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Message-ID: <20180322155723.GD3206@krava>
Date: Thu, 22 Mar 2018 16:57:23 +0100
From: Jiri Olsa <jolsa@...hat.com>
To: Quentin Monnet <quentin.monnet@...ronome.com>
Cc: Daniel Borkmann <daniel@...earbox.net>,
Jiri Olsa <jolsa@...nel.org>,
Alexei Starovoitov <ast@...nel.org>,
lkml <linux-kernel@...r.kernel.org>, netdev@...r.kernel.org
Subject: Re: [PATCH 1/2] bpf: Remove struct bpf_verifier_env argument from
print_bpf_insn
On Thu, Mar 22, 2018 at 03:35:42PM +0000, Quentin Monnet wrote:
> 2018-03-22 14:32 UTC+0100 ~ Jiri Olsa <jolsa@...hat.com>
> > On Thu, Mar 22, 2018 at 10:34:18AM +0100, Daniel Borkmann wrote:
> >> On 03/21/2018 07:37 PM, Jiri Olsa wrote:
> >>> On Wed, Mar 21, 2018 at 05:25:33PM +0000, Quentin Monnet wrote:
> >>>> 2018-03-21 16:02 UTC+0100 ~ Jiri Olsa <jolsa@...nel.org>
> >>>>> We use print_bpf_insn in user space (bpftool and soon perf),
> >>>>> so it'd be nice to keep it generic and strip it off the kernel
> >>>>> struct bpf_verifier_env argument.
> >>>>>
> >>>>> This argument can be safely removed, because its users can
> >>>>> use the struct bpf_insn_cbs::private_data to pass it.
> >>>>>
> >>>>> Signed-off-by: Jiri Olsa <jolsa@...nel.org>
> >>>>> ---
> >>>>> kernel/bpf/disasm.c | 52 +++++++++++++++++++++++++--------------------------
> >>>>> kernel/bpf/disasm.h | 5 +----
> >>>>> kernel/bpf/verifier.c | 6 +++---
> >>>>> 3 files changed, 30 insertions(+), 33 deletions(-)
> >>>>
> >>>> [...]
> >>>>
> >>>>> diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
> >>>>> index c6eff108aa99..9f27d3fa7259 100644
> >>>>> --- a/kernel/bpf/verifier.c
> >>>>> +++ b/kernel/bpf/verifier.c
> >>>>> @@ -202,8 +202,7 @@ EXPORT_SYMBOL_GPL(bpf_verifier_log_write);
> >>>>> * generic for symbol export. The function was renamed, but not the calls in
> >>>>> * the verifier to avoid complicating backports. Hence the alias below.
> >>>>> */
> >>>>> -static __printf(2, 3) void verbose(struct bpf_verifier_env *env,
> >>>>> - const char *fmt, ...)
> >>>>> +static __printf(2, 3) void verbose(void *private_data, const char *fmt, ...)
> >>>>> __attribute__((alias("bpf_verifier_log_write")));
> >>>>
> >>>> Just as a note, verbose() will be aliased to a function whose prototype
> >>>> differs (bpf_verifier_log_write() still expects a struct
> >>>> bpf_verifier_env as its first argument). I am not so familiar with
> >>>> function aliases, could this change be a concern?
> >>>
> >>> yea, but as it was pointer for pointer switch I did not
> >>> see any problem with that.. I'll check more
> >>
> >> Ok, holding off for now until we have clarification. Other option could also
> >> be to make it void *private_data everywhere and for the kernel writer then
> >> do struct bpf_verifier_env *env = private_data.
> >
> > can't find much info about the alias behaviour for this
> > case.. so how about having separate function for the
> > print_cb like below.. I still need to test it
>
> I have nothing against splitting the function. This is a solution I
> considered for verbose() and bpf_verifier_log_write(), before switching
> to function alias (on Daniel's suggestion) because the code would be
> identical for the two separate functions at that time. But with your
> change they would not have the same signature anymore, so it sounds
> reasonable. Just a note below...
