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Commit e0d40756 authored by Russell King's avatar Russell King
Browse files

ARM: fix a cockup in 48be69a0 (ARM: move signal handlers into a vdso-like page) 



Unfortunately, I never committed the fix to a nasty oops which can
occur as a result of that commit:

------------[ cut here ]------------
kernel BUG at /home/olof/work/batch/include/linux/mm.h:414!
Internal error: Oops - BUG: 0 [#1] PREEMPT SMP ARM
Modules linked in:
CPU: 0 PID: 490 Comm: killall5 Not tainted 3.11.0-rc3-00288-gabe0308 #53
task: e90acac0 ti: e9be8000 task.ti: e9be8000
PC is at special_mapping_fault+0xa4/0xc4
LR is at __do_fault+0x68/0x48c

This doesn't show up unless you do quite a bit of testing; a simple
boot test does not do this, so all my nightly tests were passing fine.

The reason for this is that install_special_mapping() expects the
page array to stick around, and as this was only inserting one page
which was stored on the kernel stack, that's why this was blowing up.

Reported-by: default avatarOlof Johansson <olof@lixom.net>
Tested-by: default avatarOlof Johansson <olof@lixom.net>
Signed-off-by: default avatarRussell King <rmk+kernel@arm.linux.org.uk>
parent a5463cd3

arch/arm/kernel/process.c

+5 −4
Original line number Diff line number Diff line
@@ -471,17 +471,18 @@ const char *arch_vma_name(struct vm_area_struct *vma) 
		 "[sigpage]" : NULL;

}



static struct page *signal_page;

extern struct page *get_signal_page(void);



int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)

{

	struct mm_struct *mm = current->mm;

	struct page *page;

	unsigned long addr;

	int ret;



	page = get_signal_page();

	if (!page)

	if (!signal_page)

		signal_page = get_signal_page();

	if (!signal_page)

		return -ENOMEM;



	down_write(&mm->mmap_sem);
@@ -493,7 +494,7 @@ int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp) 


	ret = install_special_mapping(mm, addr, PAGE_SIZE,

		VM_READ | VM_EXEC | VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC,

		&page);

		&signal_page);



	if (ret == 0)

		mm->context.sigpage = addr;

arch/arm/kernel/signal.c

+19 −22
Original line number Diff line number Diff line
@@ -614,21 +614,19 @@ do_work_pending(struct pt_regs *regs, unsigned int thread_flags, int syscall) 
	return 0;

}



static struct page *signal_page;



struct page *get_signal_page(void)

{

	if (!signal_page) {

	unsigned long ptr;

	unsigned offset;

	struct page *page;

	void *addr;



		signal_page = alloc_pages(GFP_KERNEL, 0);

	page = alloc_pages(GFP_KERNEL, 0);



		if (!signal_page)

	if (!page)

		return NULL;



		addr = page_address(signal_page);

	addr = page_address(page);



	/* Give the signal return code some randomness */

	offset = 0x200 + (get_random_int() & 0x7fc);
@@ -642,7 +640,6 @@ struct page *get_signal_page(void) 


	ptr = (unsigned long)addr + offset;

	flush_icache_range(ptr, ptr + sizeof(sigreturn_codes));

	}



	return signal_page;

	return page;

}