79 lines
2.3 KiB
C
79 lines
2.3 KiB
C
// This is a tiny wrapper that converts the extra arv[0] argument
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// from binfmt-misc with the P flag enabled to QEMU parameters.
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// It also prevents LD_* environment variables from being applied
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// to QEMU itself.
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <unistd.h>
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#ifndef TARGET_QEMU
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#error "Define TARGET_QEMU to be the path to the qemu-user binary (e.g., -DTARGET_QEMU=\"/full/path/to/qemu-riscv64\")"
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#endif
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extern char **environ;
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int main(int argc, char *argv[]) {
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if (argc < 3) {
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fprintf(stderr, "%s: This should be run as the binfmt interpreter with the P flag\n", argv[0]);
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fprintf(stderr, "%s: My preconfigured qemu-user binary: %s\n", argv[0], TARGET_QEMU);
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return 1;
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}
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size_t environ_count = 0;
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for (char **cur = environ; *cur != NULL; ++cur) {
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environ_count++;
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}
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size_t new_argc = 3;
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size_t new_argv_alloc = argc + 2 * environ_count + 2; // [ "-E", env ] for each LD_* env + [ "-0", argv0 ]
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char **new_argv = (char**)malloc((new_argv_alloc + 1) * sizeof(char*));
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if (!new_argv) {
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fprintf(stderr, "FATAL: Failed to allocate new argv array\n");
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abort();
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}
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new_argv[0] = TARGET_QEMU;
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new_argv[1] = "-0";
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new_argv[2] = argv[2];
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// Pass all LD_ env variables as -E and strip them in `new_environ`
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size_t new_environc = 0;
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char **new_environ = (char**)malloc((environ_count + 1) * sizeof(char*));
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if (!new_environ) {
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fprintf(stderr, "FATAL: Failed to allocate new environ array\n");
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abort();
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}
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for (char **cur = environ; *cur != NULL; ++cur) {
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if (strncmp("LD_", *cur, 3) == 0) {
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new_argv[new_argc++] = "-E";
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new_argv[new_argc++] = *cur;
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} else {
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new_environ[new_environc++] = *cur;
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}
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}
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new_environ[new_environc] = NULL;
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size_t new_arg_start = new_argc;
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new_argc += argc - 3 + 2; // [ "--", full_binary_path ]
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if (argc > 3) {
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memcpy(&new_argv[new_arg_start + 2], &argv[3], (argc - 3) * sizeof(char**));
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}
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new_argv[new_arg_start] = "--";
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new_argv[new_arg_start + 1] = argv[1];
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new_argv[new_argc] = NULL;
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#ifdef DEBUG
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for (size_t i = 0; i < new_argc; ++i) {
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fprintf(stderr, "argv[%zu] = %s\n", i, new_argv[i]);
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}
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#endif
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return execve(new_argv[0], new_argv, new_environ);
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}
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// vim: et:ts=4:sw=4
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