PERFORCE change 29912 for review

[Peter Wemm]

http://perforce.freebsd.org/chv.cgi?CH=29912

Change 29912 by peter at peter_daintree on 2003/04/27 18:48:04

	as a bonus, preserve %rsi and %rdi across 'syscall'.  This means we
	dont have to use PCB_FULLCTX on return from execve() which passes
	arguments in %rdi and %rsi.  It also makes life easier for things
	like the pipe(2) wrapper in libc.

Affected files ...

.. //depot/projects/hammer/sys/x86_64/x86_64/exception.s#32 edit

Differences ...

==== //depot/projects/hammer/sys/x86_64/x86_64/exception.s#32 (text+ko) ====

@@ -241,8 +241,10 @@
 	call	ast
 	jmp	1b
 2:	/* restore preserved registers */
+	movq	TF_RDI(%rsp),%rdi	/* bonus; preserve arg 1 */
+	movq	TF_RSI(%rsp),%rsi	/* bonus: preserve arg 2 */
+	movq	TF_RDX(%rsp),%rdx	/* return value 2 */
 	movq	TF_RAX(%rsp),%rax	/* return value 1 */
-	movq	TF_RDX(%rsp),%rdx	/* return value 2 */
 	movq	TF_RBX(%rsp),%rbx	/* C preserved */
 	movq	TF_RBP(%rsp),%rbp	/* C preserved */
 	movq	TF_R12(%rsp),%r12	/* C preserved */
@@ -251,8 +253,8 @@
 	movq	TF_R15(%rsp),%r15	/* C preserved */
 	movq	TF_RFLAGS(%rsp),%r11	/* original %rflags */
 	movq	TF_RIP(%rsp),%rcx	/* original %rip */
-	movq	TF_RSP(%rsp),%rdi	/* user stack pointer */
-	movq	%rdi,%rsp		/* original %rsp */
+	movq	TF_RSP(%rsp),%r9	/* user stack pointer */
+	movq	%r9,%rsp		/* original %rsp */
 	#swapgs
 	sysretq
 3:	/* Requested full context restore, use doreti for that */