klibc - Jul 2006 - [PATCH] vfork() for parisc

Implement "pid_t vfork(void)" for parisc.

Signed-off-by: Kyle McMartin <kyle at parisc-linux.org>
---

Ugh. vfork() me harder.

 Kbuild  |    2 +-
 vfork.S |   31 +++++++++++++++++++++++++++++++
 2 files changed, 32 insertions(+), 1 deletion(-)

diff --git a/usr/klibc/arch/parisc/Kbuild b/usr/klibc/arch/parisc/Kbuild
index d57a873..57ca5c2 100644
--- a/usr/klibc/arch/parisc/Kbuild
+++ b/usr/klibc/arch/parisc/Kbuild
@@ -2,7 +2,7 @@ #
 # klibc files for parisc
 #
 
-klib-y := setjmp.o syscall.o
+klib-y := setjmp.o syscall.o vfork.o
 
 always  := crt0.o
 targets := crt0.o
diff --git a/usr/klibc/arch/parisc/vfork.S b/usr/klibc/arch/parisc/vfork.S
new file mode 100644
index 0000000..97ebc8f
--- /dev/null
+++ b/usr/klibc/arch/parisc/vfork.S
@@ -0,0 +1,31 @@
+/*
+ * arch/parisc/vfork.S, "vfork() me harder. ugh." -- kyle
+ *
+ * %r20 contains the system call number, %rp contains whence we came,
+ * %rp is saved and restored across the syscall, thankfully.
+ *
+ */
+
+	.text
+	.align 64				; cache-width aligned
+	.globl	vfork
+	.type	vfork, at function
+vfork:
+	/* pid_t vfork(void) */
+	ble		0x100(%sr2, %r0)	; jump to gateway page
+	nop
+
+	ldi		-0x1000,%r19		; %r19 = -4096
+	sub		%r0,%ret0,%r22		; %r22 = -%ret0
+	cmpb,>>=,n	%r19,%ret0,1f		; if %ret0 >= -4096UL
+	ldi		-1,%ret0		; nullified on taken forward
+
+	/* store %r22 to errno... */
+	ldil		L%errno,%r1
+	ldo		R%errno(%r1),%r1
+	stw		%r22,0(%r1)
+1:
+	bv		%r0(%rp)		; jump back
+	nop
+
+	.size vfork,.-vfork

Kyle McMartin wrote:
> Implement "pid_t vfork(void)" for parisc.
> 
> --- /dev/null
> +++ b/usr/klibc/arch/parisc/vfork.S
> @@ -0,0 +1,31 @@
> +/*
> + * arch/parisc/vfork.S, "vfork() me harder. ugh." -- kyle
> + *
> + * %r20 contains the system call number, %rp contains whence we came,
> + * %rp is saved and restored across the syscall, thankfully.
> + *
> + */
Dumb question... where does %r20 get set?  This isn't invoked by a 
system call stub; it's the entire function.
> +
> +	.text
> +	.align 64				; cache-width aligned
> +	.globl	vfork
> +	.type	vfork, at function
> +vfork:
> +	/* pid_t vfork(void) */
> +	ble		0x100(%sr2, %r0)	; jump to gateway page
> +	nop
> +
> +	ldi		-0x1000,%r19		; %r19 = -4096
> +	sub		%r0,%ret0,%r22		; %r22 = -%ret0
> +	cmpb,>>=,n	%r19,%ret0,1f		; if %ret0 >= -4096UL
> +	ldi		-1,%ret0		; nullified on taken forward
> +
> +	/* store %r22 to errno... */
> +	ldil		L%errno,%r1
> +	ldo		R%errno(%r1),%r1
> +	stw		%r22,0(%r1)
> +1:
> +	bv		%r0(%rp)		; jump back
> +	nop
> +
> +	.size vfork,.-vfork
> 
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