arm64: Adjust the kernel stack pointer at the end of fork_trampoline

All other paths that return from the kernel to userspace pop the user
trapframe off of the kernel stack pointer before returning to
userspace in restore_registers.  fork_trampoline was missing this, so
all of the user faults after fork pushed another trapframe leaving a
trapframe's worth of wasted space on the kstack.

This would be fatal after a future change to remove duplicate
initialization of td_frame in cpu_fork() as without this fix each time
a thread was recycled it would "lose" another trapframe's worth of
space.

Reviewed by:	kib, andrew
Pull Request:	https://ron-dev.freebsd.org/FreeBSD/src/pulls/23

This commit is contained in:

Alfredo Mazzinghi

2026-04-22 19:46:14 -04:00

committed by

John Baldwin

parent bd15d6ef12

commit a1e07f21dc

1 changed files with 2 additions and 0 deletions

									
										sys/arm64/arm64/swtch.S
									
		+2
		
												View File
												
				@@ -276,6 +276,8 @@ ENTRY(fork_trampoline)

					ldp	x26, x27, [sp, #TF_X + 26 * 8]

					ldp	x28, x29, [sp, #TF_X + 28 * 8]

					add	sp, sp, #(TF_SIZE)

					/*

					 * No need for interrupts reenabling since PSR

					 * will be set to the desired value anyway.