>
> >
> > thanks,
> > jirka
> >
> >
> > ---
> > kernel/bpf/disasm.c | 52 +++++++++++++++++++++++++--------------------------
> > kernel/bpf/disasm.h | 5 +----
> > kernel/bpf/verifier.c | 41 +++++++++++++++++++++++++++++-----------
> > 3 files changed, 57 insertions(+), 41 deletions(-)
> >
>
> [...]
>
> > diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
> > index e9f7c20691c1..69bf7590877c 100644
> > --- a/kernel/bpf/verifier.c
> > +++ b/kernel/bpf/verifier.c
> > @@ -168,23 +168,16 @@ struct bpf_call_arg_meta {
> >
> > static DEFINE_MUTEX(bpf_verifier_lock);
> >
> > -/* log_level controls verbosity level of eBPF verifier.
> > - * bpf_verifier_log_write() is used to dump the verification trace to the log,
> > - * so the user can figure out what's wrong with the program
> > - */
> > -__printf(2, 3) void bpf_verifier_log_write(struct bpf_verifier_env *env,
> > - const char *fmt, ...)
> > +static void log_write(struct bpf_verifier_env *env, const char *fmt,
> > + va_list args)
> > {
> > struct bpf_verifer_log *log = &env->log;
> > unsigned int n;
> > - va_list args;
> >
> > if (!log->level || !log->ubuf || bpf_verifier_log_full(log))
> > return;
> >
> > - va_start(args, fmt);
> > n = vscnprintf(log->kbuf, BPF_VERIFIER_TMP_LOG_SIZE, fmt, args);
> > - va_end(args);
> >
> > WARN_ONCE(n >= BPF_VERIFIER_TMP_LOG_SIZE - 1,
> > "verifier log line truncated - local buffer too short\n");
> > @@ -197,7 +190,32 @@ __printf(2, 3) void bpf_verifier_log_write(struct bpf_verifier_env *env,
> > else
> > log->ubuf = NULL;
> > }
> > +
> > +/* log_level controls verbosity level of eBPF verifier.
> > + * bpf_verifier_log_write() is used to dump the verification trace to the log,
> > + * so the user can figure out what's wrong with the program
> > + */
> > +__printf(2, 3) void bpf_verifier_log_write(struct bpf_verifier_env *env,
> > + const char *fmt, ...)
> > +{
> > + va_list args;
> > +
> > + va_start(args, fmt);
> > + log_write(env, fmt, args);
> > + va_end(args);
> > +}
> > EXPORT_SYMBOL_GPL(bpf_verifier_log_write);
> > +
> > +__printf(2, 3) static void print_ins(void *private_data,
> > + const char *fmt, ...)
>
> Unless I am mistaken, you could just call this one "verbose()" and
> simply remove the function alias?
