xiaoxiang781216 commented on code in PR #20873:
URL: https://github.com/apache/nuttx/pull/20873#discussion_r4343552247
##########
arch/arm/include/syscall.h:
##########
@@ -135,33 +135,38 @@
#ifndef __ASSEMBLY__
+/* A system call returns with R1-R3 and R12 changed (dispatch_syscall() calls
+ * the stub function), so the macros give these registers to the compiler
+ * as outputs or as clobbered.
+ */
+
/* SVC with SYS_ call number and no parameters */
#ifdef __ghs__
-# define sys_call0(nbr) \
-({ \
- uintptr_t ret; \
- __asm__ __volatile__ \
- ( \
- "mov r0, %2\n\t" \
- "svc %1\n\t" \
- "mov %0, r0" \
- : "=r"(ret) \
- : "i"(SYS_syscall), "r"((uintptr_t)nbr) \
- : "memory", "r0" \
- ); \
- ret; \
+# define sys_call0(nbr) \
+({ \
+ uintptr_t ret; \
+ __asm__ __volatile__ \
+ ( \
+ "mov r0, %2\n\t" \
+ "svc %1\n\t" \
+ "mov %0, r0" \
+ : "=r"(ret) \
+ : "i"(SYS_syscall), "r"((uintptr_t)nbr) \
+ : "memory", "r0", "r1", "r2", "r3", "r12" \
+ ); \
+ ret; \
})
#else
# define sys_call0(nbr) \
({ \
register uintptr_t reg0 __asm__("r0") = (uintptr_t)(nbr); \
__asm__ __volatile__ \
( \
- "svc %1" \
- : "=r"(reg0) \
- : "i"(SYS_syscall), "r"(reg0) \
- : "memory" \
+ "svc %[svc]" \
+ : "+r"(reg0) \
+ : [svc] "i"(SYS_syscall) \
Review Comment:
why add svc symbol? let's algin the implementation of gcc and ghs
##########
arch/arm/src/armv7-a/arm_syscall.c:
##########
@@ -132,7 +145,8 @@ static void dispatch_syscall(void)
" str r5, [sp, #4]\n" /* Move parameter 5 (if
any) into position */
" str r6, [sp, #8]\n" /* Move parameter 6 (if
any) into position */
" str lr, [sp, #12]\n" /* Save lr in the stack
frame */
- " ldr ip, =g_stublookup\n" /* R12=The base of the
stub lookup table */
+ " ldr ip, =g_stublookup_ptr\n" /* R12=The address of the
table pointer */
Review Comment:
how about reference g_stublookup_ptr through assemble argument
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