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Rewrite brk() and sbrk()

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This change reduces the .bss memory requirement for all executables by
O(64kb). The brk system calls are now fully tested and figured out and
might be useful for tiny programs that only target System Five.
This commit is contained in:
Justine Tunney 2022-10-01 23:11:56 -07:00
parent bc8532688b
commit 5005f2e446
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GPG key ID: BE714B4575D6E328
23 changed files with 643 additions and 294 deletions
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8
libc/runtime/mmap.c
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@ -71,7 +71,7 @@ static wontreturn void OnUnrecoverableMmapError(const char *s) {
static noasan inline bool OverlapsExistingMapping(char *p, size_t n) {
int a, b, i;
assert(n > 0);
_unassert(n > 0);
a = FRAME(p);
b = FRAME(p + (n - 1));
i = FindMemoryInterval(&_mmi, a);
@ -86,7 +86,7 @@ static noasan inline bool OverlapsExistingMapping(char *p, size_t n) {
static noasan bool ChooseMemoryInterval(int x, int n, int align, int *res) {
// TODO: improve performance
int i, start, end;
assert(align > 0);
_unassert(align > 0);
if (_mmi.i) {
// find the start of the automap memory region
@ -202,8 +202,8 @@ static textwindows dontinline noasan void *MapMemories(char *addr, size_t size,
struct DirectMap dm;
bool iscow, readonlyfile;
m = (size_t)(n - 1) << 16;
assert(m < size);
assert(m + FRAMESIZE >= size);
_unassert(m < size);
_unassert(m + FRAMESIZE >= size);
oi = fd == -1 ? 0 : off + m;
sz = size - m;
dm = sys_mmap(addr + m, sz, prot, f, fd, oi);