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Kernel: Create and use USER_RANGE_CEILING

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We had an inconsistency in valid user addresses. is_user_range() was
checking against the kernel base address, but previous changes caused
the maximum valid user addressable range to be 32 MiB below that.

This patch stops mmap(MAP_FIXED) of a range between these two bounds
from panic-ing the kernel in RangeAllocator::allocate_specific.
This commit is contained in:
Andrew Kaster 2021-07-06 20:25:22 -06:00 committed by Andreas Kling
parent ab196b484a
commit 578d45b480
Notes: sideshowbarker 2024-07-18 09:18:58 +09:00 
Author: https://github.com/ADKaster
Commit: https://github.com/SerenityOS/serenity/commit/578d45b480c
Pull-request: https://github.com/SerenityOS/serenity/pull/8522
Reviewed-by: https://github.com/alimpfard
Reviewed-by: https://github.com/awesomekling
3 changed files with 4 additions and 2 deletions
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2
Kernel/Sections.h
View file

@ -19,3 +19,5 @@
#define KERNEL_QUICKMAP_PD (KERNEL_PT1024_BASE + 0x7000)
#define KERNEL_QUICKMAP_PER_CPU_BASE (KERNEL_PT1024_BASE + 0x8000)
#define KERNEL_PHYSICAL_PAGES_BASE (KERNEL_BASE + KERNEL_PD_OFFSET)
#define USER_RANGE_CEILING 0xBE000000

2
Kernel/VM/MemoryManager.h
View file

@ -278,7 +278,7 @@ void VMObject::for_each_region(Callback callback)
inline bool is_user_address(VirtualAddress vaddr)
{
return vaddr.get() < KERNEL_BASE;
return vaddr.get() < USER_RANGE_CEILING;
}
inline bool is_user_range(VirtualAddress vaddr, size_t size)

2
Kernel/VM/PageDirectory.cpp
View file

@ -63,7 +63,7 @@ UNMAP_AFTER_INIT void PageDirectory::allocate_kernel_directory()
PageDirectory::PageDirectory(const RangeAllocator* parent_range_allocator)
{
constexpr FlatPtr userspace_range_base = 0x00800000;
constexpr FlatPtr userspace_range_ceiling = 0xbe000000;
constexpr FlatPtr userspace_range_ceiling = USER_RANGE_CEILING;
ScopedSpinLock lock(s_mm_lock);
if (parent_range_allocator) {