lk/linux-kernel-test
1
0
Fork 0
Code Issues Pull Requests Releases Wiki Activity

x86/i386: Make sure stack-protector segment base is cache aligned

Browse Source 
The Intel Optimization Reference Guide says:

	In Intel Atom microarchitecture, the address generation unit
	assumes that the segment base will be 0 by default. Non-zero
	segment base will cause load and store operations to experience
	a delay.
		- If the segment base isn't aligned to a cache line
		  boundary, the max throughput of memory operations is
		  reduced to one [e]very 9 cycles.
	[...]
	Assembly/Compiler Coding Rule 15. (H impact, ML generality)
	For Intel Atom processors, use segments with base set to 0
	whenever possible; avoid non-zero segment base address that is
	not aligned to cache line boundary at all cost.

We can't avoid having a non-zero base for the stack-protector
segment, but we can make it cache-aligned.

Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Cc: <stable@kernel.org>
LKML-Reference: <4AA01893.6000507@goop.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Jeremy Fitzhardinge
2009-09-03 12:27:15 -07:00
committed by Ingo Molnar
parent 23386d63bb
commit 1ea0d14e48
5 changed files with 15 additions and 6 deletions
Download Patch File Download Diff File Expand all files Collapse all files

12
arch/x86/include/asm/processor.h
View File

@@ -403,7 +403,17 @@ extern unsigned long kernel_eflags;
extern asmlinkage void ignore_sysret(void);
#else /* X86_64 */
#ifdef CONFIG_CC_STACKPROTECTOR
DECLARE_PER_CPU(unsigned long, stack_canary);
/*
* Make sure stack canary segment base is cached-aligned:
* "For Intel Atom processors, avoid non zero segment base address
* that is not aligned to cache line boundary at all cost."
* (Optim Ref Manual Assembly/Compiler Coding Rule 15.)
*/
struct stack_canary {
char __pad[20]; /* canary at %gs:20 */
unsigned long canary;
};
DECLARE_PER_CPU(struct stack_canary, stack_canary) ____cacheline_aligned;
#endif
#endif /* X86_64 */