diff mbox series

[bpf-next,v3,1/2] bpf: Support default .validate() and .update() behavior for struct_ops links

Message ID 20230814185908.700553-2-void@manifault.com (mailing list archive)
State Accepted
Commit 8ba651ed7fa1641f7c4941b79f2e3dd4ddb58aec
Delegated to: BPF
Headers show
Series Update and document struct_ops | expand

Checks

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bpf/vmtest-bpf-next-PR success PR summary
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bpf/vmtest-bpf-next-VM_Test-3 success Logs for build for s390x with gcc
bpf/vmtest-bpf-next-VM_Test-7 success Logs for test_maps on aarch64 with gcc
bpf/vmtest-bpf-next-VM_Test-9 success Logs for test_maps on x86_64 with gcc
bpf/vmtest-bpf-next-VM_Test-10 success Logs for test_maps on x86_64 with llvm-16
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bpf/vmtest-bpf-next-VM_Test-25 success Logs for test_verifier on aarch64 with gcc
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bpf/vmtest-bpf-next-VM_Test-29 success Logs for veristat
bpf/vmtest-bpf-next-VM_Test-26 success Logs for test_verifier on s390x with gcc
bpf/vmtest-bpf-next-VM_Test-16 success Logs for test_progs_no_alu32 on s390x with gcc
bpf/vmtest-bpf-next-VM_Test-12 success Logs for test_progs on s390x with gcc
bpf/vmtest-bpf-next-VM_Test-8 success Logs for test_maps on s390x with gcc
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: 1333 this patch: 1333
netdev/cc_maintainers success CCed 13 of 13 maintainers
netdev/build_clang success Errors and warnings before: 1353 this patch: 1353
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: 1356 this patch: 1356
netdev/checkpatch success total: 0 errors, 0 warnings, 0 checks, 33 lines checked
netdev/kdoc success Errors and warnings before: 0 this patch: 0
netdev/source_inline success Was 0 now: 0

Commit Message

David Vernet Aug. 14, 2023, 6:59 p.m. UTC 
Currently, if a struct_ops map is loaded with BPF_F_LINK, it must also
define the .validate() and .update() callbacks in its corresponding
struct bpf_struct_ops in the kernel. Enabling struct_ops link is useful
in its own right to ensure that the map is unloaded if an application
crashes. For example, with sched_ext, we want to automatically unload
the host-wide scheduler if the application crashes. We would likely
never support updating elements of a sched_ext struct_ops map, so we'd
have to implement these callbacks showing that they _can't_ support
element updates just to benefit from the basic lifetime management of
struct_ops links.

Let's enable struct_ops maps to work with BPF_F_LINK even if they
haven't defined these callbacks, by assuming that a struct_ops map
element cannot be updated by default.

Acked-by: Kui-Feng Lee <thinker.li@gmail.com>
Signed-off-by: David Vernet <void@manifault.com>
---
 kernel/bpf/bpf_struct_ops.c | 15 +++++++++------
 1 file changed, 9 insertions(+), 6 deletions(-)
diff mbox series

Patch

diff --git a/kernel/bpf/bpf_struct_ops.c b/kernel/bpf/bpf_struct_ops.c
index eaff04eefb31..fdc3e8705a3c 100644
--- a/kernel/bpf/bpf_struct_ops.c
+++ b/kernel/bpf/bpf_struct_ops.c
@@ -509,9 +509,12 @@  static long bpf_struct_ops_map_update_elem(struct bpf_map *map, void *key,
 	}
 
 	if (st_map->map.map_flags & BPF_F_LINK) {
-		err = st_ops->validate(kdata);
-		if (err)
-			goto reset_unlock;
+		err = 0;
+		if (st_ops->validate) {
+			err = st_ops->validate(kdata);
+			if (err)
+				goto reset_unlock;
+		}
 		set_memory_rox((long)st_map->image, 1);
 		/* Let bpf_link handle registration & unregistration.
 		 *
@@ -663,9 +666,6 @@  static struct bpf_map *bpf_struct_ops_map_alloc(union bpf_attr *attr)
 	if (attr->value_size != vt->size)
 		return ERR_PTR(-EINVAL);
 
-	if (attr->map_flags & BPF_F_LINK && (!st_ops->validate || !st_ops->update))
-		return ERR_PTR(-EOPNOTSUPP);
-
 	t = st_ops->type;
 
 	st_map_size = sizeof(*st_map) +
@@ -823,6 +823,9 @@  static int bpf_struct_ops_map_link_update(struct bpf_link *link, struct bpf_map
 	if (!bpf_struct_ops_valid_to_reg(new_map))
 		return -EINVAL;
 
+	if (!st_map->st_ops->update)
+		return -EOPNOTSUPP;
+
 	mutex_lock(&update_mutex);
 
 	old_map = rcu_dereference_protected(st_link->map, lockdep_is_held(&update_mutex));