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1 | From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001 | |
2 | From: Andy Lutomirski <luto@kernel.org> | |
3 | Date: Thu, 2 Nov 2017 00:59:01 -0700 | |
4 | Subject: [PATCH] x86/entry/64: Simplify reg restore code in the standard IRET | |
5 | paths | |
6 | MIME-Version: 1.0 | |
7 | Content-Type: text/plain; charset=UTF-8 | |
8 | Content-Transfer-Encoding: 8bit | |
9 | ||
10 | CVE-2017-5754 | |
11 | ||
12 | The old code restored all the registers with movq instead of pop. | |
13 | ||
14 | In theory, this was done because some CPUs have higher movq | |
15 | throughput, but any gain there would be tiny and is almost certainly | |
16 | outweighed by the higher text size. | |
17 | ||
18 | This saves 96 bytes of text. | |
19 | ||
20 | Signed-off-by: Andy Lutomirski <luto@kernel.org> | |
21 | Cc: Borislav Petkov <bpetkov@suse.de> | |
22 | Cc: Brian Gerst <brgerst@gmail.com> | |
23 | Cc: Dave Hansen <dave.hansen@intel.com> | |
24 | Cc: Linus Torvalds <torvalds@linux-foundation.org> | |
25 | Cc: Peter Zijlstra <peterz@infradead.org> | |
26 | Cc: Thomas Gleixner <tglx@linutronix.de> | |
27 | Link: http://lkml.kernel.org/r/ad82520a207ccd851b04ba613f4f752b33ac05f7.1509609304.git.luto@kernel.org | |
28 | Signed-off-by: Ingo Molnar <mingo@kernel.org> | |
29 | (cherry picked from commit e872045bfd9c465a8555bab4b8567d56a4d2d3bb) | |
30 | Signed-off-by: Andy Whitcroft <apw@canonical.com> | |
31 | Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com> | |
32 | (cherry picked from commit f926575cd370de4052e89477582b349af5664a56) | |
33 | Signed-off-by: Fabian Grünbichler <f.gruenbichler@proxmox.com> | |
34 | --- | |
35 | arch/x86/entry/calling.h | 21 +++++++++++++++++++++ | |
36 | arch/x86/entry/entry_64.S | 12 ++++++------ | |
37 | 2 files changed, 27 insertions(+), 6 deletions(-) | |
38 | ||
39 | diff --git a/arch/x86/entry/calling.h b/arch/x86/entry/calling.h | |
40 | index 640aafebdc00..0b9dd8123701 100644 | |
41 | --- a/arch/x86/entry/calling.h | |
42 | +++ b/arch/x86/entry/calling.h | |
43 | @@ -151,6 +151,27 @@ For 32-bit we have the following conventions - kernel is built with | |
44 | UNWIND_HINT_REGS offset=\offset extra=0 | |
45 | .endm | |
46 | ||
47 | + .macro POP_EXTRA_REGS | |
48 | + popq %r15 | |
49 | + popq %r14 | |
50 | + popq %r13 | |
51 | + popq %r12 | |
52 | + popq %rbp | |
53 | + popq %rbx | |
54 | + .endm | |
55 | + | |
56 | + .macro POP_C_REGS | |
57 | + popq %r11 | |
58 | + popq %r10 | |
59 | + popq %r9 | |
60 | + popq %r8 | |
61 | + popq %rax | |
62 | + popq %rcx | |
63 | + popq %rdx | |
64 | + popq %rsi | |
65 | + popq %rdi | |
66 | + .endm | |
67 | + | |
68 | .macro RESTORE_C_REGS_HELPER rstor_rax=1, rstor_rcx=1, rstor_r11=1, rstor_r8910=1, rstor_rdx=1 | |
69 | .if \rstor_r11 | |
70 | movq 6*8(%rsp), %r11 | |
71 | diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S | |
72 | index 7c8258e3ad2d..a1a86e782a0e 100644 | |
73 | --- a/arch/x86/entry/entry_64.S | |
74 | +++ b/arch/x86/entry/entry_64.S | |
75 | @@ -618,9 +618,9 @@ GLOBAL(swapgs_restore_regs_and_return_to_usermode) | |
76 | 1: | |
77 | #endif | |
78 | SWAPGS | |
79 | - RESTORE_EXTRA_REGS | |
80 | - RESTORE_C_REGS | |
81 | - REMOVE_PT_GPREGS_FROM_STACK 8 | |
82 | + POP_EXTRA_REGS | |
83 | + POP_C_REGS | |
84 | + addq $8, %rsp /* skip regs->orig_ax */ | |
85 | INTERRUPT_RETURN | |
86 | ||
87 | ||
88 | @@ -650,9 +650,9 @@ GLOBAL(restore_regs_and_return_to_kernel) | |
89 | ud2 | |
90 | 1: | |
91 | #endif | |
92 | - RESTORE_EXTRA_REGS | |
93 | - RESTORE_C_REGS | |
94 | - REMOVE_PT_GPREGS_FROM_STACK 8 | |
95 | + POP_EXTRA_REGS | |
96 | + POP_C_REGS | |
97 | + addq $8, %rsp /* skip regs->orig_ax */ | |
98 | INTERRUPT_RETURN | |
99 | ||
100 | ENTRY(native_iret) | |
101 | -- | |
102 | 2.14.2 | |
103 |