1. 10 3月, 2016 1 次提交
  2. 25 2月, 2016 1 次提交
  3. 21 12月, 2015 1 次提交
  4. 19 12月, 2015 1 次提交
  5. 14 12月, 2015 1 次提交
  6. 23 11月, 2015 2 次提交
  7. 18 10月, 2015 1 次提交
  8. 11 10月, 2015 1 次提交
  9. 09 10月, 2015 7 次提交
  10. 07 10月, 2015 2 次提交
  11. 14 8月, 2015 1 次提交
  12. 24 7月, 2015 1 次提交
  13. 09 7月, 2015 1 次提交
  14. 07 7月, 2015 3 次提交
  15. 06 7月, 2015 1 次提交
    • D
      x86/asm/entry/32: Replace RESTORE_RSI_RDI with open-coded 32-bit reads · c73e36b7
      Denys Vlasenko 提交于
      This doesn't change much, but uses shorter 32-bit insns:
      
              -48 8b 74 24 68         mov    0x68(%rsp),%rsi
              -48 8b 7c 24 70         mov    0x70(%rsp),%rdi
              -48 8b 54 24 60         mov    0x60(%rsp),%rdx
              +8b 54 24 60            mov    0x60(%rsp),%edx
              +8b 74 24 68            mov    0x68(%rsp),%esi
              +8b 7c 24 70            mov    0x70(%rsp),%edi
      
      and does the loads in pt_regs order.
      
      Since these are the only uses of RESTORE_RSI_RDI[_RDX], drop
      these macros.
      Signed-off-by: NDenys Vlasenko <dvlasenk@redhat.com>
      Cc: Alexei Starovoitov <ast@plumgrid.com>
      Cc: Andy Lutomirski <luto@amacapital.net>
      Cc: Borislav Petkov <bp@alien8.de>
      Cc: Frederic Weisbecker <fweisbec@gmail.com>
      Cc: H. Peter Anvin <hpa@zytor.com>
      Cc: Kees Cook <keescook@chromium.org>
      Cc: Linus Torvalds <torvalds@linux-foundation.org>
      Cc: Oleg Nesterov <oleg@redhat.com>
      Cc: Peter Zijlstra <peterz@infradead.org>
      Cc: Steven Rostedt <rostedt@goodmis.org>
      Cc: Thomas Gleixner <tglx@linutronix.de>
      Cc: Will Drewry <wad@chromium.org>
      Link: http://lkml.kernel.org/r/1435954742-2545-1-git-send-email-dvlasenk@redhat.comSigned-off-by: NIngo Molnar <mingo@kernel.org>
      c73e36b7
  16. 10 6月, 2015 3 次提交
    • D
      x86/asm/entry/32: Shorten __audit_syscall_entry() args preparation · a92fde25
      Denys Vlasenko 提交于
      We use three MOVs to swap edx and ecx. We can use one XCHG
      instead.
      
      Expand the comments. It's difficult to keep track which arg#
      every register corresponds to, so spell it out.
      Signed-off-by: NDenys Vlasenko <dvlasenk@redhat.com>
      Cc: Alexei Starovoitov <ast@plumgrid.com>
      Cc: Andrew Morton <akpm@linux-foundation.org>
      Cc: Andy Lutomirski <luto@amacapital.net>
      Cc: Borislav Petkov <bp@alien8.de>
      Cc: Brian Gerst <brgerst@gmail.com>
      Cc: Frederic Weisbecker <fweisbec@gmail.com>
      Cc: H. Peter Anvin <hpa@zytor.com>
      Cc: Kees Cook <keescook@chromium.org>
      Cc: Linus Torvalds <torvalds@linux-foundation.org>
      Cc: Oleg Nesterov <oleg@redhat.com>
      Cc: Peter Zijlstra <peterz@infradead.org>
      Cc: Steven Rostedt <rostedt@goodmis.org>
      Cc: Thomas Gleixner <tglx@linutronix.de>
      Cc: Will Drewry <wad@chromium.org>
      Link: http://lkml.kernel.org/r/1433876051-26604-3-git-send-email-dvlasenk@redhat.com
      [ Expanded the comments some more. ]
      Signed-off-by: NIngo Molnar <mingo@kernel.org>
      a92fde25
    • D
      x86/asm/entry/32: Explain reloading of registers after __audit_syscall_entry() · 1536bb46
      Denys Vlasenko 提交于
      Here it is not obvious why we load pt_regs->cx to %esi etc.
      Lets improve comments.
      
