[RFC bpf-next 1/3] bpf: add BPF_F_COMPARE flag and compare fields to map elem UAPI

[Gyutae Bae]

From: Gyutae Bae <gyutae.bae@xxxxxxxxxxxxx>

Introduce the UAPI surface for a compare-and-delete primitive: a new map
flag BPF_F_COMPARE plus compare/compare_offset/compare_size fields let
a delete request name an expected value region.  Behaviour is wired up in
the following patch; this adds the flag and fields (kernel + tools/ copy)
only.

Co-developed-by: Minsu Jeon <minsu.jeon@xxxxxxxxxxxxx>
Signed-off-by: Minsu Jeon <minsu.jeon@xxxxxxxxxxxxx>
Co-developed-by: Siwan Kim <siwan.kim@xxxxxxxxxxxxx>
Signed-off-by: Siwan Kim <siwan.kim@xxxxxxxxxxxxx>
Co-developed-by: Jonghyeon Kim <jong-hyeon.kim@xxxxxxxxxxxxx>
Signed-off-by: Jonghyeon Kim <jong-hyeon.kim@xxxxxxxxxxxxx>
Signed-off-by: Gyutae Bae <gyutae.bae@xxxxxxxxxxxxx>
---
 include/uapi/linux/bpf.h       | 6 +++++-
 tools/include/uapi/linux/bpf.h | 6 +++++-
 2 files changed, 10 insertions(+), 2 deletions(-)

diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 89b36de5fdbb..4705b02fb6a4 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -1397,7 +1397,7 @@ enum bpf_addr_space_cast {
 	BPF_ADDR_SPACE_CAST = 1,
 };
 
-/* flags for BPF_MAP_UPDATE_ELEM command */
+/* flags for BPF_MAP_UPDATE_ELEM / BPF_MAP_DELETE_ELEM commands */
 enum {
 	BPF_ANY		= 0, /* create new element or update existing */
 	BPF_NOEXIST	= 1, /* create new element if it didn't exist */
@@ -1405,6 +1405,7 @@ enum {
 	BPF_F_LOCK	= 4, /* spin_lock-ed map_lookup/map_update */
 	BPF_F_CPU	= 8, /* cpu flag for percpu maps, upper 32-bit of flags is a cpu number */
 	BPF_F_ALL_CPUS	= 16, /* update value across all CPUs for percpu maps */
+	BPF_F_COMPARE	= 32, /* compare-and-delete: delete elem only if value region == compare */
 };
 
 /* flags for BPF_MAP_CREATE command */
@@ -1586,6 +1587,9 @@ union bpf_attr {
 			__aligned_u64 next_key;
 		};
 		__u64		flags;
+		__aligned_u64	compare;	/* user ptr to expected bytes (BPF_F_COMPARE) */
+		__u32		compare_offset;	/* start offset within value */
+		__u32		compare_size;	/* bytes to compare; 0 == whole value */
 	};
 
 	struct { /* struct used by BPF_MAP_*_BATCH commands */
diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index 89b36de5fdbb..4705b02fb6a4 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -1397,7 +1397,7 @@ enum bpf_addr_space_cast {
 	BPF_ADDR_SPACE_CAST = 1,
 };
 
-/* flags for BPF_MAP_UPDATE_ELEM command */
+/* flags for BPF_MAP_UPDATE_ELEM / BPF_MAP_DELETE_ELEM commands */
 enum {
 	BPF_ANY		= 0, /* create new element or update existing */
 	BPF_NOEXIST	= 1, /* create new element if it didn't exist */
@@ -1405,6 +1405,7 @@ enum {
 	BPF_F_LOCK	= 4, /* spin_lock-ed map_lookup/map_update */
 	BPF_F_CPU	= 8, /* cpu flag for percpu maps, upper 32-bit of flags is a cpu number */
 	BPF_F_ALL_CPUS	= 16, /* update value across all CPUs for percpu maps */
+	BPF_F_COMPARE	= 32, /* compare-and-delete: delete elem only if value region == compare */
 };
 
 /* flags for BPF_MAP_CREATE command */
@@ -1586,6 +1587,9 @@ union bpf_attr {
 			__aligned_u64 next_key;
 		};
 		__u64		flags;
+		__aligned_u64	compare;	/* user ptr to expected bytes (BPF_F_COMPARE) */
+		__u32		compare_offset;	/* start offset within value */
+		__u32		compare_size;	/* bytes to compare; 0 == whole value */
 	};
 
 	struct { /* struct used by BPF_MAP_*_BATCH commands */
-- 
2.39.5 (Apple Git-154)