82 lines
1.8 KiB
C
82 lines
1.8 KiB
C
/*
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* crt1.c
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* Minimal C runtime startup for MontaukOS userspace programs
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* Copyright (c) 2026 Daniel Hammer
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*
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* This startup shim is intentionally small: it fetches the raw
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* command-line buffer from the kernel, tokenizes it into argc/argv,
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* calls main(), then exits with main()'s return code.
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*/
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static inline long _sys1(long nr, long a1) {
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long ret;
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__asm__ volatile(
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"mov %[a1], %%rdi\n\t"
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"syscall"
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: "=a"(ret)
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: "a"(nr), [a1] "r"(a1)
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: "rcx", "r11", "rdi", "rsi", "rdx", "r8", "r9", "r10", "memory");
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return ret;
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}
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static inline long _sys2(long nr, long a1, long a2) {
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long ret;
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__asm__ volatile(
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"mov %[a1], %%rdi\n\t"
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"mov %[a2], %%rsi\n\t"
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"syscall"
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: "=a"(ret)
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: "a"(nr), [a1] "r"(a1), [a2] "r"(a2)
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: "rcx", "r11", "rdi", "rsi", "rdx", "r8", "r9", "r10", "memory");
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return ret;
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}
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#define SYS_EXIT 0
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#define SYS_GETARGS 25
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extern int main(int argc, char** argv);
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void _start(void) {
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char argbuf[256];
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int len = (int)_sys2(SYS_GETARGS, (long)argbuf, (long)sizeof(argbuf));
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char* argv[32];
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int argc = 0;
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argv[argc++] = (char*)"prog";
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if (len > 0) {
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if (len > 255) {
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len = 255;
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}
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argbuf[len] = '\0';
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char* p = argbuf;
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while (*p != '\0' && argc < 31) {
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while (*p == ' ') {
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p++;
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}
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if (*p == '\0') {
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break;
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}
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argv[argc++] = p;
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while (*p != '\0' && *p != ' ') {
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p++;
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}
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if (*p != '\0') {
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*p++ = '\0';
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}
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}
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}
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argv[argc] = 0;
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_sys1(SYS_EXIT, (long)main(argc, argv));
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__builtin_unreachable();
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}
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