arch/at91sam3x8e: use r0 for syscall number

arch/at91sam3x8e/entry.c

@@ -9,29 +9,32 @@
 
 #include <errno.h>
 #include <stddef.h>
+#include <unistd.h>
 
-void arch_syscall(void *sp)
+void arch_enter(void *sp)
 {
 	struct reg_snapshot *regs = sp;
 	enum syscall sc_num = arch_syscall_num(regs);
-	int (*handler)(sysarg_t arg1, sysarg_t arg2, sysarg_t arg3,
-		       sysarg_t arg4, sysarg_t arg5, sysarg_t arg6);
+	int (*handler)(sysarg_t arg1, sysarg_t arg2, sysarg_t arg3, sysarg_t arg4);
 	int sc_ret;
 
+	if (sc_num == SYSCALL_WRITE)
+		*(uint32_t *)0x400E1030U = 1 << 27;
+
 	if (sc_num > NSYSCALLS) {
 		arch_syscall_set_rval(regs, -EINVAL);
 		return;
 	}
 
-	handler = syscall_table[sc_num];
+	handler = sys_table[sc_num];
 	if (handler == NULL) {
 		arch_syscall_set_rval(regs, -EINVAL);
 		return;
 	}
 
 	/* TODO: not every syscall uses the max amount of parameters (duh) */
-	sc_ret = handler(arch_syscall_arg1(regs), arch_syscall_arg2(regs), arch_syscall_arg3(regs),
-			 arch_syscall_arg4(regs), arch_syscall_arg5(regs), arch_syscall_arg6(regs));
+	sc_ret = handler(arch_syscall_arg1(regs), arch_syscall_arg2(regs),
+			 arch_syscall_arg3(regs), arch_syscall_arg4(regs));
 
 	arch_syscall_set_rval(regs, sc_ret);
 }

arch/at91sam3x8e/irq_svc.S

@@ -6,7 +6,7 @@
 
 .text
 
-.extern arch_syscall
+.extern arch_enter
 
 .thumb_func
 .global irq_svc
@@ -41,7 +41,7 @@ irq_svc:
 	push	{r3-r7}			/* r8-r11, lr */
 
 	mov	r0,	sp
-	bl	arch_syscall		/* arch_syscall(sp); */
+	bl	arch_enter		/* arch_enter(sp); */
 
 	pop	{r3-r7}			/* r8-r11, lr */
 	mov	lr,	r7

arch/at91sam3x8e/syscall.S

@@ -1,26 +1,20 @@
 /* SPDX-License-Identifier: BSD-3-Clause */
 /* See the end of this file for copyright, licensing, and warranty information. */
 
-/*
- * This is a collection of system calls that are exported to userspace.
- * The Ardix syscall ABI for parameter passing is aligned with the AAPCS, making
- * these wrappers extremely simple because all parameters are already in the
- * correct registers.
- */
-
 .syntax unified
 .thumb
 
-/* these syscalls are only there to be exported to userspace */
+/* this is only invoked from user space, obviously */
 .section .text.shared
 
 .thumb_func
-.global pwrite
-.type pwrite, %function
-pwrite:
+.global syscall
+.type syscall, %function
+/* int syscall(int number, int arg1, int arg2, int arg3, int arg4); */
+syscall:
 	svc	#1
 	bx	lr
-.size pwrite, .-pwrite
+.size syscall, .-syscall
 
 /*
  * Copyright (c) 2020 Felix Kopp <sandtler@sandtler.club>

include/arch/at91sam3x8e/hardware.h

@@ -54,15 +54,13 @@ struct reg_snapshot {
 	struct reg_hw_snapshot hw;
 };
 
