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Fix munmap(2) shrink from right logic.

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This fixes a rather nasty issue where gcc's garbage collection triggered a
munmap call with the effect that it began unmapping huge amounts of kernel
data until the system triple faulted.
This commit is contained in:
Jonas 'Sortie' Termansen 2015-09-28 01:21:34 +02:00
parent 40c2fd12dc
commit 4c2a93ea02
1 changed files with 10 additions and 5 deletions
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15
kernel/memorymanagement.cpp
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@ -1,6 +1,6 @@
/*******************************************************************************
Copyright(C) Jonas 'Sortie' Termansen 2011, 2012, 2013.
Copyright(C) Jonas 'Sortie' Termansen 2011, 2012, 2013, 2015.
This file is part of Sortix.
@ -69,6 +69,11 @@ void UnmapMemory(Process* process, uintptr_t addr, size_t size)
assert(Page::IsAligned(size));
assert(process == CurrentProcess());
if ( UINTPTR_MAX - addr < size )
size = Page::AlignDown(UINTPTR_MAX - addr);
if ( !size )
return;
struct segment unmap_segment;
unmap_segment.addr = addr;
unmap_segment.size = size;
@ -77,7 +82,7 @@ void UnmapMemory(Process* process, uintptr_t addr, size_t size)
&unmap_segment) )
{
// Delete the segment if covered entirely by our request.
if ( addr <= conflict->addr && conflict->addr + conflict->size - addr <= size )
if ( addr <= conflict->addr && conflict->addr + conflict->size <= addr + size )
{
uintptr_t conflict_offset = (uintptr_t) conflict - (uintptr_t) process->segments;
size_t conflict_index = conflict_offset / sizeof(struct segment);
@ -122,11 +127,11 @@ void UnmapMemory(Process* process, uintptr_t addr, size_t size)
}
// Delete the part of the segment covered partially from the right.
if ( conflict->addr + size <= addr + size )
if ( conflict->addr <= addr + size )
{
Memory::UnmapRange(addr, addr + conflict->size + conflict->addr, PAGE_USAGE_USER_SPACE);
Memory::UnmapRange(addr, conflict->addr + conflict->size - addr, PAGE_USAGE_USER_SPACE);
Memory::Flush();
conflict->size -= conflict->size + conflict->addr;
conflict->size -= conflict->addr + conflict->size - addr;
continue;
}
}