diff options
Diffstat (limited to 'arch/x86/entry/entry_64.S')
| -rw-r--r-- | arch/x86/entry/entry_64.S | 106 |
1 files changed, 93 insertions, 13 deletions
diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S index 273bc5b8d491..99bce319df0c 100644 --- a/arch/x86/entry/entry_64.S +++ b/arch/x86/entry/entry_64.S @@ -212,6 +212,13 @@ entry_SYSCALL_64_fastpath: movq RIP(%rsp), %rcx movq EFLAGS(%rsp), %r11 RESTORE_C_REGS_EXCEPT_RCX_R11 + /* + * This opens a window where we have a user CR3, but are + * running in the kernel. This makes using the CS + * register useless for telling whether or not we need to + * switch CR3 in NMIs. Normal interrupts are OK because + * they are off here. + */ SWITCH_USER_CR3 movq RSP(%rsp), %rsp /* @@ -350,11 +357,25 @@ GLOBAL(int_ret_from_sys_call) syscall_return_via_sysret: /* rcx and r11 are already restored (see code above) */ RESTORE_C_REGS_EXCEPT_RCX_R11 + /* + * This opens a window where we have a user CR3, but are + * running in the kernel. This makes using the CS + * register useless for telling whether or not we need to + * switch CR3 in NMIs. Normal interrupts are OK because + * they are off here. + */ SWITCH_USER_CR3 movq RSP(%rsp), %rsp USERGS_SYSRET64 opportunistic_sysret_failed: + /* + * This opens a window where we have a user CR3, but are + * running in the kernel. This makes using the CS + * register useless for telling whether or not we need to + * switch CR3 in NMIs. Normal interrupts are OK because + * they are off here. + */ SWITCH_USER_CR3 SWAPGS jmp restore_c_regs_and_iret @@ -1059,6 +1080,13 @@ ENTRY(error_entry) cld SAVE_C_REGS 8 SAVE_EXTRA_REGS 8 + /* + * error_entry() always returns with a kernel gsbase and + * CR3. We must also have a kernel CR3/gsbase before + * calling TRACE_IRQS_*. Just unconditionally switch to + * the kernel CR3 here. + */ + SWITCH_KERNEL_CR3 xorl %ebx, %ebx testb $3, CS+8(%rsp) jz .Lerror_kernelspace @@ -1069,7 +1097,6 @@ ENTRY(error_entry) * from user mode due to an IRET fault. */ SWAPGS - SWITCH_KERNEL_CR3 .Lerror_entry_from_usermode_after_swapgs: /* @@ -1122,7 +1149,7 @@ ENTRY(error_entry) * Switch to kernel gsbase: */ SWAPGS - SWITCH_KERNEL_CR3 + /* * Pretend that the exception came from user mode: set up pt_regs * as if we faulted immediately after IRET and clear EBX so that @@ -1222,7 +1249,10 @@ ENTRY(nmi) */ SWAPGS_UNSAFE_STACK - SWITCH_KERNEL_CR3_NO_STACK + /* + * percpu variables are mapped with user CR3, so no need + * to switch CR3 here. + */ cld movq %rsp, %rdx movq PER_CPU_VAR(cpu_current_top_of_stack), %rsp @@ -1256,14 +1286,33 @@ ENTRY(nmi) movq %rsp, %rdi movq $-1, %rsi +#ifdef CONFIG_KAISER + /* Unconditionally use kernel CR3 for do_nmi() */ + /* %rax is saved above, so OK to clobber here */ + movq %cr3, %rax + pushq %rax +#ifdef CONFIG_KAISER_REAL_SWITCH + andq $(~0x1000), %rax +#endif + movq %rax, %cr3 +#endif call do_nmi + /* + * Unconditionally restore CR3. I know we return to + * kernel code that needs user CR3, but do we ever return + * to "user mode" where we need the kernel CR3? + */ +#ifdef CONFIG_KAISER + popq %rax + mov %rax, %cr3 +#endif /* * Return back to user mode. We must *not* do the normal exit - * work, because we don't want to enable interrupts. Fortunately, - * do_nmi doesn't modify pt_regs. + * work, because we don't want to enable interrupts. Do not + * switch to user CR3: we might be going back to kernel code + * that had a user CR3 set. */ - SWITCH_USER_CR3 SWAPGS jmp restore_c_regs_and_iret @@ -1459,23 +1508,54 @@ end_repeat_nmi: ALLOC_PT_GPREGS_ON_STACK /* - * Use paranoid_entry to handle SWAPGS, but no need to use paranoid_exit - * as we should not be calling schedule in NMI context. - * Even with normal interrupts enabled. An NMI should not be - * setting NEED_RESCHED or anything that normal interrupts and - * exceptions might do. + * Use the same approach as paranoid_entry to handle SWAPGS, but + * without CR3 handling since we do that differently in NMIs. No + * need to use paranoid_exit as we should not be calling schedule + * in NMI context. Even with normal interrupts enabled. An NMI + * should not be setting NEED_RESCHED or anything that normal + * interrupts and exceptions might do. */ - call paranoid_entry + cld + SAVE_C_REGS + SAVE_EXTRA_REGS + movl $1, %ebx + movl $MSR_GS_BASE, %ecx + rdmsr + testl %edx, %edx + js 1f /* negative -> in kernel */ + SWAPGS + xorl %ebx, %ebx +1: +#ifdef CONFIG_KAISER + /* Unconditionally use kernel CR3 for do_nmi() */ + /* %rax is saved above, so OK to clobber here */ + movq %cr3, %rax + pushq %rax +#ifdef CONFIG_KAISER_REAL_SWITCH + andq $(~0x1000), %rax +#endif + movq %rax, %cr3 +#endif /* paranoidentry do_nmi, 0; without TRACE_IRQS_OFF */ movq %rsp, %rdi + addq $8, %rdi /* point %rdi at ptregs, fixed up for CR3 */ movq $-1, %rsi call do_nmi + /* + * Unconditionally restore CR3. We might be returning to + * kernel code that needs user CR3, like just just before + * a sysret. + */ +#ifdef CONFIG_KAISER + popq %rax + mov %rax, %cr3 +#endif testl %ebx, %ebx /* swapgs needed? */ jnz nmi_restore nmi_swapgs: - SWITCH_USER_CR3_NO_STACK + /* We fixed up CR3 above, so no need to switch it here */ SWAPGS_UNSAFE_STACK nmi_restore: RESTORE_EXTRA_REGS |