      Explain that here we combine two things: first, we reload
      registers since some of them are clobbered by the C function we
      just called; and we also convert 32-bit syscall params to 64-bit
      C ABI, because we are going to jump back to syscall dispatch
      code.
      
      Move reloading of 6th argument into the macro instead of having
      it after each of two macro invocations.
      
      No actual code changes here.
      Signed-off-by: NDenys Vlasenko <dvlasenk@redhat.com>
      Cc: Alexei Starovoitov <ast@plumgrid.com>
      Cc: Andrew Morton <akpm@linux-foundation.org>
      Cc: Andy Lutomirski <luto@amacapital.net>
      Cc: Borislav Petkov <bp@alien8.de>
      Cc: Frederic Weisbecker <fweisbec@gmail.com>
      Cc: H. Peter Anvin <hpa@zytor.com>
      Cc: Kees Cook <keescook@chromium.org>
      Cc: Linus Torvalds <torvalds@linux-foundation.org>
      Cc: Oleg Nesterov <oleg@redhat.com>
      Cc: Peter Zijlstra <peterz@infradead.org>
      Cc: Steven Rostedt <rostedt@goodmis.org>
      Cc: Thomas Gleixner <tglx@linutronix.de>
      Cc: Will Drewry <wad@chromium.org>
      Link: http://lkml.kernel.org/r/1433876051-26604-2-git-send-email-dvlasenk@redhat.comSigned-off-by: NIngo Molnar <mingo@kernel.org>
      1536bb46
    • D
      x86/asm/entry/32: Fix fallout from the R9 trick removal in the SYSCALL code · aee4b013
      Denys Vlasenko 提交于
      I put %ebp restoration code too late. Under strace, it is not
      reached and %ebp is not restored upon return to userspace.
      
      This is the fix. Run-tested.
      Signed-off-by: NDenys Vlasenko <dvlasenk@redhat.com>
      Cc: Alexei Starovoitov <ast@plumgrid.com>
      Cc: Andrew Morton <akpm@linux-foundation.org>
      Cc: Andy Lutomirski <luto@amacapital.net>
      Cc: Borislav Petkov <bp@alien8.de>
      Cc: Frederic Weisbecker <fweisbec@gmail.com>
      Cc: H. Peter Anvin <hpa@zytor.com>
      Cc: Kees Cook <keescook@chromium.org>
      Cc: Linus Torvalds <torvalds@linux-foundation.org>
      Cc: Oleg Nesterov <oleg@redhat.com>
      Cc: Peter Zijlstra <peterz@infradead.org>
      Cc: Steven Rostedt <rostedt@goodmis.org>
      Cc: Thomas Gleixner <tglx@linutronix.de>
      Cc: Will Drewry <wad@chromium.org>
      Link: http://lkml.kernel.org/r/1433876051-26604-1-git-send-email-dvlasenk@redhat.comSigned-off-by: NIngo Molnar <mingo@kernel.org>
      aee4b013
  17. 09 6月, 2015 2 次提交
    • D
      x86/asm/entry: Clean up entry*.S style, final bits · 9b47feb7
      Denys Vlasenko 提交于
      A few bits were missed.
      Signed-off-by: NDenys Vlasenko <dvlasenk@redhat.com>
      Cc: Andrew Morton <akpm@linux-foundation.org>
      Cc: H. Peter Anvin <hpa@zytor.com>
      Cc: Linus Torvalds <torvalds@linux-foundation.org>
      Cc: Peter Zijlstra <peterz@infradead.org>
      Cc: Thomas Gleixner <tglx@linutronix.de>
      Signed-off-by: NIngo Molnar <mingo@kernel.org>
      9b47feb7
    • D
      x86/asm/entry/32: Reinstate clearing of pt_regs->r8..r11 on EFAULT path · eb478544
      Denys Vlasenko 提交于
      I broke this recently when I changed pt_regs->r8..r11 clearing
      logic in INT 80 code path.
      
