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use mmap instead of brk in mem.alloc to fix a glibc segfault

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This commit is contained in:
Antoni Piasecki
2026-03-12 14:23:57 +01:00
parent 1e7657ea2a
commit 70640b3062
1 changed files with 38 additions and 9 deletions
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45
src/std/std.zr
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@@ -28,13 +28,17 @@ func mem._split_block[blk: mem.Block, needed: i64] : void
mem.write64(_builtin_heap_tail(), new_blk) mem.write64(_builtin_heap_tail(), new_blk)
func mem._request_space[size: i64] : mem.Block func mem._request_space[size: i64] : mem.Block
let blk: mem.Block = _builtin_syscall(SYS_brk, 0) let needed: i64 = size + MEM_BLOCK_SIZE
let new_brk: ptr = blk + MEM_BLOCK_SIZE + size let alloc_size: i64 = (needed + 4095) & -4096
let result: ptr = _builtin_syscall(SYS_brk, new_brk)
if result != new_brk // PROT_READ | PROT_WRITE = 3
// MAP_PRIVATE | MAP_ANONYMOUS = 34
// fd = -1, offset = 0
let blk: mem.Block = _builtin_syscall(SYS_mmap, 0, alloc_size, 3, 34, -1, 0)
if blk == -1
return 0 return 0
blk->size = size blk->size = alloc_size - MEM_BLOCK_SIZE
blk->free = false blk->free = false
blk->next = 0 blk->next = 0
@@ -47,14 +51,35 @@ func mem._request_space[size: i64] : mem.Block
func mem._coalesce[] : void func mem._coalesce[] : void
let cur: mem.Block = mem.read64(_builtin_heap_head()) let cur: mem.Block = mem.read64(_builtin_heap_head())
while cur && cur->next let prev: mem.Block = 0
while cur
let next: mem.Block = cur->next let next: mem.Block = cur->next
if cur->free && next->free let expected_next: mem.Block = cur + MEM_BLOCK_SIZE + cur->size
if cur->free && next && next->free && expected_next == next
cur->size = cur->size + MEM_BLOCK_SIZE + next->size cur->size = cur->size + MEM_BLOCK_SIZE + next->size
cur->next = next->next cur->next = next->next
if !cur->next if !cur->next
mem.write64(_builtin_heap_tail(), cur) mem.write64(_builtin_heap_tail(), cur)
continue
let block_total: i64 = cur->size + MEM_BLOCK_SIZE
if cur->free && (cur & 4095) == 0 && (block_total & 4095) == 0
if prev
prev->next = cur->next
if !cur->next
mem.write64(_builtin_heap_tail(), prev)
else else
mem.write64(_builtin_heap_head(), cur->next)
if !cur->next
mem.write64(_builtin_heap_tail(), 0)
_builtin_syscall(SYS_munmap, cur, block_total)
cur = cur->next
continue
prev = cur
cur = cur->next cur = cur->next
func mem.alloc[size: i64] : ptr func mem.alloc[size: i64] : ptr
@@ -78,6 +103,8 @@ func mem.alloc[size: i64] : ptr
if !mem.read64(_builtin_heap_head()) if !mem.read64(_builtin_heap_head())
mem.write64(_builtin_heap_head(), blk) mem.write64(_builtin_heap_head(), blk)
mem._split_block(blk, size)
return blk + MEM_BLOCK_SIZE return blk + MEM_BLOCK_SIZE
func mem.free[x: ptr] : void func mem.free[x: ptr] : void
@@ -104,7 +131,9 @@ func mem.realloc[x: ptr, new_size: i64] : ptr
return x return x
let next: mem.Block = blk->next let next: mem.Block = blk->next
if next && next->free let expected_next: mem.Block = blk + MEM_BLOCK_SIZE + blk->size
if next && next->free && expected_next == next
let combined: i64 = blk->size + MEM_BLOCK_SIZE + next->size let combined: i64 = blk->size + MEM_BLOCK_SIZE + next->size
if combined >= new_size if combined >= new_size
blk->size = combined blk->size = combined