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powerpc: Rearrange copy_thread child stack creation

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This makes it a bit clearer where the stack frame is created, and will
allow easier use of some of the stack offset constants in a later
change.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20221127124942.1665522-5-npiggin@gmail.com
This commit is contained in:
Nicholas Piggin 2022-11-27 22:49:29 +10:00 committed by Michael Ellerman
parent 32c5209214
commit bc0677363d
1 changed files with 6 additions and 5 deletions
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11
arch/powerpc/kernel/process.c
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@ -1755,13 +1755,16 @@ int copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
klp_init_thread_info(p);
/* Create initial stack frame. */
sp -= (sizeof(struct pt_regs) + STACK_FRAME_OVERHEAD);
((unsigned long *)sp)[0] = 0;
/* Copy registers */
sp -= sizeof(struct pt_regs);
childregs = (struct pt_regs *) sp;
childregs = (struct pt_regs *)(sp + STACK_FRAME_OVERHEAD);
if (unlikely(args->fn)) {
/* kernel thread */
memset(childregs, 0, sizeof(struct pt_regs));
childregs->gpr[1] = sp + sizeof(struct pt_regs);
childregs->gpr[1] = sp + (sizeof(struct pt_regs) + STACK_FRAME_OVERHEAD);
/* function */
if (args->fn)
childregs->gpr[14] = ppc_function_entry((void *)args->fn);
@ -1796,7 +1799,6 @@ int copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
f = ret_from_fork;
}
childregs->msr &= ~(MSR_FP|MSR_VEC|MSR_VSX);
sp -= STACK_FRAME_OVERHEAD;
/*
* The way this works is that at some point in the future
@ -1806,7 +1808,6 @@ int copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
* do some house keeping and then return from the fork or clone
* system call, using the stack frame created above.
*/
((unsigned long *)sp)[0] = 0;
sp -= sizeof(struct pt_regs);
kregs = (struct pt_regs *) sp;
sp -= STACK_FRAME_OVERHEAD;