xiaoxiang781216 commented on a change in pull request #5782:
URL: https://github.com/apache/incubator-nuttx/pull/5782#discussion_r837106706
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File path: arch/risc-v/include/syscall.h
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@@ -391,6 +396,64 @@ static inline uintptr_t sys_call6(unsigned int nbr,
uintptr_t parm1,
return r0;
}
+#ifdef CONFIG_ARCH_USE_S_MODE
+
+/* In S-mode the kernel cannot ecall to itself, because ecall will raise
+ * privileges to M-mode, which is not what we want. Instead, use the syscall
+ * trampoline to do the same.
+ */
+
+static inline uintptr_t ksys_call3(unsigned int nbr, uintptr_t parm1,
Review comment:
> The reason I chose the name ksys_call() and made the separate
functions is analogous to how for example the memory allocators are implemented
now. There are separate malloc/kmalloc functions for example. Both are needed.
This is the case with the syscall functions also.
But kmm_malloc will map to malloc in flat build, which make kmm_malloc work
in all possible mode(flat, protected and kernel). sys_callx should hand in the
same way, which mean that either user or kernel could call these function if
the want to invoke the kernel function, its the responsibility of sys_callx to
map the implementation to the right action base on the environment.
If we leave the old implementation as before, it's hard to ensure all place
which call sys_callx convert to ksys_callx.
BTW, the new contributor who doesn't understand the S-mode detail, may still
call sys_callx and then introduce the problem.
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