Bpf/override arm ci#10678
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The usage of BPF_TRAMP_F_ORIG_STACK in __arch_prepare_bpf_trampoline() is wrong, and it should be BPF_TRAMP_F_CALL_ORIG, which caused crash as Andreas reported: Insufficient stack space to handle exception! Task stack: [0xff20000000010000..0xff20000000014000] Overflow stack: [0xff600000ffdad070..0xff600000ffdae070] CPU: 1 UID: 0 PID: 1 Comm: systemd Not tainted 6.18.0-rc5+ kernel-patches#15 PREEMPT(voluntary) Hardware name: riscv-virtio qemu/qemu, BIOS 2025.10 10/01/2025 epc : copy_from_kernel_nofault+0xa/0x198 ra : bpf_probe_read_kernel+0x20/0x60 epc : ffffffff802b732a ra : ffffffff801e6070 sp : ff2000000000ffe0 gp : ffffffff82262ed0 tp : 0000000000000000 t0 : ffffffff80022320 t1 : ffffffff801e6056 t2 : 0000000000000000 s0 : ff20000000010040 s1 : 0000000000000008 a0 : ff20000000010050 a1 : ff60000083b3d320 a2 : 0000000000000008 a3 : 0000000000000097 a4 : 0000000000000000 a5 : 0000000000000000 a6 : 0000000000000021 a7 : 0000000000000003 s2 : ff20000000010050 s3 : ff6000008459fc18 s4 : ff60000083b3d340 s5 : ff20000000010060 s6 : 0000000000000000 s7 : ff20000000013aa8 s8 : 0000000000000000 s9 : 0000000000008000 s10: 000000000058dcb0 s11: 000000000058dca7 t3 : 000000006925116d t4 : ff6000008090f026 t5 : 00007fff9b0cbaa8 t6 : 0000000000000016 status: 0000000200000120 badaddr: 0000000000000000 cause: 8000000000000005 Kernel panic - not syncing: Kernel stack overflow CPU: 1 UID: 0 PID: 1 Comm: systemd Not tainted 6.18.0-rc5+ kernel-patches#15 PREEMPT(voluntary) Hardware name: riscv-virtio qemu/qemu, BIOS 2025.10 10/01/2025 Call Trace: [<ffffffff8001a1f8>] dump_backtrace+0x28/0x38 [<ffffffff80002502>] show_stack+0x3a/0x50 [<ffffffff800122be>] dump_stack_lvl+0x56/0x80 [<ffffffff80012300>] dump_stack+0x18/0x22 [<ffffffff80002abe>] vpanic+0xf6/0x328 [<ffffffff80002d2e>] panic+0x3e/0x40 [<ffffffff80019ef0>] handle_bad_stack+0x98/0xa0 [<ffffffff801e6070>] bpf_probe_read_kernel+0x20/0x60 Just fix it. Fixes: 47c9214 ("bpf: fix the usage of BPF_TRAMP_F_SKIP_FRAME") Reported-by: Andreas Schwab <schwab@linux-m68k.org> Signed-off-by: Menglong Dong <dongml2@chinatelecom.cn> Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Link: https://lore.kernel.org/bpf/20251219142948.204312-1-dongml2@chinatelecom.cn Closes: https://lore.kernel.org/bpf/874ipnkfvt.fsf@igel.home/
Mahe reported issue with bpf_override_return helper not working when executed from kprobe.multi bpf program on arm. The problem is that on arm we use alternate storage for pt_regs object that is passed to bpf_prog_run and if any register is changed (which is the case of bpf_override_return) it's not propagated back to actual pt_regs object. Fixing this by introducing and calling ftrace_partial_regs_update function to propagate the values of changed registers (ip and stack). Reported-by: Mahe Tardy <mahe.tardy@gmail.com> Signed-off-by: Jiri Olsa <jolsa@kernel.org>
We do not actually test the bpf_override_return helper functionality itself at the moment, only the bpf program being able to attach it. Adding test that override prctl syscall return value on top of kprobe and kprobe.multi. Acked-by: Song Liu <song@kernel.org> Signed-off-by: Jiri Olsa <jolsa@kernel.org>
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