xiaoxiang781216 commented on a change in pull request #5782:
URL: https://github.com/apache/incubator-nuttx/pull/5782#discussion_r837863612
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File path: arch/risc-v/src/common/riscv_swint.c
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@@ -179,6 +187,31 @@ int riscv_swint(int irq, void *context, void *arg)
riscv_registerdump(regs);
#endif
+ /* Handle the syscall */
+
+ regs = riscv_handle_syscall(regs);
+
+ /* Report what happened. That might difficult in the case of a context
+ * switch
+ */
+
+#ifdef CONFIG_DEBUG_SYSCALL_INFO
+ if (regs != CURRENT_REGS)
+ {
+ svcinfo("SWInt Return: Context switch!\n");
+ riscv_registerdump((const uintptr_t *)CURRENT_REGS);
+ }
+ else
+ {
+ svcinfo("SWInt Return: %d\n", regs[REG_A0]);
+ }
+#endif
+
+ return OK;
+}
+
+void *riscv_handle_syscall(uintptr_t *regs)
Review comment:
> There were two points:
>
> 1. int riscv_swint(int irq, void *context, void *arg), irq is not active
as the call comes from thread, arg is not used / set, but then again irq is not
used either so it does not matter...
We can pass the fix value here.
> 2. The handling of CURRENT_REGS, e.g. DEBUGASSERT(regs && regs ==
CURRENT_REGS); The function has 1 global variable so it is not really re-entrant
>
> riscv_syscall_dispatch is re-entrant, always
it isn't a problem since you need disable interrupt anyway to simulate ECALL.
>
> If you think that removing the test for regs == CURRENT_REGS is fine, then
the function can be combined. To me splitting the logical part (the switch
case) out of the already massive function made sense.
I think it's better to call up_doirq just like execption_common once
riscv_syscall_dispatch finish to prepare the environment.
From the concept, RISCV kernel mode different from ARM is just because
S-mode can't generate the exception to self. So, the change really needed is
simulate ECALL inside ssy_callx, other part should be shared with M-mode and
S-mode as much as possible.
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