diff options
Diffstat (limited to 'arch/x86/kernel/entry_64.S')
| -rw-r--r-- | arch/x86/kernel/entry_64.S | 972 |
1 files changed, 467 insertions, 505 deletions
diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S index 1d74d161687c..c7b238494b31 100644 --- a/arch/x86/kernel/entry_64.S +++ b/arch/x86/kernel/entry_64.S @@ -14,27 +14,14 @@ * NOTE: This code handles signal-recognition, which happens every time * after an interrupt and after each system call. * - * Normal syscalls and interrupts don't save a full stack frame, this is - * only done for syscall tracing, signals or fork/exec et.al. - * * A note on terminology: - * - top of stack: Architecture defined interrupt frame from SS to RIP + * - iret frame: Architecture defined interrupt frame from SS to RIP * at the top of the kernel process stack. - * - partial stack frame: partially saved registers up to R11. - * - full stack frame: Like partial stack frame, but all register saved. * * Some macro usage: * - CFI macros are used to generate dwarf2 unwind information for better * backtraces. They don't change any code. - * - SAVE_ALL/RESTORE_ALL - Save/restore all registers - * - SAVE_ARGS/RESTORE_ARGS - Save/restore registers that C functions modify. - * There are unfortunately lots of special cases where some registers - * not touched. The macro is a big mess that should be cleaned up. - * - SAVE_REST/RESTORE_REST - Handle the registers not saved by SAVE_ARGS. - * Gives a full stack frame. * - ENTRY/END Define functions in the symbol table. - * - FIXUP_TOP_OF_STACK/RESTORE_TOP_OF_STACK - Fix up the hardware stack - * frame that is otherwise undefined after a SYSCALL * - TRACE_IRQ_* - Trace hard interrupt state for lock debugging. * - idtentry - Define exception entry points. */ @@ -70,10 +57,6 @@ .section .entry.text, "ax" -#ifndef CONFIG_PREEMPT -#define retint_kernel retint_restore_args -#endif - #ifdef CONFIG_PARAVIRT ENTRY(native_usergs_sysret64) swapgs @@ -82,9 +65,9 @@ ENDPROC(native_usergs_sysret64) #endif /* CONFIG_PARAVIRT */ -.macro TRACE_IRQS_IRETQ offset=ARGOFFSET +.macro TRACE_IRQS_IRETQ #ifdef CONFIG_TRACE_IRQFLAGS - bt $9,EFLAGS-\offset(%rsp) /* interrupts off? */ + bt $9,EFLAGS(%rsp) /* interrupts off? */ jnc 1f TRACE_IRQS_ON 1: @@ -116,8 +99,8 @@ ENDPROC(native_usergs_sysret64) call debug_stack_reset .endm -.macro TRACE_IRQS_IRETQ_DEBUG offset=ARGOFFSET - bt $9,EFLAGS-\offset(%rsp) /* interrupts off? */ +.macro TRACE_IRQS_IRETQ_DEBUG + bt $9,EFLAGS(%rsp) /* interrupts off? */ jnc 1f TRACE_IRQS_ON_DEBUG 1: @@ -130,34 +113,7 @@ ENDPROC(native_usergs_sysret64) #endif /* - * C code is not supposed to know about undefined top of stack. Every time - * a C function with an pt_regs argument is called from the SYSCALL based - * fast path FIXUP_TOP_OF_STACK is needed. - * RESTORE_TOP_OF_STACK syncs the syscall state after any possible ptregs - * manipulation. - */ - - /* %rsp:at FRAMEEND */ - .macro FIXUP_TOP_OF_STACK tmp offset=0 - movq PER_CPU_VAR(old_rsp),\tmp - movq \tmp,RSP+\offset(%rsp) - movq $__USER_DS,SS+\offset(%rsp) - movq $__USER_CS,CS+\offset(%rsp) - movq RIP+\offset(%rsp),\tmp /* get rip */ - movq \tmp,RCX+\offset(%rsp) /* copy it to rcx as sysret would do */ - movq R11+\offset(%rsp),\tmp /* get eflags */ - movq \tmp,EFLAGS+\offset(%rsp) - .endm - - .macro RESTORE_TOP_OF_STACK tmp offset=0 - movq RSP+\offset(%rsp),\tmp - movq \tmp,PER_CPU_VAR(old_rsp) - movq EFLAGS+\offset(%rsp),\tmp - movq \tmp,R11+\offset(%rsp) - .endm - -/* - * initial frame state for interrupts (and exceptions without error code) + * empty frame */ .macro EMPTY_FRAME start=1 offset=0 .if \start @@ -173,12 +129,12 @@ ENDPROC(native_usergs_sysret64) * initial frame state for interrupts (and exceptions without error code) */ .macro INTR_FRAME start=1 offset=0 - EMPTY_FRAME \start, SS+8+\offset-RIP - /*CFI_REL_OFFSET ss, SS+\offset-RIP*/ - CFI_REL_OFFSET rsp, RSP+\offset-RIP - /*CFI_REL_OFFSET rflags, EFLAGS+\offset-RIP*/ - /*CFI_REL_OFFSET cs, CS+\offset-RIP*/ - CFI_REL_OFFSET rip, RIP+\offset-RIP + EMPTY_FRAME \start, 5*8+\offset + /*CFI_REL_OFFSET ss, 4*8+\offset*/ + CFI_REL_OFFSET rsp, 3*8+\offset + /*CFI_REL_OFFSET rflags, 2*8+\offset*/ + /*CFI_REL_OFFSET cs, 1*8+\offset*/ + CFI_REL_OFFSET rip, 0*8+\offset .endm /* @@ -186,30 +142,23 @@ ENDPROC(native_usergs_sysret64) * with vector already pushed) */ .macro XCPT_FRAME start=1 offset=0 - INTR_FRAME \start, RIP+\offset-ORIG_RAX - .endm - -/* - * frame that enables calling into C. - */ - .macro PARTIAL_FRAME start=1 offset=0 - XCPT_FRAME \start, ORIG_RAX+\offset-ARGOFFSET - CFI_REL_OFFSET rdi, RDI+\offset-ARGOFFSET - CFI_REL_OFFSET rsi, RSI+\offset-ARGOFFSET - CFI_REL_OFFSET rdx, RDX+\offset-ARGOFFSET - CFI_REL_OFFSET rcx, RCX+\offset-ARGOFFSET - CFI_REL_OFFSET rax, RAX+\offset-ARGOFFSET - CFI_REL_OFFSET r8, R8+\offset-ARGOFFSET - CFI_REL_OFFSET