[PATCH 12/15] bpf: Remove bpf_image tree

Jiri Olsa
2020-03-12T19:57:26Z

Now that we have all the objects (bpf_prog, bpf_trampoline,
bpf_dispatcher) linked in bpf_tree, there's no need to have
separate bpf_image tree for images.

Reverting the bpf_image tree together with struct bpf_image,
because it's no longer needed.

Also removing bpf_image_alloc function and adding the original
bpf_jit_alloc_exec_page interface instead.

The kernel_text_address function can now rely only on is_bpf_text_address,
because it checks the bpf_tree that contains all the objects.

Keeping bpf_image_ksym_add and bpf_image_ksym_del because they are
useful wrappers with perf's ksymbol interface calls.

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
---
include/linux/bpf.h | 8 +---
kernel/bpf/dispatcher.c | 4 +-
kernel/bpf/trampoline.c | 83 +++++------------------------------------
kernel/extable.c | 2 -
4 files changed, 13 insertions(+), 84 deletions(-)

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 95e13efe658a..8c9175320d6c 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -583,14 +583,8 @@ void bpf_trampoline_put(struct bpf_trampoline *tr);
#define BPF_DISPATCHER_PTR(name) (&bpf_dispatcher_##name)
void bpf_dispatcher_change_prog(struct bpf_dispatcher *d, struct bpf_prog *from,
struct bpf_prog *to);
-struct bpf_image {
- struct latch_tree_node tnode;
- unsigned char data[];
-};
-#define BPF_IMAGE_SIZE (PAGE_SIZE - sizeof(struct bpf_image))
-bool is_bpf_image_address(unsigned long address);
-void *bpf_image_alloc(void);
/* Called only from JIT-enabled code, so there's no need for stubs. */
+void *bpf_jit_alloc_exec_page(void);
void bpf_image_ksym_add(void *data, struct bpf_ksym *ksym);
void bpf_image_ksym_del(struct bpf_ksym *ksym);
void bpf_ksym_add(struct bpf_ksym *ksym);
diff --git a/kernel/bpf/dispatcher.c b/kernel/bpf/dispatcher.c
index a2679bae9e73..2444bd15cc2d 100644
--- a/kernel/bpf/dispatcher.c
+++ b/kernel/bpf/dispatcher.c
@@ -113,7 +113,7 @@ static void bpf_dispatcher_update(struct bpf_dispatcher *d, int prev_num_progs)
noff = 0;
} else {
old = d->image + d->image_off;
- noff = d->image_off ^ (BPF_IMAGE_SIZE / 2);
+ noff = d->image_off ^ (PAGE_SIZE / 2);
}

new = d->num_progs ? d->image + noff : NULL;
@@ -140,7 +140,7 @@ void bpf_dispatcher_change_prog(struct bpf_dispatcher *d, struct bpf_prog *from,

mutex_lock(&d->mutex);
if (!d->image) {
- d->image = bpf_image_alloc();
+ d->image = bpf_jit_alloc_exec_page();
if (!d->image)
goto out;
bpf_image_ksym_add(d->image, &d->ksym);
diff --git a/kernel/bpf/trampoline.c b/kernel/bpf/trampoline.c
index 36549c9afec4..f42f700c1d28 100644
--- a/kernel/bpf/trampoline.c
+++ b/kernel/bpf/trampoline.c
@@ -18,12 +18,11 @@ const struct bpf_prog_ops bpf_extension_prog_ops = {
#define TRAMPOLINE_TABLE_SIZE (1 << TRAMPOLINE_HASH_BITS)

static struct hlist_head trampoline_table[TRAMPOLINE_TABLE_SIZE];
-static struct latch_tree_root image_tree __cacheline_aligned;

-/* serializes access to trampoline_table and image_tree */
+/* serializes access to trampoline_table */
static DEFINE_MUTEX(trampoline_mutex);

-static void *bpf_jit_alloc_exec_page(void)
+void *bpf_jit_alloc_exec_page(void)
{
void *image;

