linux-kernel - [PATCH bpf-next v3 1/2] arm64: stacktrace: Implement arch_bpf_stack

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Date: Thu,  1 Feb 2024 12:52:24 +0000
From: Puranjay Mohan <puranjay12@...il.com>
To: Alexei Starovoitov <ast@...nel.org>,
	Daniel Borkmann <daniel@...earbox.net>,
	Andrii Nakryiko <andrii@...nel.org>,
	Martin KaFai Lau <martin.lau@...ux.dev>,
	Song Liu <song@...nel.org>,
	Yonghong Song <yonghong.song@...ux.dev>,
	John Fastabend <john.fastabend@...il.com>,
	KP Singh <kpsingh@...nel.org>,
	Stanislav Fomichev <sdf@...gle.com>,
	Hao Luo <haoluo@...gle.com>,
	Jiri Olsa <jolsa@...nel.org>,
	Zi Shen Lim <zlim.lnx@...il.com>,
	Catalin Marinas <catalin.marinas@....com>,
	Will Deacon <will@...nel.org>,
	bpf@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org,
	Kumar Kartikeya Dwivedi <memxor@...il.com>
Cc: puranjay12@...il.com
Subject: [PATCH bpf-next v3 1/2] arm64: stacktrace: Implement arch_bpf_stack_walk() for the BPF JIT

This will be used by bpf_throw() to unwind till the program marked as
exception boundary and run the callback with the stack of the main
program.

This is required for supporting BPF exceptions on ARM64.

Signed-off-by: Puranjay Mohan <puranjay12@...il.com>
---
 arch/arm64/kernel/stacktrace.c | 26 ++++++++++++++++++++++++++
 1 file changed, 26 insertions(+)

diff --git a/arch/arm64/kernel/stacktrace.c b/arch/arm64/kernel/stacktrace.c
index 7f88028a00c0..66cffc5fc0be 100644
--- a/arch/arm64/kernel/stacktrace.c
+++ b/arch/arm64/kernel/stacktrace.c
@@ -7,6 +7,7 @@
 #include <linux/kernel.h>
 #include <linux/efi.h>
 #include <linux/export.h>
+#include <linux/filter.h>
 #include <linux/ftrace.h>
 #include <linux/kprobes.h>
 #include <linux/sched.h>
@@ -266,6 +267,31 @@ noinline noinstr void arch_stack_walk(stack_trace_consume_fn consume_entry,
 	kunwind_stack_walk(arch_kunwind_consume_entry, &data, task, regs);
 }
 
+struct bpf_unwind_consume_entry_data {
+	bool (*consume_entry)(void *cookie, u64 ip, u64 sp, u64 fp);
+	void *cookie;
+};
+
+static bool
+arch_bpf_unwind_consume_entry(const struct kunwind_state *state, void *cookie)
+{
+	struct bpf_unwind_consume_entry_data *data = cookie;
+
+	return data->consume_entry(data->cookie, state->common.pc, 0,
+				   state->common.fp);
+}
+
+noinline noinstr void arch_bpf_stack_walk(bool (*consume_entry)(void *cookie, u64 ip, u64 sp,
+								u64 fp), void *cookie)
+{
+	struct bpf_unwind_consume_entry_data data = {
+		.consume_entry = consume_entry,
+		.cookie = cookie,
+	};
+
+	kunwind_stack_walk(arch_bpf_unwind_consume_entry, &data, current, NULL);
+}
+
 static bool dump_backtrace_entry(void *arg, unsigned long where)
 {
 	char *loglvl = arg;
-- 
2.40.1