powerpc: Don't search for paca in freed memory
Starting with1426d5a3bd
(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. Sincec1854e0072
(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 requiresc1854e0072
(powerpc: Set nr_cpu_ids early and use it to free PACAs) to function. Also9d07bc841c
(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>
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@ -218,13 +218,19 @@ generic_secondary_common_init:
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*/
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LOAD_REG_ADDR(r13, paca) /* Load paca pointer */
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ld r13,0(r13) /* Get base vaddr of paca array */
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#ifndef CONFIG_SMP
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addi r13,r13,PACA_SIZE /* know r13 if used accidentally */
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b .kexec_wait /* wait for next kernel if !SMP */
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#else
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LOAD_REG_ADDR(r7, nr_cpu_ids) /* Load nr_cpu_ids address */
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lwz r7,0(r7) /* also the max paca allocated */
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li r5,0 /* logical cpu id */
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1: lhz r6,PACAHWCPUID(r13) /* Load HW procid from paca */
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cmpw r6,r24 /* Compare to our id */
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beq 2f
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addi r13,r13,PACA_SIZE /* Loop to next PACA on miss */
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addi r5,r5,1
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cmpwi r5,NR_CPUS
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cmpw r5,r7 /* Check if more pacas exist */
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blt 1b
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mr r3,r24 /* not found, copy phys to r3 */
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@ -259,9 +265,6 @@ generic_secondary_common_init:
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4: HMT_LOW
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lbz r23,PACAPROCSTART(r13) /* Test if this processor should */
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/* start. */
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#ifndef CONFIG_SMP
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b 4b /* Never go on non-SMP */
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#else
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cmpwi 0,r23,0
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beq 4b /* Loop until told to go */
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@ -273,7 +276,7 @@ generic_secondary_common_init:
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subi r1,r1,STACK_FRAME_OVERHEAD
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b __secondary_start
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#endif
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#endif /* SMP */
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/*
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* Turn the MMU off.
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