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b2441318 | 1 | /* SPDX-License-Identifier: GPL-2.0 */ |
478dc89c | 2 | #include <linux/jump_label.h> |
8c1f7558 | 3 | #include <asm/unwind_hints.h> |
8a09317b DH |
4 | #include <asm/cpufeatures.h> |
5 | #include <asm/page_types.h> | |
6fd166aa PZ |
6 | #include <asm/percpu.h> |
7 | #include <asm/asm-offsets.h> | |
8 | #include <asm/processor-flags.h> | |
478dc89c | 9 | |
0c2bd5a5 | 10 | /* |
063f8913 IM |
11 | |
12 | x86 function call convention, 64-bit: | |
13 | ------------------------------------- | |
14 | arguments | callee-saved | extra caller-saved | return | |
15 | [callee-clobbered] | | [callee-clobbered] | | |
16 | --------------------------------------------------------------------------- | |
17 | rdi rsi rdx rcx r8-9 | rbx rbp [*] r12-15 | r10-11 | rax, rdx [**] | |
18 | ||
19 | ( rsp is obviously invariant across normal function calls. (gcc can 'merge' | |
20 | functions when it sees tail-call optimization possibilities) rflags is | |
21 | clobbered. Leftover arguments are passed over the stack frame.) | |
22 | ||
23 | [*] In the frame-pointers case rbp is fixed to the stack frame. | |
24 | ||
25 | [**] for struct return values wider than 64 bits the return convention is a | |
26 | bit more complex: up to 128 bits width we return small structures | |
27 | straight in rax, rdx. For structures larger than that (3 words or | |
28 | larger) the caller puts a pointer to an on-stack return struct | |
29 | [allocated in the caller's stack frame] into the first argument - i.e. | |
30 | into rdi. All other arguments shift up by one in this case. | |
31 | Fortunately this case is rare in the kernel. | |
32 | ||
33 | For 32-bit we have the following conventions - kernel is built with | |
34 | -mregparm=3 and -freg-struct-return: | |
35 | ||
36 | x86 function calling convention, 32-bit: | |
37 | ---------------------------------------- | |
38 | arguments | callee-saved | extra caller-saved | return | |
39 | [callee-clobbered] | | [callee-clobbered] | | |
40 | ------------------------------------------------------------------------- | |
41 | eax edx ecx | ebx edi esi ebp [*] | <none> | eax, edx [**] | |
42 | ||
43 | ( here too esp is obviously invariant across normal function calls. eflags | |
44 | is clobbered. Leftover arguments are passed over the stack frame. ) | |
45 | ||
46 | [*] In the frame-pointers case ebp is fixed to the stack frame. | |
47 | ||
48 | [**] We build with -freg-struct-return, which on 32-bit means similar | |
49 | semantics as on 64-bit: edx can be used for a second return value | |
50 | (i.e. covering integer and structure sizes up to 64 bits) - after that | |
51 | it gets more complex and more expensive: 3-word or larger struct returns | |
52 | get done in the caller's frame and the pointer to the return struct goes | |
53 | into regparm0, i.e. eax - the other arguments shift up and the | |
