Subject: linux-next: build failure after merge of the tip tree

From: Stephen Rothwell <[email-masked]>
Date: Fri, 31 Oct 2025 12:02:43 +1100

Hi all,

After merging the tip tree, today's linux-next build (arm64 defconfig)
failed like this:

arch/arm64/kernel/entry-common.c: In function 'arm64_exit_to_user_mode':
arch/arm64/kernel/entry-common.c:103:9: error: implicit declaration of function 'exit_to_user_mode_prepare'; did you mean 'arch_exit_to_user_mode_prepare'? [-Wimplicit-function-declaration]
  103 |         exit_to_user_mode_prepare(regs);
      |         ^~~~~~~~~~~~~~~~~~~~~~~~~
      |         arch_exit_to_user_mode_prepare
In file included from arch/arm64/include/asm/current.h:5,
                 from include/linux/sched.h:12,
                 from include/linux/context_tracking.h:5,
                 from include/linux/irq-entry-common.h:5,
                 from kernel/entry/common.c:3:
kernel/entry/common.c: In function 'exit_to_user_mode_loop':
kernel/entry/common.c:77:29: error: implicit declaration of function 'rseq_exit_to_user_mode_restart'; did you mean 'arch_exit_to_user_mode_prepare'? [-Wimplicit-function-declaration]
   77 |                 if (likely(!rseq_exit_to_user_mode_restart(regs, ti_work)))
      |                             ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
include/linux/compiler.h:76:45: note: in definition of macro 'likely'
   76 | # define likely(x)      __builtin_expect(!!(x), 1)
      |                                             ^

Caused by commit

  d58930640310 ("entry: Split up exit_to_user_mode_prepare()")

and maybe following ones.

I have reverted these commits for today:

  69c8e3d16105 ("rseq: Switch to TIF_RSEQ if supported")
  1b3dd1c538a8 ("rseq: Split up rseq_exit_to_user_mode()")
  d58930640310 ("entry: Split up exit_to_user_mode_prepare()")

-- 
Cheers,
Stephen Rothwell