lkml.org 
[lkml]   [2015]   [Feb]   [23]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
Date
SubjectRe: [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@redhat.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@redhat.com>
> CC: Linus Torvalds <torvalds@linux-foundation.org>
> CC: Oleg Nesterov <oleg@redhat.com>
> CC: Borislav Petkov <bp@alien8.de>
> CC: "H. Peter Anvin" <hpa@zytor.com>
> CC: Andy Lutomirski <luto@amacapital.net>
> CC: Frederic Weisbecker <fweisbec@gmail.com>
> CC: X86 ML <x86@kernel.org>
> CC: Alexei Starovoitov <ast@plumgrid.com>
> CC: Will Drewry <wad@chromium.org>
> CC: Kees Cook <keescook@chromium.org>
> CC: linux-kernel@vger.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


\
 
 \ /
  Last update: 2015-02-24 02:01    [W:0.266 / U:0.068 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site