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x86: Add straight-line-speculation mitigation

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[ Upstream commit e463a09af2f0677b9485a7e8e4e70b396b2ffb6f ]

Make use of an upcoming GCC feature to mitigate
straight-line-speculation for x86:

  https://gcc.gnu.org/g:53a643f8568067d7700a9f2facc8ba39974973d3
  https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102952
  https://bugs.llvm.org/show_bug.cgi?id=52323

It's built tested on x86_64-allyesconfig using GCC-12 and GCC-11.

Maintenance overhead of this should be fairly low due to objtool
validation.

Size overhead of all these additional int3 instructions comes to:

     text	   data	    bss	    dec	    hex	filename
  22267751	6933356	2011368	31212475	1dc43bb	defconfig-build/vmlinux
  22804126	6933356	1470696	31208178	1dc32f2	defconfig-build/vmlinux.sls

Or roughly 2.4% additional text.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lore.kernel.org/r/20211204134908.140103474@infradead.org
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Peter Zijlstra
2021-12-04 14:43:44 +01:00
committed by Greg Kroah-Hartman
parent d11f96d0c0
commit 370d33da35
10 changed files with 38 additions and 7 deletions
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3
scripts/Makefile.build
View File

@@ -232,7 +232,8 @@ objtool_args = \
$(if $(CONFIG_GCOV_KERNEL)$(CONFIG_LTO_CLANG), --no-unreachable)\
$(if $(CONFIG_RETPOLINE), --retpoline) \
$(if $(CONFIG_X86_SMAP), --uaccess) \
$(if $(CONFIG_FTRACE_MCOUNT_USE_OBJTOOL), --mcount)
$(if $(CONFIG_FTRACE_MCOUNT_USE_OBJTOOL), --mcount) \
$(if $(CONFIG_SLS), --sls)
ifndef CONFIG_LTO_CLANG

3
scripts/link-vmlinux.sh
View File

@@ -139,6 +139,9 @@ objtool_link()
if [ -n "${CONFIG_X86_SMAP}" ]; then
objtoolopt="${objtoolopt} --uaccess"
fi
if [ -n "${CONFIG_SLS}" ]; then
objtoolopt="${objtoolopt} --sls"
fi
info OBJTOOL ${1}
tools/objtool/objtool ${objtoolcmd} ${objtoolopt} ${1}
fi