      There is a branch from SYSENTER/SYSCALL code to INT 80 code:
      if we fail to retrieve arg6, we return EFAULT. Before this
      patch, in this case we don't clear pt_regs->r8..r11.
      
      This patch fixes this. The resulting code is smaller and
      simpler.
      
      While at it, remove incorrect comment about syscall dispatching
      CALL insn: it does not use RIP-relative addressing form (the
      comment was meant to be "TODO: make this rip-relative", and
      morphed since then, dropping "TODO").
      Signed-off-by: NDenys Vlasenko <dvlasenk@redhat.com>
      Cc: Alexei Starovoitov <ast@plumgrid.com>
      Cc: Andrew Morton <akpm@linux-foundation.org>
      Cc: Andy Lutomirski <luto@amacapital.net>
      Cc: Borislav Petkov <bp@alien8.de>
      Cc: Frederic Weisbecker <fweisbec@gmail.com>
      Cc: H. Peter Anvin <hpa@zytor.com>
      Cc: Kees Cook <keescook@chromium.org>
      Cc: Linus Torvalds <torvalds@linux-foundation.org>
      Cc: Oleg Nesterov <oleg@redhat.com>
      Cc: Peter Zijlstra <peterz@infradead.org>
      Cc: Steven Rostedt <rostedt@goodmis.org>
      Cc: Thomas Gleixner <tglx@linutronix.de>
      Cc: Will Drewry <wad@chromium.org>
      Link: http://lkml.kernel.org/r/1433701470-28800-1-git-send-email-dvlasenk@redhat.comSigned-off-by: NIngo Molnar <mingo@kernel.org>
      eb478544
  18. 08 6月, 2015 2 次提交
    • I
      x86/asm/entry: Untangle 'ia32_sysenter_target' into two entry points:... · 4c8cd0c5
      Ingo Molnar 提交于
      x86/asm/entry: Untangle 'ia32_sysenter_target' into two entry points: entry_SYSENTER_32 and entry_SYSENTER_compat
      
      So the SYSENTER instruction is pretty quirky and it has different behavior
      depending on bitness and CPU maker.
      
      Yet we create a false sense of coherency by naming it 'ia32_sysenter_target'
      in both of the cases.
      
      Split the name into its two uses:
      
      	ia32_sysenter_target (32)    -> entry_SYSENTER_32
      	ia32_sysenter_target (64)    -> entry_SYSENTER_compat
      
      As per the generic naming scheme for x86 system call entry points:
      
      	entry_MNEMONIC_qualifier
      
      where 'qualifier' is one of _32, _64 or _compat.
      
      Cc: Andy Lutomirski <luto@amacapital.net>
      Cc: Borislav Petkov <bp@alien8.de>
      Cc: Brian Gerst <brgerst@gmail.com>
      Cc: Denys Vlasenko <dvlasenk@redhat.com>
      Cc: H. Peter Anvin <hpa@zytor.com>
      Cc: Linus Torvalds <torvalds@linux-foundation.org>
      Cc: Peter Zijlstra <peterz@infradead.org>
      Cc: Thomas Gleixner <tglx@linutronix.de>
      Cc: linux-kernel@vger.kernel.org
      Signed-off-by: NIngo Molnar <mingo@kernel.org>
      4c8cd0c5
    • I
      x86/asm/entry: Rename compat syscall entry points · 2cd23553
      Ingo Molnar 提交于
      Rename the following system call entry points:
      
      	ia32_cstar_target       -> entry_SYSCALL_compat
      	ia32_syscall            -> entry_INT80_compat
      
      The generic naming scheme for x86 system call entry points is:
      
      	entry_MNEMONIC_qualifier
      
      where 'qualifier' is one of _32, _64 or _compat.
      
