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powerpc: Don't search for paca in freed memory

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Starting with 1426d5a3bd (powerpc:
Dynamically allocate pacas) we free the memory for pacas beyond
cpu_possible, but we failed to update the loop the secondary cpus use
to find their paca.  If the system has running cpu threads for which
the kernel did not allocate a paca for they will search the memory that
was freed.  For instance this could happen when the device tree for
a kdump kernel was not updated after a cpu hotplug, or the kernel is
running with more cpus than the kernel was configured.

Since c1854e0072 (powerpc: Set nr_cpu_ids
early and use it to free PACAs) we set nr_cpu_ids before telling the
cpus to advance, so use that to limit the search.

We can't reference nr_cpu_ids without CONFIG_SMP because it is defined
as 1 instead of a memory location, but any extra threads should be sent
to kexec_wait in that case anyways, so make that explicit and remove
the search loop for UP.

Note to stable: The fix also requires
c1854e0072 (powerpc: Set
nr_cpu_ids early and use it to free PACAs) to function.  Also
9d07bc841c (Properly handshake CPUs going
out of boot spin loop) affects the second chunk, specifically the branch
target was 3b before and is 4b after that patch, and there was a blank
line before the #ifdef CONFIG_SMP that was removed

Cc: <stable@kernel.org> # .34.x: c1854e0072 powerpc: Set nr_cpu_ids early
Cc: <stable@kernel.org> # .34.x
Signed-off-by: Milton Miller <miltonm@bga.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
This commit is contained in:
Milton Miller 2011-05-10 19:28:37 +00:00 committed by Benjamin Herrenschmidt
parent 3d2cea732d
commit 768d18ad6d
1 changed files with 8 additions and 5 deletions
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13
arch/powerpc/kernel/head_64.S
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@ -218,13 +218,19 @@ generic_secondary_common_init:
*/ */
LOAD_REG_ADDR(r13, paca) /* Load paca pointer */ LOAD_REG_ADDR(r13, paca) /* Load paca pointer */
ld r13,0(r13) /* Get base vaddr of paca array */ ld r13,0(r13) /* Get base vaddr of paca array */
#ifndef CONFIG_SMP
addi r13,r13,PACA_SIZE /* know r13 if used accidentally */
b .kexec_wait /* wait for next kernel if !SMP */
#else
LOAD_REG_ADDR(r7, nr_cpu_ids) /* Load nr_cpu_ids address */
lwz r7,0(r7) /* also the max paca allocated */
li r5,0 /* logical cpu id */ li r5,0 /* logical cpu id */
1: lhz r6,PACAHWCPUID(r13) /* Load HW procid from paca */ 1: lhz r6,PACAHWCPUID(r13) /* Load HW procid from paca */
cmpw r6,r24 /* Compare to our id */ cmpw r6,r24 /* Compare to our id */
beq 2f beq 2f
addi r13,r13,PACA_SIZE /* Loop to next PACA on miss */ addi r13,r13,PACA_SIZE /* Loop to next PACA on miss */
addi r5,r5,1 addi r5,r5,1
cmpwi r5,NR_CPUS cmpw r5,r7 /* Check if more pacas exist */
blt 1b blt 1b
mr r3,r24 /* not found, copy phys to r3 */ mr r3,r24 /* not found, copy phys to r3 */
@ -259,9 +265,6 @@ generic_secondary_common_init:
4: HMT_LOW 4: HMT_LOW
lbz r23,PACAPROCSTART(r13) /* Test if this processor should */ lbz r23,PACAPROCSTART(r13) /* Test if this processor should */
/* start. */ /* start. */
#ifndef CONFIG_SMP
b 4b /* Never go on non-SMP */
#else
cmpwi 0,r23,0 cmpwi 0,r23,0
beq 4b /* Loop until told to go */ beq 4b /* Loop until told to go */
@ -273,7 +276,7 @@ generic_secondary_common_init:
subi r1,r1,STACK_FRAME_OVERHEAD subi r1,r1,STACK_FRAME_OVERHEAD
b __secondary_start b __secondary_start
#endif #endif /* SMP */
/* /*
* Turn the MMU off. * Turn the MMU off.