[PATCH] libgloss: pru: Fix _open syscal arguments

[Dimitar Dimitrov <dimitar@dinux.eu>]

The _open() C function is declared as having variable arguments in
newlib, so second and third arguments are passed on stack. Add code to
move them into registers, since that's where the PRU simulator expects
them.

Issue was exposed by the GCC test gcc.c-torture/execute/fprintf-2.c,
which relies on tmpnam implementation to pass correct flags to _open.

Signed-off-by: Dimitar Dimitrov <dimitar@dinux.eu>
---
 libgloss/pru/syscalls.S | 18 +++++++++++++++++-
 1 file changed, 17 insertions(+), 1 deletion(-)

diff --git a/libgloss/pru/syscalls.S b/libgloss/pru/syscalls.S
index 252231e90..80486d1f9 100644
--- a/libgloss/pru/syscalls.S
+++ b/libgloss/pru/syscalls.S
@@ -68,7 +68,6 @@ __SC_ret_skip_errno_set:
 	   users use other methods for communicating with
 	   the host - remoteproc, rpmsg, shared memory.  */
 	SC	_exit, SYS_exit
-	SC	_open, SYS_open
 	SC	_close, SYS_close
 	SC	_read, SYS_read
 	SC	_write, SYS_write
@@ -77,3 +76,20 @@ __SC_ret_skip_errno_set:
 	SC	_getpid, SYS_getpid
 	SC	_kill, SYS_kill
 	SC	_fstat, SYS_fstat
+
+
+	/* _open is special because it has VA declaration. */
+	.section .text._open, "ax"
+	.global	_open
+	.type	_open,@function
+	.func
+_open:
+	/* Pop the second and third argument from stack, per VA ABI.
+	   Thus simulator can get all arguments from registers
+	   for any supported syscall.  */
+	lbbo    r16, sp, 4, 4
+	lbbo    r15, sp, 0, 4
+	ldi	r1, SYS_open
+	halt
+	jmp	__SC_ret
+	.endfunc
-- 
2.35.1