      Cc: Andy Lutomirski <luto@amacapital.net>
      Cc: Borislav Petkov <bp@alien8.de>
      Cc: Brian Gerst <brgerst@gmail.com>
      Cc: Denys Vlasenko <dvlasenk@redhat.com>
      Cc: H. Peter Anvin <hpa@zytor.com>
      Cc: Linus Torvalds <torvalds@linux-foundation.org>
      Cc: Peter Zijlstra <peterz@infradead.org>
      Cc: Thomas Gleixner <tglx@linutronix.de>
      Cc: linux-kernel@vger.kernel.org
      Signed-off-by: NIngo Molnar <mingo@kernel.org>
      2cd23553
  19. 07 6月, 2015 1 次提交
    • I
      x86/asm/entry/64/compat: Rename ia32entry.S -> entry_64_compat.S · 138bd56a
      Ingo Molnar 提交于
      So we now have the following system entry code related
      files, which define the following system call instruction
      and other entry paths:
      
         entry_32.S            # 32-bit binaries on 32-bit kernels
         entry_64.S            # 64-bit binaries on 64-bit kernels
         entry_64_compat.S	 # 32-bit binaries on 64-bit kernels
      
      Cc: Alexei Starovoitov <ast@plumgrid.com>
      Cc: Andrew Morton <akpm@linux-foundation.org>
      Cc: Andy Lutomirski <luto@amacapital.net>
      Cc: Borislav Petkov <bp@alien8.de>
      Cc: Brian Gerst <brgerst@gmail.com>
      Cc: Denys Vlasenko <dvlasenk@redhat.com>
      Cc: Frederic Weisbecker <fweisbec@gmail.com>
      Cc: H. Peter Anvin <hpa@zytor.com>
      Cc: Josh Triplett <josh@joshtriplett.org>
      Cc: Kees Cook <keescook@chromium.org>
      Cc: Linus Torvalds <torvalds@linux-foundation.org>
      Cc: Oleg Nesterov <oleg@redhat.com>
      Cc: Peter Zijlstra <peterz@infradead.org>
      Cc: Steven Rostedt <rostedt@goodmis.org>
      Cc: Thomas Gleixner <tglx@linutronix.de>
      Cc: Will Drewry <wad@chromium.org>
      Cc: linux-kernel@vger.kernel.org
      Signed-off-by: NIngo Molnar <mingo@kernel.org>
      138bd56a
  20. 05 6月, 2015 7 次提交
    • D
      x86/asm/entry/32: Remove unnecessary optimization in stub32_clone · 7a5a9824
      Denys Vlasenko 提交于
      Really swap arguments #4 and #5 in stub32_clone instead of
      "optimizing" it into a move.
      
      Yes, tls_val is currently unused. Yes, on some CPUs XCHG is a
      little bit more expensive than MOV. But a cycle or two on an
      expensive syscall like clone() is way below noise floor, and
      this optimization is simply not worth the obfuscation of logic.
      
