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i386 syscall audit fast-path

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This adds fast paths for 32-bit syscall entry and exit when
TIF_SYSCALL_AUDIT is set, but no other kind of syscall tracing.
These paths does not need to save and restore all registers as
the general case of tracing does.  Avoiding the iret return path
when syscall audit is enabled helps performance a lot.

Signed-off-by: Roland McGrath <roland@redhat.com>
This commit is contained in:
Roland McGrath 2008-06-24 04:16:52 -07:00
parent 5cbf1565f2
commit af0575bba0
1 changed files with 53 additions and 2 deletions
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55
arch/x86/kernel/entry_32.S
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@ -54,6 +54,16 @@
#include <asm/ftrace.h>
#include <asm/irq_vectors.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
/*
* We use macros for low-level operations which need to be overridden
* for paravirtualization. The following will never clobber any registers:
@ -333,7 +343,8 @@ sysenter_past_esp:
/* Note, _TIF_SECCOMP is bit number 8, and so it needs testw and not testb */
testw $_TIF_WORK_SYSCALL_ENTRY,TI_flags(%ebp)
jnz syscall_trace_entry
jnz sysenter_audit
sysenter_do_call:
cmpl $(nr_syscalls), %eax
jae syscall_badsys
call *sys_call_table(,%eax,4)
@ -343,7 +354,8 @@ sysenter_past_esp:
TRACE_IRQS_OFF
movl TI_flags(%ebp), %ecx
testw $_TIF_ALLWORK_MASK, %cx
jne syscall_exit_work
jne sysexit_audit
sysenter_exit:
/* if something modifies registers it must also disable sysexit */
movl PT_EIP(%esp), %edx
movl PT_OLDESP(%esp), %ecx
@ -351,6 +363,45 @@ sysenter_past_esp:
TRACE_IRQS_ON
1: mov PT_FS(%esp), %fs
ENABLE_INTERRUPTS_SYSEXIT
#ifdef CONFIG_AUDITSYSCALL
sysenter_audit:
testw $(_TIF_WORK_SYSCALL_ENTRY & ~_TIF_SYSCALL_AUDIT),TI_flags(%ebp)
jnz syscall_trace_entry
addl $4,%esp
CFI_ADJUST_CFA_OFFSET -4
/* %esi already in 8(%esp) 6th arg: 4th syscall arg */
/* %edx already in 4(%esp) 5th arg: 3rd syscall arg */
/* %ecx already in 0(%esp) 4th arg: 2nd syscall arg */
movl %ebx,%ecx /* 3rd arg: 1st syscall arg */
movl %eax,%edx /* 2nd arg: syscall number */
movl $AUDIT_ARCH_I386,%eax /* 1st arg: audit arch */
call audit_syscall_entry
pushl %ebx
CFI_ADJUST_CFA_OFFSET 4
movl PT_EAX(%esp),%eax /* reload syscall number */
jmp sysenter_do_call
sysexit_audit:
testw $(_TIF_ALLWORK_MASK & ~_TIF_SYSCALL_AUDIT), %cx
jne syscall_exit_work
TRACE_IRQS_ON
ENABLE_INTERRUPTS(CLBR_ANY)
movl %eax,%edx /* second arg, syscall return value */
cmpl $0,%eax /* is it < 0? */
setl %al /* 1 if so, 0 if not */
movzbl %al,%eax /* zero-extend that */
inc %eax /* first arg, 0->1(AUDITSC_SUCCESS), 1->2(AUDITSC_FAILURE) */
call audit_syscall_exit
DISABLE_INTERRUPTS(CLBR_ANY)
TRACE_IRQS_OFF
movl TI_flags(%ebp), %ecx
testw $(_TIF_ALLWORK_MASK & ~_TIF_SYSCALL_AUDIT), %cx
jne syscall_exit_work
movl PT_EAX(%esp),%eax /* reload syscall return value */
jmp sysenter_exit
#endif
CFI_ENDPROC
.pushsection .fixup,"ax"
2: movl $0,PT_FS(%esp)