| 1 | /* |
| 2 | * Test modifying code using the MVC instruction. |
| 3 | * |
| 4 | * SPDX-License-Identifier: GPL-2.0-or-later |
| 5 | */ |
| 6 | |
| 7 | #include <minilib.h> |
| 8 | |
| 9 | #define PAGE_SIZE 4096 |
| 10 | #define BR_14_SIZE 2 |
| 11 | #define RWX_OFFSET 2 |
| 12 | |
| 13 | static unsigned char rw[PAGE_SIZE + BR_14_SIZE]; |
| 14 | static unsigned char rwx[RWX_OFFSET + sizeof(rw)] |
| 15 | __attribute__((aligned(PAGE_SIZE))); |
| 16 | |
| 17 | typedef unsigned long (*function_t)(unsigned long); |
| 18 | |
| 19 | static int emit_function(unsigned char *p, int n) |
| 20 | { |
| 21 | int i = 0, val = 0; |
| 22 | |
| 23 | while (i < n - 2) { |
| 24 | /* aghi %r2,1 */ |
| 25 | p[i++] = 0xa7; |
| 26 | p[i++] = 0x2b; |
| 27 | p[i++] = 0x00; |
| 28 | p[i++] = 0x01; |
| 29 | val++; |
| 30 | } |
| 31 | |
| 32 | /* br %r14 */ |
| 33 | p[i++] = 0x07; |
| 34 | p[i++] = 0xfe; |
| 35 | |
| 36 | return val; |
| 37 | } |
| 38 | |
| 39 | static void memcpy_mvc(void *dest, void *src, unsigned long n) |
| 40 | { |
| 41 | while (n >= 256) { |
| 42 | asm("mvc 0(256,%[dest]),0(%[src])" |
| 43 | : |
| 44 | : [dest] "a" (dest) |
| 45 | , [src] "a" (src) |
| 46 | : "memory"); |
| 47 | dest += 256; |
| 48 | src += 256; |
| 49 | n -= 256; |
| 50 | } |
| 51 | asm("exrl %[n],0f\n" |
| 52 | "j 1f\n" |
| 53 | "0: mvc 0(1,%[dest]),0(%[src])\n" |
| 54 | "1:" |
| 55 | : |
| 56 | : [dest] "a" (dest) |
| 57 | , [src] "a" (src) |
| 58 | , [n] "a" (n) |
| 59 | : "memory"); |
| 60 | } |
| 61 | |
| 62 | int main(void) |
| 63 | { |
| 64 | int expected, size; |
| 65 | |
| 66 | /* Create a TB. */ |
| 67 | size = sizeof(rwx) - RWX_OFFSET - 4; |
| 68 | expected = emit_function(rwx + RWX_OFFSET, size); |
| 69 | if (((function_t)(rwx + RWX_OFFSET))(0) != expected) { |
| 70 | return 1; |
| 71 | } |
| 72 | |
| 73 | /* Overwrite the TB. */ |
| 74 | size += 4; |
| 75 | expected = emit_function(rw, size); |
| 76 | memcpy_mvc(rwx + RWX_OFFSET, rw, size); |
| 77 | if (((function_t)(rwx + RWX_OFFSET))(0) != expected) { |
| 78 | return 2; |
| 79 | } |
| 80 | |
| 81 | return 0; |
| 82 | } |