bpf: Move trampoline JIT image allocation to a function

Refactor the image allocation in the BPF trampoline code into a
separate function, so it can be shared with the BPF dispatcher in
upcoming commits.

Signed-off-by: Björn Töpel <bjorn.topel@intel.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20191213175112.30208-2-bjorn.topel@gmail.com

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 35903f148be5968ad1b85807d0bfb7c06c249897..5d744828b399b02386030fc0d35e67443b23623f 100644 (file)
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -475,6 +475,7 @@ struct bpf_trampoline *bpf_trampoline_lookup(u64 key);
 int bpf_trampoline_link_prog(struct bpf_prog *prog);
 int bpf_trampoline_unlink_prog(struct bpf_prog *prog);
 void bpf_trampoline_put(struct bpf_trampoline *tr);
+void *bpf_jit_alloc_exec_page(void);
 #else
 static inline struct bpf_trampoline *bpf_trampoline_lookup(u64 key)
 {

diff --git a/kernel/bpf/trampoline.c b/kernel/bpf/trampoline.c
index 7e89f1f49d7712d6f530bba2c6572b57ae702b1f..5ee301ddbd005be2283dd062b5ea7c6f0c90ddca 100644 (file)
--- a/kernel/bpf/trampoline.c
+++ b/kernel/bpf/trampoline.c
@@ -13,6 +13,22 @@ static struct hlist_head trampoline_table[TRAMPOLINE_TABLE_SIZE];
 /* serializes access to trampoline_table */
 static DEFINE_MUTEX(trampoline_mutex);
 
+void *bpf_jit_alloc_exec_page(void)
+{
+       void *image;
+
+       image = bpf_jit_alloc_exec(PAGE_SIZE);
+       if (!image)
+               return NULL;
+
+       set_vm_flush_reset_perms(image);
+       /* Keep image as writeable. The alternative is to keep flipping ro/rw
+        * everytime new program is attached or detached.
+        */
+       set_memory_x((long)image, 1);
+       return image;
+}
+
 struct bpf_trampoline *bpf_trampoline_lookup(u64 key)
 {
        struct bpf_trampoline *tr;
@@ -33,7 +49,7 @@ struct bpf_trampoline *bpf_trampoline_lookup(u64 key)
                goto out;
 
        /* is_root was checked earlier. No need for bpf_jit_charge_modmem() */
-       image = bpf_jit_alloc_exec(PAGE_SIZE);
+       image = bpf_jit_alloc_exec_page();
        if (!image) {
                kfree(tr);
                tr = NULL;
@@ -47,12 +63,6 @@ struct bpf_trampoline *bpf_trampoline_lookup(u64 key)
        mutex_init(&tr->mutex);
        for (i = 0; i < BPF_TRAMP_MAX; i++)
                INIT_HLIST_HEAD(&tr->progs_hlist[i]);
-
-       set_vm_flush_reset_perms(image);
-       /* Keep image as writeable. The alternative is to keep flipping ro/rw
-        * everytime new program is attached or detached.
-        */
-       set_memory_x((long)image, 1);
        tr->image = image;
 out:
        mutex_unlock(&trampoline_mutex);