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Message-ID: <20211013180834.73e2653e@gandalf.local.home>
Date: Wed, 13 Oct 2021 18:08:34 -0400
From: Steven Rostedt <rostedt@...dmis.org>
To: Kalesh Singh <kaleshsingh@...gle.com>
Cc: surenb@...gle.com, hridya@...gle.com, namhyung@...nel.org,
samitolvanen@...gle.com, ndesaulniers@...gle.com,
kernel-team@...roid.com, Ingo Molnar <mingo@...hat.com>,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH] tracing/cfi: Fix cmp_entries_* functions signature
mismatch
On Thu, 23 Sep 2021 17:09:07 +0000
Kalesh Singh <kaleshsingh@...gle.com> wrote:
This finally popped up into my queue (from all my traveling and running of
conferences :-p )
> If CONFIG_CFI_CLANG=y, attempting to read an event histogram will cause
> the kernel to panic due to failed CFI check.
>
> 1. echo 'hist:keys=common_pid' >> events/sched/sched_switch/trigger
> 2. cat >> events/sched/sched_switch/hist
Do you mean:
2. cat events/sched/sched_switch/hist
?
Small nits below.
> 3. kernel panices on attempting to read hist
>
> This happens because the sort() function expects a generic
> int (*)(const void *, const void *) pointer for the compare function.
> To prevent this CFI failure, change tracing map cmp_entries_* function
> signatures to match this.
>
> Signed-off-by: Kalesh Singh <kaleshsingh@...gle.com>
> ---
> kernel/trace/tracing_map.c | 40 ++++++++++++++++++++++----------------
> 1 file changed, 23 insertions(+), 17 deletions(-)
>
> diff --git a/kernel/trace/tracing_map.c b/kernel/trace/tracing_map.c
> index d6bddb157ef2..a8c80ebbf9da 100644
> --- a/kernel/trace/tracing_map.c
> +++ b/kernel/trace/tracing_map.c
> @@ -834,19 +834,21 @@ int tracing_map_init(struct tracing_map *map)
> return err;
> }
>
> -static int cmp_entries_dup(const struct tracing_map_sort_entry **a,
> - const struct tracing_map_sort_entry **b)
> +static int cmp_entries_dup(const void *__a, const void *__b)
Instead of __a and __b, have it as:
const void *A, const void *B
> {
> int ret = 0;
> + const struct tracing_map_sort_entry *a
> + = *(const struct tracing_map_sort_entry **)__a;
> + const struct tracing_map_sort_entry *b
> + = *(const struct tracing_map_sort_entry **)__b;
Please put these before the ret, we like to have a "upside down xmas tree"
type of declaration, where longer lines come before shorter ones. Also,
this can be "prettified" as:
const struct tracing_map_sort_entry **pa = A;
const struct tracing_map_sort_entry **pb = B;
const struct tracing_map_sort_entry *a = *pa;
const struct tracing_map_sort_entry *b = *pb;
int ret = 0;
>
> - if (memcmp((*a)->key, (*b)->key, (*a)->elt->map->key_size))
> + if (memcmp(a->key, b->key, a->elt->map->key_size))
> ret = 1;
>
> return ret;
> }
>
> -static int cmp_entries_sum(const struct tracing_map_sort_entry **a,
> - const struct tracing_map_sort_entry **b)
> +static int cmp_entries_sum(const void *__a, const void *__b)
> {
> const struct tracing_map_elt *elt_a, *elt_b;
> struct tracing_map_sort_key *sort_key;
> @@ -854,9 +856,13 @@ static int cmp_entries_sum(const struct tracing_map_sort_entry **a,
> tracing_map_cmp_fn_t cmp_fn;
> void *val_a, *val_b;
> int ret = 0;
> + const struct tracing_map_sort_entry *a
> + = *(const struct tracing_map_sort_entry **)__a;
> + const struct tracing_map_sort_entry *b
> + = *(const struct tracing_map_sort_entry **)__b;
Same here.
>
> - elt_a = (*a)->elt;
> - elt_b = (*b)->elt;
> + elt_a = a->elt;
> + elt_b = b->elt;
>
> sort_key = &elt_a->map->sort_key;
>
> @@ -873,8 +879,7 @@ static int cmp_entries_sum(const struct tracing_map_sort_entry **a,
> return ret;
> }
>
> -static int cmp_entries_key(const struct tracing_map_sort_entry **a,
> - const struct tracing_map_sort_entry **b)
> +static int cmp_entries_key(const void *__a, const void *__b)
> {
> const struct tracing_map_elt *elt_a, *elt_b;
> struct tracing_map_sort_key *sort_key;
> @@ -882,9 +887,13 @@ static int cmp_entries_key(const struct tracing_map_sort_entry **a,
> tracing_map_cmp_fn_t cmp_fn;
> void *val_a, *val_b;
> int ret = 0;
> + const struct tracing_map_sort_entry *a
> + = *(const struct tracing_map_sort_entry **)__a;
> + const struct tracing_map_sort_entry *b
> + = *(const struct tracing_map_sort_entry **)__b;
And here.
Thanks, and sorry for the long delay.
-- Steve
>
> - elt_a = (*a)->elt;
> - elt_b = (*b)->elt;
> + elt_a = a->elt;
> + elt_b = b->elt;
>
> sort_key = &elt_a->map->sort_key;
>
> @@ -989,10 +998,8 @@ static void sort_secondary(struct tracing_map *map,
> struct tracing_map_sort_key *primary_key,
> struct tracing_map_sort_key *secondary_key)
> {
> - int (*primary_fn)(const struct tracing_map_sort_entry **,
> - const struct tracing_map_sort_entry **);
> - int (*secondary_fn)(const struct tracing_map_sort_entry **,
> - const struct tracing_map_sort_entry **);
> + int (*primary_fn)(const void *, const void *);
> + int (*secondary_fn)(const void *, const void *);
> unsigned i, start = 0, n_sub = 1;
>
> if (is_key(map, primary_key->field_idx))
> @@ -1061,8 +1068,7 @@ int tracing_map_sort_entries(struct tracing_map *map,
> unsigned int n_sort_keys,
> struct tracing_map_sort_entry ***sort_entries)
> {
> - int (*cmp_entries_fn)(const struct tracing_map_sort_entry **,
> - const struct tracing_map_sort_entry **);
> + int (*cmp_entries_fn)(const void *, const void *);
> struct tracing_map_sort_entry *sort_entry, **entries;
> int i, n_entries, ret;
>
>
> base-commit: 58e2cf5d794616b84f591d4d1276c8953278ce24
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