diff options
| author | Joshua Kinard <kumba@gentoo.org> | 2017-01-28 22:24:16 -0500 |
|---|---|---|
| committer | James Hogan <james.hogan@imgtec.com> | 2017-02-14 09:00:23 +0000 |
| commit | 573deec09436c9136fff6d78e0325e052a1ad6be (patch) | |
| tree | f85723490be8ef015f86c7a7e374ec99aae35dba /arch/mips | |
| parent | 93e502b3c2d44dcb964141cbf82930282de8e40b (diff) | |
MIPS: Disable stack checks on MIPS kernels
Disable stack checking on MIPS kernels. Some distribution toolchains
might pass the -fstack-check option to gcc. This results in a
store-doubleword instruction being emitted at the top of all
functions that checks the available stack space. E.g.,
a80000000001d740 <per_cpu_init>:
a80000000001d740: ffa0bfc0 sd zero,-16448(sp)
a80000000001d744: 2405ffc9 li a1,-55
a80000000001d748: 67bdffc0 daddiu sp,sp,-64
Generally, this is undesirable, and especially on the SGI IP27
platform, it will trigger a NULL pointer dereference in
'_raw_spin_lock_irq' during early init.
Signed-off-by: Joshua Kinard <kumba@gentoo.org>
Suggested-by: James Hogan <james.hogan@imgtec.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: "Maciej W. Rozycki" <macro@linux-mips.org>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/15132/
Signed-off-by: James Hogan <james.hogan@imgtec.com>
Diffstat (limited to 'arch/mips')
| -rw-r--r-- | arch/mips/Makefile | 15 |
1 files changed, 15 insertions, 0 deletions
diff --git a/arch/mips/Makefile b/arch/mips/Makefile index 6ea306b28ae9..8ef9c02747fa 100644 --- a/arch/mips/Makefile +++ b/arch/mips/Makefile @@ -131,6 +131,21 @@ cflags-$(CONFIG_CPU_LITTLE_ENDIAN) += $(shell $(CC) -dumpmachine |grep -q 'mips. cflags-$(CONFIG_SB1XXX_CORELIS) += $(call cc-option,-mno-sched-prolog) \ -fno-omit-frame-pointer + +# Some distribution-specific toolchains might pass the -fstack-check +# option during the build, which adds a simple stack-probe at the beginning +# of every function. This stack probe is to ensure that there is enough +# stack space, else a SEGV is generated. This is not desirable for MIPS +# as kernel stacks are small, placed in unmapped virtual memory, and do not +# grow when overflowed. Especially on SGI IP27 platforms, this check will +# lead to a NULL pointer dereference in _raw_spin_lock_irq. +# +# In disassembly, this stack probe appears at the top of a function as: +# sd zero,<offset>(sp) +# Where <offset> is a negative value. +# +cflags-y += -fno-stack-check + # # CPU-dependent compiler/assembler options for optimization. # |