r9, R9+\offset-ARGOFFSET - CFI_REL_OFFSET r10, R10+\offset-ARGOFFSET - CFI_REL_OFFSET r11, R11+\offset-ARGOFFSET + INTR_FRAME \start, 1*8+\offset .endm /* * frame that enables passing a complete pt_regs to a C function. */ .macro DEFAULT_FRAME start=1 offset=0 - PARTIAL_FRAME \start, R11+\offset-R15 + XCPT_FRAME \start, ORIG_RAX+\offset + CFI_REL_OFFSET rdi, RDI+\offset + CFI_REL_OFFSET rsi, RSI+\offset + CFI_REL_OFFSET rdx, RDX+\offset + CFI_REL_OFFSET rcx, RCX+\offset + CFI_REL_OFFSET rax, RAX+\offset + CFI_REL_OFFSET r8, R8+\offset + CFI_REL_OFFSET r9, R9+\offset + CFI_REL_OFFSET r10, R10+\offset + CFI_REL_OFFSET r11, R11+\offset CFI_REL_OFFSET rbx, RBX+\offset CFI_REL_OFFSET rbp, RBP+\offset CFI_REL_OFFSET r12, R12+\offset @@ -218,105 +167,30 @@ ENDPROC(native_usergs_sysret64) CFI_REL_OFFSET r15, R15+\offset .endm -ENTRY(save_paranoid) - XCPT_FRAME 1 RDI+8 - cld - movq %rdi, RDI+8(%rsp) - movq %rsi, RSI+8(%rsp) - movq_cfi rdx, RDX+8 - movq_cfi rcx, RCX+8 - movq_cfi rax, RAX+8 - movq %r8, R8+8(%rsp) - movq %r9, R9+8(%rsp) - movq %r10, R10+8(%rsp) - movq %r11, R11+8(%rsp) - movq_cfi rbx, RBX+8 - movq %rbp, RBP+8(%rsp) - movq %r12, R12+8(%rsp) - movq %r13, R13+8(%rsp) - movq %r14, R14+8(%rsp) - movq %r15, R15+8(%rsp) - movl $1,%ebx - movl $MSR_GS_BASE,%ecx - rdmsr - testl %edx,%edx - js 1f /* negative -> in kernel */ - SWAPGS - xorl %ebx,%ebx -1: ret - CFI_ENDPROC -END(save_paranoid) - /* - * A newly forked process directly context switches into this address. + * 64bit SYSCALL instruction entry. Up to 6 arguments in registers. * - * rdi: prev task we switched from - */ -ENTRY(ret_from_fork) - DEFAULT_FRAME - - LOCK ; btr $TIF_FORK,TI_flags(%r8) - - pushq_cfi $0x0002 - popfq_cfi # reset kernel eflags - - call schedule_tail # rdi: 'prev' task parameter - - GET_THREAD_INFO(%rcx) - - RESTORE_REST - - testl $3, CS-ARGOFFSET(%rsp) # from kernel_thread? - jz 1f - - /* - * By the time we get here, we have no idea whether our pt_regs, - * ti flags, and ti status came from the 64-bit SYSCALL fast path, - * the slow path, or one of the ia32entry paths. - * Use int_ret_from_sys_call to return, since it can safely handle - * all of the above. - */ - jmp int_ret_from_sys_call - -1: - subq $REST_SKIP, %rsp # leave space for volatiles - CFI_ADJUST_CFA_OFFSET REST_SKIP - movq %rbp, %rdi - call *%rbx - movl $0, RAX(%rsp) - RESTORE_REST - jmp int_ret_from_sys_call - CFI_ENDPROC -END(ret_from_fork) - -/* - * System call entry. Up to 6 arguments in registers are supported. + * 64bit SYSCALL saves rip to rcx, clears rflags.RF, then saves rflags to r11, + * then loads new ss, cs, and rip from previously programmed MSRs. + * rflags gets masked by a value from another MSR (so CLD and CLAC + * are not needed). SYSCALL does not save anything on the stack + * and does not change rsp. * - * SYSCALL does not save anything on the stack and does not change the - * stack pointer. However, it does mask the flags register for us, so - * CLD and CLAC are not needed. - */ - -/* - * Register setup: + * Registers on entry: * rax system call number + * rcx return address + * r11 saved rflags (note: r11 is callee-clobbered register in C ABI) * rdi arg0 - * rcx return address for syscall/sysret, C arg3 * rsi arg1 * rdx arg2 - * r10 arg3 (--> moved to rcx for C) + * r10 arg3 (needs to be moved to rcx to conform to C ABI) * r8 arg4 * r9 arg5 - * r11 eflags for syscall/sysret, temporary for C - * r12-r15,rbp,rbx saved by C code, not touched. + * (note: r12-r15,rbp,rbx are callee-preserved in C ABI) * - * Interrupts are off on entry. * Only called from user space. * - * XXX if we had a free scratch register we could save the RSP into the stack frame - * and report it properly in ps. Unfortunately we haven't. - * - * When user can change the frames always force IRET. That is because + * When user can change pt_regs->foo always force IRET. That is because * it deals with uncanonical addresses better. SYSRET has trouble * with them due to bugs in both AMD and Intel CPUs. */ @@ -324,9 +198,15 @@ END(ret_from_fork) ENTRY(system_call) CFI_STARTPROC simple CFI_SIGNAL_FRAME - CFI_DEF_CFA rsp,KERNEL_STACK_OFFSET + CFI_DEF_CFA rsp,0 CFI_REGISTER rip,rcx /*CFI_REGISTER rflags,r11*/ + + /* + * Interrupts are off on entry. + * We do not frame this tiny irq-off block with TRACE_IRQS_OFF/ON, + * it is too small to ever cause noticeable irq latency. + */ SWAPGS_UNSAFE_STACK /* * A hypervisor implementation might want to use a label @@ -335,18 +215,38 @@ ENTRY(system_call) */ GLOBAL(system_call_after_swapgs) - movq %rsp,PER_CPU_VAR(old_rsp) + movq %rsp,PER_CPU_VAR(rsp_scratch) movq PER_CPU_VAR(kernel_stack),%rsp + + /* Construct struct pt_regs on stack */ + pushq_cfi $__USER_DS /* pt_regs->ss */ + pushq_cfi PER_CPU_VAR(rsp_scratch) /* pt_regs->sp */ /* - * No need to follow this irqs off/on section - it's straight - * and short: + * Re-enable interrupts. + * We use 'rsp_scratch' as a scratch space, hence irq-off block above + * must execute atomically in the face of possible interrupt-driven + * task preemption. We must enable interrupts only after we're done + * with using rsp_scratch: */ ENABLE_INTERRUPTS(CLBR_NONE) - SAVE_ARGS 8, 0, rax_enosys=1 - movq_cfi rax,(ORIG_RAX-ARGOFFSET) - movq %rcx,RIP-ARGOFFSET(%rsp) - CFI_REL_OFFSET rip,RIP-ARGOFFSET - testl $_TIF_WORK_SYSCALL_ENTRY,TI_flags+THREAD_INFO(%rsp,RIP-ARGOFFSET) + pushq_cfi %r11 /* pt_regs->flags */ + pushq_cfi $__USER_CS /* pt_regs->cs */ + pushq_cfi %rcx /* pt_regs->ip */ + CFI_REL_OFFSET rip,0 + pushq_cfi_reg rax /* pt_regs->orig_ax */ + pushq_cfi_reg rdi /* pt_regs->di */ + pushq_cfi_reg rsi /* pt_regs->si */ + pushq_cfi_reg rdx /* pt_regs->dx */ + pushq_cfi_reg rcx /* pt_regs->cx */ + pushq_cfi $-ENOSYS /* pt_regs->ax */ + pushq_cfi_reg r8 /* pt_regs->r8 */ + pushq_cfi_reg r9 /* pt_regs->r9 */ + pushq_cfi_reg r10 /* pt_regs->r10 */ + pushq_cfi_reg r11 /* pt_regs->r11 */ + sub $(6*8),%rsp /* pt_regs->bp,bx,r12-15 not saved */ + CFI_ADJUST_CFA_OFFSET 6*8 + + testl $_TIF_WORK_SYSCALL_ENTRY, ASM_THREAD_INFO(TI_flags, %rsp, SIZEOF_PTREGS) jnz tracesys system_call_fastpath: #if __SYSCALL_MASK == ~0 @@ -355,82 +255,96 @@ system_call_fastpath: andl $__SYSCALL_MASK,%eax cmpl $__NR_syscall_max,%eax #endif - ja ret_from_sys_call /* and return regs->ax */ + ja 1f /* return -ENOSYS (already in pt_regs->ax) */ movq %r10,%rcx - call *sys_call_table(,%rax,8) # XXX: rip relative - movq %rax,RAX-ARGOFFSET(%rsp) + call *sys_call_table(,%rax,8) + movq %rax,RAX(%rsp) +1: /* - * Syscall return path ending with SYSRET (fast path) - * Has incomplete stack frame and undefined top of stack. + * Syscall return path ending with SYSRET (fast path). + * Has incompletely filled pt_regs. */ -ret_from_sys_call: - testl $_TIF_ALLWORK_MASK,TI_flags+THREAD_INFO(%rsp,RIP-ARGOFFSET) - jnz int_ret_from_sys_call_fixup /* Go the the slow path */ - LOCKDEP_SYS_EXIT + /* + * We do not frame this tiny irq-off block with TRACE_IRQS_OFF/ON, + * it is too small to ever cause noticeable irq latency. + */ DISABLE_INTERRUPTS(CLBR_NONE) - TRACE_IRQS_OFF - CFI_REMEMBER_STATE + /* - * sysretq will re-enable interrupts: + * We must check ti flags with interrupts (or at least preemption) + * off because we must *never* return to userspace without + * processing exit work that is enqueued if we're preempted here. + * In particular, returning to userspace with any of the one-shot + * flags (TIF_NOTIFY_RESUME, TIF_USER_RETURN_NOTIFY, etc) set is + * very bad. */ - TRACE_IRQS_ON - movq RIP-ARGOFFSET(%rsp),%rcx + testl $_TIF_ALLWORK_MASK, ASM_THREAD_INFO(TI_flags, %rsp, SIZEOF_PTREGS) + jnz int_ret_from_sys_call_irqs_off /* Go to the slow path */ + + CFI_REMEMBER_STATE + + RESTORE_C_REGS_EXCEPT_RCX_R11 + movq RIP(%rsp),%rcx CFI_REGISTER rip,rcx - RESTORE_ARGS 1,-ARG_SKIP,0 + movq EFLAGS(%rsp),%r11 /*CFI_REGISTER rflags,r11*/ - movq PER_CPU_VAR(old_rsp), %rsp + movq RSP(%rsp),%rsp + /* + * 64bit SYSRET restores rip from rcx, + * rflags from r11 (but RF and VM bits are forced to 0), + * cs and ss are loaded from MSRs. + * Restoration of rflags re-enables interrupts. + */ USERGS_SYSRET64 CFI_RESTORE_STATE -int_ret_from_sys_call_fixup: - FIXUP_TOP_OF_STACK %r11, -ARGOFFSET - jmp int_ret_from_sys_call - - /* Do syscall tracing */ + /* Do syscall entry tracing */ tracesys: - leaq -REST_SKIP(%rsp), %rdi - movq $AUDIT_ARCH_X86_64, %rsi + movq %rsp, %rdi + movl $AUDIT_ARCH_X86_64, %esi call syscall_trace_enter_phase1 test %rax, %rax jnz tracesys_phase2 /* if needed, run the slow path */ - LOAD_ARGS 0 /* else restore clobbered regs */ + RESTORE_C_REGS_EXCEPT_RAX /* else restore clobbered regs */ + movq ORIG_RAX(%rsp), %rax jmp system_call_fastpath /* and return to the fast path */ tracesys_phase2: - SAVE_REST - FIXUP_TOP_OF_STACK %rdi + SAVE_EXTRA_REGS movq %rsp, %rdi - movq $AUDIT_ARCH_X86_64, %rsi + movl $AUDIT_ARCH_X86_64, %esi movq %rax,%rdx call syscall_trace_enter_phase2 /* - * Reload arg registers from stack in case ptrace changed them. + * Reload registers from stack in case ptrace changed them. * We don't reload %rax because syscall_trace_entry_phase2() returned * the value it wants us to use in the table lookup. */ - LOAD_ARGS ARGOFFSET, 1 - RESTORE_REST + RESTORE_C_REGS_EXCEPT_RAX + RESTORE_EXTRA_REGS #if __SYSCALL_MASK == ~0 cmpq $__NR_syscall_max,%rax #else andl $__SYSCALL_MASK,%eax cmpl $__NR_syscall_max,%eax #endif - ja int_ret_from_sys_call /* RAX(%rsp) is already set */ + ja 1f /* return -ENOSYS (already in pt_regs->ax) */ movq %r10,%rcx /* fixup for C */ call *sys_call_table(,%rax,8) - movq %rax,RAX-ARGOFFSET(%rsp) - /* Use IRET because user could have changed frame */ + movq %rax,RAX(%rsp) +1: + /* Use IRET because user could have changed