diff options
| -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 eb71ec794732..82d93ea13c0c 100644 --- a/arch/x86/include/asm/processor.h +++ b/arch/x86/include/asm/processor.h | |||
| @@ -893,7 +893,13 @@ extern unsigned long thread_saved_pc(struct task_struct *tsk); | |||
| 893 | 893 | ||
| 894 | #else | 894 | #else |
| 895 | /* | 895 | /* |
| 896 | * User space process size. 47bits minus one guard page. | 896 | * User space process size. 47bits minus one guard page. The guard |
| 897 | * page is necessary on Intel CPUs: if a SYSCALL instruction is at | ||
| 898 | * the highest possible canonical userspace address, then that | ||
| 899 | * syscall will enter the kernel with a non-canonical return | ||
| 900 | * address, and SYSRET will explode dangerously. We avoid this | ||
| 901 | * particular problem by preventing anything from being mapped | ||
| 902 | * at the maximum canonical address. | ||
| 897 | */ | 903 | */ |
| 898 | #define TASK_SIZE_MAX ((1UL << 47) - PAGE_SIZE) | 904 | #define TASK_SIZE_MAX ((1UL << 47) - PAGE_SIZE) |
| 899 | 905 | ||