-#define arch_syscall_num(reg_snap) ( ((uint8_t *)((reg_snap)->hw.lr))[1] )
-#define arch_syscall_arg1(reg_snap) ((reg_snap)->hw.r0)
-#define arch_syscall_arg2(reg_snap) ((reg_snap)->hw.r1)
-#define arch_syscall_arg3(reg_snap) ((reg_snap)->hw.r2)
-#define arch_syscall_arg4(reg_snap) ((reg_snap)->hw.r3)
-#define arch_syscall_arg5(reg_snap) ((reg_snap)->sw.r8)
-#define arch_syscall_arg6(reg_snap) ((reg_snap)->sw.r9)
-
-#define arch_syscall_set_rval(reg_snap, val) ((reg_snap)->hw.r0 = (uint32_t)(val));
+#define arch_syscall_num(reg_snap) ((reg_snap)->hw.r0)
+#define arch_syscall_arg1(reg_snap) ((reg_snap)->hw.r1)
+#define arch_syscall_arg2(reg_snap) ((reg_snap)->hw.r2)
+#define arch_syscall_arg3(reg_snap) ((reg_snap)->hw.r3)
+#define arch_syscall_arg4(reg_snap) ((reg_snap)->hw.r12)
+
+#define arch_syscall_set_rval(reg_snap, val) ((reg_snap)->hw.r0 = (val));
 
 /*
  * Real-time Timer (RTT)

include/arch/entry.h

@@ -12,7 +12,7 @@
  *
  * @param sp: The current stack pointer.
  */
-void arch_syscall(void *sp);
+void arch_enter(void *sp);
 
 /*
  * Copyright (c) 2020 Felix Kopp <sandtler@sandtler.club>

include/ardix/syscall.h

@@ -16,9 +16,12 @@ enum syscall {
 	NSYSCALLS
 };
 
+/** Perform an indirect system call. */
+int syscall(enum syscall number, sysarg_t arg1, sysarg_t arg2, sysarg_t arg3, sysarg_t arg4);
+
 /** The table of system call handlers, indexed by syscall number. */
-extern const int (*syscall_table[NSYSCALLS])(sysarg_t arg1, sysarg_t arg2, sysarg_t arg3,
-					     sysarg_t arg4, sysarg_t arg5, sysarg_t arg6);
+extern const int (*sys_table[NSYSCALLS])(sysarg_t arg1, sysarg_t arg2,
+					 sysarg_t arg3, sysarg_t arg4);
 
 /* catchall handler that returns -ENOSYS */
 int sys_stub(void);

kernel/syscall.c

@@ -5,14 +5,13 @@
 
 #include <toolchain.h>
 
-#define syscall_entry(number, func) \
-	[number] (int (*)(sysarg_t, sysarg_t, sysarg_t, sysarg_t, sysarg_t, sysarg_t))(func)
+#define sys_table_entry(number, func) \
+	[number] (int (*)(sysarg_t, sysarg_t, sysarg_t, sysarg_t))(func)
 
 __rodata
-const int (*syscall_table[NSYSCALLS])(sysarg_t arg1, sysarg_t arg2, sysarg_t arg3,
-				      sysarg_t arg4, sysarg_t arg5, sysarg_t arg6) = {
-	syscall_entry(SYSCALL_READ, &sys_stub),
-	syscall_entry(SYSCALL_WRITE, &sys_write),
+const int (*sys_table[NSYSCALLS])(sysarg_t arg1, sysarg_t arg2, sysarg_t arg3, sysarg_t arg4) = {
+	sys_table_entry(SYSCALL_READ, &sys_stub),
+	sys_table_entry(SYSCALL_WRITE, &sys_write),
 };
 
 int sys_stub(void)

lib/Makefile

@@ -29,4 +29,5 @@ ARDIX_SOURCES += \
 	$(ARDIX_LIB_PWD)/ctype.c \
 	$(ARDIX_LIB_PWD)/list.c \
 	$(ARDIX_LIB_PWD)/malloc.c \
-	$(ARDIX_LIB_PWD)/string.c
+	$(ARDIX_LIB_PWD)/string.c \
+	$(ARDIX_LIB_PWD)/unistd.c

lib/unistd.c

@@ -8,9 +8,16 @@
 #include <toolchain.h>
 #include <unistd.h>
 
+__shared ssize_t pwrite(int fildes, const void *buf, size_t nbyte, off_t offset)
+{
+	return syscall(SYSCALL_WRITE, (sysarg_t)fildes, (sysarg_t)buf, (sysarg_t)nbyte,
+		       (sysarg_t)offset);
+}
+
 __shared ssize_t write(int fildes, const void *buf, size_t nbyte)
 {
-	return pwrite(fildes, buf, nbyte, 0);
+	return syscall(SYSCALL_WRITE, (sysarg_t)fildes, (sysarg_t)buf, (sysarg_t)nbyte,
+		       (sysarg_t)0);
 }
 
 /*