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Date: Mon, 23 Feb 2015 16:37:49 -0800 From: Andy Lutomirski <luto@...capital.net> To: Denys Vlasenko <dvlasenk@...hat.com> Cc: Linus Torvalds <torvalds@...ux-foundation.org>, Oleg Nesterov <oleg@...hat.com>, Borislav Petkov <bp@...en8.de>, "H. Peter Anvin" <hpa@...or.com>, Frederic Weisbecker <fweisbec@...il.com>, X86 ML <x86@...nel.org>, Alexei Starovoitov <ast@...mgrid.com>, Will Drewry <wad@...omium.org>, Kees Cook <keescook@...omium.org>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org> Subject: Re: [PATCH 3/6] x86: entry_64.S: rename save_paranoid to paranoid_entry, no code changes On Mon, Feb 23, 2015 at 4:12 PM, Denys Vlasenko <dvlasenk@...hat.com> wrote: > 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. Applied. > > Signed-off-by: Denys Vlasenko <dvlasenk@...hat.com> > CC: Linus Torvalds <torvalds@...ux-foundation.org> > CC: Oleg Nesterov <oleg@...hat.com> > CC: Borislav Petkov <bp@...en8.de> > CC: "H. Peter Anvin" <hpa@...or.com> > CC: Andy Lutomirski <luto@...capital.net> > CC: Frederic Weisbecker <fweisbec@...il.com> > CC: X86 ML <x86@...nel.org> > CC: Alexei Starovoitov <ast@...mgrid.com> > CC: Will Drewry <wad@...omium.org> > CC: Kees Cook <keescook@...omium.org> > CC: linux-kernel@...r.kernel.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 71b549a..03498d0 100644 > --- a/arch/x86/kernel/entry_64.S > +++ b/arch/x86/kernel/entry_64.S > @@ -981,10 +981,11 @@ 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 > > @@ -1015,10 +1016,11 @@ 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 > @@ -1253,8 +1255,13 @@ 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 > @@ -1267,20 +1274,19 @@ 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) > @@ -1301,13 +1307,11 @@ 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 > @@ -1320,12 +1324,12 @@ 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 > @@ -1355,7 +1359,7 @@ 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 > @@ -1581,13 +1585,13 @@ 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 > > /* > -- > 1.8.1.4 > -- Andy Lutomirski AMA Capital Management, LLC -- 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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