      [ There's also ongoing work on the clone() ABI by Josh Triplett
        that will depend on this change later on. ]
      Signed-off-by: NDenys Vlasenko <dvlasenk@redhat.com>
      Cc: Alexei Starovoitov <ast@plumgrid.com>
      Cc: Andrew Morton <akpm@linux-foundation.org>
      Cc: Andy Lutomirski <luto@amacapital.net>
      Cc: Borislav Petkov <bp@alien8.de>
      Cc: Brian Gerst <brgerst@gmail.com>
      Cc: Frederic Weisbecker <fweisbec@gmail.com>
      Cc: H. Peter Anvin <hpa@zytor.com>
      Cc: Josh Triplett <josh@joshtriplett.org>
      Cc: Kees Cook <keescook@chromium.org>
      Cc: Linus Torvalds <torvalds@linux-foundation.org>
      Cc: Oleg Nesterov <oleg@redhat.com>
      Cc: Peter Zijlstra <peterz@infradead.org>
      Cc: Steven Rostedt <rostedt@goodmis.org>
      Cc: Thomas Gleixner <tglx@linutronix.de>
      Cc: Will Drewry <wad@chromium.org>
      Link: http://lkml.kernel.org/r/1433339930-20880-2-git-send-email-dvlasenk@redhat.comSigned-off-by: NIngo Molnar <mingo@kernel.org>
      7a5a9824
    • D
      x86/asm/entry/32: Explain the stub32_clone logic · 5cdc683b
      Denys Vlasenko 提交于
      The reason for copying of %r8 to %rcx is quite non-obvious.
      Add a comment which explains why it is done.
      Signed-off-by: NDenys Vlasenko <dvlasenk@redhat.com>
      Cc: Alexei Starovoitov <ast@plumgrid.com>
      Cc: Andrew Morton <akpm@linux-foundation.org>
      Cc: Andy Lutomirski <luto@amacapital.net>
      Cc: Borislav Petkov <bp@alien8.de>
      Cc: Brian Gerst <brgerst@gmail.com>
      Cc: Frederic Weisbecker <fweisbec@gmail.com>
      Cc: H. Peter Anvin <hpa@zytor.com>
      Cc: Kees Cook <keescook@chromium.org>
      Cc: Linus Torvalds <torvalds@linux-foundation.org>
      Cc: Oleg Nesterov <oleg@redhat.com>
      Cc: Peter Zijlstra <peterz@infradead.org>
      Cc: Steven Rostedt <rostedt@goodmis.org>
      Cc: Thomas Gleixner <tglx@linutronix.de>
      Cc: Will Drewry <wad@chromium.org>
      Link: http://lkml.kernel.org/r/1433339930-20880-1-git-send-email-dvlasenk@redhat.comSigned-off-by: NIngo Molnar <mingo@kernel.org>
      5cdc683b
    • I
      x86/asm/entry/32: Improve code readability · 54ad726c
      Ingo Molnar 提交于
      Make the 64-bit compat 32-bit syscall entry code a bit more readable:
      
       - eliminate whitespace noise
      
       - use consistent vertical spacing
      
       - use consistent assembly coding style similar to entry_64.S
      
       - fix various comments
      
      No code changed:
      
      arch/x86/entry/ia32entry.o:
      
         text	   data	    bss	    dec	    hex	filename
         1391	      0	      0	   1391	    56f	ia32entry.o.before
         1391	      0	      0	   1391	    56f	ia32entry.o.after
      
      md5:
         f28501dcc366e68b557313942c6496d6  ia32entry.o.before.asm
         f28501dcc366e68b557313942c6496d6  ia32entry.o.after.asm
      
      Cc: Andrew Morton <akpm@linux-foundation.org>
      Cc: Andy Lutomirski <luto@amacapital.net>
      Cc: Borislav Petkov <bp@alien8.de>
      Cc: Brian Gerst <brgerst@gmail.com>
      Cc: Denys Vlasenko <dvlasenk@redhat.com>
      Cc: H. Peter Anvin <hpa@zytor.com>
      Cc: Linus Torvalds <torvalds@linux-foundation.org>
      Cc: Peter Zijlstra <peterz@infradead.org>
      Cc: Thomas Gleixner <tglx@linutronix.de>
      Cc: linux-kernel@vger.kernel.org
      Signed-off-by: NIngo Molnar <mingo@kernel.org>
      54ad726c
    • D
      x86/asm/entry/32: Do not use R9 in SYSCALL32 entry point · 53e9accf
      Denys Vlasenko 提交于
      SYSENTER and SYSCALL 32-bit entry points differ in handling of
      arg2 and arg6.
      
