diff options
| -rw-r--r-- | arch/x86/entry/entry_32.S | 4 | ||||
| -rw-r--r-- | arch/x86/include/asm/segment.h | 12 |
2 files changed, 14 insertions, 2 deletions
diff --git a/arch/x86/entry/entry_32.S b/arch/x86/entry/entry_32.S index f83ca5aa8b77..3f847d843e47 100644 --- a/arch/x86/entry/entry_32.S +++ b/arch/x86/entry/entry_32.S @@ -172,7 +172,7 @@ ALTERNATIVE "jmp .Lend_\@", "", X86_FEATURE_PTI .if \no_user_check == 0 /* coming from usermode? */ - testl $SEGMENT_RPL_MASK, PT_CS(%esp) + testl $USER_SEGMENT_RPL_MASK, PT_CS(%esp) jz .Lend_\@ .endif /* On user-cr3? */ @@ -217,7 +217,7 @@ testl $X86_EFLAGS_VM, 4*4(%esp) jnz .Lfrom_usermode_no_fixup_\@ #endif - testl $SEGMENT_RPL_MASK, 3*4(%esp) + testl $USER_SEGMENT_RPL_MASK, 3*4(%esp) jnz .Lfrom_usermode_no_fixup_\@ orl $CS_FROM_KERNEL, 3*4(%esp) diff --git a/arch/x86/include/asm/segment.h b/arch/x86/include/asm/segment.h index ac3892920419..6669164abadc 100644 --- a/arch/x86/include/asm/segment.h +++ b/arch/x86/include/asm/segment.h @@ -31,6 +31,18 @@ */ #define SEGMENT_RPL_MASK 0x3 +/* + * When running on Xen PV, the actual privilege level of the kernel is 1, + * not 0. Testing the Requested Privilege Level in a segment selector to + * determine whether the context is user mode or kernel mode with + * SEGMENT_RPL_MASK is wrong because the PV kernel's privilege level + * matches the 0x3 mask. + * + * Testing with USER_SEGMENT_RPL_MASK is valid for both native and Xen PV + * kernels because privilege level 2 is never used. + */ +#define USER_SEGMENT_RPL_MASK 0x2 + /* User mode is privilege level 3: */ #define USER_RPL 0x3 |