54 | function's register parameters degenerate to regparm=2 in essence. | |
55 | ||
56 | */ | |
57 | ||
1a338ac3 PZ |
58 | #ifdef CONFIG_X86_64 |
59 | ||
063f8913 | 60 | /* |
1b2b23d8 TG |
61 | * 64-bit system call stack frame layout defines and helpers, |
62 | * for assembly code: | |
0c2bd5a5 | 63 | */ |
1da177e4 | 64 | |
76f5df43 DV |
65 | /* The layout forms the "struct pt_regs" on the stack: */ |
66 | /* | |
67 | * C ABI says these regs are callee-preserved. They aren't saved on kernel entry | |
68 | * unless syscall needs a complete, fully filled "struct pt_regs". | |
69 | */ | |
70 | #define R15 0*8 | |
71 | #define R14 1*8 | |
72 | #define R13 2*8 | |
73 | #define R12 3*8 | |
74 | #define RBP 4*8 | |
75 | #define RBX 5*8 | |
76 | /* These regs are callee-clobbered. Always saved on kernel entry. */ | |
77 | #define R11 6*8 | |
78 | #define R10 7*8 | |
79 | #define R9 8*8 | |
80 | #define R8 9*8 | |
81 | #define RAX 10*8 | |
82 | #define RCX 11*8 | |
83 | #define RDX 12*8 | |
84 | #define RSI 13*8 | |
85 | #define RDI 14*8 | |
86 | /* | |
87 | * On syscall entry, this is syscall#. On CPU exception, this is error code. | |
88 | * On hw interrupt, it's IRQ number: | |
89 | */ | |
90 | #define ORIG_RAX 15*8 | |
91 | /* Return frame for iretq */ | |
92 | #define RIP 16*8 | |
93 | #define CS 17*8 | |
94 | #define EFLAGS 18*8 | |
95 | #define RSP 19*8 | |
96 | #define SS 20*8 | |
97 | ||
911d2bb5 DV |
98 | #define SIZEOF_PTREGS 21*8 |
99 | ||
9e809d15 | 100 | .macro PUSH_AND_CLEAR_REGS rdx=%rdx rax=%rax save_ret=0 |
9e809d15 DB |
101 | .if \save_ret |
102 | pushq %rsi /* pt_regs->si */ | |
103 | movq 8(%rsp), %rsi /* temporarily store the return address in %rsi */ | |
104 | movq %rdi, 8(%rsp) /* pt_regs->di (overwriting original return address) */ | |
105 | .else | |
3f01daec DB |
106 | pushq %rdi /* pt_regs->di */ |
107 | pushq %rsi /* pt_regs->si */ | |
9e809d15 | 108 | .endif |
30907fd1 | 109 | pushq \rdx /* pt_regs->dx */ |
3f01daec | 110 | pushq %rcx /* pt_regs->cx */ |
30907fd1 | 111 | pushq \rax /* pt_regs->ax */ |
3f01daec | 112 | pushq %r8 /* pt_regs->r8 */ |
3f01daec | 113 | pushq %r9 /* pt_regs->r9 */ |
3f01daec | 114 | pushq %r10 /* pt_regs->r10 */ |
3f01daec | 115 | pushq %r11 /* pt_regs->r11 */ |
3f01daec | 116 | pushq %rbx /* pt_regs->rbx */ |
3f01daec | 117 | pushq %rbp /* pt_regs->rbp */ |
3f01daec | 118 | pushq %r12 /* pt_regs->r12 */ |
3f01daec | 119 | pushq %r13 /* pt_regs->r13 */ |
3f01daec | 120 | pushq %r14 /* pt_regs->r14 */ |
3f01daec | 121 | pushq %r15 /* pt_regs->r15 */ |
3f01daec | 122 | UNWIND_HINT_REGS |
06a9750e | 123 | |
9e809d15 DB |
124 | .if \save_ret |
125 | pushq %rsi /* return address on top of stack */ | |
126 | .endif | |
06a9750e JP |
127 | |
128 | /* | |
129 | * Sanitize registers of values that a speculation attack might | |
130 | * otherwise want to exploit. The lower registers are likely clobbered | |