      SYSENTER:
       * ecx  arg2
       * ebp  user stack
       * 0(%ebp) arg6
      
      SYSCALL:
       * ebp  arg2
       * esp  user stack
       * 0(%esp) arg6
      
      Sysenter code loads 0(%ebp) to %ebp right away.
      (This destroys %ebp. It means we do not preserve it on return.
      It's not causing problems since userspace VDSO code does not
      depend on it, and SYSENTER insn can't be sanely used outside of
      VDSO).
      
      Syscall code loads 0(%ebp) to %r9. This allows to eliminate one
      MOV insn (r9 is a register where arg6 should be for 64-bit ABI),
      but on audit/ptrace code paths this requires juggling of r9 and
      ebp: (1) ptrace expects arg6 to be in pt_regs->bp;
      (2) r9 is callee-clobbered register and needs to be
      saved/restored     around calls to C functions.
      
      This patch changes syscall code to load 0(%ebp) to %ebp, making
      it more similar to sysenter code. It's a bit smaller:
      
         text    data     bss     dec     hex filename
         1407       0       0    1407     57f ia32entry.o.before
         1391       0       0    1391     56f ia32entry.o
      
      To preserve ABI compat, we restore ebp on exit.
      
      Run-tested.
      Signed-off-by: NDenys Vlasenko <dvlasenk@redhat.com>
      Cc: Alexei Starovoitov <ast@plumgrid.com>
      Cc: Andrew Morton <akpm@linux-foundation.org>
      Cc: Andy Lutomirski <luto@amacapital.net>
      Cc: Borislav Petkov <bp@alien8.de>
      Cc: Brian Gerst <brgerst@gmail.com>
      Cc: Frederic Weisbecker <fweisbec@gmail.com>
      Cc: H. Peter Anvin <hpa@zytor.com>
      Cc: Kees Cook <keescook@chromium.org>
      Cc: Linus Torvalds <torvalds@linux-foundation.org>
      Cc: Oleg Nesterov <oleg@redhat.com>
      Cc: Peter Zijlstra <peterz@infradead.org>
      Cc: Steven Rostedt <rostedt@goodmis.org>
      Cc: Thomas Gleixner <tglx@linutronix.de>
      Cc: Will Drewry <wad@chromium.org>
      Link: http://lkml.kernel.org/r/1433336169-18964-1-git-send-email-dvlasenk@redhat.comSigned-off-by: NIngo Molnar <mingo@kernel.org>
      53e9accf
    • D
      x86/asm/entry/32: Open-code LOAD_ARGS32 · 73cbf687
      Denys Vlasenko 提交于
      This macro is small, has only three callsites, and one of them
      is slightly different using a conditional parameter.
      
      A few saved lines aren't worth the resulting obfuscation.
      
      Generated machine code is identical.
      Signed-off-by: NDenys Vlasenko <dvlasenk@redhat.com>
      Cc: Alexei Starovoitov <ast@plumgrid.com>
      Cc: Andrew Morton <akpm@linux-foundation.org>
      Cc: Andy Lutomirski <luto@amacapital.net>
      Cc: Borislav Petkov <bp@alien8.de>
      Cc: Brian Gerst <brgerst@gmail.com>
      Cc: Frederic Weisbecker <fweisbec@gmail.com>
      Cc: H. Peter Anvin <hpa@zytor.com>
      Cc: Kees Cook <keescook@chromium.org>
      Cc: Linus Torvalds <torvalds@linux-foundation.org>
      Cc: Oleg Nesterov <oleg@redhat.com>
      Cc: Peter Zijlstra <peterz@infradead.org>
      Cc: Steven Rostedt <rostedt@goodmis.org>
      Cc: Thomas Gleixner <tglx@linutronix.de>
      Cc: Will Drewry <wad@chromium.org>
      Link: http://lkml.kernel.org/r/1433271842-9139-2-git-send-email-dvlasenk@redhat.comSigned-off-by: NIngo Molnar <mingo@kernel.org>
      73cbf687
    • D
      x86/asm/entry/32: Open-code CLEAR_RREGS · ef0cd5dc
      Denys Vlasenko 提交于
      This macro is small, has only four callsites, and one of them is
      slightly different using a conditional parameter.
      
