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Date: Wed, 4 Mar 2015 14:55:31 -0800 From: tip-bot for Denys Vlasenko <tipbot@...or.com> To: linux-tip-commits@...r.kernel.org Cc: hpa@...or.com, linux-kernel@...r.kernel.org, keescook@...omium.org, ast@...mgrid.com, tglx@...utronix.de, wad@...omium.org, fweisbec@...il.com, torvalds@...ux-foundation.org, mingo@...nel.org, dvlasenk@...hat.com, oleg@...hat.com, bp@...en8.de, luto@...capital.net Subject: [tip:x86/asm] x86/asm/entry/64: Clean up and document various entry code details Commit-ID: ebfc453e27c676e104378366a0b027e5c6918631 Gitweb: http://git.kernel.org/tip/ebfc453e27c676e104378366a0b027e5c6918631 Author: Denys Vlasenko <dvlasenk@...hat.com> AuthorDate: Thu, 26 Feb 2015 14:40:34 -0800 Committer: Ingo Molnar <mingo@...nel.org> CommitDate: Wed, 4 Mar 2015 22:50:51 +0100 x86/asm/entry/64: Clean up and document various entry code details 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 its 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 <dvlasenk@...hat.com> Signed-off-by: Andy Lutomirski <luto@...capital.net> Cc: Alexei Starovoitov <ast@...mgrid.com> Cc: Borislav Petkov <bp@...en8.de> Cc: Frederic Weisbecker <fweisbec@...il.com> Cc: H. Peter Anvin <hpa@...or.com> Cc: Kees Cook <keescook@...omium.org> Cc: Linus Torvalds <torvalds@...ux-foundation.org> Cc: Oleg Nesterov <oleg@...hat.com> Cc: Will Drewry <wad@...omium.org> Link: http://lkml.kernel.org/r/4640f9fcd5ea46eb299b1cd6d3f5da3167d2f78d.1424989793.git.luto@amacapital.net Signed-off-by: Ingo Molnar <mingo@...nel.org> --- arch/x86/kernel/entry_64.S | 68 ++++++++++++++++++++++++---------------------- 1 file changed, 36 insertions(+), 32 deletions(-) diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S index 9e33d49..4669477 100644 --- a/arch/x86/kernel/entry_64.S +++ b/arch/x86/kernel/entry_64.S @@ -982,10 +982,11 @@ 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 @@ -1016,10 +1017,11 @@ 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 .if \paranoid == 1 @@ -1257,8 +1259,13 @@ 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 @@ -1271,20 +1278,19 @@ ENTRY(save_paranoid) xorl %ebx,%ebx 1: ret CFI_ENDPROC -END(save_paranoid) - - /* - * "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. - */ +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) @@ -1305,13 +1311,11 @@ paranoid_exit_restore: 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 @@ -1324,12 +1328,12 @@ 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 @@ -1359,7 +1363,7 @@ 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 @@ -1585,13 +1589,13 @@ end_repeat_nmi: 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 /* -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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