 10:30, Madhavan Srinivasan a écrit :
Currently exec-target.c file is linked as static and this
post a requirement to install libc dev package to build.
Without it, build-breaks when compiling selftest/powerpc/benchmark.
CC exec_target
/usr/bin/ld: cannot find -lc: No such file or directory
collect2: error: ld returned 1 exit status
exec_target.c is using "syscall" library function which
could be replaced with a inline assembly and the same is
proposed as a fix here.
Suggested-by: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
Signed-off-by: Madhavan Srinivasan <maddy@xxxxxxxxxxxxx>
---
tools/testing/selftests/powerpc/benchmarks/Makefile | 2 +-
.../testing/selftests/powerpc/benchmarks/exec_target.c | 10
++++++++--
2 files changed, 9 insertions(+), 3 deletions(-)
diff --git a/tools/testing/selftests/powerpc/benchmarks/Makefile
b/tools/testing/selftests/powerpc/benchmarks/Makefile
index 1321922038d0..ca4483c238b9 100644
--- a/tools/testing/selftests/powerpc/benchmarks/Makefile
+++ b/tools/testing/selftests/powerpc/benchmarks/Makefile
@@ -18,4 +18,4 @@ $(OUTPUT)/context_switch: LDLIBS += -lpthread
$(OUTPUT)/fork: LDLIBS += -lpthread
-$(OUTPUT)/exec_target: CFLAGS += -static -nostartfiles
+$(OUTPUT)/exec_target: CFLAGS += -nostartfiles
diff --git
a/tools/testing/selftests/powerpc/benchmarks/exec_target.c
b/tools/testing/selftests/powerpc/benchmarks/exec_target.c
index c14b0fc1edde..20027a23b594 100644
--- a/tools/testing/selftests/powerpc/benchmarks/exec_target.c
+++ b/tools/testing/selftests/powerpc/benchmarks/exec_target.c
@@ -7,10 +7,16 @@
*/
#define _GNU_SOURCE
-#include <unistd.h>
#include <sys/syscall.h>
void _start(void)
{
- syscall(SYS_exit, 0);
+ asm volatile (
+ "li %%r0, %[sys_exit];"
+ "li %%r3, 0;"
+ "sc;"
+ :
+ : [sys_exit] "i" (SYS_exit)
+ : "r0", "r3"
+ );
That looks ok because SYS_exit() is not supposed to return, but in
the general case you should take a lot more precautions regarding
which registers get clobbered when using sc.
Maybe it is worth a comment.
ok sure and something like this will help?
+ : "r0", "r3" //clobber registers, r0 - syscall number, r3 -
exit value
Not really.
sc will clobber r0 and r3-r12, also SO bit in CR.
Here the reason why you have no problem with that is that SYS_exit
never returns. At the end, even your "r0" and "r3" clobber are
unnecessary because of that.
ah nice. thanks for the details.
I will add comment and post a v2 soon.
Maddy
Christophe
