riscv: Move syscall parameter from a7 to t0

To prepare for RV32E support.

Signed-off-by: Carlo Caione <[email protected]>

Author: carlocaione

arch/riscv/core/isr.S

@@ -303,16 +303,16 @@ is_kernel_syscall:
 	csrs mstatus, t1
 #endif
 
-	/* Determine what to do. Operation code is in a7. */
-	lr a7, __z_arch_esf_t_a7_OFFSET(sp)
+	/* Determine what to do. Operation code is in t0. */
+	lr t0, __z_arch_esf_t_t0_OFFSET(sp)
 
 	ASSUME_EQUAL(RV_ECALL_RUNTIME_EXCEPT, 0)
-	beqz a7, do_fault
+	beqz t0, do_fault
 
 #if defined(CONFIG_IRQ_OFFLOAD)
-	addi a7, a7, -1
+	addi t0, t0, -1
 	ASSUME_EQUAL(RV_ECALL_IRQ_OFFLOAD, 1)
-	beqz a7, do_irq_offload
+	beqz t0, do_irq_offload
 #endif
 
 	/* default fault code is K_ERR_KERNEL_OOPS */
@@ -386,24 +386,24 @@ is_user_syscall:
 	lr a3, __z_arch_esf_t_a3_OFFSET(sp)
 	lr a4, __z_arch_esf_t_a4_OFFSET(sp)
 	lr a5, __z_arch_esf_t_a5_OFFSET(sp)
+	lr t0, __z_arch_esf_t_t0_OFFSET(sp)
 	mv a6, sp
-	lr a7, __z_arch_esf_t_a7_OFFSET(sp)
 
 	/* validate syscall limit */
-	li t0, K_SYSCALL_LIMIT
-	bltu a7, t0, valid_syscall_id
+	li t1, K_SYSCALL_LIMIT
+	bltu t0, t1, valid_syscall_id
 
 	/* bad syscall id.  Set arg1 to bad id and set call_id to SYSCALL_BAD */
-	mv a0, a7
-	li a7, K_SYSCALL_BAD
+	mv a0, t0
+	li t0, K_SYSCALL_BAD
 
 valid_syscall_id:
 
-	la t0, _k_syscall_table
+	la t2, _k_syscall_table
 
-	slli t1, a7, RV_REGSHIFT	# Determine offset from indice value
-	add t0, t0, t1			# Table addr + offset = function addr
-	lr t2, 0(t0)			# Load function address
+	slli t1, t0, RV_REGSHIFT	# Determine offset from indice value
+	add t2, t2, t1			# Table addr + offset = function addr
+	lr t2, 0(t2)			# Load function address
 
 	/* Execute syscall function */
 	jalr ra, t2, 0

include/zephyr/arch/riscv/syscall.h

@@ -46,12 +46,12 @@ static inline uintptr_t arch_syscall_invoke6(uintptr_t arg1, uintptr_t arg2,
 	register ulong_t a3 __asm__ ("a3") = arg4;
 	register ulong_t a4 __asm__ ("a4") = arg5;
 	register ulong_t a5 __asm__ ("a5") = arg6;
-	register ulong_t a7 __asm__ ("a7") = call_id;
+	register ulong_t t0 __asm__ ("t0") = call_id;
 
 	__asm__ volatile ("ecall"
 			  : "+r" (a0)
 			  : "r" (a1), "r" (a2), "r" (a3), "r" (a4), "r" (a5),
-			  "r" (a7)
+			  "r" (t0)
 			  : "memory");
 	return a0;
 }
@@ -66,11 +66,11 @@ static inline uintptr_t arch_syscall_invoke5(uintptr_t arg1, uintptr_t arg2,
 	register ulong_t a2 __asm__ ("a2") = arg3;
 	register ulong_t a3 __asm__ ("a3") = arg4;
 	register ulong_t a4 __asm__ ("a4") = arg5;
-	register ulong_t a7 __asm__ ("a7") = call_id;
+	register ulong_t t0 __asm__ ("t0") = call_id;
 
