54 lines
1.1 KiB
C
54 lines
1.1 KiB
C
#include <stdint.h>
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#if defined(__x86_64__)
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#define SYS_EXIT 60
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void exit(int8_t status) {
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asm volatile(
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"syscall"
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:
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: "a"(SYS_EXIT), "D"(status)
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:
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);
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for(;;);
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}
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#define SYS_WRITE 1
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intptr_t write(int32_t fd, const void* buf, intptr_t size) {
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intptr_t n_written = 0;
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asm volatile (
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"syscall\n"
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"movq %0, %%rax\n"
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: "=r"(n_written)
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: "a"(SYS_WRITE), "D"(fd), "S"(buf), "d"(size) // RDI, RSI, RDX are used in x86-64 for write args
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: "rcx", "r11", "memory"
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);
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return n_written;
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}
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#define SYS_READ 0
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intptr_t read(int32_t fd, const void* buf, intptr_t size) {
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intptr_t n_read = 0;
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asm volatile (
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"syscall\n"
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"movq %0, %%rax\n"
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: "=r"(n_read)
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: "a"(SYS_READ), "D"(fd), "S"(buf), "d"(size) // RDI, RSI, RDX are used in x86-64 for write args
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: "rcx", "r11", "memory"
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);
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return n_read;
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}
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#define SYS_FORK 57
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uint32_t fork() {
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uint64_t rtn;
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asm volatile(
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"syscall\n" // syscall
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"movq %0, %%rax\n" // save return value
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: "=r"(rtn)
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: "a"(SYS_FORK)
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:
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);
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return (uint32_t)rtn;
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}
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#endif /* ifdef __x86_64__ */
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