diff options
| author | Dominik Brodowski <linux@dominikbrodowski.net> | 2018-02-11 11:49:45 +0100 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2018-02-13 09:04:53 +0100 |
| commit | 3f01daecd545e818098d84fd1ad43e19a508d705 (patch) | |
| tree | d70e4a362d5c8c41ef771107726a8e0ff4972d69 | |
| parent | f7bafa2b05ef25eda1d9179fd930b0330cf2b7d1 (diff) | |
x86/entry/64: Introduce the PUSH_AND_CLEAN_REGS macro
Those instances where ALLOC_PT_GPREGS_ON_STACK is called just before
SAVE_AND_CLEAR_REGS can trivially be replaced by PUSH_AND_CLEAN_REGS.
This macro uses PUSH instead of MOV and should therefore be faster, at
least on newer CPUs.
Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Dominik Brodowski <linux@dominikbrodowski.net>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: dan.j.williams@intel.com
Link: http://lkml.kernel.org/r/20180211104949.12992-5-linux@dominikbrodowski.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>
| -rw-r--r-- | arch/x86/entry/calling.h | 36 | ||||
| -rw-r--r-- | arch/x86/entry/entry_64.S | 6 |
2 files changed, 38 insertions, 4 deletions
diff --git a/arch/x86/entry/calling.h b/arch/x86/entry/calling.h index a05cbb81268d..57b1b87a04f0 100644 --- a/arch/x86/entry/calling.h +++ b/arch/x86/entry/calling.h @@ -137,6 +137,42 @@ For 32-bit we have the following conventions - kernel is built with UNWIND_HINT_REGS offset=\offset .endm + .macro PUSH_AND_CLEAR_REGS + /* + * Push registers and sanitize registers of values that a + * speculation attack might otherwise want to exploit. The + * lower registers are likely clobbered well before they + * could be put to use in a speculative execution gadget. + * Interleave XOR with PUSH for better uop scheduling: + */ + pushq %rdi /* pt_regs->di */ + pushq %rsi /* pt_regs->si */ + pushq %rdx /* pt_regs->dx */ + pushq %rcx /* pt_regs->cx */ + pushq %rax /* pt_regs->ax */ + pushq %r8 /* pt_regs->r8 */ + xorq %r8, %r8 /* nospec r8 */ + pushq %r9 /* pt_regs->r9 */ + xorq %r9, %r9 /* nospec r9 */ + pushq %r10 /* pt_regs->r10 */ + xorq %r10, %r10 /* nospec r10 */ + pushq %r11 /* pt_regs->r11 */ + xorq %r11, %r11 /* nospec r11*/ + pushq %rbx /* pt_regs->rbx */ + xorl %ebx, %ebx /* nospec rbx*/ + pushq %rbp /* pt_regs->rbp */ + xorl %ebp, %ebp /* nospec rbp*/ + pushq %r12 /* pt_regs->r12 */ + xorq %r12, %r12 /* nospec r12*/ + pushq %r13 /* pt_regs->r13 */ + xorq %r13, %r13 /* nospec r13*/ + pushq %r14 /* pt_regs->r14 */ + xorq %r14, %r14 /* nospec r14*/ + pushq %r15 /* pt_regs->r15 */ + xorq %r15, %r15 /* nospec r15*/ + UNWIND_HINT_REGS + .endm + .macro POP_REGS pop_rdi=1 skip_r11rcx=0 popq %r15 popq %r14 diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S index 07692b44800d..cf4a9ae558f3 100644 --- a/arch/x86/entry/entry_64.S +++ b/arch/x86/entry/entry_64.S @@ -564,8 +564,7 @@ END(irq_entries_start) call switch_to_thread_stack 1: - ALLOC_PT_GPREGS_ON_STACK - SAVE_AND_CLEAR_REGS + PUSH_AND_CLEAR_REGS ENCODE_FRAME_POINTER testb $3, CS(%rsp) @@ -1112,8 +1111,7 @@ ENTRY(xen_failsafe_callback) addq $0x30, %rsp UNWIND_HINT_IRET_REGS pushq $-1 /* orig_ax = -1 => not a system call */ - ALLOC_PT_GPREGS_ON_STACK - SAVE_AND_CLEAR_REGS + PUSH_AND_CLEAR_REGS ENCODE_FRAME_POINTER jmp error_exit END(xen_failsafe_callback) |