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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>
This commit is contained in:
Andy Lutomirski 2015-07-31 14:41:08 -07:00 committed by Ingo Molnar
parent decd275e62
commit c5f69fde26
1 changed files with 2 additions and 46 deletions
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48
arch/x86/entry/entry_32.S
View File

@ -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