Messages in this thread Patch in this message | | | Subject | [PATCH] Fix lguest page-pinning logic ("lguest: bad stack page 0xc057a000") | From | Rusty Russell <> | Date | Tue, 28 Aug 2007 02:09:59 +1000 |
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If the stack pointer is 0xc057a000, then the first stack page is at 0xc0579000 (the stack pointer is decremented before use). Not calculating this correctly caused guests with CONFIG_DEBUG_PAGEALLOC=y to be killed with a "bad stack page" message: the initial kernel stack was just preceeding the .smp_locks section which CONFIG_DEBUG_PAGEALLOC marks read-only when freeing.
Thanks to Frederik Deweerdt for the bug report!
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
diff -r cb71c5b0bbb5 drivers/lguest/interrupts_and_traps.c --- a/drivers/lguest/interrupts_and_traps.c Sun Aug 26 10:31:53 2007 +1000 +++ b/drivers/lguest/interrupts_and_traps.c Sun Aug 26 10:34:44 2007 +1000 @@ -270,8 +270,11 @@ void pin_stack_pages(struct lguest *lg) /* Depending on the CONFIG_4KSTACKS option, the Guest can have one or * two pages of stack space. */ for (i = 0; i < lg->stack_pages; i++) - /* The stack grows *upwards*, hence the subtraction */ - pin_page(lg, lg->esp1 - i * PAGE_SIZE); + /* The stack grows *upwards*, so the address we're given is the + * start of the page after the kernel stack. Subtract one to + * get back onto the first stack page, and keep subtracting to + * get to the rest of the stack pages. */ + pin_page(lg, lg->esp1 - 1 - i * PAGE_SIZE); } /* Direct traps also mean that we need to know whenever the Guest wants to use
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