pt_regs->foo */ /* * Syscall return path ending with IRET. - * Has correct top of stack, but partial stack frame. + * Has correct iret frame. */ GLOBAL(int_ret_from_sys_call) DISABLE_INTERRUPTS(CLBR_NONE) +int_ret_from_sys_call_irqs_off: /* jumps come here from the irqs-off SYSRET path */ TRACE_IRQS_OFF movl $_TIF_ALLWORK_MASK,%edi /* edi: mask to check */ @@ -440,8 +354,8 @@ GLOBAL(int_with_check) movl TI_flags(%rcx),%edx andl %edi,%edx jnz int_careful - andl $~TS_COMPAT,TI_status(%rcx) - jmp retint_swapgs + andl $~TS_COMPAT,TI_status(%rcx) + jmp syscall_return /* Either reschedule or signal or syscall exit tracking needed. */ /* First do a reschedule test. */ @@ -458,12 +372,11 @@ int_careful: TRACE_IRQS_OFF jmp int_with_check - /* handle signals and tracing -- both require a full stack frame */ + /* handle signals and tracing -- both require a full pt_regs */ int_very_careful: TRACE_IRQS_ON ENABLE_INTERRUPTS(CLBR_NONE) -int_check_syscall_exit_work: - SAVE_REST + SAVE_EXTRA_REGS /* Check for syscall exit trace */ testl $_TIF_WORK_SYSCALL_EXIT,%edx jz int_signal @@ -482,86 +395,192 @@ int_signal: call do_notify_resume 1: movl $_TIF_WORK_MASK,%edi int_restore_rest: - RESTORE_REST + RESTORE_EXTRA_REGS DISABLE_INTERRUPTS(CLBR_NONE) TRACE_IRQS_OFF jmp int_with_check + +syscall_return: + /* The IRETQ could re-enable interrupts: */ + DISABLE_INTERRUPTS(CLBR_ANY) + TRACE_IRQS_IRETQ + + /* + * Try to use SYSRET instead of IRET if we're returning to + * a completely clean 64-bit userspace context. + */ + movq RCX(%rsp),%rcx + cmpq %rcx,RIP(%rsp) /* RCX == RIP */ + jne opportunistic_sysret_failed + + /* + * On Intel CPUs, SYSRET with non-canonical RCX/RIP will #GP + * in kernel space. This essentially lets the user take over + * the kernel, since userspace controls RSP. It's not worth + * testing for canonicalness exactly -- this check detects any + * of the 17 high bits set, which is true for non-canonical + * or kernel addresses. (This will pessimize vsyscall=native. + * Big deal.) + * + * If virtual addresses ever become wider, this will need + * to be updated to remain correct on both old and new CPUs. + */ + .ifne __VIRTUAL_MASK_SHIFT - 47 + .error "virtual address width changed -- SYSRET checks need update" + .endif + shr $__VIRTUAL_MASK_SHIFT, %rcx + jnz opportunistic_sysret_failed + + cmpq $__USER_CS,CS(%rsp) /* CS must match SYSRET */ + jne opportunistic_sysret_failed + + movq R11(%rsp),%r11 + cmpq %r11,EFLAGS(%rsp) /* R11 == RFLAGS */ + jne opportunistic_sysret_failed + + /* + * SYSRET can't restore RF. SYSRET can restore TF, but unlike IRET, + * restoring TF results in a trap from userspace immediately after + * SYSRET. This would cause an infinite loop whenever #DB happens + * with register state that satisfies the opportunistic SYSRET + * conditions. For example, single-stepping this user code: + * + * movq $stuck_here,%rcx + * pushfq + * popq %r11 + * stuck_here: + * + * would never get past 'stuck_here'. + */ + testq $(X86_EFLAGS_RF|X86_EFLAGS_TF), %r11 + jnz opportunistic_sysret_failed + + /* nothing to check for RSP */ + + cmpq $__USER_DS,SS(%rsp) /* SS must match SYSRET */ + jne opportunistic_sysret_failed + + /* + * We win! This label is here just for ease of understanding + * perf profiles. Nothing jumps here. + */ +syscall_return_via_sysret: + CFI_REMEMBER_STATE + /* r11 is already restored (see code above) */ + RESTORE_C_REGS_EXCEPT_R11 + movq RSP(%rsp),%rsp + USERGS_SYSRET64 + CFI_RESTORE_STATE + +opportunistic_sysret_failed: + SWAPGS + jmp restore_c_regs_and_iret CFI_ENDPROC END(system_call) + .macro FORK_LIKE func ENTRY(stub_\func) CFI_STARTPROC - popq %r11 /* save return address */ - PARTIAL_FRAME 0 - SAVE_REST - pushq %r11 /* put it back on stack */ - FIXUP_TOP_OF_STACK %r11, 8 - DEFAULT_FRAME 0 8 /* offset 8: return address */ - call sys_\func - RESTORE_TOP_OF_STACK %r11, 8 - ret $REST_SKIP /* pop extended registers */ + DEFAULT_FRAME 0, 8 /* offset 8: return address */ + SAVE_EXTRA_REGS 8 + jmp sys_\func CFI_ENDPROC END(stub_\func) .endm - .macro FIXED_FRAME label,func -ENTRY(\label) - CFI_STARTPROC - PARTIAL_FRAME 0 8 /* offset 8: return address */ - FIXUP_TOP_OF_STACK %r11, 8-ARGOFFSET - call \func - RESTORE_TOP_OF_STACK %r11, 8-ARGOFFSET - ret - CFI_ENDPROC -END(\label) - .endm - FORK_LIKE clone FORK_LIKE fork FORK_LIKE vfork - FIXED_FRAME stub_iopl, sys_iopl ENTRY(stub_execve) CFI_STARTPROC - addq $8, %rsp - PARTIAL_FRAME 0 - SAVE_REST - FIXUP_TOP_OF_STACK %r11 - call sys_execve - movq %rax,RAX(%rsp) - RESTORE_REST - jmp int_ret_from_sys_call + DEFAULT_FRAME 0, 8 + call sys_execve +return_from_execve: + testl %eax, %eax + jz 1f + /* exec failed, can use fast SYSRET code path in this case */ + ret +1: + /* must use IRET code path (pt_regs->cs may have changed) */ + addq $8, %rsp + CFI_ADJUST_CFA_OFFSET -8 + ZERO_EXTRA_REGS + movq %rax,RAX(%rsp) + jmp int_ret_from_sys_call CFI_ENDPROC END(stub_execve) - -ENTRY(stub_execveat) +/* + * Remaining execve stubs are only 7 bytes long. + * ENTRY() often aligns to 16 bytes, which in this case has no benefits. + */ + .align 8 +GLOBAL(stub_execveat) CFI_STARTPROC - addq $8, %rsp - PARTIAL_FRAME 0 - SAVE_REST - FIXUP_TOP_OF_STACK %r11 - call sys_execveat - RESTORE_TOP_OF_STACK %r11 - movq %rax,RAX(%rsp) - RESTORE_REST - jmp int_ret_from_sys_call + DEFAULT_FRAME 0, 8 + call sys_execveat + jmp return_from_execve CFI_ENDPROC END(stub_execveat) +#ifdef CONFIG_X86_X32_ABI + .align 8 +GLOBAL(stub_x32_execve) + CFI_STARTPROC + DEFAULT_FRAME 0, 8 + call compat_sys_execve + jmp return_from_execve + CFI_ENDPROC +END(stub_x32_execve) + .align 8 +GLOBAL(stub_x32_execveat) + CFI_STARTPROC + DEFAULT_FRAME 0, 8 + call compat_sys_execveat + jmp return_from_execve + CFI_ENDPROC +END(stub_x32_execveat) +#endif + +#ifdef CONFIG_IA32_EMULATION + .align 8 +GLOBAL(stub32_execve) + CFI_STARTPROC + call compat_sys_execve + jmp return_from_execve + CFI_ENDPROC +END(stub32_execve) + .align 8 +GLOBAL(stub32_execveat) + CFI_STARTPROC + call compat_sys_execveat + jmp return_from_execve + CFI_ENDPROC +END(stub32_execveat) +#endif + /* * sigreturn is special because it needs to restore all registers on return. * This cannot be done with SYSRET, so use the IRET return path instead. */ ENTRY(stub_rt_sigreturn) CFI_STARTPROC - addq $8, %rsp - PARTIAL_FRAME 0 - SAVE_REST - FIXUP_TOP_OF_STACK %r11 + DEFAULT_FRAME 0, 8 + /* + * SAVE_EXTRA_REGS result is not normally needed: + * sigreturn overwrites all pt_regs->GPREGS. + * But sigreturn can fail (!), and there is no easy way to detect that. + * To make sure RESTORE_EXTRA_REGS doesn't restore garbage on error, + * we SAVE_EXTRA_REGS here. + */ + SAVE_EXTRA_REGS 8 call sys_rt_sigreturn - movq %rax,RAX(%rsp) # fixme, this could be done at the higher layer - RESTORE_REST +return_from_stub: + addq $8, %rsp + CFI_ADJUST_CFA_OFFSET -8 + RESTORE_EXTRA_REGS + movq %rax,RAX(%rsp) jmp int_ret_from_sys_call CFI_ENDPROC END(stub_rt_sigreturn) @@ -569,86 +588,70 @@ END(stub_rt_sigreturn) #ifdef CONFIG_X86_X32_ABI ENTRY(stub_x32_rt_sigreturn) CFI_STARTPROC - addq $8, %rsp - PARTIAL_FRAME 0 - SAVE_REST - FIXUP_TOP_OF_STACK %r11 + DEFAULT_FRAME 0, 8 + SAVE_EXTRA_REGS 8 call sys32_x32_rt_sigreturn - movq %rax,RAX(%rsp) # fixme, this could be done at the higher layer - RESTORE_REST - jmp int_ret_from_sys_call + jmp return_from_stub CFI_ENDPROC END(stub_x32_rt_sigreturn) +#endif -ENTRY(stub_x32_execve) - CFI_STARTPROC - addq $8, %rsp - PARTIAL_FRAME 0 - SAVE_REST - FIXUP_TOP_OF_STACK %r11 - call compat_sys_execve - RESTORE_TOP_OF_STACK %r11 - movq %rax,RAX(%rsp) - RESTORE_REST - jmp int_ret_from_sys_call - CFI_ENDPROC -END(stub_x32_execve) +/* + * A newly forked process directly context switches into this address. + * + * rdi: prev task we switched from + */ +ENTRY(ret_from_fork) + DEFAULT_FRAME -ENTRY(stub_x32_execveat) - CFI_STARTPROC - addq $8, %rsp - PARTIAL_FRAME 0 - SAVE_REST - FIXUP_TOP_OF_STACK %r11 - call compat_sys_execveat - RESTORE_TOP_OF_STACK %r11 - movq %rax,RAX(%rsp) - RESTORE_REST + LOCK ; btr $TIF_FORK,TI_flags(%r8) + + pushq_cfi $0x0002 + popfq_cfi # reset kernel eflags + + call schedule_tail # rdi: 'prev' task parameter + + RESTORE_EXTRA_REGS + + testl $3,CS(%rsp) # from kernel_thread? + + /* + * By the time we get here, we have no idea whether our pt_regs, + * ti flags, and ti status came from the 64-bit SYSCALL fast path, + * the slow path, or one of the ia32entry paths. + * Use IRET code path to return, since it can safely handle + * all of the above. + */ + jnz int_ret_from_sys_call + + /* We came from kernel_thread */ + /* nb: we depend on RESTORE_EXTRA_REGS above */ + movq %rbp, %rdi + call *%rbx + movl $0, RAX(%rsp) + RESTORE_EXTRA_REGS jmp int_ret_from_sys_call CFI_ENDPROC -END(stub_x32_execveat) - -#endif +END(ret_from_fork) /* - * Build the entry stubs and pointer table with some assembler magic. - * We pack 7 stubs into a single 32-byte chunk, which will fit in a - * single cache line on all modern x86 implementations. + * Build the entry stubs with some assembler magic. + * We pack 1 stub into every 8-byte block. */ - .section .init.rodata,"a" -ENTRY(interrupt) - .section .entry.text - .p2align 5 - .p2align CONFIG_X86_L1_CACHE_SHIFT + .align 8 ENTRY(irq_entries_start) INTR_FRAME -vector=FIRST_EXTERNAL_VECTOR -.rept (FIRST_SYSTEM_VECTOR-FIRST_EXTERNAL_VECTOR+6)/7 - .balign 32 - .rept 7 - .if vector < FIRST_SYSTEM_VECTOR - .if vector <> FIRST_EXTERNAL_VECTOR + vector=FIRST_EXTERNAL_VECTOR + .rept (FIRST_SYSTEM_VECTOR - FIRST_EXTERNAL_VECTOR) + pushq_cfi $(~vector+0x80) /* Note: always in signed byte range */ + vector=vector+1 + jmp common_interrupt CFI_ADJUST_CFA_OFFSET -8 - .endif -1: pushq_cfi $(~vector+0x80) /* Note: