diff options
Diffstat (limited to 'arch/x86/include/asm/mmu_context.h')
-rw-r--r-- | arch/x86/include/asm/mmu_context.h | 55 |
1 files changed, 0 insertions, 55 deletions
diff --git a/arch/x86/include/asm/mmu_context.h b/arch/x86/include/asm/mmu_context.h index 2985d06660aa..47562147e70b 100644 --- a/arch/x86/include/asm/mmu_context.h +++ b/arch/x86/include/asm/mmu_context.h @@ -215,59 +215,4 @@ static inline bool arch_vma_access_permitted(struct vm_area_struct *vma, unsigned long __get_current_cr3_fast(void); -typedef struct { - struct mm_struct *mm; -} temp_mm_state_t; - -/* - * Using a temporary mm allows to set temporary mappings that are not accessible - * by other CPUs. Such mappings are needed to perform sensitive memory writes - * that override the kernel memory protections (e.g., W^X), without exposing the - * temporary page-table mappings that are required for these write operations to - * other CPUs. Using a temporary mm also allows to avoid TLB shootdowns when the - * mapping is torn down. - * - * Context: The temporary mm needs to be used exclusively by a single core. To - * harden security IRQs must be disabled while the temporary mm is - * loaded, thereby preventing interrupt handler bugs from overriding - * the kernel memory protection. - */ -static inline temp_mm_state_t use_temporary_mm(struct mm_struct *mm) -{ - temp_mm_state_t temp_state; - - lockdep_assert_irqs_disabled(); - temp_state.mm = this_cpu_read(cpu_tlbstate.loaded_mm); - switch_mm_irqs_off(NULL, mm, current); - - /* - * If breakpoints are enabled, disable them while the temporary mm is - * used. Userspace might set up watchpoints on addresses that are used - * in the temporary mm, which would lead to wrong signals being sent or - * crashes. - * - * Note that breakpoints are not disabled selectively, which also causes - * kernel breakpoints (e.g., perf's) to be disabled. This might be - * undesirable, but still seems reasonable as the code that runs in the - * temporary mm should be short. - */ - if (hw_breakpoint_active()) - hw_breakpoint_disable(); - - return temp_state; -} - -static inline void unuse_temporary_mm(temp_mm_state_t prev_state) -{ - lockdep_assert_irqs_disabled(); - switch_mm_irqs_off(NULL, prev_state.mm, current); - - /* - * Restore the breakpoints if they were disabled before the temporary mm - * was loaded. - */ - if (hw_breakpoint_active()) - hw_breakpoint_restore(); -} - #endif /* _ASM_X86_MMU_CONTEXT_H */ |