syscall: fix call source detection

arch/at91sam3x8e/entry.c

@@ -13,7 +13,7 @@
 
 #ifdef CONFIG_CHECK_SYSCALL_SOURCE
 /* syscall.S */
-extern uintptr_t __syscall_entry_point;
+extern uint16_t __syscall_return_point;
 #endif
 
 void arch_enter(void *sp)
@@ -27,10 +27,11 @@ void arch_enter(void *sp)
 #	ifdef CONFIG_CHECK_SYSCALL_SOURCE
 	/*
 	 * We need to ignore the program counter's LSB because the CPU uses
-	 * that as a flag for whether it's operating in ARM or Thumb mode
-	 * (1 for Thumb); the instructions are always 2-byte aligned.
+	 * that as a flag for whether it's operating in ARM or Thumb mode;
+	 * the instructions are always 2-byte aligned.  Additionally, the PC
+	 * points to the instruction *after* the SVC, not SVC itself.
 	 */
-	if ((regs->hw.pc & 0xfffffffe) != __syscall_entry_point) {
+	if (((uintptr_t)regs->hw.pc & 0xfffffffe) != (uintptr_t)&__syscall_return_point) {
 		arch_syscall_set_rval(regs, -EACCES);
 		return;
 	}

arch/at91sam3x8e/include/arch/hardware.h

@@ -29,7 +29,7 @@ struct reg_sw_snapshot {
 	 * lr is saved by hardware, but we need to store it twice
 	 * because the IRQ entry overwrites it
 	 */
-	uintptr_t lr;	/* alias r14 */
+	void *lr;	/* alias r14 */
 };
 
 /**
@@ -42,8 +42,8 @@ struct reg_hw_snapshot {
 	word_t r2;
 	word_t r3;
 	word_t r12;
-	uintptr_t lr;	/* alias r14 */
-	uintptr_t pc;	/* alias r15 */
+	void *lr;	/* alias r14 */
+	void *pc;	/* alias r15 */
 	word_t psr;
 };
 

arch/at91sam3x8e/sched.c

@@ -61,9 +61,9 @@ void arch_sched_task_init(struct task *task, void (*entry)(void))
 	task->sp = regs;
 
 	memset(regs, 0, sizeof(*regs));
-	regs->hw.pc = (uintptr_t)entry;
-	regs->hw.psr = 0x01000000U;
-	regs->sw.lr = 0xfffffff9U;
+	regs->hw.pc = entry;
+	regs->hw.psr = 0x01000000;
+	regs->sw.lr = (void *)0xfffffff9;
 }
 
 void yield(enum task_state state)

arch/at91sam3x8e/syscall.S

@@ -5,6 +5,8 @@
 /* this is only invoked from user space, obviously */
 .section .text.shared
 
+.global __syscall_return_point
+
 /* int syscall(int number, int arg1, int arg2, int arg3, int arg4, int arg5, int arg6); */
 func_begin syscall
 
@@ -32,10 +34,9 @@ func_begin syscall
 	ldr	r4,	[sp, #16]	/* arg5 */
 	ldr	r5,	[sp, #20]	/* arg6 */
 
-.global __syscall_entry_point
-__syscall_entry_point:
 	svc	#0
 
+__syscall_return_point:
 	pop	{r4-r5,r7}
 
 	/* r0 (return value) is set by the kernel */