Messages in this thread Patch in this message | | | Date | Mon, 28 Jan 2008 11:34:39 +0100 | From | Ingo Molnar <> | Subject | Re: [PATCH] x86_64: mark x86_cpu_to_node_map_init to __initdata like other xx_init |
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* Yinghai Lu <Yinghai.Lu@Sun.COM> wrote:
> -int x86_cpu_to_node_map_init[NR_CPUS] = { > +int x86_cpu_to_node_map_init[NR_CPUS] __initdata = { > [0 ... NR_CPUS-1] = NUMA_NO_NODE > };
i remember some linker warning here. While this array should indeed only be used in early init, that decision is dynamic and our linker warnings do not notice it. There's a special marker for such cases: __initdata_refok. But ... i'm slightly nervous about turning off a vital warning like that.
Sam, it would be nice to have a DEBUG_INITDATA mode of operation: in this case free_initmem() would not truly free those pages but would unmap them via:
kernel_map_pages(page, nrpages, 0);
could be made dependent on DEBUG_PAGEALLOC.
If this debugging is enabled then if any code references it, we get a hard page fault. If we had a debug mode like that then bugs in this area would not go unnoticed.
Or perhaps just make this part of normal DEBUG_PAGEALLOC. Like the patch below on top of latest x86.git. Hm?
Ingo
-------------------> Subject: x86: init memory debugging From: Ingo Molnar <mingo@elte.hu>
debug incorrect/late access to init memory, by permanently unmapping the init memory ranges. Depends on CONFIG_DEBUG_PAGEALLOC=y.
Signed-off-by: Ingo Molnar <mingo@elte.hu> --- arch/x86/mm/init_32.c | 12 ++++++++++++ arch/x86/mm/init_64.c | 11 +++++++++++ 2 files changed, 23 insertions(+)
Index: linux-x86.q/arch/x86/mm/init_32.c =================================================================== --- linux-x86.q.orig/arch/x86/mm/init_32.c +++ linux-x86.q/arch/x86/mm/init_32.c @@ -794,6 +794,18 @@ void free_init_pages(char *what, unsigne unsigned long addr; /* + * If debugging page accesses then do not free this memory but + * mark them not present - any buggy init-section access will + * create a kernel page fault: + */ +#ifdef CONFIG_DEBUG_PAGEALLOC + printk(KERN_INFO "debug: unmapping init memory %08lx..%08lx\n", + begin, PAGE_ALIGN(end)); + set_memory_np(begin, (end - begin) >> PAGE_SHIFT); + return; +#endif + set_memory_rw(begin, (end - begin) >> PAGE_SHIFT); + /* * We just marked the kernel text read only above, now that * we are going to free part of that, we need to make that * writeable first. Index: linux-x86.q/arch/x86/mm/init_64.c =================================================================== --- linux-x86.q.orig/arch/x86/mm/init_64.c +++ linux-x86.q/arch/x86/mm/init_64.c @@ -580,6 +580,17 @@ void free_init_pages(char *what, unsigne if (begin >= end) return; + /* + * If debugging page accesses then do not free this memory but + * mark them not present - any buggy init-section access will + * create a kernel page fault: + */ +#ifdef CONFIG_DEBUG_PAGEALLOC + printk(KERN_INFO "debug: unmapping init memory %08lx..%08lx\n", + begin, PAGE_ALIGN(end)); + set_memory_np(begin, (end - begin) >> PAGE_SHIFT); + return; +#endif printk(KERN_INFO "Freeing %s: %luk freed\n", what, (end - begin) >> 10); for (addr = begin; addr < end; addr += PAGE_SIZE) {
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