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Subject[PATCH v3] tracing/cfi: Fix cmp_entries_* functions signature mismatch
From
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
3. kernel panics 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.

Also, fix the build error reported by the kernel test robot [1].

[1] https://lore.kernel.org/r/202110141140.zzi4dRh4-lkp@intel.com/

Signed-off-by: Kalesh Singh <kaleshsingh@google.com>
Reported-by: kernel test robot <lkp@intel.com>
---
Changes in v3:
- Fix build error, reported by kernel test robot

Changes in v2:
- Code style clean up, per Steve
- Commit message typo fix, per Steve


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..39bb56d2dcbe 100644
--- a/kernel/trace/tracing_map.c
+++ b/kernel/trace/tracing_map.c
@@ -834,29 +834,35 @@ 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)
{
+ const struct tracing_map_sort_entry *a, *b;
int ret = 0;

- if (memcmp((*a)->key, (*b)->key, (*a)->elt->map->key_size))
+ a = *(const struct tracing_map_sort_entry **)A;
+ b = *(const struct tracing_map_sort_entry **)B;
+
+ 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;
+ const struct tracing_map_sort_entry *a, *b;
struct tracing_map_sort_key *sort_key;
struct tracing_map_field *field;
tracing_map_cmp_fn_t cmp_fn;
void *val_a, *val_b;
int ret = 0;

- elt_a = (*a)->elt;
- elt_b = (*b)->elt;
+ a = *(const struct tracing_map_sort_entry **)A;
+ b = *(const struct tracing_map_sort_entry **)B;
+
+ elt_a = a->elt;
+ elt_b = b->elt;

sort_key = &elt_a->map->sort_key;

@@ -873,18 +879,21 @@ 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;
+ const struct tracing_map_sort_entry *a, *b;
struct tracing_map_sort_key *sort_key;
struct tracing_map_field *field;
tracing_map_cmp_fn_t cmp_fn;
void *val_a, *val_b;
int ret = 0;

- elt_a = (*a)->elt;
- elt_b = (*b)->elt;
+ a = *(const struct tracing_map_sort_entry **)A;
+ b = *(const struct tracing_map_sort_entry **)B;
+
+ 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: 348949d9a4440abdab3b1dc99a9bb660e8c7da7c
--
2.33.0.1079.g6e70778dc9-goog

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