diff options
author | Anders Roxell <anders.roxell@linaro.org> | 2016-08-10 12:11:15 +0200 |
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committer | Anders Roxell <anders.roxell@linaro.org> | 2016-08-10 12:11:15 +0200 |
commit | a44038112d3379f49df8a9db3e1259d9e945faee (patch) | |
tree | 198f8ef7dcba389b87dbd3cac861d896b5bfd77d /arch/x86/include/asm/thread_info.h | |
parent | 590e935df0c94b2d7a4584bb26906666176a6133 (diff) | |
parent | 0e790100f1c49f32a390d0cc55801230fd04ba56 (diff) |
Merge remote-tracking branch 'lsk/linux-linaro-lsk-v3.18' into linux-linaro-lsk-v3.18-rtlsk-v3.18-16.09-rtlinux-linaro-lsk-v3.18-rt-test
Signed-off-by: Anders Roxell <anders.roxell@linaro.org>
Conflicts:
kernel/futex.c
kernel/printk/printk.c
kernel/softirq.c
mm/slub.c
mm/swap.c
Diffstat (limited to 'arch/x86/include/asm/thread_info.h')
-rw-r--r-- | arch/x86/include/asm/thread_info.h | 27 |
1 files changed, 27 insertions, 0 deletions
diff --git a/arch/x86/include/asm/thread_info.h b/arch/x86/include/asm/thread_info.h index 223b9f0d463f..766fa5cc15b4 100644 --- a/arch/x86/include/asm/thread_info.h +++ b/arch/x86/include/asm/thread_info.h @@ -13,6 +13,33 @@ #include <asm/types.h> /* + * TOP_OF_KERNEL_STACK_PADDING is a number of unused bytes that we + * reserve at the top of the kernel stack. We do it because of a nasty + * 32-bit corner case. On x86_32, the hardware stack frame is + * variable-length. Except for vm86 mode, struct pt_regs assumes a + * maximum-length frame. If we enter from CPL 0, the top 8 bytes of + * pt_regs don't actually exist. Ordinarily this doesn't matter, but it + * does in at least one case: + * + * If we take an NMI early enough in SYSENTER, then we can end up with + * pt_regs that extends above sp0. On the way out, in the espfix code, + * we can read the saved SS value, but that value will be above sp0. + * Without this offset, that can result in a page fault. (We are + * careful that, in this case, the value we read doesn't matter.) + * + * In vm86 mode, the hardware frame is much longer still, but we neither + * access the extra members from NMI context, nor do we write such a + * frame at sp0 at all. + * + * x86_64 has a fixed-length stack frame. + */ +#ifdef CONFIG_X86_32 +# define TOP_OF_KERNEL_STACK_PADDING 8 +#else +# define TOP_OF_KERNEL_STACK_PADDING 0 +#endif + +/* * low level task data that entry.S needs immediate access to * - this struct should fit entirely inside of one cache line * - this struct shares the supervisor stack pages |