2015-11-19 07:46:28

by Wang Nan

Subject: [PATCH] tools build: Clean CFLAGS and LDFLAGS for fixdep

Sometimes variables passed to tools/build is dangerous. For example, on
my platform there is a gcc problem (gcc 4.8.1):

It passes stackprotector-all feature check:
$ gcc -fstack-protector-all./test.c
$ echo $?
0

But requires LDFLAGS support if separete compiling and linking:
$ gcc -fstack-protector-all -c ./test.c
$ gcc ./test.o
./test.o: In function `main':
test.c:(.text+0xb): undefined reference to `__stack_chk_guard'
test.c:(.text+0x21): undefined reference to `__stack_chk_guard'
collect2: error: ld returned 1 exit status
$ gcc -fstack-protector-all ./test.o
$ echo $?
0
$ gcc ./test.o -lssp
$ echo $?
0

In this environment perf building throws an error:

$ make
BUILD: Doing 'make -j24' parallel build
config/Makefile:344: No libunwind found. Please install libunwind-dev[el] >= 1.1 and/or set LIBUNWIND_DIR
config/Makefile:403: No libaudit.h found, disables 'trace' tool, please install audit-libs-devel or libaudit-dev
config/Makefile:418: slang not found, disables TUI support. Please install slang-devel or libslang-dev
config/Makefile:432: GTK2 not found, disables GTK2 support. Please install gtk2-devel or libgtk2.0-dev
config/Makefile:564: No bfd.h/libbfd found, please install binutils-dev[el]/zlib-static/libiberty-dev to gain symbol demangling
config/Makefile:606: No numa.h found, disables 'perf bench numa mem' benchmark, please install numactl-devel/libnuma-devel/libnuma-dev
CC fixdep.o
LD fixdep-in.o
LINK fixdep
fixdep-in.o: In function `parse_dep_file':
/kernel/tools/build/fixdep.c:47: undefined reference to `__stack_chk_guard'
/kernel/tools/build/fixdep.c:117: undefined reference to `__stack_chk_guard'
fixdep-in.o: In function `main':
/kernel-hydrogen/tools/build/fixdep.c:156: undefined reference to `__stack_chk_guard'
/kernel/tools/build/fixdep.c:168: undefined reference to `__stack_chk_guard'
collect2: error: ld returned 1 exit status
make[2]: *** [fixdep] Error 1
make[1]: *** [fixdep] Error 2
make: *** [all] Error 2

This is because CFLAGS in perf building pollutes CFLAGS used for fixdep,
passes -fstack-protector-all to fixdep builder which is obviously not
required. Since fixdep is a small host side tool, we should keep its
CFLAGS/LDFLAGS simple anc clean.

This patch clear CFLAGS and LDFLAGS passed to fixdep building, so such
gcc problem won't block perf building.

Signed-off-by: Wang Nan <[email protected]>
Cc: Arnaldo Carvalho de Melo <[email protected]>
Cc: Jiri Olsa <[email protected]>
---
tools/build/Makefile.include | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/build/Makefile.include b/tools/build/Makefile.include
index 4e09ad6..6254760 100644
--- a/tools/build/Makefile.include
+++ b/tools/build/Makefile.include
@@ -4,7 +4,7 @@ ifdef CROSS_COMPILE
fixdep:
else
fixdep:
- $(Q)$(MAKE) -C $(srctree)/tools/build fixdep
+ $(Q)$(MAKE) -C $(srctree)/tools/build CFLAGS= LDFLAGS= fixdep
endif

.PHONY: fixdep
--
1.8.3.4

2015-11-19 14:14:25

by Jiri Olsa

Subject: Re: [PATCH] tools build: Clean CFLAGS and LDFLAGS for fixdep

On Thu, Nov 19, 2015 at 07:46:01AM +0000, Wang Nan wrote:

SNIP

>
> This is because CFLAGS in perf building pollutes CFLAGS used for fixdep,
> passes -fstack-protector-all to fixdep builder which is obviously not
> required. Since fixdep is a small host side tool, we should keep its
> CFLAGS/LDFLAGS simple anc clean.
>
> This patch clear CFLAGS and LDFLAGS passed to fixdep building, so such
> gcc problem won't block perf building.
>
> Signed-off-by: Wang Nan <[email protected]>
> Cc: Arnaldo Carvalho de Melo <[email protected]>
> Cc: Jiri Olsa <[email protected]>

Acked-by: Jiri Olsa <[email protected]>

thanks,
jirka