[PATCH bpf 0/2] s390/bpf: Fix backchain issues in the trampoline

[Ilya Leoshkevich <iii@linux.ibm.com>]

Hi,

Song reported that a patch he wrote was causing kernel panics on s390.
The disassembly printed by the kernel indicated that the stored
backchain was not a valid pointer; setting a watchpoint in GDB has
shown the culprit: the trampoline.

Currently it's implemented without regard for backchain: it clobbers
the caller's backchain and causes the issue reported by Song, and also
doesn't store its own, making it impossible to unwind past itself.

This series fixes both problems.

Best regards,
Ilya

[1] https://lore.kernel.org/bpf/20231004004350.533234-1-song@kernel.org/

Ilya Leoshkevich (2):
  s390/bpf: Fix clobbering the caller's backchain in the trampoline
  s390/bpf: Fix unwinding past the trampoline

 arch/s390/net/bpf_jit_comp.c | 25 ++++++++++++++++++++-----
 1 file changed, 20 insertions(+), 5 deletions(-)

-- 
2.41.0