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OpenCloudOS-Kernel
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[S390] kernel: Initialize register 14 when starting new CPU 

When starting a new CPU we currently jump to start_secondary() without
setting register 14 (the return address) correctly. Therefore on the stack
frame for start_secondary an invalid return address is stored. This leads
to wrong stack back traces in kernel dumps.

Example:

 #00 [1f33fe48] cpu_idle at 10614a
 #01 [1f33fe90] start_secondary at 54fa88
 #02 [1f33feb8] (null) at 0                 <--- invalid

To fix this start_secondary() is called now with basr/brasl that sets
register 14 correctly. The output of the stack backtrace looks then
like the following:

 #00 [1f33fe48] cpu_idle at 10614a
 #01 [1f33fe90] start_secondary at 54fa88
 #02 [1f33feb8] restart_base at 54f41e      <--- correct

Signed-off-by: Michael Holzheu <holzheu@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
This commit is contained in:
Michael Holzheu 2011-05-10 17:13:39 +02:00 committed by Martin Schwidefsky
parent aade6c0dfb
commit 8eb4bd666f
2 changed files with 2 additions and 2 deletions
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2
arch/s390/kernel/entry.S
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@ -836,7 +836,7 @@ restart_base:
stosm __SF_EMPTY(%r15),0x04 # now we can turn dat on
basr %r14,0
l %r14,restart_addr-.(%r14)
br %r14 # branch to start_secondary
basr %r14,%r14 # branch to start_secondary
restart_addr:
.long start_secondary
.align 8

2
arch/s390/kernel/entry64.S
View File

@ -841,7 +841,7 @@ restart_base:
mvc __LC_SYSTEM_TIMER(8),__TI_system_timer(%r1)
xc __LC_STEAL_TIMER(8),__LC_STEAL_TIMER
stosm __SF_EMPTY(%r15),0x04 # now we can turn dat on
jg start_secondary
brasl %r14,start_secondary
.align 8
restart_vtime:
.long 0x7fffffff,0xffffffff