always in signed byte range */ - .if ((vector-FIRST_EXTERNAL_VECTOR)%7) <> 6 - jmp 2f - .endif - .previous - .quad 1b - .section .entry.text -vector=vector+1 - .endif - .endr -2: jmp common_interrupt -.endr + .align 8 + .endr CFI_ENDPROC END(irq_entries_start) -.previous -END(interrupt) -.previous - /* * Interrupt entry/exit. * @@ -659,47 +662,45 @@ END(interrupt) /* 0(%rsp): ~(interrupt number) */ .macro interrupt func - /* reserve pt_regs for scratch regs and rbp */ - subq $ORIG_RAX-RBP, %rsp - CFI_ADJUST_CFA_OFFSET ORIG_RAX-RBP cld - /* start from rbp in pt_regs and jump over */ - movq_cfi rdi, (RDI-RBP) - movq_cfi rsi, (RSI-RBP) - movq_cfi rdx, (RDX-RBP) - movq_cfi rcx, (RCX-RBP) - movq_cfi rax, (RAX-RBP) - movq_cfi r8, (R8-RBP) - movq_cfi r9, (R9-RBP) - movq_cfi r10, (R10-RBP) - movq_cfi r11, (R11-RBP) - - /* Save rbp so that we can unwind from get_irq_regs() */ - movq_cfi rbp, 0 - - /* Save previous stack value */ - movq %rsp, %rsi + /* + * Since nothing in interrupt handling code touches r12...r15 members + * of "struct pt_regs", and since interrupts can nest, we can save + * four stack slots and simultaneously provide + * an unwind-friendly stack layout by saving "truncated" pt_regs + * exactly up to rbp slot, without these members. + */ + ALLOC_PT_GPREGS_ON_STACK -RBP + SAVE_C_REGS -RBP + /* this goes to 0(%rsp) for unwinder, not for saving the value: */ + SAVE_EXTRA_REGS_RBP -RBP - leaq -RBP(%rsp),%rdi /* arg1 for handler */ - testl $3, CS-RBP(%rsi) + leaq -RBP(%rsp),%rdi /* arg1 for \func (pointer to pt_regs) */ + + testl $3, CS-RBP(%rsp) je 1f SWAPGS +1: /* + * Save previous stack pointer, optionally switch to interrupt stack. * irq_count is used to check if a CPU is already on an interrupt stack * or not. While this is essentially redundant with preempt_count it is * a little cheaper to use a separate counter in the PDA (short of * moving irq_enter into assembly, which would be too much work) */ -1: incl PER_CPU_VAR(irq_count) + movq %rsp, %rsi + incl PER_CPU_VAR(irq_count) cmovzq PER_CPU_VAR(irq_stack_ptr),%rsp CFI_DEF_CFA_REGISTER rsi - - /* Store previous stack value */ pushq %rsi + /* + * For debugger: + * "CFA (Current Frame Address) is the value on stack + offset" + */ CFI_ESCAPE 0x0f /* DW_CFA_def_cfa_expression */, 6, \ - 0x77 /* DW_OP_breg7 */, 0, \ + 0x77 /* DW_OP_breg7 (rsp) */, 0, \ 0x06 /* DW_OP_deref */, \ - 0x08 /* DW_OP_const1u */, SS+8-RBP, \ + 0x08 /* DW_OP_const1u */, SIZEOF_PTREGS-RBP, \ 0x22 /* DW_OP_plus */ /* We entered an interrupt context - irqs are off: */ TRACE_IRQS_OFF @@ -717,7 +718,7 @@ common_interrupt: ASM_CLAC addq $-0x80,(%rsp) /* Adjust vector to [-256,-1] range */ interrupt do_IRQ - /* 0(%rsp): old_rsp-ARGOFFSET */ + /* 0(%rsp): old RSP */ ret_from_intr: DISABLE_INTERRUPTS(CLBR_NONE) TRACE_IRQS_OFF @@ -725,19 +726,18 @@ ret_from_intr: /* Restore saved previous stack */ popq %rsi - CFI_DEF_CFA rsi,SS+8-RBP /* reg/off reset after def_cfa_expr */ - leaq ARGOFFSET-RBP(%rsi), %rsp + CFI_DEF_CFA rsi,SIZEOF_PTREGS-RBP /* reg/off reset after def_cfa_expr */ + /* return code expects complete pt_regs - adjust rsp accordingly: */ + leaq -RBP(%rsi),%rsp CFI_DEF_CFA_REGISTER rsp - CFI_ADJUST_CFA_OFFSET RBP-ARGOFFSET + CFI_ADJUST_CFA_OFFSET RBP -exit_intr: - GET_THREAD_INFO(%rcx) - testl $3,CS-ARGOFFSET(%rsp) + testl $3,CS(%rsp) je retint_kernel - /* Interrupt came from user space */ + + GET_THREAD_INFO(%rcx) /* - * Has a correct top of stack, but a partial stack frame * %rcx: thread info. Interrupts off. */ retint_with_reschedule: @@ -756,70 +756,34 @@ retint_swapgs: /* return to user-space */ DISABLE_INTERRUPTS(CLBR_ANY) TRACE_IRQS_IRETQ - /* - * Try to use SYSRET instead of IRET if we're returning to - * a completely clean 64-bit userspace context. - */ - movq (RCX-R11)(%rsp), %rcx - cmpq %rcx,(RIP-R11)(%rsp) /* RCX == RIP */ - jne opportunistic_sysret_failed - - /* - * On Intel CPUs, sysret with non-canonical RCX/RIP will #GP - * in kernel space. This essentially lets the user take over - * the kernel, since userspace controls RSP. It's not worth - * testing for canonicalness exactly -- this check detects any - * of the 17 high bits set, which is true for non-canonical - * or kernel addresses. (This will pessimize vsyscall=native. - * Big deal.) - * - * If virtual addresses ever become wider, this will need - * to be updated to remain correct on both old and new CPUs. - */ - .ifne __VIRTUAL_MASK_SHIFT - 47 - .error "virtual address width changed -- sysret checks need update" - .endif - shr $__VIRTUAL_MASK_SHIFT, %rcx - jnz opportunistic_sysret_failed - - cmpq $__USER_CS,(CS-R11)(%rsp) /* CS must match SYSRET */ - jne opportunistic_sysret_failed - - movq (R11-ARGOFFSET)(%rsp), %r11 - cmpq %r11,(EFLAGS-ARGOFFSET)(%rsp) /* R11 == RFLAGS */ - jne opportunistic_sysret_failed - - testq $X86_EFLAGS_RF,%r11 /* sysret can't restore RF */ - jnz opportunistic_sysret_failed - - /* nothing to check for RSP */ - - cmpq $__USER_DS,(SS-ARGOFFSET)(%rsp) /* SS must match SYSRET */ - jne opportunistic_sysret_failed - - /* - * We win! This label is here just for ease of understanding - * perf profiles. Nothing jumps here. - */ -irq_return_via_sysret: - CFI_REMEMBER_STATE - RESTORE_ARGS 1,8,1 - movq (RSP-RIP)(%rsp),%rsp - USERGS_SYSRET64 - CFI_RESTORE_STATE - -opportunistic_sysret_failed: SWAPGS - jmp restore_args + jmp restore_c_regs_and_iret -retint_restore_args: /* return to kernel space */ - DISABLE_INTERRUPTS(CLBR_ANY) +/* Returning to kernel space */ +retint_kernel: +#ifdef CONFIG_PREEMPT + /* Interrupts are off */ + /* Check if we need preemption */ + bt $9,EFLAGS(%rsp) /* interrupts were off? */ + jnc 1f +0: cmpl $0,PER_CPU_VAR(__preempt_count) + jnz 1f + call preempt_schedule_irq + jmp 0b +1: +#endif /* * The iretq could re-enable interrupts: */ TRACE_IRQS_IRETQ -restore_args: - RESTORE_ARGS 1,8,1 + +/* + * At this label, code paths which return to kernel and to user, + * which come from interrupts/exception and from syscalls, merge. + */ +restore_c_regs_and_iret: + RESTORE_C_REGS + REMOVE_PT_GPREGS_FROM_STACK 8 irq_return: INTERRUPT_RETURN @@ -890,28 +854,17 @@ retint_signal: jz retint_swapgs TRACE_IRQS_ON ENABLE_INTERRUPTS(CLBR_NONE) - SAVE_REST + SAVE_EXTRA_REGS movq $-1,ORIG_RAX(%rsp) xorl %esi,%esi # oldset movq %rsp,%rdi # &pt_regs call do_notify_resume - RESTORE_REST + RESTORE_EXTRA_REGS DISABLE_INTERRUPTS(CLBR_NONE) TRACE_IRQS_OFF GET_THREAD_INFO(%rcx) jmp retint_with_reschedule -#ifdef CONFIG_PREEMPT - /* Returning to kernel space. Check if we need preemption */ - /* rcx: threadinfo. interrupts off. */ -ENTRY(retint_kernel) - cmpl $0,PER_CPU_VAR(__preempt_count) - jnz retint_restore_args - bt $9,EFLAGS-ARGOFFSET(%rsp) /* interrupts off? */ - jnc retint_restore_args - call preempt_schedule_irq - jmp exit_intr -#endif CFI_ENDPROC END(common_interrupt) @@ -1000,7 +953,7 @@ apicinterrupt IRQ_WORK_VECTOR \ /* * Exception entry points. */ -#define INIT_TSS_IST(x) PER_CPU_VAR(init_tss) + (TSS_ist + ((x) - 1) * 8) +#define CPU_TSS_IST(x) PER_CPU_VAR(cpu_tss) + (TSS_ist + ((x) - 1) * 8) .macro idtentry sym do_sym has_error_code:req paranoid=0 shift_ist=-1 ENTRY(\sym) @@ -1022,8 +975,7 @@ ENTRY(\sym) pushq_cfi $-1 /* ORIG_RAX: no syscall to restart */ .endif - subq $ORIG_RAX-R15, %rsp - CFI_ADJUST_CFA_OFFSET ORIG_RAX-R15 + ALLOC_PT_GPREGS_ON_STACK .if \paranoid .if \paranoid == 1 @@ -1031,10 +983,11 @@ ENTRY(\sym) testl $3, CS(%rsp) /* If coming from userspace, switch */ jnz 1f /* stacks. */ .endif - call save_paranoid + call paranoid_entry .else call error_entry .endif + /* returned flag: ebx=0: need swapgs on exit, ebx=1: don't need it */ DEFAULT_FRAME 0 @@ -1056,19 +1009,20 @@ ENTRY(\sym) .endif .if \shift_ist != -1 - subq $EXCEPTION_STKSZ, INIT_TSS_IST(\shift_ist) + subq $EXCEPTION_STKSZ, CPU_TSS_IST(\shift_ist) .endif call \do_sym .if \shift_ist != -1 - addq $EXCEPTION_STKSZ, INIT_TSS_IST(\shift_ist) + addq $EXCEPTION_STKSZ, CPU_TSS_IST(\shift_ist) .endif + /* these procedures expect "no swapgs" flag in ebx */ .if \paranoid - jmp paranoid_exit /* %ebx: no swapgs flag */ + jmp paranoid_exit .else - jmp error_exit /* %ebx: no swapgs flag */ + jmp error_exit .endif .if \paranoid == 1 @@ -1272,7 +1226,9 @@ ENTRY(xen_failsafe_callback) addq $0x30,%rsp CFI_ADJUST_CFA_OFFSET -0x30 pushq_cfi $-1 /* orig_ax = -1 => not a system call */ - SAVE_ALL + ALLOC_PT_GPREGS_ON_STACK + SAVE_C_REGS + SAVE_EXTRA_REGS jmp error_exit CFI_ENDPROC END(xen_failsafe_callback) @@ -1304,59 +1260,66 @@ idtentry async_page_fault do_async_page_fault has_error_code=1 idtentry machine_check has_error_code=0 paranoid=1 do_sym=*machine_check_vector(%rip) #endif - /* - * "Paranoid" exit path from exception stack. This is invoked - * only on return from non-NMI IST interrupts that came - * from kernel space. - * - * We may be returning to very strange contexts (e.g. very early - * in syscall entry), so checking for preemption here would - * be complicated. Fortunately, we there's no good reason - * to try to handle preemption here. - */ +/* + * Save all registers in pt_regs, and switch gs if needed. + * Use slow, but surefire "are we in kernel?" check. + * Return: ebx=0: need swapgs on exit, ebx=1: otherwise + */ +ENTRY(paranoid_entry) + XCPT_FRAME 1 15*8 + cld + SAVE_C_REGS 8 + SAVE_EXTRA_REGS 8 + movl $1,%ebx + movl $MSR_GS_BASE,%ecx + rdmsr + testl %edx,%edx + js 1f /* negative -> in kernel */ + SWAPGS + xorl %ebx,%ebx +1: ret + CFI_ENDPROC +END(paranoid_entry) - /* ebx: no swapgs flag */ +/* + * "Paranoid" exit path from exception stack. This is invoked + * only on return from non-NMI IST interrupts that came + * from kernel space. + * + * We may be returning to very strange contexts (e.g. very early + * in syscall entry), so checking for preemption here would + * be complicated. Fortunately, we there's no good reason + * to try to handle preemption here. + */ +/* On entry, ebx is "no swapgs" flag (1: don't need swapgs, 0: need it) */ ENTRY(paranoid_exit) DEFAULT_FRAME DISABLE_INTERRUPTS(CLBR_NONE) TRACE_IRQS_OFF_DEBUG testl %ebx,%ebx /* swapgs needed? */ - jnz paranoid_restore - TRACE_IRQS_IRETQ 0 + jnz paranoid_exit_no_swapgs + TRACE_IRQS_IRETQ SWAPGS_UNSAFE_STACK - RESTORE_ALL 8 - INTERRUPT_RETURN -paranoid_restore: - TRACE_IRQS_IRETQ_DEBUG 0 - RESTORE_ALL 8 + jmp paranoid_exit_restore +paranoid_exit_no_swapgs: + TRACE_IRQS_IRETQ_DEBUG +paranoid_exit_restore: + RESTORE_EXTRA_REGS + RESTORE_C_REGS + REMOVE_PT_GPREGS_FROM_STACK 8 INTERRUPT_RETURN CFI_ENDPROC END(paranoid_exit) /* - * Exception entry point. This expects an error code/orig_rax on the stack. - * returns in "no swapgs flag" in %ebx. + * Save all registers in pt_regs, and switch gs if needed. + * Return: ebx=0: need swapgs on exit, ebx=1: otherwise */ ENTRY(error_entry) - XCPT_FRAME - CFI_ADJUST_CFA_OFFSET 15*8 - /* oldrax contains error code */ + XCPT_FRAME 1 15*8 cld - movq %rdi, RDI+8(%rsp) - movq %rsi, RSI+8(%rsp) - movq %rdx, RDX+8(%rsp) - movq %rcx, RCX+8(%rsp) - movq %rax, RAX+8(%rsp) - movq %r8, R8+8(%rsp) - movq %r9, R9+8(%rsp) - movq %r10, R10+8(%rsp) - movq %r11, R11+8(%rsp) - movq_cfi rbx, RBX+8 - movq %rbp, RBP+8(%rsp) - movq %r12, R12+8(%rsp) - movq %r13, R13+8(%rsp) - movq %r14, R14+8(%rsp) - movq %r15, R15+8(%rsp) + SAVE_C_REGS 8 + SAVE_EXTRA_REGS 8 xorl %ebx,%ebx testl $3,CS+8(%rsp) je error_kernelspace @@ -1366,12 +1329,12 @@ error_sti: TRACE_IRQS_OFF ret -/* - * There are two places in the kernel that can potentially fault with - * usergs. Handle them here. B stepping K8s sometimes report a - * truncated RIP for IRET exceptions returning to compat mode. Check - * for these here too. - */ + /* + * There are two places in the kernel that can potentially fault with + * usergs. Handle them here. B stepping K8s sometimes report a + * truncated RIP for IRET exceptions returning to compat mode. Check + * for these here too. + */ error_kernelspace: CFI_REL_OFFSET rcx, RCX+8 incl %ebx @@ -1401,11 +1364,11 @@ error_bad_iret: END(error_entry) -/* ebx: no swapgs flag (1: don't need swapgs, 0: need it) */ +/* On entry, ebx is "no swapgs" flag (1: don't need swapgs, 0: need it) */ ENTRY(error_exit) DEFAULT_FRAME movl %ebx,%eax - RESTORE_REST + RESTORE_EXTRA_REGS DISABLE_INTERRUPTS(CLBR_NONE) TRACE_IRQS_OFF GET_THREAD_INFO(%rcx) @@ -1420,19 +1383,7 @@ ENTRY(error_exit) CFI_ENDPROC END(error_exit) -/* - * Test if a given stack is an NMI stack or not. - */ - .macro test_in_nmi reg stack nmi_ret normal_ret - cmpq %\reg, \stack - ja \normal_ret - subq $EXCEPTION_STKSZ, %\reg - cmpq %\reg, \stack - jb \normal_ret - jmp \nmi_ret - .endm - - /* runs on exception stack */ +/* Runs on exception stack */ ENTRY(nmi) INTR_FRAME PARAVIRT_ADJUST_EXCEPTION_FRAME @@ -1468,7 +1419,7 @@ ENTRY(nmi) * NMI. */ - /* Use %rdx as out temp variable throughout */ + /* Use %rdx as our temp variable throughout */ pushq_cfi %rdx CFI_REL_OFFSET rdx, 0 @@ -1493,8 +1444,17 @@ ENTRY(nmi) * We check the variable because the first NMI could be in a * breakpoint routine using a breakpoint stack. */ - lea 6*8(%rsp), %rdx - test_in_nmi rdx, 4*8(%rsp), nested_nmi, first_nmi + lea 6*8(%rsp), %rdx + /* Compare the NMI stack (rdx) with the stack we came from (4*8(%rsp)) */ + cmpq %rdx, 4*8(%rsp) + /* If the stack pointer is above the NMI stack, this is a normal NMI */ + ja first_nmi + subq $EXCEPTION_STKSZ, %rdx + cmpq %rdx, 4*8(%rsp) + /* If it is below the NMI stack, it is a normal NMI */ + jb first_nmi + /* Ah, it is within the NMI stack, treat it as nested */ + CFI_REMEMBER_STATE nested_nmi: @@ -1587,7 +1547,7 @@ first_nmi: .rept 5 pushq_cfi 11*8(%rsp) .endr - CFI_DEF_CFA_OFFSET SS+8-RIP + CFI_DEF_CFA_OFFSET 5*8 /* Everything up to here is safe from nested NMIs */ @@ -1615,7 +1575,7 @@ repeat_nmi: pushq_cfi -6*8(%rsp) .endr subq $(5*8), %rsp - CFI_DEF_CFA_OFFSET SS+8-RIP + CFI_DEF_CFA_OFFSET 5*8 end_repeat_nmi: /* @@ -1624,16 +1584,16 @@ end_repeat_nmi: * so that we repeat another NMI. */ pushq_cfi $-1 /* ORIG_RAX: no syscall to restart */ - subq $ORIG_RAX-R15, %rsp - CFI_ADJUST_CFA_OFFSET ORIG_RAX-R15 + ALLOC_PT_GPREGS_ON_STACK + /* - * Use save_paranoid to handle SWAPGS, but no need to use paranoid_exit + * 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. */ - call save_paranoid + call paranoid_entry DEFAULT_FRAME 0 /* @@ -1664,8 +1624,10 @@ end_repeat_nmi: nmi_swapgs: SWAPGS_UNSAFE_STACK nmi_restore: + RESTORE_EXTRA_REGS + RESTORE_C_REGS /* Pop the extra iret frame at once */ - RESTORE_ALL 6*8 + REMOVE_PT_GPREGS_FROM_STACK 6*8 /* Clear the NMI executing stack variable */ movq $0, 5*8(%rsp) |