[GitHub] [incubator-nuttx] pussuw commented on a change in pull request #5782: RISC-V: Implement option to run NuttX in supervisor mode (S-mode)

[GitBox]

pussuw commented on a change in pull request #5782:
URL: https://github.com/apache/incubator-nuttx/pull/5782#discussion_r834615075



##########
File path: arch/risc-v/src/common/riscv_assert.c
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@@ -338,6 +338,10 @@ static void riscv_dumpstate(void)
   else
     {
       riscv_saveusercontext(rtcb->xcp.regs);
+
+      /* riscv_saveusercontext modifies the local context (a0), restore it */
+
+      rtcb = running_task();

Review comment:
       the prototype is int riscv_saveusercontext (regs);
   
   /* SYS call 0:
    *
    * int riscv_saveusercontext(uint64_t *saveregs);
    *
    * Return:
    * 0: Normal Return
    * 1: Context Switch Return
    */
   
   I did what this comment says. So the asm function returns 0 in a0 to the 
caller, and 1 to the context.
   
   > 
   >   li         s0, 1                     /* return 1 (in context) */ <<- 
This destroys rtcb!
   >   REGSTORE   s0, REG_A0(a0)
   > 
   >   li         a0, 0                     /* return 0 (back to caller) */
   >   ret
   > 
   
   So in the context (caller) a0 is destroyed. That is rtcb so it must be 
re-acquired.




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