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bpf: Add bpf_verifier_vlog() and bpf_verifier_log_needed()

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The BTF (BPF Type Format) verifier needs to reuse the current
BPF verifier log.  Hence, it requires the following changes:

(1) Expose log_write() in verifier.c for other users.
    Its name is renamed to bpf_verifier_vlog().

(2) The BTF verifier also needs to check
'log->level && log->ubuf && !bpf_verifier_log_full(log);'
independently outside of the current log_write().  It is
because the BTF verifier will do one-check before
making multiple calls to btf_verifier_vlog to log
the details of a type.

Hence, this check is also re-factored to a new function
bpf_verifier_log_needed().  Since it is re-factored,
we can check it before va_start() in the current
bpf_verifier_log_write() and verbose().

Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Acked-by: Alexei Starovoitov <ast@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
This commit is contained in:
Martin KaFai Lau 2018-03-24 11:44:23 -07:00 committed by Daniel Borkmann
parent b9193c1b61
commit 77d2e05abd
2 changed files with 18 additions and 8 deletions
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7
include/linux/bpf_verifier.h
View File

@ -166,6 +166,11 @@ static inline bool bpf_verifier_log_full(const struct bpf_verifier_log *log)
return log->len_used >= log->len_total - 1;
}
static inline bool bpf_verifier_log_needed(const struct bpf_verifier_log *log)
{
return log->level && log->ubuf && !bpf_verifier_log_full(log);
}
#define BPF_MAX_SUBPROGS 256
/* single container for all structs
@ -192,6 +197,8 @@ struct bpf_verifier_env {
u32 subprog_cnt;
};
void bpf_verifier_vlog(struct bpf_verifier_log *log, const char *fmt,
va_list args);
__printf(2, 3) void bpf_verifier_log_write(struct bpf_verifier_env *env,
const char *fmt, ...);

19
kernel/bpf/verifier.c
View File

@ -168,15 +168,11 @@ struct bpf_call_arg_meta {
static DEFINE_MUTEX(bpf_verifier_lock);
static void log_write(struct bpf_verifier_env *env, const char *fmt,
va_list args)
void bpf_verifier_vlog(struct bpf_verifier_log *log, const char *fmt,
va_list args)
{
struct bpf_verifier_log *log = &env->log;
unsigned int n;
if (!log->level || !log->ubuf || bpf_verifier_log_full(log))
return;
n = vscnprintf(log->kbuf, BPF_VERIFIER_TMP_LOG_SIZE, fmt, args);
WARN_ONCE(n >= BPF_VERIFIER_TMP_LOG_SIZE - 1,
@ -200,18 +196,25 @@ __printf(2, 3) void bpf_verifier_log_write(struct bpf_verifier_env *env,
{
va_list args;
if (!bpf_verifier_log_needed(&env->log))
return;
va_start(args, fmt);
log_write(env, fmt, args);
bpf_verifier_vlog(&env->log, fmt, args);
va_end(args);
}
EXPORT_SYMBOL_GPL(bpf_verifier_log_write);
__printf(2, 3) static void verbose(void *private_data, const char *fmt, ...)
{
struct bpf_verifier_env *env = private_data;
va_list args;
if (!bpf_verifier_log_needed(&env->log))
return;
va_start(args, fmt);
log_write(private_data, fmt, args);
bpf_verifier_vlog(&env->log, fmt, args);
va_end(args);
}