[PATCH 0/2] x86: entry_64.S: steps towards simpler iret frame handling

[Denys Vlasenko]

These changes make SYSENTER64 code path save flags and user's
stack pointer in pt_regs->flags and pt_regs->sp, where they belong.

As a result, we can drop stub_iopl() and thread_struct::usersp.

Usage of PER_CPU(old_rsp) is reduced to bare minimum.

FIXUP/RESTORE_TOP_OF_STACK macros are on diet too.

(This is a resend. Previous version was on top of KERNEL_STACK_OFFSET
removal patch. This one is on top of Andy's current git. Patch is run-tested.)

CC: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
CC: Steven Rostedt <rostedt@xxxxxxxxxxx>
CC: Ingo Molnar <mingo@xxxxxxxxxx>
CC: Borislav Petkov <bp@xxxxxxxxx>
CC: "H. Peter Anvin" <hpa@xxxxxxxxx>
CC: Andy Lutomirski <luto@xxxxxxxxxxxxxx>
CC: Oleg Nesterov <oleg@xxxxxxxxxx>
CC: Frederic Weisbecker <fweisbec@xxxxxxxxx>
CC: Alexei Starovoitov <ast@xxxxxxxxxxxx>
CC: Will Drewry <wad@xxxxxxxxxxxx>
CC: Kees Cook <keescook@xxxxxxxxxxxx>
CC: x86@xxxxxxxxxx
CC: linux-kernel@xxxxxxxxxxxxxxx

Denys Vlasenko (2):
  x86: save r11 into pt_regs->flags on SYSCALL64 fastpath
  x86: save user %rsp in pt_regs->sp on SYSCALL64 fastpath

 arch/x86/include/asm/calling.h   | 20 +++++++++-----
 arch/x86/include/asm/compat.h    |  2 +-
 arch/x86/include/asm/processor.h |  6 -----
 arch/x86/include/asm/ptrace.h    |  8 ++----
 arch/x86/kernel/entry_64.S       | 57 ++++++++++++++--------------------------
 arch/x86/kernel/perf_regs.c      |  2 +-
 arch/x86/kernel/process_64.c     |  8 +-----
 arch/x86/syscalls/syscall_64.tbl |  2 +-
 arch/x86/um/sys_call_table_64.c  |  2 +-
 9 files changed, 40 insertions(+), 67 deletions(-)

-- 
1.8.1.4

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