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SubjectRe: [PATCH][v3.2] Revert: x86, 64bit, mm: Mark data/bss/brk to nx
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On Mon, 2015-01-19 at 16:49 -0500, Steven Rostedt wrote:
> Testing v3.2-rt I found that after merging the latest v3.2 stable tree,
> hotplug stopped working. I tested the latest v3.2 stable, and it was
> not working there either. I bisected it down to:
>
> commit e105c8187b7101e8a8a54ac0218c9d9c9463c636
> Author: Yinghai Lu <yinghai@kernel.org>
> Date: Thu Jan 24 12:20:13 2013 -0800
>
> x86, 64bit, mm: Mark data/bss/brk to nx
>
> commit 72212675d1c96f5db8ec6fb35701879911193158 upstream.
>
> Simply doing:
>
> # echo 0 > /sys/devices/system/cpu/cpu1/online
> # echo 1 > /sys/devices/system/cpu/cpu1/online
>
> caused the system to reboot.
>
> After reverting that commit, hotplug works again on the v3.2 stable
> tree.

Yes, I know this needs fixing. It also broke suspend/resume on SMP
machines since that involves offlining and onlining CPUs 1-n.

Ben.

> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
> ---
> diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c
> index 266f71719e42..783eba48d00c 100644
> --- a/arch/x86/mm/init_64.c
> +++ b/arch/x86/mm/init_64.c
> @@ -778,7 +778,6 @@ void mark_rodata_ro(void)
> unsigned long text_end = PAGE_ALIGN((unsigned long) &__stop___ex_table);
> unsigned long rodata_end = PAGE_ALIGN((unsigned long) &__end_rodata);
> unsigned long data_start = (unsigned long) &_sdata;
> - unsigned long all_end;
>
> printk(KERN_INFO "Write protecting the kernel read-only data: %luk\n",
> (end - start) >> 10);
> @@ -787,8 +786,8 @@ void mark_rodata_ro(void)
> kernel_set_to_readonly = 1;
>
> /*
> - * The rodata/data/bss/brk section (but not the kernel text!)
> - * should also be not-executable.
> + * The rodata section (but not the kernel text!) should also be
> + * not-executable.
> *
> * We align all_end to PMD_SIZE because the existing mapping
> * is a full PMD. If we would align _brk_end to PAGE_SIZE we
> @@ -798,8 +797,7 @@ void mark_rodata_ro(void)
> * Any PMD which was setup after the one which covers _brk_end
> * has been zapped already via cleanup_highmem().
> */
> - all_end = roundup((unsigned long)_brk_end, PMD_SIZE);
> - set_memory_nx(rodata_start, (all_end - rodata_start) >> PAGE_SHIFT);
> + set_memory_nx(rodata_start, (end - rodata_start) >> PAGE_SHIFT);
>
> rodata_test();
>

--
Ben Hutchings
Larkinson's Law: All laws are basically false.
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