diff options
Diffstat (limited to 'arch/x86/entry/calling.h')
| -rw-r--r-- | arch/x86/entry/calling.h | 26 |
1 files changed, 10 insertions, 16 deletions
diff --git a/arch/x86/entry/calling.h b/arch/x86/entry/calling.h index 3ff925b17b7e..1c3b561528fd 100644 --- a/arch/x86/entry/calling.h +++ b/arch/x86/entry/calling.h @@ -244,17 +244,19 @@ For 32-bit we have the following conventions - kernel is built with .Ldone_\@: .endm -.macro RESTORE_CR3 scratch_reg:req save_reg:req +/* Restore CR3 from a kernel context. May restore a user CR3 value. */ +.macro PARANOID_RESTORE_CR3 scratch_reg:req save_reg:req ALTERNATIVE "jmp .Lend_\@", "", X86_FEATURE_PTI - ALTERNATIVE "jmp .Lwrcr3_\@", "", X86_FEATURE_PCID - /* - * KERNEL pages can always resume with NOFLUSH as we do - * explicit flushes. + * If CR3 contained the kernel page tables at the paranoid exception + * entry, then there is nothing to restore as CR3 is not modified while + * handling the exception. */ bt $PTI_USER_PGTABLE_BIT, \save_reg - jnc .Lnoflush_\@ + jnc .Lend_\@ + + ALTERNATIVE "jmp .Lwrcr3_\@", "", X86_FEATURE_PCID /* * Check if there's a pending flush for the user ASID we're @@ -262,20 +264,12 @@ For 32-bit we have the following conventions - kernel is built with */ movq \save_reg, \scratch_reg andq $(0x7FF), \scratch_reg - bt \scratch_reg, THIS_CPU_user_pcid_flush_mask - jnc .Lnoflush_\@ - btr \scratch_reg, THIS_CPU_user_pcid_flush_mask - jmp .Lwrcr3_\@ + jc .Lwrcr3_\@ -.Lnoflush_\@: SET_NOFLUSH_BIT \save_reg .Lwrcr3_\@: - /* - * The CR3 write could be avoided when not changing its value, - * but would require a CR3 read *and* a scratch register. - */ movq \save_reg, %cr3 .Lend_\@: .endm @@ -290,7 +284,7 @@ For 32-bit we have the following conventions - kernel is built with .endm .macro SAVE_AND_SWITCH_TO_KERNEL_CR3 scratch_reg:req save_reg:req .endm -.macro RESTORE_CR3 scratch_reg:req save_reg:req +.macro PARANOID_RESTORE_CR3 scratch_reg:req save_reg:req .endm #endif |