Fix vfork

arch/risc-v/include/irq.h

@@ -613,6 +613,12 @@ struct xcptcontext
 
   uintreg_t *regs;
 
+#ifdef CONFIG_LIB_SYSCALL
+  /* User integer registers upon system call entry */
+
+  uintreg_t *sregs;
+#endif
+
   /* FPU register save area */
 
 #if defined(CONFIG_ARCH_FPU) && defined(CONFIG_ARCH_LAZYFPU)

arch/risc-v/src/common/riscv_doirq.c

@@ -58,6 +58,7 @@
 
 uintreg_t *riscv_doirq(int irq, uintreg_t *regs)
 {
+  struct tcb_s **running_task = &g_running_tasks[this_cpu()];
   struct tcb_s *tcb = this_task();
 
   board_autoled_on(LED_INIRQ);
@@ -71,9 +72,10 @@ uintreg_t *riscv_doirq(int irq, uintreg_t *regs)
     {
       regs[REG_EPC] += 4;
     }
-  else
+
+  if (*running_task != NULL)
     {
-      tcb->xcp.regs = regs;
+      (*running_task)->xcp.regs = regs;
     }
 
   /* Current regs non-zero indicates that we are processing an interrupt;
@@ -97,7 +99,7 @@ uintreg_t *riscv_doirq(int irq, uintreg_t *regs)
    * returning from the interrupt.
    */
 
-  if (regs != tcb->xcp.regs)
+  if ((*running_task) != tcb)
     {
 #ifdef CONFIG_ARCH_ADDRENV
       /* Make sure that the address environment for the previously
@@ -114,15 +116,7 @@ uintreg_t *riscv_doirq(int irq, uintreg_t *regs)
        * crashes.
        */
 
-      g_running_tasks[this_cpu()] = tcb;
-
-      /* If a context switch occurred while processing the interrupt then
-       * current_regs may have change value.  If we return any value
-       * different from the input regs, then the lower level will know
-       * that a context switch occurred during interrupt processing.
-       */
-
-      regs = tcb->xcp.regs;
+      *running_task = tcb;
     }
 
   /* Set current_regs to NULL to indicate that we are no longer in an
@@ -133,5 +127,5 @@ uintreg_t *riscv_doirq(int irq, uintreg_t *regs)
 
 #endif
   board_autoled_off(LED_INIRQ);
-  return regs;
+  return tcb->xcp.regs;
 }

arch/risc-v/src/common/riscv_exit.c

@@ -78,6 +78,10 @@ void up_exit(int status)
 
   nxsched_resume_scheduler(tcb);
 
+  /* g_running_tasks is not valid now */
+
+  g_running_tasks[this_cpu()] = NULL;
+
   /* Then switch contexts */
 
   riscv_fullcontextrestore(tcb);

arch/risc-v/src/common/riscv_fork.c

@@ -108,19 +108,14 @@ pid_t riscv_fork(const struct fork_s *context)
   uintptr_t newtop;
   uintptr_t stacktop;
   uintptr_t stackutil;
-  irqstate_t flags;
 #ifdef CONFIG_SCHED_THREAD_LOCAL
   uintptr_t tp;
 #endif
   UNUSED(context);
 
-  /* parent regs may change in irq, we should disable irq here */
-
-  flags = up_irq_save();
-
   /* Allocate and initialize a TCB for the child task. */
 
-  child = nxtask_setup_fork((start_t)parent->xcp.regs[REG_RA]);
+  child = nxtask_setup_fork((start_t)parent->xcp.sregs[REG_RA]);
   if (!child)
     {
       sinfo("nxtask_setup_fork failed\n");
@@ -130,36 +125,50 @@ pid_t riscv_fork(const struct fork_s *context)
   /* Copy parent user stack to child */
 
   stacktop = (uintptr_t)parent->stack_base_ptr + parent->adj_stack_size;
-  DEBUGASSERT(stacktop > parent->xcp.regs[REG_SP]);
-  stackutil = stacktop - parent->xcp.regs[REG_SP];
+  DEBUGASSERT(stacktop > parent->xcp.sregs[REG_SP]);
+  stackutil = stacktop - parent->xcp.sregs[REG_SP];
 
-  /* Copy the parent stack contents (overwrites child's SP and TP) */
+  /* Copy goes to child's user stack top */
 
   newtop = (uintptr_t)child->cmn.stack_base_ptr + child->cmn.adj_stack_size;
   newsp = newtop - stackutil;
 
+  memcpy((void *)newsp, (const void *)parent->xcp.sregs[REG_SP], stackutil);
+
 #ifdef CONFIG_SCHED_THREAD_LOCAL
   /* Save child's thread pointer */
 
   tp = child->cmn.xcp.regs[REG_TP];
 #endif
 
-  /* Set up frame for context and copy the parent's user context there */
+  /* Determine the integer context save area */
 
-  memcpy((void *)(newsp - XCPTCONTEXT_SIZE),
-         parent->xcp.regs, XCPTCONTEXT_SIZE);
+#ifdef CONFIG_ARCH_KERNEL_STACK
+  if (child->cmn.xcp.kstack)
+    {
+      /* Set context to kernel stack */
 
