[PATCH v5 net-next 19/29] tracing: allow eBPF programs call printk()
From: Alexei Starovoitov <hidden>
Date: 2014-08-24 20:26:41
Also in:
linux-api, lkml
Subsystem:
bpf [general] (safe dynamic programs and tools), bpf [security & lsm] (security audit and enforcement using bpf), bpf [tracing], the rest, tracing · Maintainers:
Alexei Starovoitov, Daniel Borkmann, Andrii Nakryiko, Eduard Zingerman, Kumar Kartikeya Dwivedi, KP Singh, Matt Bobrowski, Song Liu, Linus Torvalds, Steven Rostedt, Masami Hiramatsu
limited printk() with %d %u %x %p modifiers only Signed-off-by: Alexei Starovoitov <redacted> --- include/uapi/linux/bpf.h | 1 + kernel/trace/bpf_trace.c | 61 ++++++++++++++++++++++++++++++++++++++++++++++ 2 files changed, 62 insertions(+)
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 9a633c5b6b0a..5adaad826471 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h@@ -415,6 +415,7 @@ enum bpf_func_id { BPF_FUNC_fetch_u8, /* u8 bpf_fetch_u8(void *unsafe_ptr) */ BPF_FUNC_memcmp, /* int bpf_memcmp(void *unsafe_ptr, void *safe_ptr, int size) */ BPF_FUNC_dump_stack, /* void bpf_dump_stack(void) */ + BPF_FUNC_printk, /* int bpf_printk(const char *fmt, int fmt_size, ...) */ __BPF_FUNC_MAX_ID, };
diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index b4751e2c0d52..ff98be5a24d6 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c@@ -60,6 +60,60 @@ static u64 bpf_dump_stack(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5) return 0; } +/* limited printk() + * only %d %u %x %ld %lu %lx %lld %llu %llx %p conversion specifiers allowed + */ +static u64 bpf_printk(u64 r1, u64 fmt_size, u64 r3, u64 r4, u64 r5) +{ + char *fmt = (char *) (long) r1; + int fmt_cnt = 0; + bool mod_l[3] = {}; + int i; + + /* bpf_check() guarantees that fmt points to bpf program stack and + * fmt_size bytes of it were initialized by bpf program + */ + if (fmt[fmt_size - 1] != 0) + return -EINVAL; + + /* check format string for allowed specifiers */ + for (i = 0; i < fmt_size; i++) + if (fmt[i] == '%') { + if (fmt_cnt >= 3) + return -EINVAL; + i++; + if (i >= fmt_size) + return -EINVAL; + + if (fmt[i] == 'l') { + mod_l[fmt_cnt] = true; + i++; + if (i >= fmt_size) + return -EINVAL; + } else if (fmt[i] == 'p') { + mod_l[fmt_cnt] = true; + fmt_cnt++; + continue; + } + + if (fmt[i] == 'l') { + mod_l[fmt_cnt] = true; + i++; + if (i >= fmt_size) + return -EINVAL; + } + + if (fmt[i] != 'd' && fmt[i] != 'u' && fmt[i] != 'x') + return -EINVAL; + fmt_cnt++; + } + + return __trace_printk((unsigned long) __builtin_return_address(3), fmt, + mod_l[0] ? r3 : (u32) r3, + mod_l[1] ? r4 : (u32) r4, + mod_l[2] ? r5 : (u32) r5); +} + static struct bpf_func_proto tracing_filter_funcs[] = { #define FETCH(SIZE) \ [BPF_FUNC_fetch_##SIZE] = { \
@@ -86,6 +140,13 @@ static struct bpf_func_proto tracing_filter_funcs[] = { .gpl_only = false, .ret_type = RET_VOID, }, + [BPF_FUNC_printk] = { + .func = bpf_printk, + .gpl_only = true, + .ret_type = RET_INTEGER, + .arg1_type = ARG_PTR_TO_STACK, + .arg2_type = ARG_CONST_STACK_SIZE, + }, [BPF_FUNC_map_lookup_elem] = { .func = bpf_map_lookup_elem, .gpl_only = false,
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1.7.9.5