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Fix apelink shell script corruption bug

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We were using a shell heredoc value '@' to terminate the dos stub, but
that's not sufficiently safe. We found out sh doesn't consider control
characters as contributing to the start of a line, and had the unlucky
chance of the linker choosing the number 2624 for e_lfanew, and that's
"@\n" in ASCII, which compromised the APE shell script.

We now use the heredoc 'justineXXXXXX' with 31 bits of entropy, that's
determistically generated by hashing apelink inputs w/ crc32 / blake2b
This commit is contained in:
Justine Tunney 2023-08-13 17:36:06 -07:00
parent 2366848db5
commit a033b65a33
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GPG key ID: BE714B4575D6E328
3 changed files with 48 additions and 77 deletions
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47
examples/fastmod.c
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@ -1,47 +0,0 @@
#if 0
/*─────────────────────────────────────────────────────────────────╗
│ To the extent possible under law, Justine Tunney has waived │
│ all copyright and related or neighboring rights to this file, │
│ as it is written in the following disclaimers: │
│ • http://unlicense.org/ │
│ • http://creativecommons.org/publicdomain/zero/1.0/ │
╚─────────────────────────────────────────────────────────────────*/
#endif
#include "libc/stdio/stdio.h"
#include "libc/testlib/ezbench.h"
/**
* @fileoverview Fast Modulus Using Multiplication Tutorial
*
* Expected program output:
*
* 23 / 3 = 7
* 0x5555555555555556 1 1
* modulus l: 15𝑐 5𝑛𝑠
* fastmod l: 4𝑐 1𝑛𝑠
* precomp l: 18𝑐 6𝑛𝑠
*/
struct Modulus {
uint64_t c;
uint64_t d;
};
struct Modulus GetModulus(uint64_t d) {
return (struct Modulus){0xFFFFFFFFFFFFFFFFull / d + 1, d};
}
uint64_t Modulus(uint64_t x, struct Modulus m) {
return ((uint128_t)(m.c * x) * m.d) >> 64;
}
int main(int argc, char *argv[]) {
printf("%#lx %% %d = %d\n", 0x23, 3, Modulus(23, GetModulus(3)));
printf("%#lx %% %d = %d\n", 0x123, 17, Modulus(0x123, GetModulus(17)));
volatile struct Modulus v = GetModulus(3);
volatile uint64_t x = 23, y = 3, z;
EZBENCH2("modulus", donothing, z = x % y);
EZBENCH2("fastmod", donothing, z = Modulus(x, v));
EZBENCH2("precomp", donothing, v = GetModulus(y));
return 0;
}