right you are ;-) I haven't realized that struct bpf_verifier_env *env
will cleanly cast to void *
new version attached.. I'll make some tests and send full patch
jirka
---
diff --git a/kernel/bpf/disasm.c b/kernel/bpf/disasm.c
index 8740406df2cd..d6b76377cb6e 100644
--- a/kernel/bpf/disasm.c
+++ b/kernel/bpf/disasm.c
@@ -113,16 +113,16 @@ static const char *const bpf_jmp_string[16] = {
};
static void print_bpf_end_insn(bpf_insn_print_t verbose,
- struct bpf_verifier_env *env,
+ void *private_data,
const struct bpf_insn *insn)
{
- verbose(env, "(%02x) r%d = %s%d r%d\n", insn->code, insn->dst_reg,
+ verbose(private_data, "(%02x) r%d = %s%d r%d\n",
+ insn->code, insn->dst_reg,
BPF_SRC(insn->code) == BPF_TO_BE ? "be" : "le",
insn->imm, insn->dst_reg);
}
void print_bpf_insn(const struct bpf_insn_cbs *cbs,
- struct bpf_verifier_env *env,
const struct bpf_insn *insn,
bool allow_ptr_leaks)
{
@@ -132,23 +132,23 @@ void print_bpf_insn(const struct bpf_insn_cbs *cbs,
if (class == BPF_ALU || class == BPF_ALU64) {
if (BPF_OP(insn->code) == BPF_END) {
if (class == BPF_ALU64)
- verbose(env, "BUG_alu64_%02x\n", insn->code);
+ verbose(cbs->private_data, "BUG_alu64_%02x\n", insn->code);
else
- print_bpf_end_insn(verbose, env, insn);
+ print_bpf_end_insn(verbose, cbs->private_data, insn);
} else if (BPF_OP(insn->code) == BPF_NEG) {
- verbose(env, "(%02x) r%d = %s-r%d\n",
+ verbose(cbs->private_data, "(%02x) r%d = %s-r%d\n",
insn->code, insn->dst_reg,
class == BPF_ALU ? "(u32) " : "",
insn->dst_reg);
} else if (BPF_SRC(insn->code) == BPF_X) {
- verbose(env, "(%02x) %sr%d %s %sr%d\n",
+ verbose(cbs->private_data, "(%02x) %sr%d %s %sr%d\n",
insn->code, class == BPF_ALU ? "(u32) " : "",
insn->dst_reg,
bpf_alu_string[BPF_OP(insn->code) >> 4],
class == BPF_ALU ? "(u32) " : "",
insn->src_reg);
} else {
- verbose(env, "(%02x) %sr%d %s %s%d\n",
+ verbose(cbs->private_data, "(%02x) %sr%d %s %s%d\n",
insn->code, class == BPF_ALU ? "(u32) " : "",
insn->dst_reg,
bpf_alu_string[BPF_OP(insn->code) >> 4],
@@ -157,46 +157,46 @@ void print_bpf_insn(const struct bpf_insn_cbs *cbs,
}
} else if (class == BPF_STX) {
if (BPF_MODE(insn->code) == BPF_MEM)
- verbose(env, "(%02x) *(%s *)(r%d %+d) = r%d\n",
+ verbose(cbs->private_data, "(%02x) *(%s *)(r%d %+d) = r%d\n",
insn->code,
bpf_ldst_string[BPF_SIZE(insn->code) >> 3],
insn->dst_reg,
insn->off, insn->src_reg);
else if (BPF_MODE(insn->code) == BPF_XADD)
- verbose(env, "(%02x) lock *(%s *)(r%d %+d) += r%d\n",
+ verbose(cbs->private_data, "(%02x) lock *(%s *)(r%d %+d) += r%d\n",
insn->code,
bpf_ldst_string[BPF_SIZE(insn->code) >> 3],
insn->dst_reg, insn->off,
insn->src_reg);
else
- verbose(env, "BUG_%02x\n", insn->code);
+ verbose(cbs->private_data, "BUG_%02x\n", insn->code);
} else if (class == BPF_ST) {
if (BPF_MODE(insn->code) != BPF_MEM) {
- verbose(env, "BUG_st_%02x\n", insn->code);
+ verbose(cbs->private_data, "BUG_st_%02x\n", insn->code);
return;
}
- verbose(env, "(%02x) *(%s *)(r%d %+d) = %d\n",
+ verbose(cbs->private_data, "(%02x) *(%s *)(r%d %+d) = %d\n",
insn->code,
bpf_ldst_string[BPF_SIZE(insn->code) >> 3],
insn->dst_reg,
insn->off, insn->imm);
} else if (class == BPF_LDX) {
if (BPF_MODE(insn->code) != BPF_MEM) {
- verbose(env, "BUG_ldx_%02x\n", insn->code);
+ verbose(cbs->private_data, "BUG_ldx_%02x\n", insn->code);
return;
}
- verbose(env, "(%02x) r%d = *(%s *)(r%d %+d)\n",
+ verbose(cbs->private_data, "(%02x) r%d = *(%s *)(r%d %+d)\n",
insn->code, insn->dst_reg,
