40 lines
1.3 KiB
C
40 lines
1.3 KiB
C
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/*
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* Test s390x-linux-user precise self-modifying code handling.
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*
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* SPDX-License-Identifier: GPL-2.0-or-later
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*/
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#include <assert.h>
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#include <sys/mman.h>
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#include <stdint.h>
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#include <stdlib.h>
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extern __uint128_t __attribute__((__aligned__(1))) smc;
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extern __uint128_t __attribute__((__aligned__(1))) patch;
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int main(void)
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{
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char *aligned_smc = (char *)((uintptr_t)&smc & ~0xFFFULL);
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char *smc_end = (char *)&smc + sizeof(smc);
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uint64_t value = 21;
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int err;
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err = mprotect(aligned_smc, smc_end - aligned_smc,
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PROT_READ | PROT_WRITE | PROT_EXEC);
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assert(err == 0);
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asm("jg 0f\n" /* start a new TB */
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"patch: .byte 0,0,0,0,0,0\n" /* replaces padding */
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".byte 0,0,0,0,0,0\n" /* replaces vstl */
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"agr %[value],%[value]\n" /* replaces sgr */
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"smc: .org . + 6\n" /* pad patched code to 16 bytes */
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"0: vstl %[patch],%[idx],%[smc]\n" /* start writing before TB */
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"sgr %[value],%[value]" /* this becomes `agr %r0,%r0` */
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: [smc] "=R" (smc)
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, [value] "+r" (value)
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: [patch] "v" (patch)
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, [idx] "r" (sizeof(patch) - 1)
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: "cc");
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return value == 42 ? EXIT_SUCCESS : EXIT_FAILURE;
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}
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