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authorJP Kobryn <inwardvessel@gmail.com>2023-03-22 12:47:54 -0700
committerAlexei Starovoitov <ast@kernel.org>2023-03-22 15:11:30 -0700
commitd7ba4cc900bf1eea2d8c807c6b1fc6bd61f41237 (patch)
tree980f432af2432a9480cdd981ca9b2b99491ea532 /kernel/bpf/cpumap.c
parent830154cdc57971b06f81d4ffc39b868e3d7693de (diff)
bpf: return long from bpf_map_ops funcs
This patch changes the return types of bpf_map_ops functions to long, where previously int was returned. Using long allows for bpf programs to maintain the sign bit in the absence of sign extension during situations where inlined bpf helper funcs make calls to the bpf_map_ops funcs and a negative error is returned. The definitions of the helper funcs are generated from comments in the bpf uapi header at `include/uapi/linux/bpf.h`. The return type of these helpers was previously changed from int to long in commit bdb7b79b4ce8. For any case where one of the map helpers call the bpf_map_ops funcs that are still returning 32-bit int, a compiler might not include sign extension instructions to properly convert the 32-bit negative value a 64-bit negative value. For example: bpf assembly excerpt of an inlined helper calling a kernel function and checking for a specific error: ; err = bpf_map_update_elem(&mymap, &key, &val, BPF_NOEXIST); ... 46: call 0xffffffffe103291c ; htab_map_update_elem ; if (err && err != -EEXIST) { 4b: cmp $0xffffffffffffffef,%rax ; cmp -EEXIST,%rax kernel function assembly excerpt of return value from `htab_map_update_elem` returning 32-bit int: movl $0xffffffef, %r9d ... movl %r9d, %eax ...results in the comparison: cmp $0xffffffffffffffef, $0x00000000ffffffef Fixes: bdb7b79b4ce8 ("bpf: Switch most helper return values from 32-bit int to 64-bit long") Tested-by: Eduard Zingerman <eddyz87@gmail.com> Signed-off-by: JP Kobryn <inwardvessel@gmail.com> Link: https://lore.kernel.org/r/20230322194754.185781-3-inwardvessel@gmail.com Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Diffstat (limited to 'kernel/bpf/cpumap.c')
-rw-r--r--kernel/bpf/cpumap.c8
1 files changed, 4 insertions, 4 deletions
diff --git a/kernel/bpf/cpumap.c b/kernel/bpf/cpumap.c
index 871809e71b4e..8ec18faa74ac 100644
--- a/kernel/bpf/cpumap.c
+++ b/kernel/bpf/cpumap.c
@@ -540,7 +540,7 @@ static void __cpu_map_entry_replace(struct bpf_cpu_map *cmap,
}
}
-static int cpu_map_delete_elem(struct bpf_map *map, void *key)
+static long cpu_map_delete_elem(struct bpf_map *map, void *key)
{
struct bpf_cpu_map *cmap = container_of(map, struct bpf_cpu_map, map);
u32 key_cpu = *(u32 *)key;
@@ -553,8 +553,8 @@ static int cpu_map_delete_elem(struct bpf_map *map, void *key)
return 0;
}
-static int cpu_map_update_elem(struct bpf_map *map, void *key, void *value,
- u64 map_flags)
+static long cpu_map_update_elem(struct bpf_map *map, void *key, void *value,
+ u64 map_flags)
{
struct bpf_cpu_map *cmap = container_of(map, struct bpf_cpu_map, map);
struct bpf_cpumap_val cpumap_value = {};
@@ -667,7 +667,7 @@ static int cpu_map_get_next_key(struct bpf_map *map, void *key, void *next_key)
return 0;
}
-static int cpu_map_redirect(struct bpf_map *map, u64 index, u64 flags)
+static long cpu_map_redirect(struct bpf_map *map, u64 index, u64 flags)
{
return __bpf_xdp_redirect_map(map, index, flags, 0,
__cpu_map_lookup_elem);