@@ -39,78 +38,20 @@ static void *bpf_jit_alloc_exec_page(void)
return image;
}

-static __always_inline bool image_tree_less(struct latch_tree_node *a,
- struct latch_tree_node *b)
-{
- struct bpf_image *ia = container_of(a, struct bpf_image, tnode);
- struct bpf_image *ib = container_of(b, struct bpf_image, tnode);
-
- return ia < ib;
-}
-
-static __always_inline int image_tree_comp(void *addr, struct latch_tree_node *n)
-{
- void *image = container_of(n, struct bpf_image, tnode);
-
- if (addr < image)
- return -1;
- if (addr >= image + PAGE_SIZE)
- return 1;
-
- return 0;
-}
-
-static const struct latch_tree_ops image_tree_ops = {
- .less = image_tree_less,
- .comp = image_tree_comp,
-};
-
-static void *__bpf_image_alloc(bool lock)
-{
- struct bpf_image *image;
-
- image = bpf_jit_alloc_exec_page();
- if (!image)
- return NULL;
-
- if (lock)
- mutex_lock(&trampoline_mutex);
- latch_tree_insert(&image->tnode, &image_tree, &image_tree_ops);
- if (lock)
- mutex_unlock(&trampoline_mutex);
- return image->data;
-}
-
-void *bpf_image_alloc(void)
-{
- return __bpf_image_alloc(true);
-}
-
-bool is_bpf_image_address(unsigned long addr)
-{
- bool ret;
-
- rcu_read_lock();
- ret = latch_tree_find((void *) addr, &image_tree, &image_tree_ops) != NULL;
- rcu_read_unlock();
-
- return ret;
-}
-
void bpf_image_ksym_add(void *data, struct bpf_ksym *ksym)
{
ksym->start = (unsigned long) data;
- ksym->end = ksym->start + BPF_IMAGE_SIZE;
+ ksym->end = ksym->start + PAGE_SIZE;
bpf_ksym_add(ksym);
perf_event_ksymbol(PERF_RECORD_KSYMBOL_TYPE_BPF, ksym->start,
- BPF_IMAGE_SIZE, false, ksym->name);
+ PAGE_SIZE, false, ksym->name);
}

void bpf_image_ksym_del(struct bpf_ksym *ksym)
{
bpf_ksym_del(ksym);
perf_event_ksymbol(PERF_RECORD_KSYMBOL_TYPE_BPF, ksym->start,
- BPF_IMAGE_SIZE, true, ksym->name);
+ PAGE_SIZE, true, ksym->name);
}

static void bpf_trampoline_ksym_add(struct bpf_trampoline *tr)
@@ -141,7 +82,7 @@ struct bpf_trampoline *bpf_trampoline_lookup(u64 key)
goto out;

/* is_root was checked earlier. No need for bpf_jit_charge_modmem() */
- image = __bpf_image_alloc(false);
+ image = bpf_jit_alloc_exec_page();
if (!image) {
kfree(tr);
tr = NULL;
@@ -243,8 +184,8 @@ bpf_trampoline_get_progs(const struct bpf_trampoline *tr, int *total)

static int bpf_trampoline_update(struct bpf_trampoline *tr)
{
- void *old_image = tr->image + ((tr->selector + 1) & 1) * BPF_IMAGE_SIZE/2;
- void *new_image = tr->image + (tr->selector & 1) * BPF_IMAGE_SIZE/2;
+ void *old_image = tr->image + ((tr->selector + 1) & 1) * PAGE_SIZE/2;
+ void *new_image = tr->image + (tr->selector & 1) * PAGE_SIZE/2;
struct bpf_tramp_progs *tprogs;
u32 flags = BPF_TRAMP_F_RESTORE_REGS;
int err, total;
@@ -272,7 +213,7 @@ static int bpf_trampoline_update(struct bpf_trampoline *tr)

synchronize_rcu_tasks();

- err = arch_prepare_bpf_trampoline(new_image, new_image + BPF_IMAGE_SIZE / 2,
+ err = arch_prepare_bpf_trampoline(new_image, new_image + PAGE_SIZE / 2,
&tr->func.model, flags, tprogs,
tr->func.addr);
if (err < 0)
@@ -383,8 +324,6 @@ int bpf_trampoline_unlink_prog(struct bpf_prog *prog)

void bpf_trampoline_put(struct bpf_trampoline *tr)
{
- struct bpf_image *image;
-
if (!tr)
return;
mutex_lock(&trampoline_mutex);
@@ -396,11 +335,9 @@ void bpf_trampoline_put(struct bpf_trampoline *tr)
if (WARN_ON_ONCE(!hlist_empty(&tr->progs_hlist[BPF_TRAMP_FEXIT])))
goto out;
bpf_image_ksym_del(&tr->ksym);
- image = container_of(tr->image, struct bpf_image, data);
- latch_tree_erase(&image->tnode, &image_tree, &image_tree_ops);
/* wait for tasks to get out of trampoline before freeing it */
synchronize_rcu_tasks();
- bpf_jit_free_exec(image);
+ bpf_jit_free_exec(tr->image);
hlist_del(&tr->hlist);
kfree(tr);
out:
diff --git a/kernel/extable.c b/kernel/extable.c
index a0024f27d3a1..7681f87e89dd 100644
--- a/kernel/extable.c
+++ b/kernel/extable.c
@@ -149,8 +149,6 @@ int kernel_text_address(unsigned long addr)
goto out;
if (is_bpf_text_address(addr))
goto out;
- if (is_bpf_image_address(addr))
- goto out;
ret = 0;
out:
if (no_rcu)
--
2.24.1