1. 03 Jul, 2019 2 commits
    • Sasha Levin's avatar
      Revert "x86/uaccess, ftrace: Fix ftrace_likely_update() vs. SMAP" · 0d1d9244
      Sasha Levin authored
      This reverts commit b65b70ba, which was
      upstream commit 4a6c91fb.
      
      On Tue, Jun 25, 2019 at 09:39:45AM +0200, Sebastian Andrzej Siewior wrote:
      >Please backport commit e74deb11 to
      >stable _or_ revert the backport of commit 4a6c91fb ("x86/uaccess,
      >ftrace: Fix ftrace_likely_update() vs. SMAP"). It uses
      >user_access_{save|restore}() which has been introduced in the following
      >commit.
      Signed-off-by: default avatarSasha Levin <sashal@kernel.org>
      0d1d9244
    • Nathan Chancellor's avatar
      arm64: Don't unconditionally add -Wno-psabi to KBUILD_CFLAGS · 507ad93a
      Nathan Chancellor authored
      commit fa63da2a upstream.
      
      This is a GCC only option, which warns about ABI changes within GCC, so
      unconditionally adding it breaks Clang with tons of:
      
      warning: unknown warning option '-Wno-psabi' [-Wunknown-warning-option]
      
      and link time failures:
      
      ld.lld: error: undefined symbol: __efistub___stack_chk_guard
      >>> referenced by arm-stub.c:73
      (/home/nathan/cbl/linux/drivers/firmware/efi/libstub/arm-stub.c:73)
      >>>               arm-stub.stub.o:(__efistub_install_memreserve_table)
      in archive ./drivers/firmware/efi/libstub/lib.a
      
      These failures come from the lack of -fno-stack-protector, which is
      added via cc-option in drivers/firmware/efi/libstub/Makefile. When an
      unknown flag is added to KBUILD_CFLAGS, clang will noisily warn that it
      is ignoring the option like above, unlike gcc, who will just error.
      
      $ echo "int main() { return 0; }" > tmp.c
      
      $ clang -Wno-psabi tmp.c; echo $?
      warning: unknown warning option '-Wno-psabi' [-Wunknown-warning-option]
      1 warning generated.
      0
      
      $ gcc -Wsometimes-uninitialized tmp.c; echo $?
      gcc: error: unrecognized command line option
      ‘-Wsometimes-uninitialized’; did you mean ‘-Wmaybe-uninitialized’?
      1
      
      For cc-option to work properly with clang and behave like gcc, -Werror
      is needed, which was done in commit c3f0d0bc ("kbuild, LLVMLinux:
      Add -Werror to cc-option to support clang").
      
      $ clang -Werror -Wno-psabi tmp.c; echo $?
      error: unknown warning option '-Wno-psabi'
      [-Werror,-Wunknown-warning-option]
      1
      
      As a consequence of this, when an unknown flag is unconditionally added
      to KBUILD_CFLAGS, it will cause cc-option to always fail and those flags
      will never get added:
      
      $ clang -Werror -Wno-psabi -fno-stack-protector tmp.c; echo $?
      error: unknown warning option '-Wno-psabi'
      [-Werror,-Wunknown-warning-option]
      1
      
      This can be seen when compiling the whole kernel as some warnings that
      are normally disabled (see below) show up. The full list of flags
      missing from drivers/firmware/efi/libstub are the following (gathered
      from diffing .arm64-stub.o.cmd):
      
      -fno-delete-null-pointer-checks
      -Wno-address-of-packed-member
      -Wframe-larger-than=2048
      -Wno-unused-const-variable
      -fno-strict-overflow
      -fno-merge-all-constants
      -fno-stack-check
      -Werror=date-time
      -Werror=incompatible-pointer-types
      -ffreestanding
      -fno-stack-protector
      
      Use cc-disable-warning so that it gets disabled for GCC and does nothing
      for Clang.
      
      Fixes: ebcc5928 ("arm64: Silence gcc warnings about arch ABI drift")
      Link: https://github.com/ClangBuiltLinux/linux/issues/511Reported-by: default avatarQian Cai <cai@lca.pw>
      Acked-by: default avatarDave Martin <Dave.Martin@arm.com>
      Reviewed-by: default avatarNick Desaulniers <ndesaulniers@google.com>
      Signed-off-by: default avatarNathan Chancellor <natechancellor@gmail.com>
      Signed-off-by: default avatarWill Deacon <will.deacon@arm.com>
      Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
      507ad93a
  2. 25 Jun, 2019 38 commits