[PATCH v2 0/4] entry: Move ret_from_fork() to C and inline syscall_exit_to_user_mode()

[Charlie Jenkins <charlie@rivosinc.com>]

Similar to commit 221a164035fd ("entry: Move
syscall_enter_from_user_mode() to header file"), move
syscall_exit_to_user_mode() to the header file as well.

Testing was done with the byte-unixbench [1] syscall benchmark (which
calls getpid) and QEMU. On riscv I measured a 7.09246% improvement, on
x86 a 2.98843% improvement, on loongarch a 6.07954% improvement, and on
s390 a 11.1328% improvement.

Since this is on QEMU, I know these numbers are not perfect, but they
show a trend of general improvement across all architectures that use
the generic entry code.

[1] https://github.com/kdlucas/byte-unixbench

Signed-off-by: Charlie Jenkins <charlie@rivosinc.com>
---
Changes in v2:
- Fixup compilation issues for loongarch
- Fixup compilation issues with CONFIG_CONTEXT_TRACKING_USER
- Link to v1: https://lore.kernel.org/r/20250122-riscv_optimize_entry-v1-0-4ee95559cfd0@rivosinc.com

---
Charlie Jenkins (4):
      riscv: entry: Convert ret_from_fork() to C
      riscv: entry: Split ret_from_fork() into user and kernel
      loongarch: entry: Migrate ret_from_fork() to C
      entry: Inline syscall_exit_to_user_mode()

 arch/loongarch/include/asm/asm-prototypes.h |  5 +++
 arch/loongarch/include/asm/switch_to.h      |  8 +++++
 arch/loongarch/kernel/entry.S               | 22 ++++++-------
 arch/loongarch/kernel/process.c             | 34 ++++++++++++++++----
 arch/riscv/include/asm/asm-prototypes.h     |  2 ++
 arch/riscv/kernel/entry.S                   | 20 +++++++-----
 arch/riscv/kernel/process.c                 | 21 +++++++++++--
 include/linux/entry-common.h                | 43 +++++++++++++++++++++++--
 kernel/entry/common.c                       | 49 +----------------------------
 9 files changed, 125 insertions(+), 79 deletions(-)
---
base-commit: ffd294d346d185b70e28b1a28abe367bbfe53c04
change-id: 20240402-riscv_optimize_entry-583843420325
-- 
- Charlie