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Subject[patch 05/17] x86 Fix text_poke for vmalloced pages
The shadow vmap for DEBUG_RODATA kernel text modification uses virt_to_page to
get the pages from the pointer address and vmalloc_to_page for vmalloc'ed
pages.

- Changelog:
Deal with read-only module text.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
CC: Ingo Molnar <mingo@elte.hu>
---
arch/x86/kernel/alternative.c | 27 ++++++++++++++++-----------
1 file changed, 16 insertions(+), 11 deletions(-)
Index: linux-2.6-lttng/arch/x86/kernel/alternative.c
===================================================================
--- linux-2.6-lttng.orig/arch/x86/kernel/alternative.c 2008-03-24 10:00:30.000000000 -0400
+++ linux-2.6-lttng/arch/x86/kernel/alternative.c 2008-03-24 10:18:19.000000000 -0400
@@ -507,22 +507,27 @@ void *__kprobes text_poke(void *addr, co
unsigned long flags;
char *vaddr;
int nr_pages = 2;
+ struct page *pages[2];

BUG_ON(len > sizeof(long));
BUG_ON((((long)addr + len - 1) & ~(sizeof(long) - 1))
- ((long)addr & ~(sizeof(long) - 1)));
- {
- struct page *pages[2] = { virt_to_page(addr),
- virt_to_page(addr + PAGE_SIZE) };
- if (!pages[1])
- nr_pages = 1;
- vaddr = vmap(pages, nr_pages, VM_MAP, PAGE_KERNEL);
- WARN_ON(!vaddr);
- local_irq_save(flags);
- memcpy(&vaddr[(unsigned long)addr & ~PAGE_MASK], opcode, len);
- local_irq_restore(flags);
- vunmap(vaddr);
+ if (is_vmalloc_addr(addr)) {
+ pages[0] = vmalloc_to_page(addr);
+ pages[1] = vmalloc_to_page(addr + PAGE_SIZE);
+ } else {
+ pages[0] = virt_to_page(addr);
+ pages[1] = virt_to_page(addr + PAGE_SIZE);
}
+ BUG_ON(!pages[0]);
+ if (!pages[1])
+ nr_pages = 1;
+ vaddr = vmap(pages, nr_pages, VM_MAP, PAGE_KERNEL);
+ BUG_ON(!vaddr);
+ local_irq_save(flags);
+ memcpy(&vaddr[(unsigned long)addr & ~PAGE_MASK], opcode, len);
+ local_irq_restore(flags);
+ vunmap(vaddr);
sync_core();
/* Could also do a CLFLUSH here to speed up CPU recovery; but
that causes hangs on some VIA CPUs. */
--
Mathieu Desnoyers
Computer Engineering Ph.D. Student, Ecole Polytechnique de Montreal
OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F BA06 3F25 A8FE 3BAE 9A68


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