[GitHub] [incubator-nuttx] pussuw commented on a diff in pull request #6052: arch/riscv: Jump instead call riscv_dispatch_syscall

[GitBox <gi...@apache.org>]

pussuw commented on code in PR #6052:
URL: https://github.com/apache/incubator-nuttx/pull/6052#discussion_r848375189


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arch/risc-v/include/syscall.h:
##########
@@ -124,16 +124,10 @@
 #define SYS_signal_handler_return (7)
 #endif /* !CONFIG_BUILD_FLAT */
 
-#if defined (CONFIG_ARCH_USE_S_MODE) && defined (__KERNEL__)
-#  define ASM_SYS_CALL \
-     " addi sp, sp, -16\n"                  /* Make room */ \
-     REGSTORE " ra, 0(sp)\n"                /* Save ra */ \
-     " jal  ra, riscv_dispatch_syscall\n"   /* Dispatch (modifies ra) */ \
-     REGLOAD " ra, 0(sp)\n"                 /* Restore ra */ \
-     " addi sp, sp, 16\n"                   /* Restore sp */
+#if defined(CONFIG_ARCH_USE_S_MODE) && defined(__KERNEL__)
+#  define ASM_SYS_CALL "j riscv_dispatch_syscall\n"

Review Comment:
   I don't think this will work, up_signal_dispatch actually returns here and now the software will simply get lost. ecall knows where to return since it sets EPC.



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