 	__asm__ volatile ("ecall"
 			  : "+r" (a0)
-			  : "r" (a1), "r" (a2), "r" (a3), "r" (a4), "r" (a7)
+			  : "r" (a1), "r" (a2), "r" (a3), "r" (a4), "r" (t0)
 			  : "memory");
 	return a0;
 }
@@ -83,11 +83,11 @@ static inline uintptr_t arch_syscall_invoke4(uintptr_t arg1, uintptr_t arg2,
 	register ulong_t a1 __asm__ ("a1") = arg2;
 	register ulong_t a2 __asm__ ("a2") = arg3;
 	register ulong_t a3 __asm__ ("a3") = arg4;
-	register ulong_t a7 __asm__ ("a7") = call_id;
+	register ulong_t t0 __asm__ ("t0") = call_id;
 
 	__asm__ volatile ("ecall"
 			  : "+r" (a0)
-			  : "r" (a1), "r" (a2), "r" (a3), "r" (a7)
+			  : "r" (a1), "r" (a2), "r" (a3), "r" (t0)
 			  : "memory");
 	return a0;
 }
@@ -99,11 +99,11 @@ static inline uintptr_t arch_syscall_invoke3(uintptr_t arg1, uintptr_t arg2,
 	register ulong_t a0 __asm__ ("a0") = arg1;
 	register ulong_t a1 __asm__ ("a1") = arg2;
 	register ulong_t a2 __asm__ ("a2") = arg3;
-	register ulong_t a7 __asm__ ("a7") = call_id;
+	register ulong_t t0 __asm__ ("t0") = call_id;
 
 	__asm__ volatile ("ecall"
 			  : "+r" (a0)
-			  : "r" (a1), "r" (a2), "r" (a7)
+			  : "r" (a1), "r" (a2), "r" (t0)
 			  : "memory");
 	return a0;
 }
@@ -113,35 +113,35 @@ static inline uintptr_t arch_syscall_invoke2(uintptr_t arg1, uintptr_t arg2,
 {
 	register ulong_t a0 __asm__ ("a0") = arg1;
 	register ulong_t a1 __asm__ ("a1") = arg2;
-	register ulong_t a7 __asm__ ("a7") = call_id;
+	register ulong_t t0 __asm__ ("t0") = call_id;
 
 	__asm__ volatile ("ecall"
 			  : "+r" (a0)
-			  : "r" (a1), "r" (a7)
+			  : "r" (a1), "r" (t0)
 			  : "memory");
 	return a0;
 }
 
 static inline uintptr_t arch_syscall_invoke1(uintptr_t arg1, uintptr_t call_id)
 {
 	register ulong_t a0 __asm__ ("a0") = arg1;
-	register ulong_t a7 __asm__ ("a7") = call_id;
+	register ulong_t t0 __asm__ ("t0") = call_id;
 
 	__asm__ volatile ("ecall"
 			  : "+r" (a0)
-			  : "r" (a7)
+			  : "r" (t0)
 			  : "memory");
 	return a0;
 }
 
 static inline uintptr_t arch_syscall_invoke0(uintptr_t call_id)
 {
 	register ulong_t a0 __asm__ ("a0");
-	register ulong_t a7 __asm__ ("a7") = call_id;
+	register ulong_t t0 __asm__ ("t0") = call_id;
 
 	__asm__ volatile ("ecall"
 			  : "=r" (a0)
-			  : "r" (a7)
+			  : "r" (t0)
 			  : "memory");
 	return a0;
 }
@@ -168,7 +168,7 @@ static inline bool arch_is_user_context(void)
 	 * and omit the volatile to give the compiler a chance to cache
 	 * the result.
 	 */
-	register ulong_t is_user __asm__ ("t0");
+	register ulong_t is_user __asm__ ("t1");
 	__asm__ ("csrr %0, mscratch" : "=r" (is_user));
 	return is_user != 0;
 #else