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Sebastian Hesselbarth authored
commit 431a84b1 ("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-gd92a333a-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-gd92a333a-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: 431a84b1 ("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>
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