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f0a90c7d | 1 | /* Stack scrubbing infrastructure |
a945c346 | 2 | Copyright (C) 2021-2024 Free Software Foundation, Inc. |
f0a90c7d AO |
3 | Contributed by Alexandre Oliva <oliva@adacore.com> |
4 | ||
5 | This file is part of GCC. | |
6 | ||
7 | GCC is free software; you can redistribute it and/or modify it under | |
8 | the terms of the GNU General Public License as published by the Free | |
9 | Software Foundation; either version 3, or (at your option) any later | |
10 | version. | |
11 | ||
12 | GCC is distributed in the hope that it will be useful, but WITHOUT ANY | |
13 | WARRANTY; without even the implied warranty of MERCHANTABILITY or | |
14 | FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License | |
15 | for more details. | |
16 | ||
17 | Under Section 7 of GPL version 3, you are granted additional | |
18 | permissions described in the GCC Runtime Library Exception, version | |
19 | 3.1, as published by the Free Software Foundation. | |
20 | ||
21 | You should have received a copy of the GNU General Public License and | |
22 | a copy of the GCC Runtime Library Exception along with this program; | |
23 | see the files COPYING3 and COPYING.RUNTIME respectively. If not, see | |
24 | <http://www.gnu.org/licenses/>. */ | |
25 | ||
26 | #include "tconfig.h" | |
27 | #include "tsystem.h" | |
28 | #include "coretypes.h" | |
29 | #include "tm.h" | |
30 | #include "libgcc_tm.h" | |
31 | #include "libgcc2.h" | |
32 | ||
33 | #if ! STACK_GROWS_DOWNWARD | |
34 | # define TOPS > | |
35 | #else | |
36 | # define TOPS < | |
37 | #endif | |
38 | ||
1b83fce7 AO |
39 | /* Make sure these builtins won't be inlined, even with LTO. */ |
40 | #define ATTRIBUTE_NOINLINE \ | |
41 | __attribute__ ((__noinline__, __noclone__, __noipa__)) | |
42 | ||
43 | #define ATTRIBUTE_STRUB_CALLABLE \ | |
44 | __attribute__ ((__strub__ ("callable"))) ATTRIBUTE_NOINLINE | |
f0a90c7d AO |
45 | |
46 | /* Enter a stack scrubbing context, initializing the watermark to the caller's | |
47 | stack address. */ | |
48 | void ATTRIBUTE_STRUB_CALLABLE | |
49 | __strub_enter (void **watermark) | |
50 | { | |
51 | *watermark = __builtin_frame_address (0); | |
52 | } | |
53 | ||
54 | /* Update the watermark within a stack scrubbing context with the current stack | |
55 | pointer. */ | |
56 | void ATTRIBUTE_STRUB_CALLABLE | |
57 | __strub_update (void **watermark) | |
58 | { | |
59 | void *sp = __builtin_frame_address (0); | |
60 | ||
61 | if (sp TOPS *watermark) | |
62 | *watermark = sp; | |
63 | } | |
64 | ||
65 | #if TARGET_STRUB_USE_DYNAMIC_ARRAY && ! defined TARGET_STRUB_MAY_USE_MEMSET | |
66 | # define TARGET_STRUB_MAY_USE_MEMSET 1 | |
67 | #endif | |
68 | ||
69 | #if defined __x86_64__ && __OPTIMIZE__ | |
70 | # define TARGET_STRUB_DISABLE_RED_ZONE \ | |
71 | /* __attribute__ ((__target__ ("no-red-zone"))) // not needed when optimizing */ | |
72 | #elif !defined RED_ZONE_SIZE || defined __i386__ | |
73 | # define TARGET_STRUB_DISABLE_RED_ZONE | |
74 | #endif | |
75 | ||
76 | #ifndef TARGET_STRUB_DISABLE_RED_ZONE | |
77 | /* Dummy function, called to force the caller to not be a leaf function, so | |
78 | that it can't use the red zone. */ | |
79 | static void ATTRIBUTE_STRUB_CALLABLE | |
f0a90c7d AO |
80 | __strub_dummy_force_no_leaf (void) |
81 | { | |
82 | } | |
83 | #endif | |
84 | ||
85 | /* Leave a stack scrubbing context, clearing the stack between its top and | |
86 | *MARK. */ | |
87 | void ATTRIBUTE_STRUB_CALLABLE | |
88 | #if ! TARGET_STRUB_MAY_USE_MEMSET | |
89 | __attribute__ ((__optimize__ ("-fno-tree-loop-distribute-patterns"))) | |
90 | #endif | |
91 | #ifdef TARGET_STRUB_DISABLE_RED_ZONE | |
92 | TARGET_STRUB_DISABLE_RED_ZONE | |
93 | #endif | |
94 | __strub_leave (void **mark) | |
95 | { | |
96 | void *sp = __builtin_stack_address (); | |
97 | ||
98 | void **base, **end; | |
99 | #if ! STACK_GROWS_DOWNWARD | |
100 | base = sp; /* ??? Do we need an offset here? */ | |
101 | end = *mark; | |
102 | #else | |
103 | base = *mark; | |
104 | end = sp; /* ??? Does any platform require an offset here? */ | |
105 | #endif | |
106 | ||
107 | if (! (base < end)) | |
108 | return; | |
109 | ||
110 | #if TARGET_STRUB_USE_DYNAMIC_ARRAY | |
111 | /* Compute the length without assuming the pointers are both sufficiently | |
112 | aligned. They should be, but pointer differences expected to be exact may | |
113 | yield unexpected results when the assumption doesn't hold. Given the | |
114 | potential security implications, compute the length without that | |
115 | expectation. If the pointers are misaligned, we may leave a partial | |
116 | unscrubbed word behind. */ | |
117 | ptrdiff_t len = ((char *)end - (char *)base) / sizeof (void *); | |
118 | /* Allocate a dynamically-sized array covering the desired range, so that we | |
119 | can safely call memset on it. */ | |
120 | void *ptr[len]; | |
121 | base = &ptr[0]; | |
122 | end = &ptr[len]; | |
123 | #elifndef TARGET_STRUB_DISABLE_RED_ZONE | |
124 | /* Prevent the use of the red zone, by making this function non-leaf through | |
125 | an unreachable call that, because of the asm stmt, the compiler will | |
126 | consider reachable. */ | |
127 | asm goto ("" : : : : no_leaf); | |
128 | if (0) | |
129 | { | |
130 | no_leaf: | |
131 | __strub_dummy_force_no_leaf (); | |
132 | return; | |
133 | } | |
134 | #endif | |
135 | ||
136 | /* ldist may turn these loops into a memset (thus the conditional | |
137 | -fno-tree-loop-distribute-patterns above). Without the dynamic array | |
138 | above, that call would likely be unsafe: possibly tail-called, and likely | |
139 | scribbling over its own stack frame. */ | |
140 | #if ! STACK_GROWS_DOWNWARD | |
141 | do | |
142 | *base++ = 0; | |
143 | while (base < end); | |
144 | /* Make sure the stack overwrites are not optimized away. */ | |
145 | asm ("" : : "m" (end[0])); | |
146 | #else | |
147 | do | |
148 | *--end = 0; | |
149 | while (base < end); | |
150 | /* Make sure the stack overwrites are not optimized away. */ | |
151 | asm ("" : : "m" (base[0])); | |
152 | #endif | |
153 | } |