Messages in this thread Patch in this message |  | | From | Russell King <> | Subject | Patch: fix munmap on ARM | Date | Sat, 30 Sep 2000 23:26:06 +0100 (BST) |
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Linus, lkml,
The following patch is required so that munmap(0x8000, *) does not cause ARM kernels to hang. The problem is that the machine vectors are at virtual address 0. Unfortunately, when free_pgtables() is called, it clears first level page tables starting at 0 in this case, and takes out the machine vectors. This then results in an unrecoverable hang.
We already have FIRST_USER_PGD_NR to define the first entry in the pgd which may be cleared, so we use this to clamp "start_index" appropriately. The following patch does this. Tested on ARM.
There is only one concern that I can see with this patch - GCC may warn about comparison always zero on architectures that define FIRST_USER_PGD_NR to be zero.
--- orig/mm/mmap.c Tue Sep 5 22:22:12 2000 +++ linux/mm/mmap.c Sat Sep 30 14:24:23 2000 @@ -620,6 +620,8 @@ * old method of shifting the VA >> by PGDIR_SHIFT doesn't work. */ start_index = pgd_index(first); + if (start_index < FIRST_USER_PGD_NR) + start_index = FIRST_USER_PGD_NR; end_index = pgd_index(last); if (end_index > start_index) { clear_page_tables(mm, start_index, end_index - start_index); _____ |_____| ------------------------------------------------- ---+---+- | | Russell King rmk@arm.linux.org.uk --- --- | | | | http://www.arm.linux.org.uk/personal/aboutme.html / / | | +-+-+ --- -+- / | THE developer of ARM Linux |+| /|\ / | | | --- | +-+-+ ------------------------------------------------- /\\\ | - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org Please read the FAQ at http://www.tux.org/lkml/
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