x86/entry/32: Remove 32-bit syscall audit optimizations

The asm audit optimizations are ugly and obfuscate the code too
much. Remove them.

This will regress performance if syscall auditing is enabled on
32-bit kernels and SYSENTER is in use. If this becomes a
problem, interested parties are encouraged to implement the
equivalent of the 64-bit opportunistic SYSRET optimization.

Alternatively, a case could be made that, on 32-bit kernels, a
less messy asm audit optimization could be done. 32-bit kernels
don't have the complicated partial register saving tricks that
64-bit kernels have, so the SYSENTER post-syscall path could
just call the audit hooks directly.  Any reimplementation of
this ought to demonstrate that it only calls the audit hook once
per syscall, though, which does not currently appear to be true.

Someone would have to make the case that doing so would be
better than implementing opportunistic SYSEXIT, though.

Signed-off-by: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Eric Paris <eparis@parisplace.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/212be39dd8c90b44c4b7bbc678128d6b88bdb9912.1438378274.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>

diff --git a/arch/x86/entry/entry_32.S b/arch/x86/entry/entry_32.S
index f940e24..a3c307a 100644 (file)
--- a/arch/x86/entry/entry_32.S
+++ b/arch/x86/entry/entry_32.S
@@ -45,16 +45,6 @@
 #include <asm/asm.h>
 #include <asm/smap.h>
 
-/* Avoid __ASSEMBLER__'ifying <linux/audit.h> just for this.  */
-#include <linux/elf-em.h>
-#define AUDIT_ARCH_I386                (EM_386|__AUDIT_ARCH_LE)
-#define __AUDIT_ARCH_LE                0x40000000
-
-#ifndef CONFIG_AUDITSYSCALL
-# define sysenter_audit                syscall_trace_entry
-# define sysexit_audit         syscall_exit_work
-#endif
-
        .section .entry.text, "ax"
 
 /*
@@ -339,7 +329,7 @@ sysenter_past_esp:
        GET_THREAD_INFO(%ebp)
 
        testl   $_TIF_WORK_SYSCALL_ENTRY, TI_flags(%ebp)
-       jnz     sysenter_audit
+       jnz     syscall_trace_entry
 sysenter_do_call:
        cmpl    $(NR_syscalls), %eax
        jae     sysenter_badsys
@@ -351,7 +341,7 @@ sysenter_after_call:
        TRACE_IRQS_OFF
        movl    TI_flags(%ebp), %ecx
        testl   $_TIF_ALLWORK_MASK, %ecx
-       jnz     sysexit_audit
+       jnz     syscall_exit_work
 sysenter_exit:
 /* if something modifies registers it must also disable sysexit */
        movl    PT_EIP(%esp), %edx
@@ -362,40 +352,6 @@ sysenter_exit:
        PTGS_TO_GS
        ENABLE_INTERRUPTS_SYSEXIT
 
-#ifdef CONFIG_AUDITSYSCALL
-sysenter_audit:
-       testl   $(_TIF_WORK_SYSCALL_ENTRY & ~_TIF_SYSCALL_AUDIT), TI_flags(%ebp)
-       jnz     syscall_trace_entry
-       /* movl PT_EAX(%esp), %eax already set, syscall number: 1st arg to audit */
-       movl    PT_EBX(%esp), %edx              /* ebx/a0: 2nd arg to audit */
-       /* movl PT_ECX(%esp), %ecx already set, a1: 3nd arg to audit */
-       pushl   PT_ESI(%esp)                    /* a3: 5th arg */
-       pushl   PT_EDX+4(%esp)                  /* a2: 4th arg */
-       call    __audit_syscall_entry
-       popl    %ecx                            /* get that remapped edx off the stack */
-       popl    %ecx                            /* get that remapped esi off the stack */
-       movl    PT_EAX(%esp), %eax              /* reload syscall number */
-       jmp     sysenter_do_call
-
-sysexit_audit:
-       testl   $(_TIF_ALLWORK_MASK & ~_TIF_SYSCALL_AUDIT), %ecx
-       jnz     syscall_exit_work
-       TRACE_IRQS_ON
-       ENABLE_INTERRUPTS(CLBR_ANY)
-       movl    %eax, %edx                      /* second arg, syscall return value */
-       cmpl    $-MAX_ERRNO, %eax               /* is it an error ? */
-       setbe %al                               /* 1 if so, 0 if not */
-       movzbl %al, %eax                        /* zero-extend that */
-       call    __audit_syscall_exit
-       DISABLE_INTERRUPTS(CLBR_ANY)
-       TRACE_IRQS_OFF
-       movl    TI_flags(%ebp), %ecx
-       testl   $(_TIF_ALLWORK_MASK & ~_TIF_SYSCALL_AUDIT), %ecx
-       jnz     syscall_exit_work
-       movl    PT_EAX(%esp), %eax              /* reload syscall return value */
-       jmp     sysenter_exit
-#endif
-
 .pushsection .fixup, "ax"
 2:     movl    $0, PT_FS(%esp)
        jmp     1b