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Kernel: Retry mmap if MAP_FIXED is not in flags and addr is not 0

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If an mmap fails to allocate a region, but the addr passed in was
non-zero, non-fixed mmaps should attempt to allocate at any available
virtual address.
This commit is contained in:
Andrew Kaster 2019-12-29 00:54:10 -05:00 • committed by Andreas Kling
parent bae8e21a8b
commit cdcab7e5f4
1 changed files with 11 additions and 0 deletions
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11
Kernel/Process.cpp
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@ -259,6 +259,7 @@ void* Process::sys$mmap(const Syscall::SC_mmap_params* params)
bool map_purgeable = flags & MAP_PURGEABLE;
bool map_private = flags & MAP_PRIVATE;
bool map_stack = flags & MAP_STACK;
bool map_fixed = flags & MAP_FIXED;
if (map_shared && map_private)
return (void*)-EINVAL;
@ -277,8 +278,12 @@ void* Process::sys$mmap(const Syscall::SC_mmap_params* params)
if (map_purgeable) {
auto vmobject = PurgeableVMObject::create_with_size(size);
region = allocate_region_with_vmobject(VirtualAddress((u32)addr), size, vmobject, 0, name ? name : "mmap (purgeable)", prot);
if (!region && (!map_fixed && addr != 0))
region = allocate_region_with_vmobject({}, size, vmobject, 0, name ? name : "mmap (purgeable)", prot);
} else if (map_anonymous) {
region = allocate_region(VirtualAddress((u32)addr), size, name ? name : "mmap", prot, false);
if (!region && (!map_fixed && addr != 0))
region = allocate_region({}, size, name ? name : "mmap", prot, false);
} else {
if (offset < 0)
return (void*)-EINVAL;
@ -288,6 +293,12 @@ void* Process::sys$mmap(const Syscall::SC_mmap_params* params)
if (!description)
return (void*)-EBADF;
auto region_or_error = description->mmap(*this, VirtualAddress((u32)addr), static_cast<size_t>(offset), size, prot);
if (region_or_error.is_error()) {
// Fail if MAP_FIXED or address is 0, retry otherwise
if (map_fixed || addr == 0)
return (void*)(int)region_or_error.error();
region_or_error = description->mmap(*this, {}, static_cast<size_t>(offset), size, prot);
}
if (region_or_error.is_error())
return (void*)(int)region_or_error.error();
region = region_or_error.value();