diff mbox series

[bpf-next,4/8] bpf: Add helpers for trampoline image management

Message ID 20230920053158.3175043-5-song@kernel.org (mailing list archive)
State Superseded
Delegated to: BPF
Headers show
Series Allocate bpf trampoline on bpf_prog_pack | expand

Checks

Context Check Description
netdev/series_format success Posting correctly formatted
netdev/tree_selection success Clearly marked for bpf-next, async
netdev/fixes_present success Fixes tag not required for -next series
netdev/header_inline success No static functions without inline keyword in header files
netdev/build_32bit success Errors and warnings before: 2838 this patch: 2838
netdev/cc_maintainers warning 8 maintainers not CCed: martin.lau@linux.dev jolsa@kernel.org haoluo@google.com sdf@google.com john.fastabend@gmail.com yonghong.song@linux.dev netdev@vger.kernel.org kpsingh@kernel.org
netdev/build_clang success Errors and warnings before: 1527 this patch: 1527
netdev/verify_signedoff success Signed-off-by tag matches author and committer
netdev/deprecated_api success None detected
netdev/check_selftest success No net selftest shell script
netdev/verify_fixes success No Fixes tag
netdev/build_allmodconfig_warn success Errors and warnings before: 2924 this patch: 2924
netdev/checkpatch warning CHECK: multiple assignments should be avoided
netdev/kdoc success Errors and warnings before: 0 this patch: 0
netdev/source_inline success Was 0 now: 0
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Commit Message

Song Liu Sept. 20, 2023, 5:31 a.m. UTC 
As BPF trampoline of different archs moves from bpf_jit_[alloc|free]_exec()
to bpf_prog_pack_[alloc|free](), we need to use different _alloc, _free for
different archs during the transition. Add the following helpers for this
transition:

void *arch_alloc_bpf_trampoline(int size);
void arch_free_bpf_trampoline(void *image, int size);
void arch_protect_bpf_trampoline(void *image, int size);
void arch_unprotect_bpf_trampoline(void *image, int size);

The fallback version of these helpers require size <= PAGE_SIZE, but they
are only called with size == PAGE_SIZE. They will be called with size <
PAGE_SIZE when arch_bpf_trampoline_size() helper is introduced later.

Signed-off-by: Song Liu <song@kernel.org>
---
 include/linux/bpf.h         |  5 +++++
 kernel/bpf/bpf_struct_ops.c | 12 +++++-----
 kernel/bpf/trampoline.c     | 44 +++++++++++++++++++++++++++++++------
 3 files changed, 47 insertions(+), 14 deletions(-)

Comments

Song Liu Sept. 20, 2023, 4:31 p.m. UTC | #1 
> On Sep 19, 2023, at 10:31 PM, Song Liu <song@kernel.org> wrote:
> 
> As BPF trampoline of different archs moves from bpf_jit_[alloc|free]_exec()
> to bpf_prog_pack_[alloc|free](), we need to use different _alloc, _free for
> different archs during the transition. Add the following helpers for this
> transition:
> 
> void *arch_alloc_bpf_trampoline(int size);
> void arch_free_bpf_trampoline(void *image, int size);
> void arch_protect_bpf_trampoline(void *image, int size);
> void arch_unprotect_bpf_trampoline(void *image, int size);
> 
> The fallback version of these helpers require size <= PAGE_SIZE, but they
> are only called with size == PAGE_SIZE. They will be called with size <
> PAGE_SIZE when arch_bpf_trampoline_size() helper is introduced later.
> 
> Signed-off-by: Song Liu <song@kernel.org>
> ---
> include/linux/bpf.h         |  5 +++++
> kernel/bpf/bpf_struct_ops.c | 12 +++++-----

I just found that we need similar changes in net/bpf/bpf_dummy_struct_ops.c. 

Added it to the next version. 

