From: Abhishek Dubey <[email protected]> This function is used by bpf_throw() to unwind the stack until frame of exception-boundary during BPF exception handling.
This function is necessary to support BPF exceptions on PowerPC. Signed-off-by: Abhishek Dubey <[email protected]> --- arch/powerpc/net/bpf_jit_comp64.c | 41 +++++++++++++++++++++++++++++++ 1 file changed, 41 insertions(+) diff --git a/arch/powerpc/net/bpf_jit_comp64.c b/arch/powerpc/net/bpf_jit_comp64.c index 18da5a866447..1bba068f2c4c 100644 --- a/arch/powerpc/net/bpf_jit_comp64.c +++ b/arch/powerpc/net/bpf_jit_comp64.c @@ -247,6 +247,47 @@ void bpf_jit_build_epilogue(u32 *image, struct codegen_context *ctx) bpf_jit_build_fentry_stubs(image, ctx); } +/* + * arch_bpf_stack_walk() - BPF stack walker for PowerPC + * + * Based on arch_stack_walk() from stacktrace.c. + * PowerPC uses stack frames rather than stack pointers. See [1] for + * the equivalence between frame pointers and stack pointers. + * Additional reference at [2]. + * TODO: refactor with arch_stack_walk() + * + * [1]: https://lore.kernel.org/all/[email protected]/ + * [2]: https://lore.kernel.org/bpf/[email protected]/ + */ + +void arch_bpf_stack_walk(bool (*consume_fn)(void *, u64, u64, u64), void *cookie) +{ + // callback processing always in current context + unsigned long sp = current_stack_frame(); + + for (;;) { + unsigned long *stack = (unsigned long *) sp; + unsigned long ip; + + if (!validate_sp(sp, current)) + return; + + ip = stack[STACK_FRAME_LR_SAVE]; + if (!ip) + break; + + /* + * consume_fn common code expects stack pointer in third + * argument. There is no sp in ppc64, rather pass frame + * pointer(named sp here). + */ + if (ip && !consume_fn(cookie, ip, sp, sp)) + break; + + sp = stack[0]; + } +} + int bpf_jit_emit_func_call_rel(u32 *image, u32 *fimage, struct codegen_context *ctx, u64 func) { unsigned long func_addr = func ? ppc_function_entry((void *)func) : 0; -- 2.48.1
