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ARM: 8100/1: Fix preemption disable in iwmmxt_task_enable() 

commit 431a84b1a4
 ("ARM: 8034/1: Disable preemption in iwmmxt_task_enable()")
introduced macros {inc,dec}_preempt_count to iwmmxt_task_enable
to make it run with preemption disabled.

Unfortunately, other functions in iwmmxt.S also use concan_{save,dump,load}
sections located in iwmmxt_task_enable() to deal with iWMMXt coprocessor.
This causes an unbalanced preempt_count due to excessive dec_preempt_count
and destroyed return addresses in callers of concan_ labels due to a register
collision:

Linux version 3.16.0-rc3-00062-gd92a333-dirty (jef@armhf) (gcc version 4.8.3 (Debian 4.8.3-4) ) #5 PREEMPT Thu Jul 3 19:46:39 CEST 2014
CPU: ARMv7 Processor [560f5815] revision 5 (ARMv7), cr=10c5387d
CPU: PIPT / VIPT nonaliasing data cache, PIPT instruction cache
Machine model: SolidRun CuBox
...
PJ4 iWMMXt v2 coprocessor enabled.
...
Unable to handle kernel paging request at virtual address fffffffe
pgd = bb25c000
[fffffffe] *pgd=3bfde821, *pte=00000000, *ppte=00000000
Internal error: Oops: 80000007 [#1] PREEMPT ARM
Modules linked in:
CPU: 0 PID: 62 Comm: startpar Not tainted 3.16.0-rc3-00062-gd92a333-dirty #5
task: bb230b80 ti: bb256000 task.ti: bb256000
PC is at 0xfffffffe
LR is at iwmmxt_task_copy+0x44/0x4c
pc : [<fffffffe>]    lr : [<800130ac>]    psr: 40000033
sp : bb257de8  ip : 00000013  fp : bb257ea4
r10: bb256000  r9 : fffffdfe  r8 : 76e898e6
r7 : bb257ec8  r6 : bb256000  r5 : 7ea12760  r4 : 000000a0
r3 : ffffffff  r2 : 00000003  r1 : bb257df8  r0 : 00000000
Flags: nZcv  IRQs on  FIQs on  Mode SVC_32  ISA Thumb  Segment user
Control: 10c5387d  Table: 3b25c019  DAC: 00000015
Process startpar (pid: 62, stack limit = 0xbb256248)

This patch fixes the issue by moving concan_{save,dump,load} into separate
code sections and make iwmmxt_task_enable() call them in the same way the
other functions use concan_ symbols. The test for valid ownership is moved
to concan_save and is safe for the other user of it, iwmmxt_task_disable().
The register collision is also resolved by moving concan_ symbols as
{inc,dec}_preempt_count are now local to iwmmxt_task_enable().

Fixes: 431a84b1a4 ("ARM: 8034/1: Disable preemption in iwmmxt_task_enable()")

Signed-off-by: Sebastian Hesselbarth <sebastian.hesselbarth@gmail.com>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Reported-by: Jean-Francois Moine <moinejf@free.fr>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
This commit is contained in:
Sebastian Hesselbarth 2014-07-14 16:23:29 +01:00 committed by Russell King
parent 6b076991dc
commit 8cf2389bc4
1 changed files with 12 additions and 11 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

23
arch/arm/kernel/iwmmxt.S
View File

@ -94,13 +94,19 @@ ENTRY(iwmmxt_task_enable)
mrc p15, 0, r2, c2, c0, 0
mov r2, r2 @ cpwait
bl concan_save
teq r1, #0 @ test for last ownership
mov lr, r9 @ normal exit from exception
beq concan_load @ no owner, skip save
#ifdef CONFIG_PREEMPT_COUNT
get_thread_info r10
#endif
4: dec_preempt_count r10, r3
mov pc, r9 @ normal exit from exception
concan_save:
teq r1, #0 @ test for last ownership
beq concan_load @ no owner, skip save
tmrc r2, wCon
@ CUP? wCx
@ -138,7 +144,7 @@ concan_dump:
wstrd wR15, [r1, #MMX_WR15]
2: teq r0, #0 @ anything to load?
beq 3f
moveq pc, lr @ if not, return
concan_load:
@ -171,14 +177,9 @@ concan_load:
@ clear CUP/MUP (only if r1 != 0)
teq r1, #0
mov r2, #0
beq 3f
tmcr wCon, r2
moveq pc, lr
3:
#ifdef CONFIG_PREEMPT_COUNT
get_thread_info r10
#endif
4: dec_preempt_count r10, r3
tmcr wCon, r2
mov pc, lr
/*