bpf_ldst_string[BPF_SIZE(insn->code) >> 3],
insn->src_reg, insn->off);
} else if (class == BPF_LD) {
if (BPF_MODE(insn->code) == BPF_ABS) {
- verbose(env, "(%02x) r0 = *(%s *)skb[%d]\n",
+ verbose(cbs->private_data, "(%02x) r0 = *(%s *)skb[%d]\n",
insn->code,
bpf_ldst_string[BPF_SIZE(insn->code) >> 3],
insn->imm);
} else if (BPF_MODE(insn->code) == BPF_IND) {
- verbose(env, "(%02x) r0 = *(%s *)skb[r%d + %d]\n",
+ verbose(cbs->private_data, "(%02x) r0 = *(%s *)skb[r%d + %d]\n",
insn->code,
bpf_ldst_string[BPF_SIZE(insn->code) >> 3],
insn->src_reg, insn->imm);
@@ -212,12 +212,12 @@ void print_bpf_insn(const struct bpf_insn_cbs *cbs,
if (map_ptr && !allow_ptr_leaks)
imm = 0;
- verbose(env, "(%02x) r%d = %s\n",
+ verbose(cbs->private_data, "(%02x) r%d = %s\n",
insn->code, insn->dst_reg,
__func_imm_name(cbs, insn, imm,
tmp, sizeof(tmp)));
} else {
- verbose(env, "BUG_ld_%02x\n", insn->code);
+ verbose(cbs->private_data, "BUG_ld_%02x\n", insn->code);
return;
}
} else if (class == BPF_JMP) {
@@ -227,35 +227,35 @@ void print_bpf_insn(const struct bpf_insn_cbs *cbs,
char tmp[64];
if (insn->src_reg == BPF_PSEUDO_CALL) {
- verbose(env, "(%02x) call pc%s\n",
+ verbose(cbs->private_data, "(%02x) call pc%s\n",
insn->code,
__func_get_name(cbs, insn,
tmp, sizeof(tmp)));
} else {
strcpy(tmp, "unknown");
- verbose(env, "(%02x) call %s#%d\n", insn->code,
+ verbose(cbs->private_data, "(%02x) call %s#%d\n", insn->code,
__func_get_name(cbs, insn,
tmp, sizeof(tmp)),
insn->imm);
}
} else if (insn->code == (BPF_JMP | BPF_JA)) {
- verbose(env, "(%02x) goto pc%+d\n",
+ verbose(cbs->private_data, "(%02x) goto pc%+d\n",
insn->code, insn->off);
} else if (insn->code == (BPF_JMP | BPF_EXIT)) {
- verbose(env, "(%02x) exit\n", insn->code);
+ verbose(cbs->private_data, "(%02x) exit\n", insn->code);
} else if (BPF_SRC(insn->code) == BPF_X) {
- verbose(env, "(%02x) if r%d %s r%d goto pc%+d\n",
+ verbose(cbs->private_data, "(%02x) if r%d %s r%d goto pc%+d\n",
insn->code, insn->dst_reg,
bpf_jmp_string[BPF_OP(insn->code) >> 4],
insn->src_reg, insn->off);
} else {
- verbose(env, "(%02x) if r%d %s 0x%x goto pc%+d\n",
+ verbose(cbs->private_data, "(%02x) if r%d %s 0x%x goto pc%+d\n",
insn->code, insn->dst_reg,
bpf_jmp_string[BPF_OP(insn->code) >> 4],
insn->imm, insn->off);
}
} else {
- verbose(env, "(%02x) %s\n",
+ verbose(cbs->private_data, "(%02x) %s\n",
insn->code, bpf_class_string[class]);
}
}
diff --git a/kernel/bpf/disasm.h b/kernel/bpf/disasm.h
index 266fe8ee542b..e1324a834a24 100644
--- a/kernel/bpf/disasm.h
+++ b/kernel/bpf/disasm.h
@@ -22,14 +22,12 @@
#include <string.h>
#endif
-struct bpf_verifier_env;
-
extern const char *const bpf_alu_string[16];
extern const char *const bpf_class_string[8];
const char *func_id_name(int id);
-typedef __printf(2, 3) void (*bpf_insn_print_t)(struct bpf_verifier_env *env,
+typedef __printf(2, 3) void (*bpf_insn_print_t)(void *private_data,
const char *, ...);
typedef const char *(*bpf_insn_revmap_call_t)(void *private_data,
const struct bpf_insn *insn);
@@ -45,7 +43,6 @@ struct bpf_insn_cbs {
};
void print_bpf_insn(const struct bpf_insn_cbs *cbs,
- struct bpf_verifier_env *env,
const struct bpf_insn *insn,
bool allow_ptr_leaks);
#endif
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index e9f7c20691c1..e93a6e48641b 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -168,23 +168,16 @@ struct bpf_call_arg_meta {
static DEFINE_MUTEX(bpf_verifier_lock);
-/* log_level controls verbosity level of eBPF verifier.
