cosmopolitan/libc/runtime/mman.greg.c
Justine Tunney 94afa982c3 Fix zip executables on MacOS
Here's why we got those `Killed: 11` failures on MacOS after modifying
the contentns of the redbean.com executable. If you were inserting a
small file, such as a HelloWorld.html file, then InfoZIP might have
decreased the size of the executable to less than what the Mach-O
section had been expecting.

That's because when zipobj.com put things like time zone data in the
executable, it aligned each zip file entry on a 64-byte boundary, simply
for the sake of readability in binary dumps. But when InfoZIP edited the
file it would rewrite every entry using ZIP's usual 2-byte alignment.
Thus causing shrinkage.

The solution was to reconfigure the linker script so that zip file bits
that get put into the executable at link-time, such as timezone data,
aren't officially part of the executable image, i.e. we don't want the
operating system to load that part.

The original decision to put the linked zip files into the .data section
was mostly made so that when the executable was run in its .com.dbg form
it would still have the zip entries be accessible, even though there was
tons of GNU debug data following the central directory. We're not going
to be able to do that. The .com executable should be the canonical
executable. We have really good tools for automatically attaching and
configuring GDB correctly with debug symbols even when the .com is run.
We'll have to rely on those in cases where zip embedding is used.

See #53
See #54
See #68
2021-02-27 18:16:59 -08:00

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/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
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╞══════════════════════════════════════════════════════════════════════════════╡
│ Copyright 2020 Justine Alexandra Roberts Tunney │
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│ Permission to use, copy, modify, and/or distribute this software for │
│ any purpose with or without fee is hereby granted, provided that the │
│ above copyright notice and this permission notice appear in all copies. │
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│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR │
│ PERFORMANCE OF THIS SOFTWARE. │
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αcτµαlly pδrταblε εxεcµταblε § no-frills virtual memory management │
╚─────────────────────────────────────────────────────────────────────────────*/
#include "ape/relocations.h"
#include "libc/elf/def.h"
#include "libc/elf/struct/phdr.h"
#include "libc/macros.h"
#include "libc/nexgen32e/uart.internal.h"
#include "libc/runtime/e820.internal.h"
#include "libc/runtime/metalprintf.internal.h"
#include "libc/runtime/pc.internal.h"
#include "libc/runtime/runtime.h"
/**
* Allocates new page of physical memory.
*/
noasan texthead uint64_t __new_page(struct mman *mm) {
uint64_t p;
if (mm->pdpi == mm->e820n) {
/* TODO: reclaim free pages */
return 0;
}
while (mm->pdp >= mm->e820[mm->pdpi].addr + mm->e820[mm->pdpi].size) {
if (++mm->pdpi == mm->e820n) return 0;
mm->pdp = mm->e820[mm->pdpi].addr;
}
p = mm->pdp;
mm->pdp += 4096;
return p;
}
/**
* Returns pointer to page table entry for page at virtual address.
* Additional page tables are allocated if needed as a side-effect.
*/
noasan texthead uint64_t *__get_virtual(struct mman *mm, uint64_t *t,
int64_t vaddr, bool maketables) {
uint64_t *e, p;
unsigned char h;
for (h = 39;; h -= 9) {
e = t + ((vaddr >> h) & 511);
if (h == 12) return e;
if (!(*e & PAGE_V)) {
if (!maketables) return NULL;
if (!(p = __new_page(mm))) return NULL;
*e = p | PAGE_V | PAGE_RW;
}
t = (uint64_t *)(BANE + (*e & PAGE_TA));
}
}
/**
* Sorts, rounds, and filters BIOS memory map.
*/
static noasan textreal void __normalize_e820(struct mman *mm) {
uint64_t a, b;
uint64_t x, y;
unsigned i, j, n;
for (n = i = 0; mm->e820[i].size; ++i) {
mm->e820[n] = mm->e820[i];
x = mm->e820[n].addr;
y = mm->e820[n].addr + mm->e820[n].size;
a = ROUNDUP(x, 4096);
b = ROUNDDOWN(y, 4096) - a;
if (b > 0 && mm->e820[i].type == kMemoryUsable) {
mm->e820[n].addr = a;
mm->e820[n].size = b;
++n;
}
}
for (i = 1; i < n; ++i) {
for (j = i; j > 0 && mm->e820[i].addr < mm->e820[j - 1].addr; --j) {
mm->e820[j] = mm->e820[j - 1];
}
mm->e820[j] = mm->e820[i];
}
mm->pdp = MAX(0x80000, mm->e820[0].addr);
mm->pdpi = 0;
mm->e820n = n;
}
/**
* Identity maps all usable physical memory to its negative address.
*/
static noasan textreal void __invert_memory(struct mman *mm, uint64_t *pml4t) {
uint64_t i, j, *m, p, pe;
for (i = 0; i < mm->e820n; ++i) {
for (p = mm->e820[i].addr, pe = mm->e820[i].addr + mm->e820[i].size;
p + 0x200000 < pe; p += 4096) {
m = __get_virtual(mm, pml4t, BANE + p, true);
if (m && !(*m & PAGE_V)) {
*m = p | PAGE_V | PAGE_RW;
}
}
}
}
noasan textreal void __setup_mman(struct mman *mm, uint64_t *pml4t) {
__normalize_e820(mm);
__invert_memory(mm, pml4t);
}
/**
* Maps APE-defined ELF program headers into memory and clears BSS.
*/
noasan textreal void __map_phdrs(struct mman *mm, uint64_t *pml4t, uint64_t b) {
struct Elf64_Phdr *p;
uint64_t i, f, v, m, *e;
extern char ape_phdrs[] __attribute__((__weak__));
extern char ape_phdrs_end[] __attribute__((__weak__));
__setup_mman(mm, pml4t);
for (p = (struct Elf64_Phdr *)REAL(ape_phdrs), m = 0;
p < (struct Elf64_Phdr *)REAL(ape_phdrs_end); ++p) {
if (p->p_type == PT_LOAD || p->p_type == PT_GNU_STACK) {
f = PAGE_V | PAGE_U;
if (p->p_flags & PF_W) f |= PAGE_RW;
for (i = 0; i < p->p_memsz; i += 4096) {
if (i < p->p_filesz) {
v = b + p->p_offset + i;
m = MAX(m, v);
} else {
v = __clear_page(__new_page(mm));
}
*__get_virtual(mm, pml4t, p->p_vaddr + i, true) = (v & PAGE_TA) | f;
}
}
}
mm->pdp = MAX(mm->pdp, m);
}