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| author | Denys Vlasenko | 2015-06-09 20:54:09 +0200 |
|---|---|---|
| committer | Ingo Molnar | 2015-06-10 08:42:13 +0200 |
| commit | a92fde25231a89d7d10895482556260c1b63767d (patch) | |
| tree | 1bc361bd96e906d27879bbbb0983db164fa3037b /arch/x86/entry/entry_64_compat.S | |
| parent | x86/asm/entry/32: Explain reloading of registers after __audit_syscall_entry() (diff) | |
| download | kernel-qcow2-linux-a92fde25231a89d7d10895482556260c1b63767d.tar.gz kernel-qcow2-linux-a92fde25231a89d7d10895482556260c1b63767d.tar.xz kernel-qcow2-linux-a92fde25231a89d7d10895482556260c1b63767d.zip | |
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@redhat.com>
Cc: Alexei Starovoitov <ast@plumgrid.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Will Drewry <wad@chromium.org>
Link: http://lkml.kernel.org/r/1433876051-26604-3-git-send-email-dvlasenk@redhat.com
[ Expanded the comments some more. ]
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'arch/x86/entry/entry_64_compat.S')
| -rw-r--r-- | arch/x86/entry/entry_64_compat.S | 27 |
1 files changed, 18 insertions, 9 deletions
diff --git a/arch/x86/entry/entry_64_compat.S b/arch/x86/entry/entry_64_compat.S index 0fa108cdf182..bb187a6a877c 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 */ |