tracing: Allow BPF programs to call bpf_trace_printk() (9c959c86) · Commits · 戴 / test

include/uapi/linux/bpf.h

+1 −0

Original line number	Diff line number	Diff line
		@@ -166,6 +166,7 @@ enum bpf_func_id {
		BPF_FUNC_map_delete_elem, /* int map_delete_elem(&map, &key) */
		BPF_FUNC_probe_read, /* int bpf_probe_read(void dst, int size, void src) */
		BPF_FUNC_ktime_get_ns, /* u64 bpf_ktime_get_ns(void) */
		BPF_FUNC_trace_printk, /* int bpf_trace_printk(const char fmt, int fmt_size, ...) /
		__BPF_FUNC_MAX_ID,
		};

kernel/trace/bpf_trace.c

+78 −0

Original line number	Diff line number	Diff line
		@@ -10,6 +10,7 @@
		#include <linux/bpf.h>
		#include <linux/filter.h>
		#include <linux/uaccess.h>
		#include <linux/ctype.h>
		#include "trace.h"

		static DEFINE_PER_CPU(int, bpf_prog_active);
		@@ -90,6 +91,74 @@ static const struct bpf_func_proto bpf_ktime_get_ns_proto = {
		.ret_type = RET_INTEGER,
		};

		/*
		* limited trace_printk()
		* only %d %u %x %ld %lu %lx %lld %llu %llx %p conversion specifiers allowed
		*/
		static u64 bpf_trace_printk(u64 r1, u64 fmt_size, u64 r3, u64 r4, u64 r5)
		{
		char fmt = (char ) (long) r1;
		int mod[3] = {};
		int fmt_cnt = 0;
		int i;

		/*
		* bpf_check()->check_func_arg()->check_stack_boundary()
		* guarantees that fmt points to bpf program stack,
		* fmt_size bytes of it were initialized and fmt_size > 0
		*/
		if (fmt[--fmt_size] != 0)
		return -EINVAL;

		/* check format string for allowed specifiers */
		for (i = 0; i < fmt_size; i++) {
		if ((!isprint(fmt[i]) && !isspace(fmt[i])) \|\| !isascii(fmt[i]))
		return -EINVAL;

		if (fmt[i] != '%')
		continue;

		if (fmt_cnt >= 3)
		return -EINVAL;

		/* fmt[i] != 0 && fmt[last] == 0, so we can access fmt[i + 1] */
		i++;
		if (fmt[i] == 'l') {
		mod[fmt_cnt]++;
		i++;
		} else if (fmt[i] == 'p') {
		mod[fmt_cnt]++;
		i++;
		if (!isspace(fmt[i]) && !ispunct(fmt[i]) && fmt[i] != 0)
		return -EINVAL;
		fmt_cnt++;
		continue;
		}

		if (fmt[i] == 'l') {
		mod[fmt_cnt]++;
		i++;
		}

		if (fmt[i] != 'd' && fmt[i] != 'u' && fmt[i] != 'x')
		return -EINVAL;
		fmt_cnt++;
		}

		return __trace_printk(1/* fake ip will not be printed */, fmt,
		mod[0] == 2 ? r3 : mod[0] == 1 ? (long) r3 : (u32) r3,
		mod[1] == 2 ? r4 : mod[1] == 1 ? (long) r4 : (u32) r4,
		mod[2] == 2 ? r5 : mod[2] == 1 ? (long) r5 : (u32) r5);
		}

		static const struct bpf_func_proto bpf_trace_printk_proto = {
		.func = bpf_trace_printk,
		.gpl_only = true,
		.ret_type = RET_INTEGER,
		.arg1_type = ARG_PTR_TO_STACK,
		.arg2_type = ARG_CONST_STACK_SIZE,
		};

		static const struct bpf_func_proto *kprobe_prog_func_proto(enum bpf_func_id func_id)
		{
		switch (func_id) {
		@@ -103,6 +172,15 @@ static const struct bpf_func_proto *kprobe_prog_func_proto(enum bpf_func_id func
		return &bpf_probe_read_proto;
		case BPF_FUNC_ktime_get_ns:
		return &bpf_ktime_get_ns_proto;

		case BPF_FUNC_trace_printk:
		/*
		* this program might be calling bpf_trace_printk,
		* so allocate per-cpu printk buffers
		*/
		trace_printk_init_buffers();

		return &bpf_trace_printk_proto;
		default:
		return NULL;
		}

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