Re: [PATCH v2 3/6] powerpc: Book3S 64-bit outline-only KASAN support

Hi,

On Wed, May 18, 2022 at 08:05:31PM +1000, Paul Mackerras wrote:

From: Daniel Axtens <redacted>

Implement a limited form of KASAN for Book3S 64-bit machines running under
the Radix MMU, supporting only outline mode.

 - Enable the compiler instrumentation to check addresses and maintain the
   shadow region. (This is the guts of KASAN which we can easily reuse.)

 - Require kasan-vmalloc support to handle modules and anything else in
   vmalloc space.

 - KASAN needs to be able to validate all pointer accesses, but we can't
   instrument all kernel addresses - only linear map and vmalloc. On boot,
   set up a single page of read-only shadow that marks all iomap and
   vmemmap accesses as valid.

 - Document KASAN in powerpc docs.

With this patch applied, powerpc:allmodconfig builds fail as follows.

Building powerpc:allmodconfig ... failed
--------------
Error log:
Error: External symbol 'memset' referenced from prom_init.c
make[3]: [arch/powerpc/kernel/Makefile:202: arch/powerpc/kernel/prom_init_check] Error 1 (ignored)
powerpc64-linux-ld: drivers/gpu/drm/amd/amdgpu/../display/dc/dml/display_mode_lib.o uses hard float, drivers/gpu/drm/amd/amdgpu/../display/dc/dcn31/dcn31_resource.o uses soft float
powerpc64-linux-ld: failed to merge target specific data of file drivers/gpu/drm/amd/amdgpu/../display/dc/dcn31/dcn31_resource.o
powerpc64-linux-ld: drivers/gpu/drm/amd/amdgpu/../display/dc/dml/display_mode_lib.o uses hard float, drivers/gpu/drm/amd/amdgpu/../display/dc/dcn315/dcn315_resource.o uses soft float
powerpc64-linux-ld: failed to merge target specific data of file drivers/gpu/drm/amd/amdgpu/../display/dc/dcn315/dcn315_resource.o
powerpc64-linux-ld: drivers/gpu/drm/amd/amdgpu/../display/dc/dml/display_mode_lib.o uses hard float, drivers/gpu/drm/amd/amdgpu/../display/dc/dcn316/dcn316_resource.o uses soft float
powerpc64-linux-ld: failed to merge target specific data of file drivers/gpu/drm/amd/amdgpu/../display/dc/dcn316/dcn316_resource.o
make[5]: [scripts/Makefile.build:435: drivers/gpu/drm/amd/amdgpu/amdgpu.o] Error 1 (ignored)
make[2]: *** No rule to make target 'drivers/gpu/drm/amd/amdgpu/amdgpu.o', needed by 'modules-only.symvers'.  Stop.
make[1]: [Makefile:1753: modules] Error 2 (ignored)

This is with gcc 11.3 and binutils 2.38. I also tried with gcc 11.2 and
binutils 2.36.1, with the same results.

Reverting this patch fixes the problem.

Guenter