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| author | Vasily Gorbik <gor@linux.ibm.com> | 2021-04-09 00:15:21 +0200 |
|---|---|---|
| committer | Heiko Carstens <hca@linux.ibm.com> | 2021-04-12 12:44:31 +0200 |
| commit | a994eddb947ea9ebb7b14d9a1267001699f0a136 (patch) | |
| tree | e8067a00fd3369c26343706600ddab5df5299b74 /arch | |
| parent | b74e409ea1b18128b877a50883d92a12eba83c33 (diff) | |
| download | lwn-a994eddb947ea9ebb7b14d9a1267001699f0a136.tar.gz lwn-a994eddb947ea9ebb7b14d9a1267001699f0a136.zip | |
s390/entry: save the caller of psw_idle
Currently psw_idle does not allocate a stack frame and does not
save its r14 and r15 into the save area. Even though this is valid from
call ABI point of view, because psw_idle does not make any calls
explicitly, in reality psw_idle is an entry point for controlled
transition into serving interrupts. So, in practice, psw_idle stack
frame is analyzed during stack unwinding. Depending on build options
that r14 slot in the save area of psw_idle might either contain a value
saved by previous sibling call or complete garbage.
[task 0000038000003c28] do_ext_irq+0xd6/0x160
[task 0000038000003c78] ext_int_handler+0xba/0xe8
[task *0000038000003dd8] psw_idle_exit+0x0/0x8 <-- pt_regs
([task 0000038000003dd8] 0x0)
[task 0000038000003e10] default_idle_call+0x42/0x148
[task 0000038000003e30] do_idle+0xce/0x160
[task 0000038000003e70] cpu_startup_entry+0x36/0x40
[task 0000038000003ea0] arch_call_rest_init+0x76/0x80
So, to make a stacktrace nicer and actually point for the real caller of
psw_idle in this frequently occurring case, make psw_idle save its r14.
[task 0000038000003c28] do_ext_irq+0xd6/0x160
[task 0000038000003c78] ext_int_handler+0xba/0xe8
[task *0000038000003dd8] psw_idle_exit+0x0/0x6 <-- pt_regs
([task 0000038000003dd8] arch_cpu_idle+0x3c/0xd0)
[task 0000038000003e10] default_idle_call+0x42/0x148
[task 0000038000003e30] do_idle+0xce/0x160
[task 0000038000003e70] cpu_startup_entry+0x36/0x40
[task 0000038000003ea0] arch_call_rest_init+0x76/0x80
Reviewed-by: Sven Schnelle <svens@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
Diffstat (limited to 'arch')
| -rw-r--r-- | arch/s390/kernel/entry.S | 1 |
1 files changed, 1 insertions, 0 deletions
diff --git a/arch/s390/kernel/entry.S b/arch/s390/kernel/entry.S index 235bf2ac3359..12de7a9c85b3 100644 --- a/arch/s390/kernel/entry.S +++ b/arch/s390/kernel/entry.S @@ -443,6 +443,7 @@ INT_HANDLER io_int_handler,__LC_IO_OLD_PSW,do_io_irq * Load idle PSW. */ ENTRY(psw_idle) + stg %r14,(__SF_GPRS+8*8)(%r15) stg %r3,__SF_EMPTY(%r15) larl %r1,psw_idle_exit stg %r1,__SF_EMPTY+8(%r15) |