This patch does a lot of cleanup in comments and formatting, but it does not change any code.
Rename save_paranoid to paranoid_entry: this makes naming similar to its "non-paranoid" sibling, error_entry, and to it counterpart, paranoid_exit. Use the same CFI annotation atop paranoid_entry and error_entry. Fix irregular indentation of assembler operands. Add/fix comments on top of paranoid_entry and error_entry. Remove stale comment about "oldrax". Make comments about "no swapgs" flag in ebx more prominent. Deindent wrongly indented top-level comment atop paranoid_exit. Indent wrongly deindented comment inside error_entry. Signed-off-by: Denys Vlasenko <[email protected]> CC: Linus Torvalds <[email protected]> CC: Oleg Nesterov <[email protected]> CC: "H. Peter Anvin" <[email protected]> CC: Andy Lutomirski <[email protected]> CC: Frederic Weisbecker <[email protected]> CC: X86 ML <[email protected]> CC: Alexei Starovoitov <[email protected]> CC: Will Drewry <[email protected]> CC: Kees Cook <[email protected]> CC: [email protected] --- arch/x86/kernel/entry_64.S | 117 +++++++++++++++++++++++---------------------- 1 file changed, 59 insertions(+), 58 deletions(-) diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S index 5ad9b28..decfe25 100644 --- a/arch/x86/kernel/entry_64.S +++ b/arch/x86/kernel/entry_64.S @@ -1000,10 +1000,11 @@ ENTRY(\sym) ALLOC_PTREGS_ON_STACK .if \paranoid - 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 @@ -1034,10 +1035,11 @@ ENTRY(\sym) addq $EXCEPTION_STKSZ, INIT_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 CFI_ENDPROC @@ -1242,36 +1244,40 @@ 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 -ENTRY(save_paranoid) - XCPT_FRAME 1 RDI+8 +/* + * 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 + movl $1,%ebx + movl $MSR_GS_BASE,%ecx rdmsr - testl %edx,%edx - js 1f /* negative -> in kernel */ + testl %edx,%edx + js 1f /* negative -> in kernel */ SWAPGS - xorl %ebx,%ebx + xorl %ebx,%ebx 1: ret CFI_ENDPROC -END(save_paranoid) - - /* - * "Paranoid" exit path from exception stack. - * Paranoid because this is used by NMIs and cannot take - * any kernel state for granted. - * We don't do kernel preemption checks here, because only - * NMI should be common and it does not enable IRQs and - * cannot get reschedule ticks. - * - * "trace" is 0 for the NMI handler only, because irq-tracing - * is fundamentally NMI-unsafe. (we cannot change the soft and - * hard flags at once, atomically) - */ +END(paranoid_entry) - /* ebx: no swapgs flag */ +/* + * "Paranoid" exit path from exception stack. + * Paranoid because this is used by NMIs and cannot take + * any kernel state for granted. + * We don't do kernel preemption checks here, because only + * NMI should be common and it does not enable IRQs and + * cannot get reschedule ticks. + * + * "trace" is 0 for the NMI handler only, because irq-tracing + * is fundamentally NMI-unsafe. (we cannot change the soft and + * hard flags at once, atomically) + */ +/* On entry, ebx is "no swapgs" flag (1: don't need swapgs, 0: need it) */ ENTRY(paranoid_exit) DEFAULT_FRAME DISABLE_INTERRUPTS(CLBR_NONE) @@ -1323,53 +1329,48 @@ paranoid_schedule: 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 SAVE_C_REGS 8 SAVE_EXTRA_REGS 8 - xorl %ebx,%ebx - testl $3,CS+8(%rsp) - je error_kernelspace + xorl %ebx,%ebx + testl $3,CS+8(%rsp) + jz error_kernelspace error_swapgs: SWAPGS error_sti: TRACE_IRQS_OFF ret - -/* - * There are two places in the kernel that can potentially fault with - * usergs. Handle them here. The exception handlers after iret run with - * kernel gs again, so don't set the user space flag. B stepping K8s - * sometimes report an 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. The exception handlers after iret run with + * kernel gs again, so don't set the user space flag. B stepping K8s + * sometimes report an truncated RIP for IRET exceptions returning to + * compat mode. Check for these here too. + */ error_kernelspace: - incl %ebx - leaq irq_return_iret(%rip),%rcx - cmpq %rcx,RIP+8(%rsp) - je error_swapgs - movl %ecx,%eax /* zero extend */ - cmpq %rax,RIP+8(%rsp) - je bstep_iret - cmpq $gs_change,RIP+8(%rsp) - je error_swapgs - jmp error_sti - + incl %ebx + leaq irq_return_iret(%rip),%rcx + cmpq %rcx,RIP+8(%rsp) + je error_swapgs + movl %ecx,%eax /* zero extend */ + cmpq %rax,RIP+8(%rsp) + je bstep_iret + cmpq $gs_change,RIP+8(%rsp) + je error_swapgs + jmp error_sti bstep_iret: /* Fix truncated RIP */ - movq %rcx,RIP+8(%rsp) - jmp error_swapgs + movq %rcx,RIP+8(%rsp) + jmp error_swapgs CFI_ENDPROC 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 @@ -1595,13 +1596,13 @@ end_repeat_nmi: ALLOC_PTREGS_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 /* -- 1.8.1.4 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