131 | * well before they could be put to use in a speculative execution | |
132 | * gadget. | |
133 | */ | |
134 | xorl %edx, %edx /* nospec dx */ | |
135 | xorl %ecx, %ecx /* nospec cx */ | |
136 | xorl %r8d, %r8d /* nospec r8 */ | |
137 | xorl %r9d, %r9d /* nospec r9 */ | |
138 | xorl %r10d, %r10d /* nospec r10 */ | |
139 | xorl %r11d, %r11d /* nospec r11 */ | |
140 | xorl %ebx, %ebx /* nospec rbx */ | |
141 | xorl %ebp, %ebp /* nospec rbp */ | |
142 | xorl %r12d, %r12d /* nospec r12 */ | |
143 | xorl %r13d, %r13d /* nospec r13 */ | |
144 | xorl %r14d, %r14d /* nospec r14 */ | |
145 | xorl %r15d, %r15d /* nospec r15 */ | |
146 | ||
92816f57 | 147 | .endm |
3f01daec | 148 | |
92816f57 | 149 | .macro POP_REGS pop_rdi=1 skip_r11rcx=0 |
e872045b AL |
150 | popq %r15 |
151 | popq %r14 | |
152 | popq %r13 | |
153 | popq %r12 | |
154 | popq %rbp | |
155 | popq %rbx | |
502af0d7 DB |
156 | .if \skip_r11rcx |
157 | popq %rsi | |
158 | .else | |
e872045b | 159 | popq %r11 |
502af0d7 | 160 | .endif |
e872045b AL |
161 | popq %r10 |
162 | popq %r9 | |
163 | popq %r8 | |
164 | popq %rax | |
502af0d7 DB |
165 | .if \skip_r11rcx |
166 | popq %rsi | |
167 | .else | |
e872045b | 168 | popq %rcx |
502af0d7 | 169 | .endif |
e872045b AL |
170 | popq %rdx |
171 | popq %rsi | |
502af0d7 | 172 | .if \pop_rdi |
e872045b | 173 | popq %rdi |
502af0d7 | 174 | .endif |
92816f57 | 175 | .endm |
1a338ac3 | 176 | |
8a09317b DH |
177 | #ifdef CONFIG_PAGE_TABLE_ISOLATION |
178 | ||
6fd166aa PZ |
179 | /* |
180 | * PAGE_TABLE_ISOLATION PGDs are 8k. Flip bit 12 to switch between the two | |
181 | * halves: | |
182 | */ | |
f10ee3dc TG |
183 | #define PTI_USER_PGTABLE_BIT PAGE_SHIFT |
184 | #define PTI_USER_PGTABLE_MASK (1 << PTI_USER_PGTABLE_BIT) | |
185 | #define PTI_USER_PCID_BIT X86_CR3_PTI_PCID_USER_BIT | |
186 | #define PTI_USER_PCID_MASK (1 << PTI_USER_PCID_BIT) | |
187 | #define PTI_USER_PGTABLE_AND_PCID_MASK (PTI_USER_PCID_MASK | PTI_USER_PGTABLE_MASK) | |
8a09317b | 188 | |
6fd166aa PZ |
189 | .macro SET_NOFLUSH_BIT reg:req |
190 | bts $X86_CR3_PCID_NOFLUSH_BIT, \reg | |
8a09317b DH |
191 | .endm |
192 | ||
6fd166aa PZ |
193 | .macro ADJUST_KERNEL_CR3 reg:req |
194 | ALTERNATIVE "", "SET_NOFLUSH_BIT \reg", X86_FEATURE_PCID | |
195 | /* Clear PCID and "PAGE_TABLE_ISOLATION bit", point CR3 at kernel pagetables: */ | |
f10ee3dc | 196 | andq $(~PTI_USER_PGTABLE_AND_PCID_MASK), \reg |
8a09317b DH |
197 | .endm |
198 | ||
199 | .macro SWITCH_TO_KERNEL_CR3 scratch_reg:req | |
aa8c6248 | 200 | ALTERNATIVE "jmp .Lend_\@", "", X86_FEATURE_PTI |
8a09317b DH |
201 | mov %cr3, \scratch_reg |
202 | ADJUST_KERNEL_CR3 \scratch_reg | |
203 | mov \scratch_reg, %cr3 | |
aa8c6248 | 204 | .Lend_\@: |
8a09317b DH |
205 | .endm |
206 | ||
6fd166aa PZ |
207 | #define THIS_CPU_user_pcid_flush_mask \ |
208 | PER_CPU_VAR(cpu_tlbstate) + TLB_STATE_user_pcid_flush_mask | |
209 | ||
