diff options
| -rw-r--r-- | arch/x86/entry/entry_32.S | 114 | ||||
| -rw-r--r-- | arch/x86/kernel/asm-offsets_32.c | 5 |
2 files changed, 56 insertions, 63 deletions
diff --git a/arch/x86/entry/entry_32.S b/arch/x86/entry/entry_32.S index b2e1d44..7b3ec24 100644 --- a/arch/x86/entry/entry_32.S +++ b/arch/x86/entry/entry_32.S @@ -976,51 +976,48 @@ error_code: jmp ret_from_exception END(page_fault) -/* - * Debug traps and NMI can happen at the one SYSENTER instruction - * that sets up the real kernel stack. Check here, since we can't - * allow the wrong stack to be used. - * - * "TSS_sysenter_sp0+12" is because the NMI/debug handler will have - * already pushed 3 words if it hits on the sysenter instruction: - * eflags, cs and eip. - * - * We just load the right stack, and push the three (known) values - * by hand onto the new stack - while updating the return eip past - * the instruction that would have done it for sysenter. - */ -.macro FIX_STACK offset ok label - cmpw $__KERNEL_CS, 4(%esp) - jne \ok -\label: - movl TSS_sysenter_sp0 + \offset(%esp), %esp - pushfl - pushl $__KERNEL_CS - pushl $sysenter_past_esp -.endm - ENTRY(debug) + /* + * #DB can happen at the first instruction of + * entry_SYSENTER_32 or in Xen's SYSENTER prologue. If this + * happens, then we will be running on a very small stack. We + * need to detect this condition and switch to the thread + * stack before calling any C code at all. + * + * If you edit this code, keep in mind that NMIs can happen in here. + */ ASM_CLAC - cmpl $entry_SYSENTER_32, (%esp) - jne debug_stack_correct - FIX_STACK 12, debug_stack_correct, debug_esp_fix_insn -debug_stack_correct: pushl $-1 # mark this as an int SAVE_ALL - TRACE_IRQS_OFF xorl %edx, %edx # error code 0 movl %esp, %eax # pt_regs pointer + + /* Are we currently on the SYSENTER stack? */ + PER_CPU(cpu_tss + CPU_TSS_SYSENTER_stack + SIZEOF_SYSENTER_stack, %ecx) + subl %eax, %ecx /* ecx = (end of SYSENTER_stack) - esp */ + cmpl $SIZEOF_SYSENTER_stack, %ecx + jb .Ldebug_from_sysenter_stack + + TRACE_IRQS_OFF + call do_debug + jmp ret_from_exception + +.Ldebug_from_sysenter_stack: + /* We're on the SYSENTER stack. Switch off. */ + movl %esp, %ebp + movl PER_CPU_VAR(cpu_current_top_of_stack), %esp + TRACE_IRQS_OFF call do_debug + movl %ebp, %esp jmp ret_from_exception END(debug) /* - * NMI is doubly nasty. It can happen _while_ we're handling - * a debug fault, and the debug fault hasn't yet been able to - * clear up the stack. So we first check whether we got an - * NMI on the sysenter entry path, but after that we need to - * check whether we got an NMI on the debug path where the debug - * fault happened on the sysenter path. + * NMI is doubly nasty. It can happen on the first instruction of + * entry_SYSENTER_32 (just like #DB), but it can also interrupt the beginning + * of the #DB handler even if that #DB in turn hit before entry_SYSENTER_32 + * switched stacks. We handle both conditions by simply checking whether we + * interrupted kernel code running on the SYSENTER stack. */ ENTRY(nmi) ASM_CLAC @@ -1031,41 +1028,32 @@ ENTRY(nmi) popl %eax je nmi_espfix_stack #endif - cmpl $entry_SYSENTER_32, (%esp) - je nmi_stack_fixup - pushl %eax - movl %esp, %eax - /* - * Do not access memory above the end of our stack page, - * it might not exist. - */ - andl $(THREAD_SIZE-1), %eax - cmpl $(THREAD_SIZE-20), %eax - popl %eax - jae nmi_stack_correct - cmpl $entry_SYSENTER_32, 12(%esp) - je nmi_debug_stack_check -nmi_stack_correct: - pushl %eax + + pushl %eax # pt_regs->orig_ax SAVE_ALL xorl %edx, %edx # zero error code movl %esp, %eax # pt_regs pointer + + /* Are we currently on the SYSENTER stack? */ + PER_CPU(cpu_tss + CPU_TSS_SYSENTER_stack + SIZEOF_SYSENTER_stack, %ecx) + subl %eax, %ecx /* ecx = (end of SYSENTER_stack) - esp */ + cmpl $SIZEOF_SYSENTER_stack, %ecx + jb .Lnmi_from_sysenter_stack + + /* Not on SYSENTER stack. */ call do_nmi jmp restore_all_notrace -nmi_stack_fixup: - FIX_STACK 12, nmi_stack_correct, 1 - jmp nmi_stack_correct - -nmi_debug_stack_check: - cmpw $__KERNEL_CS, 16(%esp) - jne nmi_stack_correct - cmpl $debug, (%esp) - jb nmi_stack_correct - cmpl $debug_esp_fix_insn, (%esp) - ja nmi_stack_correct - FIX_STACK 24, nmi_stack_correct, 1 - jmp nmi_stack_correct +.Lnmi_from_sysenter_stack: + /* + * We're on the SYSENTER stack. Switch off. No one (not even debug) + * is using the thread stack right now, so it's safe for us to use it. + */ + movl %esp, %ebp + movl PER_CPU_VAR(cpu_current_top_of_stack), %esp + call do_nmi + movl %ebp, %esp + jmp restore_all_notrace #ifdef CONFIG_X86_ESPFIX32 nmi_espfix_stack: diff --git a/arch/x86/kernel/asm-offsets_32.c b/arch/x86/kernel/asm-offsets_32.c index fdeb0ce..ecdc1d2 100644 --- a/arch/x86/kernel/asm-offsets_32.c +++ b/arch/x86/kernel/asm-offsets_32.c @@ -52,6 +52,11 @@ void foo(void) DEFINE(TSS_sysenter_sp0, offsetof(struct tss_struct, x86_tss.sp0) - offsetofend(struct tss_struct, SYSENTER_stack)); + /* Offset from cpu_tss to SYSENTER_stack */ + OFFSET(CPU_TSS_SYSENTER_stack, tss_struct, SYSENTER_stack); + /* Size of SYSENTER_stack */ + DEFINE(SIZEOF_SYSENTER_stack, sizeof(((struct tss_struct *)0)->SYSENTER_stack)); + #if defined(CONFIG_LGUEST) || defined(CONFIG_LGUEST_GUEST) || defined(CONFIG_LGUEST_MODULE) BLANK(); OFFSET(LGUEST_DATA_irq_enabled, lguest_data, irq_enabled); |