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ARM: fix a cockup in 48be69a02 (ARM: move signal handlers into a vdso-like page)

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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: Olof Johansson <olof@lixom.net>
Tested-by: Olof Johansson <olof@lixom.net>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
This commit is contained in:
Russell King
2013-08-03 10:30:05 +01:00
parent a5463cd343
commit e0d407564b
2 changed files with 24 additions and 26 deletions
Download Patch File Download Diff File Expand all files Collapse all files

41
arch/arm/kernel/signal.c
View File

@@ -614,35 +614,32 @@ 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;
void *addr;
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)
return NULL;
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);
signal_return_offset = offset;
/* Give the signal return code some randomness */
offset = 0x200 + (get_random_int() & 0x7fc);
signal_return_offset = offset;
/*
* Copy signal return handlers into the vector page, and
* set sigreturn to be a pointer to these.
*/
memcpy(addr + offset, sigreturn_codes, sizeof(sigreturn_codes));
/*
* Copy signal return handlers into the vector page, and
* set sigreturn to be a pointer to these.
*/
memcpy(addr + offset, sigreturn_codes, sizeof(sigreturn_codes));
ptr = (unsigned long)addr + offset;
flush_icache_range(ptr, ptr + sizeof(sigreturn_codes));
}
ptr = (unsigned long)addr + offset;
flush_icache_range(ptr, ptr + sizeof(sigreturn_codes));
return signal_page;
return page;
}