tree 1368791791b2c57da8c2a2b4d1b963c699218d23
parent 06806ed9f5a35b811ac5f58426ffe4355e1840c7
author Nicholas Piggin <npiggin@gmail.com> 1712306110 +1000
committer Thomas Huth <thuth@redhat.com> 1713254298 +0200

powerpc: Fix stack backtrace termination

The backtrace handler terminates when it sees a NULL caller address,
but the powerpc stack setup does not keep such a NULL caller frame
at the start of the stack.

This happens to work on pseries because the memory at 0 is mapped and
it contains 0 at the location of the return address pointer if it
were a stack frame. But this is fragile, and does not work with powernv
where address 0 contains firmware instructions.

Use the existing dummy frame on stack as the NULL caller, and create a
new frame on stack for the entry code.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Message-ID: <20240405083539.374995-10-npiggin@gmail.com>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>