Commit-ID: a92fde25231a89d7d10895482556260c1b63767d Gitweb: http://git.kernel.org/tip/a92fde25231a89d7d10895482556260c1b63767d Author: Denys Vlasenko <dvlasenk@xxxxxxxxxx> AuthorDate: Tue, 9 Jun 2015 20:54:09 +0200 Committer: Ingo Molnar <mingo@xxxxxxxxxx> CommitDate: Wed, 10 Jun 2015 08:42:13 +0200 x86/asm/entry/32: Shorten __audit_syscall_entry() args preparation 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: Denys Vlasenko <dvlasenk@xxxxxxxxxx> Cc: Alexei Starovoitov <ast@xxxxxxxxxxxx> Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> Cc: Andy Lutomirski <luto@xxxxxxxxxxxxxx> Cc: Borislav Petkov <bp@xxxxxxxxx> Cc: Brian Gerst <brgerst@xxxxxxxxx> Cc: Frederic Weisbecker <fweisbec@xxxxxxxxx> Cc: H. Peter Anvin <hpa@xxxxxxxxx> Cc: Kees Cook <keescook@xxxxxxxxxxxx> Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> Cc: Oleg Nesterov <oleg@xxxxxxxxxx> Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx> Cc: Steven Rostedt <rostedt@xxxxxxxxxxx> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Cc: Will Drewry <wad@xxxxxxxxxxxx> Link: http://lkml.kernel.org/r/1433876051-26604-3-git-send-email-dvlasenk@xxxxxxxxxx [ Expanded the comments some more. ] Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx> --- arch/x86/entry/entry_64_compat.S | 27 ++++++++++++++++++--------- 1 file changed, 18 insertions(+), 9 deletions(-) diff --git a/arch/x86/entry/entry_64_compat.S b/arch/x86/entry/entry_64_compat.S index 0fa108c..bb187a6 100644 --- a/arch/x86/entry/entry_64_compat.S +++ b/arch/x86/entry/entry_64_compat.S @@ -178,17 +178,26 @@ sysexit_from_sys_call: #ifdef CONFIG_AUDITSYSCALL .macro auditsys_entry_common - movl %esi, %r8d /* 5th arg: 4th syscall arg */ - movl %ecx, %r9d /* swap with edx */ - movl %edx, %ecx /* 4th arg: 3rd syscall arg */ - movl %r9d, %edx /* 3rd arg: 2nd syscall arg */ - movl %ebx, %esi /* 2nd arg: 1st syscall arg */ - movl %eax, %edi /* 1st arg: syscall number */ + /* + * At this point, registers hold syscall args in the 32-bit syscall ABI: + * EAX is syscall number, the 6 args are in EBX,ECX,EDX,ESI,EDI,EBP. + * + * We want to pass them to __audit_syscall_entry(), which is a 64-bit + * C function with 5 parameters, so shuffle them to match what + * the function expects: RDI,RSI,RDX,RCX,R8. + */ + movl %esi, %r8d /* arg5 (R8 ) <= 4th syscall arg (ESI) */ + xchg %ecx, %edx /* arg4 (RCX) <= 3rd syscall arg (EDX) */ + /* arg3 (RDX) <= 2nd syscall arg (ECX) */ + movl %ebx, %esi /* arg2 (RSI) <= 1st syscall arg (EBX) */ + movl %eax, %edi /* arg1 (RDI) <= syscall number (EAX) */ call __audit_syscall_entry + /* - * We are going to jump back to syscall dispatch. - * Prepare syscall args as required by 64-bit C ABI. - * Clobbered registers are loaded from pt_regs on stack. + * We are going to jump back to the syscall dispatch code. + * Prepare syscall args as required by the 64-bit C ABI. + * Registers clobbered by __audit_syscall_entry() are + * loaded from pt_regs on stack: */ movl ORIG_RAX(%rsp), %eax /* syscall number */ movl %ebx, %edi /* arg1 */ -- To unsubscribe from this list: send the line "unsubscribe linux-tip-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
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