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author | Martin KaFai Lau <kafai@fb.com> | 2018-12-13 10:41:48 -0800 |
---|---|---|
committer | Alexei Starovoitov <ast@kernel.org> | 2018-12-14 14:17:34 -0800 |
commit | d9762e84ede3eae9636f5dbbe0c8f0390d37e114 (patch) | |
tree | 2810d29d1a3ece2f739b42dbce1b238df53e576d /kernel/bpf | |
parent | 23127b33ec80e656921362d7dc82a0064bac20a2 (diff) | |
download | linux-d9762e84ede3eae9636f5dbbe0c8f0390d37e114.tar.bz2 |
bpf: verbose log bpf_line_info in verifier
This patch adds bpf_line_info during the verifier's verbose.
It can give error context for debug purpose.
~~~~~~~~~~
Here is the verbose log for backedge:
while (a) {
a += bpf_get_smp_processor_id();
bpf_trace_printk(fmt, sizeof(fmt), a);
}
~> bpftool prog load ./test_loop.o /sys/fs/bpf/test_loop type tracepoint
13: while (a) {
3: a += bpf_get_smp_processor_id();
back-edge from insn 13 to 3
~~~~~~~~~~
Here is the verbose log for invalid pkt access:
Modification to test_xdp_noinline.c:
data = (void *)(long)xdp->data;
data_end = (void *)(long)xdp->data_end;
/*
if (data + 4 > data_end)
return XDP_DROP;
*/
*(u32 *)data = dst->dst;
~> bpftool prog load ./test_xdp_noinline.o /sys/fs/bpf/test_xdp_noinline type xdp
; data = (void *)(long)xdp->data;
224: (79) r2 = *(u64 *)(r10 -112)
225: (61) r2 = *(u32 *)(r2 +0)
; *(u32 *)data = dst->dst;
226: (63) *(u32 *)(r2 +0) = r1
invalid access to packet, off=0 size=4, R2(id=0,off=0,r=0)
R2 offset is outside of the packet
Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Acked-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Diffstat (limited to 'kernel/bpf')
-rw-r--r-- | kernel/bpf/verifier.c | 74 |
1 files changed, 69 insertions, 5 deletions
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 89ce2613fdb0..ba8e3134bbc2 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -26,6 +26,7 @@ #include <linux/bsearch.h> #include <linux/sort.h> #include <linux/perf_event.h> +#include <linux/ctype.h> #include "disasm.h" @@ -216,6 +217,27 @@ struct bpf_call_arg_meta { static DEFINE_MUTEX(bpf_verifier_lock); +static const struct bpf_line_info * +find_linfo(const struct bpf_verifier_env *env, u32 insn_off) +{ + const struct bpf_line_info *linfo; + const struct bpf_prog *prog; + u32 i, nr_linfo; + + prog = env->prog; + nr_linfo = prog->aux->nr_linfo; + + if (!nr_linfo || insn_off >= prog->len) + return NULL; + + linfo = prog->aux->linfo; + for (i = 1; i < nr_linfo; i++) + if (insn_off < linfo[i].insn_off) + break; + + return &linfo[i - 1]; +} + void bpf_verifier_vlog(struct bpf_verifier_log *log, const char *fmt, va_list args) { @@ -266,6 +288,42 @@ __printf(2, 3) static void verbose(void *private_data, const char *fmt, ...) va_end(args); } +static const char *ltrim(const char *s) +{ + while (isspace(*s)) + s++; + + return s; +} + +__printf(3, 4) static void verbose_linfo(struct bpf_verifier_env *env, + u32 insn_off, + const char *prefix_fmt, ...) +{ + const struct bpf_line_info *linfo; + + if (!bpf_verifier_log_needed(&env->log)) + return; + + linfo = find_linfo(env, insn_off); + if (!linfo || linfo == env->prev_linfo) + return; + + if (prefix_fmt) { + va_list args; + + va_start(args, prefix_fmt); + bpf_verifier_vlog(&env->log, prefix_fmt, args); + va_end(args); + } + + verbose(env, "%s\n", + ltrim(btf_name_by_offset(env->prog->aux->btf, + linfo->line_off))); + + env->prev_linfo = linfo; +} + static bool type_is_pkt_pointer(enum bpf_reg_type type) { return type == PTR_TO_PACKET || @@ -4561,6 +4619,7 @@ static int push_insn(int t, int w, int e, struct bpf_verifier_env *env) return 0; if (w < 0 || w >= env->prog->len) { + verbose_linfo(env, t, "%d: ", t); verbose(env, "jump out of range from insn %d to %d\n", t, w); return -EINVAL; } @@ -4578,6 +4637,8 @@ static int push_insn(int t, int w, int e, struct bpf_verifier_env *env) insn_stack[cur_stack++] = w; return 1; } else if ((insn_state[w] & 0xF0) == DISCOVERED) { + verbose_linfo(env, t, "%d: ", t); + verbose_linfo(env, w, "%d: ", w); verbose(env, "back-edge from insn %d to %d\n", t, w); return -EINVAL; } else if (insn_state[w] == EXPLORED) { @@ -4600,10 +4661,6 @@ static int check_cfg(struct bpf_verifier_env *env) int ret = 0; int i, t; - ret = check_subprogs(env); - if (ret < 0) - return ret; - insn_state = kcalloc(insn_cnt, sizeof(int), GFP_KERNEL); if (!insn_state) return -ENOMEM; @@ -5448,6 +5505,8 @@ static int do_check(struct bpf_verifier_env *env) int insn_processed = 0; bool do_print_state = false; + env->prev_linfo = NULL; + state = kzalloc(sizeof(struct bpf_verifier_state), GFP_KERNEL); if (!state) return -ENOMEM; @@ -5521,6 +5580,7 @@ static int do_check(struct bpf_verifier_env *env) .private_data = env, }; + verbose_linfo(env, insn_idx, "; "); verbose(env, "%d: ", insn_idx); print_bpf_insn(&cbs, insn, env->allow_ptr_leaks); } @@ -6755,7 +6815,7 @@ int bpf_check(struct bpf_prog **prog, union bpf_attr *attr, env->allow_ptr_leaks = capable(CAP_SYS_ADMIN); - ret = check_cfg(env); + ret = check_subprogs(env); if (ret < 0) goto skip_full_check; @@ -6763,6 +6823,10 @@ int bpf_check(struct bpf_prog **prog, union bpf_attr *attr, if (ret < 0) goto skip_full_check; + ret = check_cfg(env); + if (ret < 0) + goto skip_full_check; + ret = do_check(env); if (env->cur_state) { free_verifier_state(env->cur_state, true); |