Don't lock guardpage if the stack is growing up

Linux kernel excludes guard page when performing mlock on a VMA with
down-growing stack. However, some architectures have up-growing stack
and locking the guard page should be excluded in this case too.

This patch fixes lvm2 on PA-RISC (and possibly other architectures with
up-growing stack). lvm2 calculates number of used pages when locking and
when unlocking and reports an internal error if the numbers mismatch.

[ Patch changed fairly extensively to also fix /proc/<pid>/maps for the
grows-up case, and to move things around a bit to clean it all up and
share the infrstructure with the /proc bits.

Tested on ia64 that has both grow-up and grow-down segments - Linus ]

Signed-off-by: Mikulas Patocka <mikulas@artax.karlin.mff.cuni.cz>
Tested-by: Tony Luck <tony.luck@gmail.com>
Cc: stable@kernel.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

authored by

Mikulas Patocka and committed by

Linus Torvalds 15 years ago a09a79f6 26822eeb

+37 -15

3 changed files

expand all

proc

task_mmu.c

include

linux

mm.h

memory.c

+7 -5

fs/proc/task_mmu.c

··· 214 214 int flags = vma->vm_flags; 215 215 unsigned long ino = 0; 216 216 unsigned long long pgoff = 0; 217 - unsigned long start; 217 + unsigned long start, end; 218 218 dev_t dev = 0; 219 219 int len; 220 220 ··· 227 227 228 228 /* We don't show the stack guard page in /proc/maps */ 229 229 start = vma->vm_start; 230 - if (vma->vm_flags & VM_GROWSDOWN) 231 - if (!vma_stack_continue(vma->vm_prev, vma->vm_start)) 232 - start += PAGE_SIZE; 230 + if (stack_guard_page_start(vma, start)) 231 + start += PAGE_SIZE; 232 + end = vma->vm_end; 233 + if (stack_guard_page_end(vma, end)) 234 + end -= PAGE_SIZE; 233 235 234 236 seq_printf(m, "%08lx-%08lx %c%c%c%c %08llx %02x:%02x %lu %n", 235 237 start, 236 - vma->vm_end, 238 + end, 237 239 flags & VM_READ ? 'r' : '-', 238 240 flags & VM_WRITE ? 'w' : '-', 239 241 flags & VM_EXEC ? 'x' : '-',

+23 -1

include/linux/mm.h

··· 1011 1011 int clear_page_dirty_for_io(struct page *page); 1012 1012 1013 1013 /* Is the vma a continuation of the stack vma above it? */ 1014 - static inline int vma_stack_continue(struct vm_area_struct *vma, unsigned long addr) 1014 + static inline int vma_growsdown(struct vm_area_struct *vma, unsigned long addr) 1015 1015 { 1016 1016 return vma && (vma->vm_end == addr) && (vma->vm_flags & VM_GROWSDOWN); 1017 + } 1018 + 1019 + static inline int stack_guard_page_start(struct vm_area_struct *vma, 1020 + unsigned long addr) 1021 + { 1022 + return (vma->vm_flags & VM_GROWSDOWN) && 1023 + (vma->vm_start == addr) && 1024 + !vma_growsdown(vma->vm_prev, addr); 1025 + } 1026 + 1027 + /* Is the vma a continuation of the stack vma below it? */ 1028 + static inline int vma_growsup(struct vm_area_struct *vma, unsigned long addr) 1029 + { 1030 + return vma && (vma->vm_start == addr) && (vma->vm_flags & VM_GROWSUP); 1031 + } 1032 + 1033 + static inline int stack_guard_page_end(struct vm_area_struct *vma, 1034 + unsigned long addr) 1035 + { 1036 + return (vma->vm_flags & VM_GROWSUP) && 1037 + (vma->vm_end == addr) && 1038 + !vma_growsup(vma->vm_next, addr); 1017 1039 } 1018 1040 1019 1041 extern unsigned long move_page_tables(struct vm_area_struct *vma,

+7 -9

mm/memory.c

··· 1412 1412 1413 1413 static inline int stack_guard_page(struct vm_area_struct *vma, unsigned long addr) 1414 1414 { 1415 - return (vma->vm_flags & VM_GROWSDOWN) && 1416 - (vma->vm_start == addr) && 1417 - !vma_stack_continue(vma->vm_prev, addr); 1415 + return stack_guard_page_start(vma, addr) || 1416 + stack_guard_page_end(vma, addr+PAGE_SIZE); 1418 1417 } 1419 1418 1420 1419 /** ··· 1550 1551 continue; 1551 1552 } 1552 1553 1553 - /* 1554 - * For mlock, just skip the stack guard page. 1555 - */ 1556 - if ((gup_flags & FOLL_MLOCK) && stack_guard_page(vma, start)) 1557 - goto next_page; 1558 - 1559 1554 do { 1560 1555 struct page *page; 1561 1556 unsigned int foll_flags = gup_flags; ··· 1566 1573 int ret; 1567 1574 unsigned int fault_flags = 0; 1568 1575 1576 + /* For mlock, just skip the stack guard page. */ 1577 + if (foll_flags & FOLL_MLOCK) { 1578 + if (stack_guard_page(vma, start)) 1579 + goto next_page; 1580 + } 1569 1581 if (foll_flags & FOLL_WRITE) 1570 1582 fault_flags |= FAULT_FLAG_WRITE; 1571 1583 if (nonblocking)

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