]> git.proxmox.com Git - mirror_ubuntu-kernels.git/commit
bpf, arm64: Fix BTI type used for freplace attached functions
authorAlexander Duyck <alexanderduyck@fb.com>
Thu, 13 Jul 2023 16:49:31 +0000 (09:49 -0700)
committerAlexei Starovoitov <ast@kernel.org>
Tue, 18 Jul 2023 22:28:19 +0000 (15:28 -0700)
commita3f25d614bc73b45e8f02adc6769876dfd16ca84
tree708c5d0fa36a110c9f56b7698593f09a7ccb4d08
parenta8237cc87e3de1adb3f2f6a8056621e7e578cc00
bpf, arm64: Fix BTI type used for freplace attached functions

When running an freplace attached bpf program on an arm64 system w were
seeing the following issue:
  Unhandled 64-bit el1h sync exception on CPU47, ESR 0x0000000036000003 -- BTI

After a bit of work to track it down I determined that what appeared to be
happening is that the 'bti c' at the start of the program was somehow being
reached after a 'br' instruction. Further digging pointed me toward the
fact that the function was attached via freplace. This in turn led me to
build_plt which I believe is invoking the long jump which is triggering
this error.

To resolve it we can replace the 'bti c' with 'bti jc' and add a comment
explaining why this has to be modified as such.

Fixes: b2ad54e1533e ("bpf, arm64: Implement bpf_arch_text_poke() for arm64")
Signed-off-by: Alexander Duyck <alexanderduyck@fb.com>
Acked-by: Xu Kuohai <xukuohai@huawei.com>
Link: https://lore.kernel.org/r/168926677665.316237.9953845318337455525.stgit@ahduyck-xeon-server.home.arpa
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
arch/arm64/net/bpf_jit_comp.c