Song
diff mbox series

Patch

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 27a18c0c10ca..548f3ef34ba1 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -1083,6 +1083,11 @@  int arch_prepare_bpf_trampoline(struct bpf_tramp_image *im, void *image, void *i
 				const struct btf_func_model *m, u32 flags,
 				struct bpf_tramp_links *tlinks,
 				void *func_addr);
+void *arch_alloc_bpf_trampoline(int size);
+void arch_free_bpf_trampoline(void *image, int size);
+void arch_protect_bpf_trampoline(void *image, int size);
+void arch_unprotect_bpf_trampoline(void *image, int size);
+
 u64 notrace __bpf_prog_enter_sleepable_recur(struct bpf_prog *prog,
 					     struct bpf_tramp_run_ctx *run_ctx);
 void notrace __bpf_prog_exit_sleepable_recur(struct bpf_prog *prog, u64 start,
diff --git a/kernel/bpf/bpf_struct_ops.c b/kernel/bpf/bpf_struct_ops.c
index db6176fb64dc..e9e95879bce2 100644
--- a/kernel/bpf/bpf_struct_ops.c
+++ b/kernel/bpf/bpf_struct_ops.c
@@ -515,7 +515,7 @@  static long bpf_struct_ops_map_update_elem(struct bpf_map *map, void *key,
 			if (err)
 				goto reset_unlock;
 		}
-		set_memory_rox((long)st_map->image, 1);
+		arch_protect_bpf_trampoline(st_map->image, PAGE_SIZE);
 		/* Let bpf_link handle registration & unregistration.
 		 *
 		 * Pair with smp_load_acquire() during lookup_elem().
@@ -524,7 +524,7 @@  static long bpf_struct_ops_map_update_elem(struct bpf_map *map, void *key,
 		goto unlock;
 	}
 
-	set_memory_rox((long)st_map->image, 1);
+	arch_protect_bpf_trampoline(st_map->image, PAGE_SIZE);
 	err = st_ops->reg(kdata);
 	if (likely(!err)) {
 		/* This refcnt increment on the map here after
@@ -547,8 +547,7 @@  static long bpf_struct_ops_map_update_elem(struct bpf_map *map, void *key,
 	 * there was a race in registering the struct_ops (under the same name) to
 	 * a sub-system through different struct_ops's maps.
 	 */
-	set_memory_nx((long)st_map->image, 1);
-	set_memory_rw((long)st_map->image, 1);
+	arch_unprotect_bpf_trampoline(st_map->image, PAGE_SIZE);
 
 reset_unlock:
 	bpf_struct_ops_map_put_progs(st_map);
@@ -616,7 +615,7 @@  static void __bpf_struct_ops_map_free(struct bpf_map *map)
 		bpf_struct_ops_map_put_progs(st_map);
 	bpf_map_area_free(st_map->links);
 	if (st_map->image) {
-		bpf_jit_free_exec(st_map->image);
+		arch_free_bpf_trampoline(st_map->image, PAGE_SIZE);
 		bpf_jit_uncharge_modmem(PAGE_SIZE);
 	}
 	bpf_map_area_free(st_map->uvalue);
@@ -691,7 +690,7 @@  static struct bpf_map *bpf_struct_ops_map_alloc(union bpf_attr *attr)
 		return ERR_PTR(ret);
 	}
 
-	st_map->image = bpf_jit_alloc_exec(PAGE_SIZE);
+	st_map->image = arch_alloc_bpf_trampoline(PAGE_SIZE);
 	if (!st_map->image) {
 		/* __bpf_struct_ops_map_free() uses st_map->image as flag
 		 * for "charged or not". In this case, we need to unchange
@@ -711,7 +710,6 @@  static struct bpf_map *bpf_struct_ops_map_alloc(union bpf_attr *attr)
 	}
 
 	mutex_init(&st_map->lock);
-	set_vm_flush_reset_perms(st_map->image);
 	bpf_map_init_from_attr(map, attr);
 
