kbuild: add '-fno-stack-check' to kernel build options
authorLinus Torvalds <torvalds@linux-foundation.org>
Sat, 30 Dec 2017 01:34:43 +0000 (17:34 -0800)
committerLinus Torvalds <torvalds@linux-foundation.org>
Sat, 30 Dec 2017 17:38:03 +0000 (09:38 -0800)
commit3ce120b16cc548472f80cf8644f90eda958cf1b6
tree5e6c193f0c5b2b0985fdaab3c36d4c5a5cc49842
parent5aa90a84589282b87666f92b6c3c917c8080a9bf
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: Alexander Tsoy <alexander@tsoy.me>
Reported-and-tested-by: Toralf 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: Linus Torvalds <torvalds@linux-foundation.org>
Makefile