Commit 8eb4bd66 authored May 10, 2011 by Michael Holzheu Committed by Martin Schwidefsky May 10, 2011

[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>

parent aade6c0d

arch/s390/kernel/entry.S

+1 −1

Original line number	Diff line number	Diff line
		@@ -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

arch/s390/kernel/entry64.S

+1 −1

Original line number	Diff line number	Diff line
		@@ -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