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authorKees Cook <keescook@chromium.org>2017-09-02 13:09:45 -0700
committerIngo Molnar <mingo@kernel.org>2017-09-28 09:45:05 +0200
commit564c9cc84e2adf8a6671c1937f0a9fe3da2a4b0e (patch)
tree63777d0d4059d4034caaad6fc0cb34ed842def2d /include/asm-generic
parent30c23f29d2d5e3ce8e24f7dec550b7e15142aaef (diff)
downloadlinux-564c9cc84e2adf8a6671c1937f0a9fe3da2a4b0e.tar.bz2
locking/refcounts, x86/asm: Use unique .text section for refcount exceptions
Using .text.unlikely for refcount exceptions isn't safe because gcc may move entire functions into .text.unlikely (e.g. in6_dev_dev()), which would cause any uses of a protected refcount_t function to stay inline with the function, triggering the protection unconditionally: .section .text.unlikely,"ax",@progbits .type in6_dev_get, @function in6_dev_getx: .LFB4673: .loc 2 4128 0 .cfi_startproc ... lock; incl 480(%rbx) js 111f .pushsection .text.unlikely 111: lea 480(%rbx), %rcx 112: .byte 0x0f, 0xff .popsection 113: This creates a unique .text..refcount section and adds an additional test to the exception handler to WARN in the case of having none of OF, SF, nor ZF set so we can see things like this more easily in the future. The double dot for the section name keeps it out of the TEXT_MAIN macro namespace, to avoid collisions and so it can be put at the end with text.unlikely to keep the cold code together. See commit: cb87481ee89db ("kbuild: linker script do not match C names unless LD_DEAD_CODE_DATA_ELIMINATION is configured") ... which matches C names: [a-zA-Z0-9_] but not ".". Reported-by: Mike Galbraith <efault@gmx.de> Signed-off-by: Kees Cook <keescook@chromium.org> Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org> Cc: Elena <elena.reshetova@intel.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: linux-arch <linux-arch@vger.kernel.org> Fixes: 7a46ec0e2f48 ("locking/refcounts, x86/asm: Implement fast refcount overflow protection") Link: http://lkml.kernel.org/r/1504382986-49301-2-git-send-email-keescook@chromium.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'include/asm-generic')
-rw-r--r--include/asm-generic/vmlinux.lds.h1
1 files changed, 1 insertions, 0 deletions
diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
index 8acfc1e099e1..e549bff87c5b 100644
--- a/include/asm-generic/vmlinux.lds.h
+++ b/include/asm-generic/vmlinux.lds.h
@@ -459,6 +459,7 @@
#define TEXT_TEXT \
ALIGN_FUNCTION(); \
*(.text.hot TEXT_MAIN .text.fixup .text.unlikely) \
+ *(.text..refcount) \
*(.ref.text) \
MEM_KEEP(init.text) \
MEM_KEEP(exit.text) \