Commit 3ce120b1 authored by Linus Torvalds's avatar Linus Torvalds

kbuild: add '-fno-stack-check' to kernel build options

It appears that hardened gentoo enables "-fstack-check" by default for
gcc.

That doesn't work _at_all_ for the kernel, because the kernel stack
doesn't act like a user stack at all: it's much smaller, and it doesn't
auto-expand on use.  So the extra "probe one page below the stack" code
generated by -fstack-check just breaks the kernel in horrible ways,
causing infinite double faults etc.

[ I have to say, that the particular code gcc generates looks very
  stupid even for user space where it works, but that's a separate
  issue.  ]
Reported-and-tested-by: 's avatarAlexander Tsoy <alexander@tsoy.me>
Reported-and-tested-by: 's avatarToralf Förster <toralf.foerster@gmx.de>
Cc: stable@kernel.org
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Jiri Kosina <jikos@kernel.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Signed-off-by: 's avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 5aa90a84
......@@ -789,6 +789,9 @@ KBUILD_CFLAGS += $(call cc-disable-warning, pointer-sign)
# disable invalid "can't wrap" optimizations for signed / pointers
KBUILD_CFLAGS += $(call cc-option,-fno-strict-overflow)
# Make sure -fstack-check isn't enabled (like gentoo apparently did)
KBUILD_CFLAGS += $(call cc-option,-fno-stack-check,)
# conserve stack if available
KBUILD_CFLAGS += $(call cc-option,-fconserve-stack)
......
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