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Commit 77d2e05a authored by Martin KaFai Lau's avatar Martin KaFai Lau Committed by Daniel Borkmann
Browse files

bpf: Add bpf_verifier_vlog() and bpf_verifier_log_needed() 



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: default avatarMartin KaFai Lau <kafai@fb.com>
Acked-by: default avatarAlexei Starovoitov <ast@fb.com>
Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
parent b9193c1b

include/linux/bpf_verifier.h

+7 −0
Original line number Diff line number Diff line
@@ -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, ...);

kernel/bpf/verifier.c

+11 −8
Original line number Diff line number Diff line
@@ -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,

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);

}