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| author | Nicholas Piggin <npiggin@gmail.com> | 2022-11-27 22:49:38 +1000 |
|---|---|---|
| committer | Michael Ellerman <mpe@ellerman.id.au> | 2022-12-02 17:54:08 +1100 |
| commit | edbd0387f3249cc7e102f86d4852a9a9f3bb1305 (patch) | |
| tree | 11bb44eabf8ef727ce5f132a56fd310514aa5654 /arch/powerpc/kernel | |
| parent | 6895dfc0474170c492191c126fcfc420f7771a09 (diff) | |
| download | lwn-edbd0387f3249cc7e102f86d4852a9a9f3bb1305.tar.gz lwn-edbd0387f3249cc7e102f86d4852a9a9f3bb1305.zip | |
powerpc: copy_thread add a back chain to the switch stack frame
Stack unwinders need LR and the back chain as a minimum. The switch
stack uses regs->nip for its return pointer rather than lrsave, so
that was not set in the fork frame, and neither was the back chain.
This change sets those fields in the stack.
With this and the previous change, a stack trace in the switch or
interrupt stack goes from looking like this:
Oops: Exception in kernel mode, sig: 5 [#1]
LE PAGE_SIZE=64K MMU=Radix SMP NR_CPUS=2048 NUMA pSeries
Modules linked in:
CPU: 3 PID: 90 Comm: systemd Not tainted
NIP: c000000000011060 LR: c000000000010f68 CTR: 0000000000007fff
[ ... regs ... ]
NIP [c000000000011060] _switch+0x160/0x17c
LR [c000000000010f68] _switch+0x68/0x17c
Call Trace:
To this:
Oops: Exception in kernel mode, sig: 5 [#1]
LE PAGE_SIZE=64K MMU=Radix SMP NR_CPUS=2048 NUMA pSeries
CPU: 0 PID: 93 Comm: systemd Not tainted
NIP: c000000000011060 LR: c000000000010f68 CTR: 0000000000007fff
[ ... regs ... ]
NIP [c000000000011060] _switch+0x160/0x17c
LR [c000000000010f68] _switch+0x68/0x17c
Call Trace:
[c000000005a93e10] [c00000000000cdbc] ret_from_fork_scv+0x0/0x54
--- interrupt: 3000 at 0x7fffa72f56d8
NIP: 00007fffa72f56d8 LR: 0000000000000000 CTR: 0000000000000000
[ ... regs ... ]
NIP [00007fffa72f56d8] 0x7fffa72f56d8
LR [0000000000000000] 0x0
--- interrupt: 3000
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20221127124942.1665522-14-npiggin@gmail.com
Diffstat (limited to 'arch/powerpc/kernel')
| -rw-r--r-- | arch/powerpc/kernel/process.c | 2 |
1 files changed, 2 insertions, 0 deletions
diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c index 6b1d80bd370e..096b6ea52378 100644 --- a/arch/powerpc/kernel/process.c +++ b/arch/powerpc/kernel/process.c @@ -1810,7 +1810,9 @@ int copy_thread(struct task_struct *p, const struct kernel_clone_args *args) * do some house keeping and then return from the fork or clone * system call, using the stack frame created above. */ + ((unsigned long *)sp)[STACK_FRAME_LR_SAVE] = (unsigned long)f; sp -= STACK_SWITCH_FRAME_SIZE; + ((unsigned long *)sp)[0] = sp + STACK_SWITCH_FRAME_SIZE; kregs = (struct pt_regs *)(sp + STACK_SWITCH_FRAME_REGS); p->thread.ksp = sp; |