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@ellerman.id.au Signed-off-by: Madhavan Srinivasan maddy@linux.ibm.com --- 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" + ); }
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@ellerman.id.au Signed-off-by: Madhavan Srinivasan maddy@linux.ibm.com
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.
Christophe
}
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@ellerman.id.au Signed-off-by: Madhavan Srinivasan maddy@linux.ibm.com
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
Maddy
Christophe
}
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@ellerman.id.au Signed-off-by: Madhavan Srinivasan maddy@linux.ibm.com
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.
Christophe
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@ellerman.id.au Signed-off-by: Madhavan Srinivasan maddy@linux.ibm.com
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
Christophe Leroy christophe.leroy@csgroup.eu writes:
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@ellerman.id.au Signed-off-by: Madhavan Srinivasan maddy@linux.ibm.com
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/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.
That's my fault for just blurting out that diff on slack without thinking about it too hard.
We should probably just add the proper clobbers, in case anyone copies it in future. Which should be:
asm volatile ( "li %%r0, %[sys_exit];" "li %%r3, 0;" "sc;" : : [sys_exit] "i" (SYS_exit) : "r0", "r3", "r4", "r5", "r6", "r7", "r8", "r9", "r10", "r11", "r12", "r13", "cr0", "ctr", "xer", "memory" );
cheers
linux-kselftest-mirror@lists.linaro.org
-
Christophe Leroy -
Madhavan Srinivasan -
Michael Ellerman