- * bpf_verifier_log_write() is used to dump the verification trace to the log,
- * so the user can figure out what's wrong with the program
- */
-__printf(2, 3) void bpf_verifier_log_write(struct bpf_verifier_env *env,
- const char *fmt, ...)
+static void log_write(struct bpf_verifier_env *env, const char *fmt,
+ va_list args)
{
struct bpf_verifer_log *log = &env->log;
unsigned int n;
- va_list args;
if (!log->level || !log->ubuf || bpf_verifier_log_full(log))
return;
- va_start(args, fmt);
n = vscnprintf(log->kbuf, BPF_VERIFIER_TMP_LOG_SIZE, fmt, args);
- va_end(args);
WARN_ONCE(n >= BPF_VERIFIER_TMP_LOG_SIZE - 1,
"verifier log line truncated - local buffer too short\n");
@@ -197,14 +190,30 @@ __printf(2, 3) void bpf_verifier_log_write(struct bpf_verifier_env *env,
else
log->ubuf = NULL;
}
-EXPORT_SYMBOL_GPL(bpf_verifier_log_write);
-/* Historically bpf_verifier_log_write was called verbose, but the name was too
- * generic for symbol export. The function was renamed, but not the calls in
- * the verifier to avoid complicating backports. Hence the alias below.
+
+/* log_level controls verbosity level of eBPF verifier.
+ * bpf_verifier_log_write() is used to dump the verification trace to the log,
+ * so the user can figure out what's wrong with the program
*/
-static __printf(2, 3) void verbose(struct bpf_verifier_env *env,
- const char *fmt, ...)
- __attribute__((alias("bpf_verifier_log_write")));
+__printf(2, 3) void bpf_verifier_log_write(struct bpf_verifier_env *env,
+ const char *fmt, ...)
+{
+ va_list args;
+
+ va_start(args, fmt);
+ log_write(env, fmt, args);
+ va_end(args);
+}
+EXPORT_SYMBOL_GPL(bpf_verifier_log_write);
+
+__printf(2, 3) static void verbose(void *private_data, const char *fmt, ...)
+{
+ va_list args;
+
+ va_start(args, fmt);
+ log_write(private_data, fmt, args);
+ va_end(args);
+}
static bool type_is_pkt_pointer(enum bpf_reg_type type)
{
@@ -4600,10 +4609,11 @@ static int do_check(struct bpf_verifier_env *env)
if (env->log.level) {
const struct bpf_insn_cbs cbs = {
.cb_print = verbose,
+ .private_data = env,
};
verbose(env, "%d: ", insn_idx);
- print_bpf_insn(&cbs, env, insn, env->allow_ptr_leaks);
+ print_bpf_insn(&cbs, insn, env->allow_ptr_leaks);
}
if (bpf_prog_is_dev_bound(env->prog->aux)) {
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