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I wanted a tiny scriptable meltdown proof way to run userspace programs and visualize how program execution impacts memory. It helps to explain how things like Actually Portable Executable works. It can show you how the GCC generated code is going about manipulating matrices and more. I didn't feel fully comfortable with Qemu and Bochs because I'm not smart enough to understand them. I wanted something like gVisor but with much stronger levels of assurances. I wanted a single binary that'll run, on all major operating systems with an embedded GPL barrier ZIP filesystem that is tiny enough to transpile to JavaScript and run in browsers too. https://justine.storage.googleapis.com/emulator625.mp4
103 lines
3.7 KiB
C
103 lines
3.7 KiB
C
#if 0
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/*─────────────────────────────────────────────────────────────────╗
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│ To the extent possible under law, Justine Tunney has waived │
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│ all copyright and related or neighboring rights to this file, │
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│ as it is written in the following disclaimers: │
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│ • http://unlicense.org/ │
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│ • http://creativecommons.org/publicdomain/zero/1.0/ │
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╚─────────────────────────────────────────────────────────────────*/
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#endif
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#include "libc/calls/calls.h"
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#include "libc/calls/hefty/copyfile.h"
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#include "libc/calls/hefty/spawn.h"
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#include "libc/calls/struct/stat.h"
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#include "libc/log/check.h"
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#include "libc/macros.h"
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#include "libc/runtime/gc.h"
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#include "libc/runtime/runtime.h"
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#include "libc/stdio/stdio.h"
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#include "libc/str/str.h"
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#include "libc/sysv/consts/auxv.h"
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#include "libc/sysv/consts/clock.h"
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#include "libc/sysv/consts/fileno.h"
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#include "libc/sysv/consts/madv.h"
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#include "libc/sysv/consts/map.h"
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#include "libc/sysv/consts/o.h"
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#include "libc/sysv/consts/prot.h"
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#include "libc/time/time.h"
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#include "libc/x/x.h"
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/**
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* @fileoverview Overcommit tutorial.
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* You can allocate memory like a central banker prints money.
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*/
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/* #define kHugeAmount (10LU * 1024LU * 1024LU * 1024LU * 1024LU) */
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#define kHugeAmount (1LU * 1024LU * 1024LU * 1024LU)
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int copyfile2(const char *frompath, const char *topath, bool dontoverwrite) {
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struct stat st;
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ssize_t transferred;
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int rc, fromfd, tofd;
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int64_t inoffset, outoffset;
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rc = -1;
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if ((fromfd = open(frompath, O_RDONLY | O_DIRECT, 0)) != -1) {
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if (fstat(fromfd, &st) != -1 &&
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(tofd =
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open(topath,
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O_WRONLY | O_CREAT | O_DIRECT | (dontoverwrite ? O_EXCL : 0),
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st.st_mode & 0777)) != -1) {
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inoffset = 0;
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outoffset = 0;
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while (st.st_size &&
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(transferred = copy_file_range(fromfd, &inoffset, tofd, &outoffset,
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st.st_size, 0)) != -1) {
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st.st_size -= transferred;
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}
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if (!st.st_size) rc = 0;
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rc |= close(tofd);
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}
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rc |= close(fromfd);
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}
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return rc;
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}
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int main(int argc, char *argv[]) {
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int fd, pid;
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size_t size;
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long double t1, t2;
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const char *core, *core2, *core3;
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volatile unsigned char *mem;
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size = ROUNDUP(kHugeAmount, PAGESIZE);
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core = gc(xasprintf("%s.%s", getauxval(AT_EXECFN), "core"));
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core2 = gc(xasprintf("%s.%s", getauxval(AT_EXECFN), "core2"));
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core3 = gc(xasprintf("%s.%s", getauxval(AT_EXECFN), "core3"));
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CHECK_NE(-1, (fd = open(core, O_RDWR | O_CREAT | O_TRUNC | O_CLOEXEC, 0600)));
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CHECK_NE(-1, ftruncate(fd, size));
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CHECK_NE(MAP_FAILED,
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(mem = mmap(NULL, size, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0)));
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strcpy(&mem[0], "hello\n\n\n\n\n\n\n\n\n\n");
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strcpy(&mem[kHugeAmount / 2], "hello\n\n\n\n\n\n\n\n\n\n");
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CHECK_NE(-1, munmap(mem, size));
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CHECK_NE(-1,
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(pid = spawnve(
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0, (int[3]){STDIN_FILENO, STDOUT_FILENO, STDERR_FILENO},
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"o/examples/stat.com",
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(char *const[]){"o/examples/stat.com", core, NULL}, environ)));
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CHECK_NE(-1, waitpid(pid, NULL, 0));
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CHECK_NE(-1, close(fd));
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t1 = dtime(CLOCK_REALTIME);
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CHECK_NE(-1, copyfile(core, core2, 0));
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t2 = dtime(CLOCK_REALTIME);
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printf("%.6Lf\n", t2 - t1);
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t1 = dtime(CLOCK_REALTIME);
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CHECK_NE(-1, copyfile2(core, core3, false));
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t2 = dtime(CLOCK_REALTIME);
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printf("%.6Lf\n", t2 - t1);
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/* CHECK_NE(-1, unlink(core)); */
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return 0;
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}
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