      A few saved lines aren't worth the resulting obfuscation.
      
      Generated machine code is identical.
      Signed-off-by: NDenys Vlasenko <dvlasenk@redhat.com>
      [ Added comments. ]
      Cc: Alexei Starovoitov <ast@plumgrid.com>
      Cc: Andrew Morton <akpm@linux-foundation.org>
      Cc: Andy Lutomirski <luto@amacapital.net>
      Cc: Borislav Petkov <bp@alien8.de>
      Cc: Brian Gerst <brgerst@gmail.com>
      Cc: Frederic Weisbecker <fweisbec@gmail.com>
      Cc: H. Peter Anvin <hpa@zytor.com>
      Cc: Kees Cook <keescook@chromium.org>
      Cc: Linus Torvalds <torvalds@linux-foundation.org>
      Cc: Oleg Nesterov <oleg@redhat.com>
      Cc: Peter Zijlstra <peterz@infradead.org>
      Cc: Steven Rostedt <rostedt@goodmis.org>
      Cc: Thomas Gleixner <tglx@linutronix.de>
      Cc: Will Drewry <wad@chromium.org>
      Link: http://lkml.kernel.org/r/1433271842-9139-1-git-send-email-dvlasenk@redhat.comSigned-off-by: NIngo Molnar <mingo@kernel.org>
      ef0cd5dc
    • D
      x86/asm/entry/32: Simplify the zeroing of pt_regs->r8..r11 in the int80 code path · 61b1e3e7
      Denys Vlasenko 提交于
      32-bit syscall entry points do not save the complete pt_regs struct,
      they leave some fields uninitialized. However, they must be
      careful to not leak uninitialized data in pt_regs->r8..r11 to
      ptrace users.
      
      CLEAR_RREGS macro is used to zero these fields out when needed.
      
      However, in the int80 code path this zeroing is unconditional.
      This patch simplifies it by storing zeroes there right away,
      when pt_regs is constructed on stack.
      
      This uses shorter instructions:
      
         text    data     bss     dec     hex filename
         1423       0       0    1423     58f ia32entry.o.before
         1407       0       0    1407     57f ia32entry.o
      
      Compile-tested.
      Signed-off-by: NDenys Vlasenko <dvlasenk@redhat.com>
      Cc: Alexei Starovoitov <ast@plumgrid.com>
      Cc: Andrew Morton <akpm@linux-foundation.org>
      Cc: Andy Lutomirski <luto@amacapital.net>
      Cc: Borislav Petkov <bp@alien8.de>
      Cc: Brian Gerst <brgerst@gmail.com>
      Cc: Frederic Weisbecker <fweisbec@gmail.com>
      Cc: H. Peter Anvin <hpa@zytor.com>
      Cc: Kees Cook <keescook@chromium.org>
      Cc: Linus Torvalds <torvalds@linux-foundation.org>
      Cc: Oleg Nesterov <oleg@redhat.com>
      Cc: Peter Zijlstra <peterz@infradead.org>
      Cc: Steven Rostedt <rostedt@goodmis.org>
      Cc: Thomas Gleixner <tglx@linutronix.de>
      Cc: Will Drewry <wad@chromium.org>
      Link: http://lkml.kernel.org/r/1433266510-2938-1-git-send-email-dvlasenk@redhat.comSigned-off-by: NIngo Molnar <mingo@kernel.org>
      61b1e3e7