From fd5d27b70188379bb441d404c29a0afb111e1753 Mon Sep 17 00:00:00 2001 From: Kumar Kartikeya Dwivedi Date: Wed, 13 Sep 2023 01:31:59 +0200 Subject: arch/x86: Implement arch_bpf_stack_walk The plumbing for offline unwinding when we throw an exception in programs would require walking the stack, hence introduce a new arch_bpf_stack_walk function. This is provided when the JIT supports exceptions, i.e. bpf_jit_supports_exceptions is true. The arch-specific code is really minimal, hence it should be straightforward to extend this support to other architectures as well, as it reuses the logic of arch_stack_walk, but allowing access to unwind_state data. Once the stack pointer and frame pointer are known for the main subprog during the unwinding, we know the stack layout and location of any callee-saved registers which must be restored before we return back to the kernel. This handling will be added in the subsequent patches. Note that while we primarily unwind through BPF frames, which are effectively CONFIG_UNWINDER_FRAME_POINTER, we still need one of this or CONFIG_UNWINDER_ORC to be able to unwind through the bpf_throw frame from which we begin walking the stack. We also require both sp and bp (stack and frame pointers) from the unwind_state structure, which are only available when one of these two options are enabled. Signed-off-by: Kumar Kartikeya Dwivedi Link: https://lore.kernel.org/r/20230912233214.1518551-3-memxor@gmail.com Signed-off-by: Alexei Starovoitov --- kernel/bpf/core.c | 9 +++++++++ 1 file changed, 9 insertions(+) (limited to 'kernel') diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c index 95599df82ee4..c4ac084f2767 100644 --- a/kernel/bpf/core.c +++ b/kernel/bpf/core.c @@ -2914,6 +2914,15 @@ int __weak bpf_arch_text_invalidate(void *dst, size_t len) return -ENOTSUPP; } +bool __weak bpf_jit_supports_exceptions(void) +{ + return false; +} + +void __weak arch_bpf_stack_walk(bool (*consume_fn)(void *cookie, u64 ip, u64 sp, u64 bp), void *cookie) +{ +} + #ifdef CONFIG_BPF_SYSCALL static int __init bpf_global_ma_init(void) { -- cgit v1.2.3