On Wed, 27 Aug 2025 at 17:37, Puranjay Mohan <puranjay@xxxxxxxxxx> wrote: > > Changes in v3->v4: > v3: https://lore.kernel.org/all/20250827150113.15763-1-puranjay@xxxxxxxxxx/ > - Fixed a build issue when CONFIG_BPF_JIT=y and # CONFIG_BPF_SYSCALL is not set > > Changes in v2->v3: > v2: https://lore.kernel.org/all/20250811111828.13836-1-puranjay@xxxxxxxxxx/ > - Improved the selftest to check the exact fault address > - Dropped BPF_NO_KFUNC_PROTOTYPES and bpf_arena_alloc/free_pages() usage > - Rebased on bpf-next/master > > Changes in v1->v2: > v1: https://lore.kernel.org/all/20250806085847.18633-1-puranjay@xxxxxxxxxx/ > - Changed variable and mask names for consistency (Yonghong) > - Added Acked-by: Yonghong Song <yonghong.song@xxxxxxxxx> on two patches > > This set adds the support of reporting page faults inside arena to BPF > stderr stream. The reported address is the one that a user would expect > to see if they pass it to bpf_printk(); > > Here is an example output from a stream and bpf_printk() > > ERROR: Arena WRITE access at unmapped address 0xdeaddead0000 > CPU: 9 UID: 0 PID: 502 Comm: test_progs > Call trace: > bpf_stream_stage_dump_stack+0xc0/0x150 > bpf_prog_report_arena_violation+0x98/0xf0 > ex_handler_bpf+0x5c/0x78 > fixup_exception+0xf8/0x160 > __do_kernel_fault+0x40/0x188 > do_bad_area+0x70/0x88 > do_translation_fault+0x54/0x98 > do_mem_abort+0x4c/0xa8 > el1_abort+0x44/0x70 > el1h_64_sync_handler+0x50/0x108 > el1h_64_sync+0x6c/0x70 > bpf_prog_a64a9778d31b8e88_stream_arena_write_fault+0x84/0xc8 > *(page) = 1; @ stream.c:100 > bpf_prog_test_run_syscall+0x100/0x328 > __sys_bpf+0x508/0xb98 > __arm64_sys_bpf+0x2c/0x48 > invoke_syscall+0x50/0x120 > el0_svc_common.constprop.0+0x48/0xf8 > do_el0_svc+0x28/0x40 > el0_svc+0x48/0xf8 > el0t_64_sync_handler+0xa0/0xe8 > el0t_64_sync+0x198/0x1a0 > > Same address is seen by using bpf_printk(): > > 1389.078831: bpf_trace_printk: Read Address: 0xdeaddead0000 > > To make this possible, some extra metadata has to be passed to the bpf > exception handler, so the bpf exception handling mechanism for both > x86-64 and arm64 have been improved in this set. > > The streams selftest has been updated to also test this new feature. We also need arm64 experts to take a look before we land, since you'll respin anyway now. Xu, could you please provide acks on the patches? Thanks a lot. > > Puranjay Mohan (3): > bpf: arm64: simplify exception table handling > bpf: Report arena faults to BPF stderr > selftests/bpf: Add tests for arena fault reporting > > arch/arm64/net/bpf_jit_comp.c | 77 ++++++++++++------ > arch/x86/net/bpf_jit_comp.c | 79 ++++++++++++++++++- > include/linux/bpf.h | 5 ++ > kernel/bpf/arena.c | 20 +++++ > .../testing/selftests/bpf/prog_tests/stream.c | 33 +++++++- > tools/testing/selftests/bpf/progs/stream.c | 39 +++++++++ > 6 files changed, 226 insertions(+), 27 deletions(-) > > -- > 2.47.3 >