 	return map;
diff --git a/kernel/bpf/trampoline.c b/kernel/bpf/trampoline.c
index e114a1c7961e..5509bdf98067 100644
--- a/kernel/bpf/trampoline.c
+++ b/kernel/bpf/trampoline.c
@@ -254,7 +254,7 @@  bpf_trampoline_get_progs(const struct bpf_trampoline *tr, int *total, bool *ip_a
 static void bpf_tramp_image_free(struct bpf_tramp_image *im)
 {
 	bpf_image_ksym_del(&im->ksym);
-	bpf_jit_free_exec(im->image);
+	arch_free_bpf_trampoline(im->image, PAGE_SIZE);
 	bpf_jit_uncharge_modmem(PAGE_SIZE);
 	percpu_ref_exit(&im->pcref);
 	kfree_rcu(im, rcu);
@@ -365,10 +365,9 @@  static struct bpf_tramp_image *bpf_tramp_image_alloc(u64 key)
 		goto out_free_im;
 
 	err = -ENOMEM;
-	im->image = image = bpf_jit_alloc_exec(PAGE_SIZE);
+	im->image = image = arch_alloc_bpf_trampoline(PAGE_SIZE);
 	if (!image)
 		goto out_uncharge;
-	set_vm_flush_reset_perms(image);
 
 	err = percpu_ref_init(&im->pcref, __bpf_tramp_image_release, 0, GFP_KERNEL);
 	if (err)
@@ -381,7 +380,7 @@  static struct bpf_tramp_image *bpf_tramp_image_alloc(u64 key)
 	return im;
 
 out_free_image:
-	bpf_jit_free_exec(im->image);
+	arch_free_bpf_trampoline(im->image, PAGE_SIZE);
 out_uncharge:
 	bpf_jit_uncharge_modmem(PAGE_SIZE);
 out_free_im:
@@ -444,7 +443,7 @@  static int bpf_trampoline_update(struct bpf_trampoline *tr, bool lock_direct_mut
 	if (err < 0)
 		goto out_free;
 
-	set_memory_rox((long)im->image, 1);
+	arch_protect_bpf_trampoline(im->image, PAGE_SIZE);
 
 	WARN_ON(tr->cur_image && total == 0);
 	if (tr->cur_image)
@@ -465,8 +464,7 @@  static int bpf_trampoline_update(struct bpf_trampoline *tr, bool lock_direct_mut
 		tr->fops->trampoline = 0;
 
 		/* reset im->image memory attr for arch_prepare_bpf_trampoline */
-		set_memory_nx((long)im->image, 1);
-		set_memory_rw((long)im->image, 1);
+		arch_unprotect_bpf_trampoline(im->image, PAGE_SIZE);
 		goto again;
 	}
 #endif
@@ -1040,6 +1038,38 @@  arch_prepare_bpf_trampoline(struct bpf_tramp_image *im, void *image, void *image
 	return -ENOTSUPP;
 }
 
+void * __weak arch_alloc_bpf_trampoline(int size)
+{
+	void *image;
+
+	WARN_ON_ONCE(size > PAGE_SIZE || size <= 0);
+	image = bpf_jit_alloc_exec(PAGE_SIZE);
+	if (image)
+		set_vm_flush_reset_perms(image);
+	return image;
+}
+
+void __weak arch_free_bpf_trampoline(void *image, int size)
+{
+	/* bpf_jit_free_exec doesn't need "size", but
+	 * bpf_prog_pack_free() needs it.
+	 */
+	bpf_jit_free_exec(image);
+}
+
+void __weak arch_protect_bpf_trampoline(void *image, int size)
+{
+	WARN_ON_ONCE(size > PAGE_SIZE || size <= 0);
+	set_memory_rox((long)image, 1);
+}
+
+void __weak arch_unprotect_bpf_trampoline(void *image, int size)
+{
+	WARN_ON_ONCE(size > PAGE_SIZE || size <= 0);
+	set_memory_nx((long)image, 1);
+	set_memory_rw((long)image, 1);
+}
+
 static int __init init_trampolines(void)
 {
 	int i;