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riscv_fork.c: Fix vfork() for kernel mode + SMP #13633

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Merged
xiaoxiang781216 merged 2 commits into from
Sep 27, 2024
Merged

riscv_fork.c: Fix vfork() for kernel mode + SMP #13633

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c6a3b44
riscv_fork.c: Fix vfork() for kernel mode + SMP
pussuw Sep 26, 2024
e6d18fe
riscv_fork.c: Fix race condition when handling parent integer registers
pussuw Sep 26, 2024
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6 changes: 6 additions & 0 deletions arch/risc-v/include/irq.h
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Original file line number Diff line number Diff line change
Expand Up @@ -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)
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47 changes: 27 additions & 20 deletions arch/risc-v/src/common/riscv_fork.c
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Expand Up @@ -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");
Expand All @@ -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 */

Expand All @@ -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().
*/
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2 changes: 1 addition & 1 deletion arch/risc-v/src/common/riscv_swint.c
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Expand Up @@ -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 */

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