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| author |   Denys Vlasenko <dvlasenk@redhat.com> | 2015-03-19 18:17:46 +0100 |
|---|---|---|
| committer |   Ingo Molnar <mingo@kernel.org> | 2015-03-24 19:42:38 +0100 |
| commit | ef593260f0cae2699874f098fb5b19fb46502cb3 (patch) | |
| tree | 68b114f2e6ad9413dc030a0e0960e6fd934f9942 /arch/x86/kernel/entry_64.S | |
| parent | x86/asm/entry/64: Change the THREAD_INFO() definition to not depend on KERNEL_STACK_OFFSET (diff) | |
| download | linux-dev-ef593260f0cae2699874f098fb5b19fb46502cb3.tar.xz linux-dev-ef593260f0cae2699874f098fb5b19fb46502cb3.zip | |
x86/asm/entry: Get rid of KERNEL_STACK_OFFSET
PER_CPU_VAR(kernel_stack) was set up in a way where it points
five stack slots below the top of stack.
Presumably, it was done to avoid one "sub $5*8,%rsp"
in syscall/sysenter code paths, where iret frame needs to be
created by hand.
Ironically, none of them benefits from this optimization,
since all of them need to allocate additional data on stack
(struct pt_regs), so they still have to perform subtraction.
This patch eliminates KERNEL_STACK_OFFSET.
PER_CPU_VAR(kernel_stack) now points directly to top of stack.
pt_regs allocations are adjusted to allocate iret frame as well.
Hopefully we can merge it later with 32-bit specific
PER_CPU_VAR(cpu_current_top_of_stack) variable...
Net result in generated code is that constants in several insns
are changed.
This change is necessary for changing struct pt_regs creation
in SYSCALL64 code path from MOV to PUSH instructions.
Signed-off-by: Denys Vlasenko <dvlasenk@redhat.com>
Acked-by: Borislav Petkov <bp@suse.de>
Acked-by: Andy Lutomirski <luto@kernel.org>
Cc: Alexei Starovoitov <ast@plumgrid.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Will Drewry <wad@chromium.org>
Link: http://lkml.kernel.org/r/1426785469-15125-2-git-send-email-dvlasenk@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'arch/x86/kernel/entry_64.S')
| -rw-r--r-- | arch/x86/kernel/entry_64.S | 5 |
1 files changed, 2 insertions, 3 deletions
diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S index 8076df982a18..eae69bba3a2c 100644 --- a/arch/x86/kernel/entry_64.S +++ b/arch/x86/kernel/entry_64.S @@ -225,7 +225,7 @@ ENDPROC(native_usergs_sysret64) ENTRY(system_call) CFI_STARTPROC simple CFI_SIGNAL_FRAME - CFI_DEF_CFA rsp,KERNEL_STACK_OFFSET + CFI_DEF_CFA rsp,0 CFI_REGISTER rip,rcx /*CFI_REGISTER rflags,r11*/ SWAPGS_UNSAFE_STACK @@ -242,9 +242,8 @@ GLOBAL(system_call_after_swapgs) * so we can enable interrupts only after we're done with using rsp_scratch: */ movq %rsp,PER_CPU_VAR(rsp_scratch) - /* kernel_stack is set so that 5 slots (iret frame) are preallocated */ movq PER_CPU_VAR(kernel_stack),%rsp - ALLOC_PT_GPREGS_ON_STACK 8 /* +8: space for orig_ax */ + ALLOC_PT_GPREGS_ON_STACK 6*8 /* 6*8: space for orig_ax and iret frame */ movq %rcx,RIP(%rsp) movq PER_CPU_VAR(rsp_scratch),%rcx movq %r11,EFLAGS(%rsp) |