-  /* Save FPU */
+      stacktop = (uintptr_t)child->cmn.xcp.ktopstk;
+    }
+  else
+#endif
+    {
+      /* Set context to user stack */
 
-  riscv_savefpu(child->cmn.xcp.regs, riscv_fpuregs(&child->cmn));
+      stacktop = newsp;
+    }
 
-  /* Copy the parent stack contents */
+  /* Set the new register restore area to the new stack top */
 
-  memcpy((void *)newsp, (const void *)parent->xcp.regs[REG_SP], stackutil);
+  child->cmn.xcp.regs = (void *)(stacktop - XCPTCONTEXT_SIZE);
 
-  /* Set the new register restore area to the new stack top */
+  /* Copy the parent integer context (overwrites child's SP and TP) */
 
-  child->cmn.xcp.regs = (void *)(newsp - XCPTCONTEXT_SIZE);
+  memcpy(child->cmn.xcp.regs, parent->xcp.sregs, XCPTCONTEXT_SIZE);
+
+  /* Save FPU */
+
+  riscv_savefpu(child->cmn.xcp.regs, riscv_fpuregs(&child->cmn));
 
   /* Return 0 to child */
 
@@ -169,8 +178,6 @@ pid_t riscv_fork(const struct fork_s *context)
   child->cmn.xcp.regs[REG_TP] = tp;
 #endif
 
-  up_irq_restore(flags);
-
   /* And, finally, start the child task.  On a failure, nxtask_start_fork()
    * will discard the TCB by calling nxtask_abort_fork().
    */

arch/risc-v/src/common/riscv_internal.h

@@ -109,10 +109,6 @@
 #define PMP_ACCESS_DENIED   (-1)    /* Access set and denied */
 #define PMP_ACCESS_FULL     (1)     /* Access set and allowed */
 
-/* Return values from riscv_swint */
-
-#define SWINT_CONTEXT_SWITCH (1)    /* Indicate we need context switch */
-
 #ifndef __ASSEMBLY__
 
 /* Use ASM as rv64ilp32 compiler generated address is limited */

arch/risc-v/src/common/riscv_sigdeliver.c

@@ -162,6 +162,10 @@ void riscv_sigdeliver(void)
   rtcb->irqcount--;
 #endif
 
+  /* g_running_tasks is not valid now */
+
+  g_running_tasks[this_cpu()] = NULL;
+
   rtcb->xcp.regs = regs;
   riscv_fullcontextrestore(rtcb);
 }

arch/risc-v/src/common/riscv_swint.c

@@ -161,7 +161,7 @@ uintptr_t dispatch_syscall(unsigned int nbr, uintptr_t parm1,
 
   /* Set the user register context to TCB */
 
-  rtcb->xcp.regs = context;
+  rtcb->xcp.sregs = context;
 
   /* Indicate that we are in a syscall handler */
 
@@ -257,7 +257,6 @@ int riscv_swint(int irq, void *context, void *arg)
           struct tcb_s *next = (struct tcb_s *)(uintptr_t)regs[REG_A2];
 
           DEBUGASSERT(regs[REG_A1] != 0 && regs[REG_A2] != 0);
-          prev->xcp.regs = regs;
           riscv_savecontext(prev);
           new_regs = next->xcp.regs;
           riscv_restorecontext(next);
@@ -496,7 +495,6 @@ int riscv_swint(int irq, void *context, void *arg)
   if (regs != new_regs)
     {
       restore_critical_section(this_task(), this_cpu());
-      return SWINT_CONTEXT_SWITCH;
     }
 
   return OK;

arch/risc-v/src/common/supervisor/riscv_perform_syscall.c

@@ -37,19 +37,24 @@
 
 void *riscv_perform_syscall(uintreg_t *regs)
 {
+  struct tcb_s **running_task = &g_running_tasks[this_cpu()];
   struct tcb_s *tcb;
-  int cpu;
-  int ret;
+
+  if (*running_task != NULL)
+    {
+      (*running_task)->xcp.regs = regs;
+    }
 
   /* Set up the interrupt register set needed by swint() */
 
   up_set_current_regs(regs);
 
   /* Run the system call handler (swint) */
 
-  ret = riscv_swint(0, regs, NULL);
+  riscv_swint(0, regs, NULL);
+  tcb = this_task();
 
-  if (ret == SWINT_CONTEXT_SWITCH)
+  if ((*running_task) != tcb)
     {
 #ifdef CONFIG_ARCH_ADDRENV
       /* Make sure that the address environment for the previously
@@ -65,20 +70,10 @@ void *riscv_perform_syscall(uintreg_t *regs)
        * assertion logic for reporting crashes.
        */
 
-      cpu = this_cpu();
-      tcb = current_task(cpu);
-      g_running_tasks[cpu] = tcb;
-
-      /* If a context switch occurred while processing the interrupt then
-       * current_regs may have change value.  If we return any value
-       * different from the input regs, then the lower level will know
-       * that a context switch occurred during interrupt processing.
-       */
-
-      regs = tcb->xcp.regs;
+      *running_task = tcb;
     }
 
   up_set_current_regs(NULL);
 
-  return regs;
+  return tcb->xcp.regs;
 }