diff options
Diffstat (limited to 'arch/x86/entry/calling.h')
| -rw-r--r-- | arch/x86/entry/calling.h | 40 |
1 files changed, 19 insertions, 21 deletions
diff --git a/arch/x86/entry/calling.h b/arch/x86/entry/calling.h index 3bda31736a7b..a05cbb81268d 100644 --- a/arch/x86/entry/calling.h +++ b/arch/x86/entry/calling.h @@ -101,44 +101,42 @@ For 32-bit we have the following conventions - kernel is built with addq $-(15*8), %rsp .endm - .macro SAVE_REGS offset=0 + .macro SAVE_AND_CLEAR_REGS offset=0 + /* + * Save 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: + */ movq %rdi, 14*8+\offset(%rsp) movq %rsi, 13*8+\offset(%rsp) movq %rdx, 12*8+\offset(%rsp) movq %rcx, 11*8+\offset(%rsp) movq %rax, 10*8+\offset(%rsp) movq %r8, 9*8+\offset(%rsp) + xorq %r8, %r8 /* nospec r8 */ movq %r9, 8*8+\offset(%rsp) + xorq %r9, %r9 /* nospec r9 */ movq %r10, 7*8+\offset(%rsp) + xorq %r10, %r10 /* nospec r10 */ movq %r11, 6*8+\offset(%rsp) + xorq %r11, %r11 /* nospec r11 */ movq %rbx, 5*8+\offset(%rsp) + xorl %ebx, %ebx /* nospec rbx */ movq %rbp, 4*8+\offset(%rsp) + xorl %ebp, %ebp /* nospec rbp */ movq %r12, 3*8+\offset(%rsp) + xorq %r12, %r12 /* nospec r12 */ movq %r13, 2*8+\offset(%rsp) + xorq %r13, %r13 /* nospec r13 */ movq %r14, 1*8+\offset(%rsp) + xorq %r14, %r14 /* nospec r14 */ movq %r15, 0*8+\offset(%rsp) + xorq %r15, %r15 /* nospec r15 */ UNWIND_HINT_REGS offset=\offset .endm - /* - * 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: - */ - .macro CLEAR_REGS_NOSPEC - xorl %ebp, %ebp - xorl %ebx, %ebx - xorq %r8, %r8 - xorq %r9, %r9 - xorq %r10, %r10 - xorq %r11, %r11 - xorq %r12, %r12 - xorq %r13, %r13 - xorq %r14, %r14 - xorq %r15, %r15 - .endm - .macro POP_REGS pop_rdi=1 skip_r11rcx=0 popq %r15 popq %r14 @@ -177,7 +175,7 @@ For 32-bit we have the following conventions - kernel is built with * is just setting the LSB, which makes it an invalid stack address and is also * a signal to the unwinder that it's a pt_regs pointer in disguise. * - * NOTE: This macro must be used *after* SAVE_REGS because it corrupts + * NOTE: This macro must be used *after* SAVE_AND_CLEAR_REGS because it corrupts * the original rbp. */ .macro ENCODE_FRAME_POINTER ptregs_offset=0 |