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scanf to printf on AArch64
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| #include <stdio.h> | |
| #include <stdint.h> | |
| #include <sys/mman.h> | |
| int main() | |
| { | |
| mprotect((void *)((unsigned long)main & (~0xfff)), 4096, | |
| PROT_EXEC|PROT_WRITE); | |
| { // gcc and clang puts the "0:", "1:" etc labels below at different places | |
| char *p; | |
| __asm__("adr %[p], 0f\n" | |
| : /* ouputs */ [p] "=r" (p) | |
| : /* inputs */ | |
| : /* clobbers */ "x10" | |
| ); | |
| printf("0f: 0x%p\n", p); | |
| __asm__("adr %[p], 1f\n" | |
| : /* ouputs */ [p] "=r" (p) | |
| : /* inputs */ | |
| : /* clobbers */ "x10" | |
| ); | |
| printf("1f: 0x%p\n", p); | |
| __asm__("adr %[p], 2f\n" | |
| : /* ouputs */ [p] "=r" (p) | |
| : /* inputs */ | |
| : /* clobbers */ "x10" | |
| ); | |
| printf("2f: 0x%p\n", p); | |
| } | |
| #if defined(__clang__) | |
| #define HELLO1_LABEL "0f" | |
| #define HELLO2_LABEL "1f" | |
| #elif defined(__GNUC__) | |
| #define HELLO1_LABEL "(1f-4)" | |
| #define HELLO2_LABEL "(2f-4)" | |
| #endif | |
| uint32_t dst; | |
| __asm__("ldr %w[dst], " HELLO1_LABEL "\n" | |
| : /* ouputs */ [dst] "=r" (dst) | |
| : /* inputs */ | |
| : /* clobbers */ | |
| ); | |
| // bl PCREL26 | |
| printf("dst: 0x%0x\n", dst); | |
| dst = ((int32_t)(dst << 6)) >> 4; | |
| printf("dst: %d\n", dst); | |
| __asm__( | |
| "sub %w[dst], %w[dst], " HELLO2_LABEL "-" HELLO1_LABEL "\n" | |
| : /* ouputs */ [dst] "+r" (dst) | |
| : /* inputs */ | |
| : /* clobbers */ | |
| ); | |
| printf("dst: %d\n", dst); | |
| dst = 0x94000000 | (((uint32_t)(dst >> 2)) & (0x03ffffff)); | |
| printf("dst: 0x%0x\n", dst); | |
| __asm__ volatile ( | |
| "adr x10, " HELLO2_LABEL "\n" | |
| "str %w[dst], [x10]\n" | |
| : /* ouputs */ | |
| : /* inputs */ [dst] "r" (dst) | |
| : /* clobbers */ "x10", "memory" | |
| ); | |
| // Write back and invalidate data and instruction caches | |
| __builtin___clear_cache((char*)main, (char*)main+1024); | |
| // Jump to target after codegen. | |
| __asm__ volatile ("b 0f"); | |
| __asm__("0:"); | |
| // In practice, the code works on Apple M2 and Amazon Graviton | |
| // without "__builtin___clear_cache()" and "b 0f" above. | |
| printf("Hello 1\n"); | |
| __asm__ volatile ("1:"); | |
| scanf("Hello 2\n"); | |
| __asm__ volatile ("2:"); | |
| return 0; | |
| } |
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