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| 1 | +/* SPDX-License-Identifier: GPL-2.0-only */ |
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1 | 2 | /* |
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2 | 3 | * Copyright (C) 2018 Linaro Ltd <ard.biesheuvel@linaro.org> |
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3 | | - * |
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4 | | - * This program is free software; you can redistribute it and/or modify |
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5 | | - * it under the terms of the GNU General Public License version 2 as |
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6 | | - * published by the Free Software Foundation. |
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7 | 4 | */ |
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8 | 5 | |
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9 | 6 | #include <linux/linkage.h> |
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| 7 | +#include <asm/assembler.h> |
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10 | 8 | |
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11 | | -ENTRY(__efi_rt_asm_wrapper) |
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| 9 | +SYM_FUNC_START(__efi_rt_asm_wrapper) |
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12 | 10 | stp x29, x30, [sp, #-32]! |
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13 | 11 | mov x29, sp |
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14 | 12 | |
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.. | .. |
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18 | 16 | * (such as UEFI) should never touch it. |
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19 | 17 | */ |
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20 | 18 | stp x1, x18, [sp, #16] |
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| 19 | + |
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| 20 | + ldr_l x16, efi_rt_stack_top |
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| 21 | + mov sp, x16 |
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| 22 | +#ifdef CONFIG_SHADOW_CALL_STACK |
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| 23 | + str x18, [sp, #-16]! |
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| 24 | +#endif |
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21 | 25 | |
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22 | 26 | /* |
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23 | 27 | * We are lucky enough that no EFI runtime services take more than |
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.. | .. |
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32 | 36 | mov x4, x6 |
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33 | 37 | blr x8 |
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34 | 38 | |
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| 39 | + mov sp, x29 |
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35 | 40 | ldp x1, x2, [sp, #16] |
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36 | 41 | cmp x2, x18 |
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37 | 42 | ldp x29, x30, [sp], #32 |
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38 | 43 | b.ne 0f |
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39 | 44 | ret |
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40 | 45 | 0: |
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41 | | -#ifdef CONFIG_SHADOW_CALL_STACK |
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42 | 46 | /* |
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43 | | - * Restore x18 before returning to instrumented code. This is |
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44 | | - * safe because the wrapper is called with preemption disabled and |
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45 | | - * a separate shadow stack is used for interrupts. |
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| 47 | + * With CONFIG_SHADOW_CALL_STACK, the kernel uses x18 to store a |
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| 48 | + * shadow stack pointer, which we need to restore before returning to |
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| 49 | + * potentially instrumented code. This is safe because the wrapper is |
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| 50 | + * called with preemption disabled and a separate shadow stack is used |
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| 51 | + * for interrupts. |
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46 | 52 | */ |
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47 | | - mov x18, x2 |
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| 53 | +#ifdef CONFIG_SHADOW_CALL_STACK |
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| 54 | + ldr_l x18, efi_rt_stack_top |
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| 55 | + ldr x18, [x18, #-16] |
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48 | 56 | #endif |
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| 57 | + |
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49 | 58 | b efi_handle_corrupted_x18 // tail call |
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50 | | -ENDPROC(__efi_rt_asm_wrapper) |
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| 59 | +SYM_FUNC_END(__efi_rt_asm_wrapper) |
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