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| author |   Denys Vlasenko <dvlasenk@redhat.com> | 2015-03-17 14:52:24 +0100 |
|---|---|---|
| committer |   Ingo Molnar <mingo@kernel.org> | 2015-03-17 16:01:40 +0100 |
| commit | 33db1fd48ac3d90385b412b41a8a6525096ac6d5 (patch) | |
| tree | 4cefb59f4ec2913069f94d8a6b1398637f39752d /arch/x86/kernel/entry_64.S | |
| parent | x86/asm/entry: Document and clean up the enable_sep_cpu() and syscall32_cpu_init() functions (diff) | |
| download | linux-dev-33db1fd48ac3d90385b412b41a8a6525096ac6d5.tar.xz linux-dev-33db1fd48ac3d90385b412b41a8a6525096ac6d5.zip | |
x86/asm/entry/64: Enable interrupts *after* we fetch PER_CPU_VAR(old_rsp)
We want to use PER_CPU_VAR(old_rsp) as a simple temporary register,
to shuffle user-space RSP into (and from) when we set up the system
call stack frame. At that point we cannot shuffle values into general
purpose registers, because we have not saved them yet.
To be able to do this shuffling into a memory location, we must be
atomic and must not be preempted while we do the shuffling, otherwise
the 'temporary' register gets overwritten by some other task's
temporary register contents ...
Tested-by: Borislav Petkov <bp@alien8.de>
Signed-off-by: Denys Vlasenko <dvlasenk@redhat.com>
Acked-by: Borislav Petkov <bp@alien8.de>
Cc: Alexei Starovoitov <ast@plumgrid.com>
Cc: Andy Lutomirski <luto@amacapital.net>
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/1426600344-8254-1-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 | 10 |
1 files changed, 5 insertions, 5 deletions
diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S index d86788c3257b..aed3f11c373b 100644 --- a/arch/x86/kernel/entry_64.S +++ b/arch/x86/kernel/entry_64.S @@ -241,16 +241,16 @@ GLOBAL(system_call_after_swapgs) movq %rsp,PER_CPU_VAR(old_rsp) /* kernel_stack is set so that 5 slots (iret frame) are preallocated */ movq PER_CPU_VAR(kernel_stack),%rsp - /* - * No need to follow this irqs off/on section - it's straight - * and short: - */ - ENABLE_INTERRUPTS(CLBR_NONE) ALLOC_PT_GPREGS_ON_STACK 8 /* +8: space for orig_ax */ movq %rcx,RIP(%rsp) movq PER_CPU_VAR(old_rsp),%rcx movq %r11,EFLAGS(%rsp) movq %rcx,RSP(%rsp) + /* + * No need to follow this irqs off/on section - it's straight + * and short: + */ + ENABLE_INTERRUPTS(CLBR_NONE) movq_cfi rax,ORIG_RAX SAVE_C_REGS_EXCEPT_RAX_RCX_R11 movq $-ENOSYS,RAX(%rsp) |