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f4f4caab0e
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
25 lines
959 B
C
25 lines
959 B
C
#ifndef COSMOPOLITAN_LIBC_INTRIN_REPSTOSB_H_
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#define COSMOPOLITAN_LIBC_INTRIN_REPSTOSB_H_
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#if !(__ASSEMBLER__ + __LINKER__ + 0)
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static void *repstosb(void *dest, unsigned char al, size_t cx) {
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unsigned char *di = (unsigned char *)dest;
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while (cx) *di++ = al, cx--;
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return di;
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}
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#if defined(__GNUC__) && (defined(__i386__) || defined(__x86_64__))
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#define repstosb(DI, AL, CX) \
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({ \
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void *Di = (DI); \
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size_t Cx = (CX); \
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unsigned char Al = (AL); \
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asm("rep stosb" \
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: "=D"(Di), "=c"(Cx), "=m"(*(char(*)[Cx])Di) \
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: "0"(Di), "1"(Cx), "a"(Al)); \
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Di; \
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})
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#endif
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#endif /* !(__ASSEMBLER__ + __LINKER__ + 0) */
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#endif /* COSMOPOLITAN_LIBC_INTRIN_REPSTOSB_H_ */
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