Subject: Re: [PATCH 3/4] powerpc: Optimise 64bit syscall auditing entry path

From: Eric Paris <[email-masked]>
Date: Wed, 10 Apr 2013 12:56:43 -0400 (EDT)

Patches 1 and 2 I applied for 3.10, but I'd really like to have someone who knows PPC ack 3 and 4.  Especially if there is a hope that it goes through my tree...

Link to original messages for your ease of review...

http://marc.info/?l=linux-kernel&m=135768892320439&w=2
http://marc.info/?l=linux-kernel&m=135768895320472&w=2

-Eric

----- Original Message -----
> 
> Add an assembly fast path for the syscall audit entry path on
> 64bit. Some distros enable auditing by default which forces us
> through the syscall auditing path even if there are no rules.
> 
> I wrote some test cases to validate the patch:
> 
> http://ozlabs.org/~anton/junkcode/audit_tests.tar.gz
> 
> And to test the performance I ran a simple null syscall
> microbenchmark on a POWER7 box:
> 
> http://ozlabs.org/~anton/junkcode/null_syscall.c
> 
> Baseline: 949.2 cycles
> Patched:  920.6 cycles
> 
> An improvement of 3%. Most of the potential gains are masked by
> the syscall audit exit path which will be fixed in a
> subsequent patch.
> 
> Signed-off-by: Anton Blanchard <[email-masked]>
> ---
> 
> Index: b/arch/powerpc/kernel/entry_64.S
> ===================================================================
> --- a/arch/powerpc/kernel/entry_64.S
> +++ b/arch/powerpc/kernel/entry_64.S
> @@ -34,6 +34,12 @@
>  #include <asm/ftrace.h>
>  #include <asm/hw_irq.h>
>  
> +/* Avoid __ASSEMBLER__'ifying <linux/audit.h> just for this.  */
> +#include <linux/elf-em.h>
> +#define AUDIT_ARCH_PPC		(EM_PPC)
> +#define AUDIT_ARCH_PPC64	(EM_PPC64|__AUDIT_ARCH_64BIT)
> +#define __AUDIT_ARCH_64BIT 0x80000000
> +
>  /*
>   * System calls.
>   */
> @@ -244,6 +250,10 @@ syscall_error:
>  	
>  /* Traced system call support */
>  syscall_dotrace:
> +#ifdef CONFIG_AUDITSYSCALL
> +	andi.	r11,r10,(_TIF_SYSCALL_T_OR_A & ~_TIF_SYSCALL_AUDIT)
> +	beq	audit_entry
> +#endif
>  	bl	.save_nvgprs
>  	addi	r3,r1,STACK_FRAME_OVERHEAD
>  	bl	.do_syscall_trace_enter
> @@ -253,6 +263,7 @@ syscall_dotrace:
>  	 * for the call number to look up in the table (r0).
>  	 */
>  	mr	r0,r3
> +.Laudit_entry_return:
>  	ld	r3,GPR3(r1)
>  	ld	r4,GPR4(r1)
>  	ld	r5,GPR5(r1)
> @@ -264,6 +275,34 @@ syscall_dotrace:
>  	ld	r10,TI_FLAGS(r10)
>  	b	.Lsyscall_dotrace_cont
>  
> +#ifdef CONFIG_AUDITSYSCALL
> +audit_entry:
> +	ld	r4,GPR0(r1)
> +	ld	r5,GPR3(r1)
> +	ld	r6,GPR4(r1)
> +	ld	r7,GPR5(r1)
> +	ld	r8,GPR6(r1)
> +
> +	andi.	r11,r10,_TIF_32BIT
> +	beq	1f
> +
> +	lis	r3,AUDIT_ARCH_PPC@h
> +	ori	r3,r3,AUDIT_ARCH_PPC@l
> +	clrldi	r5,r5,32
> +	clrldi	r6,r6,32
> +	clrldi	r7,r7,32
> +	clrldi	r8,r8,32
> +	bl	.__audit_syscall_entry
> +	ld	r0,GPR0(r1)
> +	b	.Laudit_entry_return
> +
> +1:	lis	r3,AUDIT_ARCH_PPC64@h
> +	ori	r3,r3,AUDIT_ARCH_PPC64@l
> +	bl	.__audit_syscall_entry
> +	ld	r0,GPR0(r1)
> +	b	.Laudit_entry_return
> +#endif
> +
>  syscall_enosys:
>  	li	r3,-ENOSYS
>  	b	syscall_exit
>