210 | .macro SWITCH_TO_USER_CR3_NOSTACK scratch_reg:req scratch_reg2:req | |
aa8c6248 | 211 | ALTERNATIVE "jmp .Lend_\@", "", X86_FEATURE_PTI |
8a09317b | 212 | mov %cr3, \scratch_reg |
6fd166aa PZ |
213 | |
214 | ALTERNATIVE "jmp .Lwrcr3_\@", "", X86_FEATURE_PCID | |
215 | ||
216 | /* | |
217 | * Test if the ASID needs a flush. | |
218 | */ | |
219 | movq \scratch_reg, \scratch_reg2 | |
220 | andq $(0x7FF), \scratch_reg /* mask ASID */ | |
221 | bt \scratch_reg, THIS_CPU_user_pcid_flush_mask | |
222 | jnc .Lnoflush_\@ | |
223 | ||
224 | /* Flush needed, clear the bit */ | |
225 | btr \scratch_reg, THIS_CPU_user_pcid_flush_mask | |
226 | movq \scratch_reg2, \scratch_reg | |
f10ee3dc | 227 | jmp .Lwrcr3_pcid_\@ |
6fd166aa PZ |
228 | |
229 | .Lnoflush_\@: | |
230 | movq \scratch_reg2, \scratch_reg | |
231 | SET_NOFLUSH_BIT \scratch_reg | |
232 | ||
f10ee3dc TG |
233 | .Lwrcr3_pcid_\@: |
234 | /* Flip the ASID to the user version */ | |
235 | orq $(PTI_USER_PCID_MASK), \scratch_reg | |
236 | ||
6fd166aa | 237 | .Lwrcr3_\@: |
f10ee3dc TG |
238 | /* Flip the PGD to the user version */ |
239 | orq $(PTI_USER_PGTABLE_MASK), \scratch_reg | |
8a09317b | 240 | mov \scratch_reg, %cr3 |
aa8c6248 | 241 | .Lend_\@: |
8a09317b DH |
242 | .endm |
243 | ||
6fd166aa PZ |
244 | .macro SWITCH_TO_USER_CR3_STACK scratch_reg:req |
245 | pushq %rax | |
246 | SWITCH_TO_USER_CR3_NOSTACK scratch_reg=\scratch_reg scratch_reg2=%rax | |
247 | popq %rax | |
248 | .endm | |
249 | ||
8a09317b | 250 | .macro SAVE_AND_SWITCH_TO_KERNEL_CR3 scratch_reg:req save_reg:req |
aa8c6248 | 251 | ALTERNATIVE "jmp .Ldone_\@", "", X86_FEATURE_PTI |
8a09317b DH |
252 | movq %cr3, \scratch_reg |
253 | movq \scratch_reg, \save_reg | |
254 | /* | |
f10ee3dc TG |
255 | * Test the user pagetable bit. If set, then the user page tables |
256 | * are active. If clear CR3 already has the kernel page table | |
257 | * active. | |
8a09317b | 258 | */ |
f10ee3dc TG |
259 | bt $PTI_USER_PGTABLE_BIT, \scratch_reg |
260 | jnc .Ldone_\@ | |
8a09317b DH |
261 | |
262 | ADJUST_KERNEL_CR3 \scratch_reg | |
263 | movq \scratch_reg, %cr3 | |
264 | ||
265 | .Ldone_\@: | |
266 | .endm | |
267 | ||
21e94459 | 268 | .macro RESTORE_CR3 scratch_reg:req save_reg:req |
aa8c6248 | 269 | ALTERNATIVE "jmp .Lend_\@", "", X86_FEATURE_PTI |
21e94459 PZ |
270 | |
271 | ALTERNATIVE "jmp .Lwrcr3_\@", "", X86_FEATURE_PCID | |
272 | ||
273 | /* | |
274 | * KERNEL pages can always resume with NOFLUSH as we do | |
275 | * explicit flushes. | |
276 | */ | |
f10ee3dc | 277 | bt $PTI_USER_PGTABLE_BIT, \save_reg |
21e94459 PZ |
278 | jnc .Lnoflush_\@ |
279 | ||
280 | /* | |
281 | * Check if there's a pending flush for the user ASID we're | |
282 | * about to set. | |
283 | */ | |
284 | movq \save_reg, \scratch_reg | |
285 | andq $(0x7FF), \scratch_reg | |
286 | bt \scratch_reg, THIS_CPU_user_pcid_flush_mask | |
287 | jnc .Lnoflush_\@ | |
288 | ||
