[PATCH v2 0/6] x86: Rewrite switch_to()

Brian Gerst
2016-06-18T20:56:32Z

This patch set simplifies the switch_to() code, by moving the stack switch
code out of line into an asm stub before calling __switch_to(). This ends
up being more readable, and using the C calling convention instead of
clobbering all registers improves code generation. It also allows newly
forked processes to construct a special stack frame to seamlessly flow
to ret_from_fork, instead of using a test and branch, or an unbalanced
call/ret.

Changes from v1:
- Added struct inactive_task_frame
- Added comments about kernel threads returning to userspace
- Cleaned up some incorrect uses of thread.sp

Brian Gerst (6):
x86-32, kgdb: Don't use thread.ip in sleeping_thread_to_gdb_regs()
x86-64, kgdb: clear GDB_PS on 64-bit
x86: Add struct inactive_task_frame
x86: Rewrite switch_to() code
x86: Pass kernel thread parameters in fork_frame
x86: Fix thread_saved_pc()

arch/x86/entry/entry_32.S | 68 +++++++++++++-----
arch/x86/entry/entry_64.S | 76 ++++++++++++++------
arch/x86/include/asm/processor.h | 13 +---
arch/x86/include/asm/stacktrace.h | 4 +-
arch/x86/include/asm/switch_to.h | 142 +++++++------------------------------
arch/x86/include/asm/thread_info.h | 2 -
arch/x86/kernel/asm-offsets.c | 6 ++
arch/x86/kernel/asm-offsets_32.c | 5 ++
arch/x86/kernel/asm-offsets_64.c | 5 ++
arch/x86/kernel/kgdb.c | 8 +--
arch/x86/kernel/process.c | 13 +++-
arch/x86/kernel/process_32.c | 29 +++-----
arch/x86/kernel/process_64.c | 19 ++---
arch/x86/kernel/smpboot.c | 1 -
14 files changed, 187 insertions(+), 204 deletions(-)