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| author | Linus Torvalds <torvalds@linux-foundation.org> | 2014-12-11 01:24:20 +0300 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2014-12-11 01:24:20 +0300 |
| commit | 3100e448e7d74489a96cb7b45d88fe6962774eaa (patch) | |
| tree | 53e46a702bd191ca43639b560d2bb1d3b0ad18c8 /arch/x86/include/asm/processor.h | |
| parent | c9f861c77269bc9950c16c6404a9476062241671 (diff) | |
| parent | 26893107aa717cd11010f0c278d02535defa1ac9 (diff) | |
| download | linux-3100e448e7d74489a96cb7b45d88fe6962774eaa.tar.xz | |
Merge branch 'x86-vdso-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull x86 vdso updates from Ingo Molnar:
"Various vDSO updates from Andy Lutomirski, mostly cleanups and
reorganization to improve maintainability, but also some
micro-optimizations and robustization changes"
* 'x86-vdso-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
x86_64/vsyscall: Restore orig_ax after vsyscall seccomp
x86_64: Add a comment explaining the TASK_SIZE_MAX guard page
x86_64,vsyscall: Make vsyscall emulation configurable
x86_64, vsyscall: Rewrite comment and clean up headers in vsyscall code
x86_64, vsyscall: Turn vsyscalls all the way off when vsyscall==none
x86,vdso: Use LSL unconditionally for vgetcpu
x86: vdso: Fix build with older gcc
x86_64/vdso: Clean up vgetcpu init and merge the vdso initcalls
x86_64/vdso: Remove jiffies from the vvar page
x86/vdso: Make the PER_CPU segment 32 bits
x86/vdso: Make the PER_CPU segment start out accessed
x86/vdso: Change the PER_CPU segment to use struct desc_struct
x86_64/vdso: Move getcpu code from vsyscall_64.c to vdso/vma.c
x86_64/vsyscall: Move all of the gate_area code to vsyscall_64.c
Diffstat (limited to 'arch/x86/include/asm/processor.h')
| -rw-r--r-- | arch/x86/include/asm/processor.h | 8 |
1 files changed, 7 insertions, 1 deletions
diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h index 25b8de0f21c0..a092a0cce0b7 100644 --- a/arch/x86/include/asm/processor.h +++ b/arch/x86/include/asm/processor.h @@ -894,7 +894,13 @@ extern unsigned long thread_saved_pc(struct task_struct *tsk); #else /* - * User space process size. 47bits minus one guard page. + * User space process size. 47bits minus one guard page. The guard + * page is necessary on Intel CPUs: if a SYSCALL instruction is at + * the highest possible canonical userspace address, then that + * syscall will enter the kernel with a non-canonical return + * address, and SYSRET will explode dangerously. We avoid this + * particular problem by preventing anything from being mapped + * at the maximum canonical address. */ #define TASK_SIZE_MAX ((1UL << 47) - PAGE_SIZE) |