289 | btr \scratch_reg, THIS_CPU_user_pcid_flush_mask | |
290 | jmp .Lwrcr3_\@ | |
291 | ||
292 | .Lnoflush_\@: | |
293 | SET_NOFLUSH_BIT \save_reg | |
294 | ||
295 | .Lwrcr3_\@: | |
8a09317b DH |
296 | /* |
297 | * The CR3 write could be avoided when not changing its value, | |
298 | * but would require a CR3 read *and* a scratch register. | |
299 | */ | |
300 | movq \save_reg, %cr3 | |
aa8c6248 | 301 | .Lend_\@: |
8a09317b DH |
302 | .endm |
303 | ||
304 | #else /* CONFIG_PAGE_TABLE_ISOLATION=n: */ | |
305 | ||
306 | .macro SWITCH_TO_KERNEL_CR3 scratch_reg:req | |
307 | .endm | |
6fd166aa PZ |
308 | .macro SWITCH_TO_USER_CR3_NOSTACK scratch_reg:req scratch_reg2:req |
309 | .endm | |
310 | .macro SWITCH_TO_USER_CR3_STACK scratch_reg:req | |
8a09317b DH |
311 | .endm |
312 | .macro SAVE_AND_SWITCH_TO_KERNEL_CR3 scratch_reg:req save_reg:req | |
313 | .endm | |
21e94459 | 314 | .macro RESTORE_CR3 scratch_reg:req save_reg:req |
8a09317b DH |
315 | .endm |
316 | ||
317 | #endif | |
318 | ||
18ec54fd JP |
319 | /* |
320 | * Mitigate Spectre v1 for conditional swapgs code paths. | |
321 | * | |
322 | * FENCE_SWAPGS_USER_ENTRY is used in the user entry swapgs code path, to | |
323 | * prevent a speculative swapgs when coming from kernel space. | |
324 | * | |
325 | * FENCE_SWAPGS_KERNEL_ENTRY is used in the kernel entry non-swapgs code path, | |
326 | * to prevent the swapgs from getting speculatively skipped when coming from | |
327 | * user space. | |
328 | */ | |
329 | .macro FENCE_SWAPGS_USER_ENTRY | |
330 | ALTERNATIVE "", "lfence", X86_FEATURE_FENCE_SWAPGS_USER | |
331 | .endm | |
332 | .macro FENCE_SWAPGS_KERNEL_ENTRY | |
333 | ALTERNATIVE "", "lfence", X86_FEATURE_FENCE_SWAPGS_KERNEL | |
334 | .endm | |
335 | ||
afaef01c AP |
336 | .macro STACKLEAK_ERASE_NOCLOBBER |
337 | #ifdef CONFIG_GCC_PLUGIN_STACKLEAK | |
338 | PUSH_AND_CLEAR_REGS | |
339 | call stackleak_erase | |
340 | POP_REGS | |
341 | #endif | |
342 | .endm | |
343 | ||
1a338ac3 PZ |
344 | #endif /* CONFIG_X86_64 */ |
345 | ||
afaef01c AP |
346 | .macro STACKLEAK_ERASE |
347 | #ifdef CONFIG_GCC_PLUGIN_STACKLEAK | |
348 | call stackleak_erase | |
349 | #endif | |
350 | .endm | |
351 | ||
478dc89c AL |
352 | /* |
353 | * This does 'call enter_from_user_mode' unless we can avoid it based on | |
354 | * kernel config or using the static jump infrastructure. | |
355 | */ | |
356 | .macro CALL_enter_from_user_mode | |
357 | #ifdef CONFIG_CONTEXT_TRACKING | |
e9666d10 | 358 | #ifdef CONFIG_JUMP_LABEL |
74c57875 | 359 | STATIC_JUMP_IF_FALSE .Lafter_call_\@, context_tracking_key, def=0 |
478dc89c AL |
360 | #endif |
361 | call enter_from_user_mode | |
362 | .Lafter_call_\@: | |
363 | #endif | |
364 | .endm | |
55aedddb PZ |
365 | |
366 | #ifdef CONFIG_PARAVIRT_XXL | |
367 | #define GET_CR2_INTO(reg) GET_CR2_INTO_AX ; _ASM_MOV %_ASM_AX, reg | |
368 | #else | |
369 | #define GET_CR2_INTO(reg) _ASM_MOV %cr2, reg | |
370 | #endif |