Re: [PATCH v2] selftest/powerpc/benchmark: remove requirement libc-dev

[Madhavan Srinivasan]

On 8/13/24 1:11 PM, Michael Ellerman wrote:
Madhavan Srinivasan<ma...@linux.ibm.com>  writes:
Currently exec-target.c file is linked as static and this
post a requirement to install libc dev package to build.
I think specifically the problem is that the test requires a static
libc, which is packaged separately in some distros from the regular libc
headers, am I right?
Thats right
On Fedora the package is glibc-static, as opposed to glibc-devel, which
the tests still require.
So this patch removes the requirement to have glibc-static installed.
Any idea what the package is called on Debian/Ubuntu?
This is what i could find in ubuntu VM, package is "libgcc-13-dev"
Description about this package

Binary package "libgcc-13-dev" in ubuntu noble Noble (24.04) 
libgcc-13-dev GCC support library (development files) This package 
contains the headers and static library files necessary for building C 
programs which use libgcc, libgomp, libquadmath, libssp or libitm.

Maddy

cheers

Without it, build-break 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<m...@ellerman.id.au>
Signed-off-by: Madhavan Srinivasan<ma...@linux.ibm.com>
---
Chnagelog v1:
- Add comment for clobber register and proper list of
   clobber registers as suggested by Michael Ellerman and
   Christophe Leroy

  .../selftests/powerpc/benchmarks/Makefile        |  2 +-
  .../selftests/powerpc/benchmarks/exec_target.c   | 16 ++++++++++++++--
  2 files changed, 15 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..a6408d3f26cd 100644
--- a/tools/testing/selftests/powerpc/benchmarks/exec_target.c
+++ b/tools/testing/selftests/powerpc/benchmarks/exec_target.c
@@ -7,10 +7,22 @@
   */
  
  #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)
+               /*
+                * "sc" will clobber r0, r3-r13, cr0, ctr, xer and memory.
+                * Even though sys_exit never returns, handle clobber
+                * registers.
+                */
+               : "r0", "r3", "r4", "r5", "r6", "r7", "r8", "r9", "r10",
+                 "r11", "r12", "r13", "cr0", "ctr", "xer", "memory"
+       );
  }
--
2.45.2