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bpf: return long from bpf_map_ops funcs

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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 bdb7b79b4c. 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: bdb7b79b4c ("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>
This commit is contained in:
JP Kobryn
2023-03-22 12:47:54 -07:00
committed by Alexei Starovoitov
parent 830154cdc5
commit d7ba4cc900
21 changed files with 110 additions and 110 deletions
Download Patch File Download Diff File Expand all files Collapse all files
kernel/bpf/queue_stack_maps.c
+11 -11
View File
@@ -95,7 +95,7 @@ static void queue_stack_map_free(struct bpf_map *map)
bpf_map_area_free(qs);
}
static int __queue_map_get(struct bpf_map *map, void *value, bool delete)
static long __queue_map_get(struct bpf_map *map, void *value, bool delete)
{
struct bpf_queue_stack *qs = bpf_queue_stack(map);
unsigned long flags;
@@ -124,7 +124,7 @@ out:
}
static int __stack_map_get(struct bpf_map *map, void *value, bool delete)
static long __stack_map_get(struct bpf_map *map, void *value, bool delete)
{
struct bpf_queue_stack *qs = bpf_queue_stack(map);
unsigned long flags;
@@ -156,32 +156,32 @@ out:
}
/* Called from syscall or from eBPF program */
static int queue_map_peek_elem(struct bpf_map *map, void *value)
static long queue_map_peek_elem(struct bpf_map *map, void *value)
{
return __queue_map_get(map, value, false);
}
/* Called from syscall or from eBPF program */
static int stack_map_peek_elem(struct bpf_map *map, void *value)
static long stack_map_peek_elem(struct bpf_map *map, void *value)
{
return __stack_map_get(map, value, false);
}
/* Called from syscall or from eBPF program */
static int queue_map_pop_elem(struct bpf_map *map, void *value)
static long queue_map_pop_elem(struct bpf_map *map, void *value)
{
return __queue_map_get(map, value, true);
}
/* Called from syscall or from eBPF program */
static int stack_map_pop_elem(struct bpf_map *map, void *value)
static long stack_map_pop_elem(struct bpf_map *map, void *value)
{
return __stack_map_get(map, value, true);
}
/* Called from syscall or from eBPF program */
static int queue_stack_map_push_elem(struct bpf_map *map, void *value,
u64 flags)
static long queue_stack_map_push_elem(struct bpf_map *map, void *value,
u64 flags)
{
struct bpf_queue_stack *qs = bpf_queue_stack(map);
unsigned long irq_flags;
@@ -227,14 +227,14 @@ static void *queue_stack_map_lookup_elem(struct bpf_map *map, void *key)
}
/* Called from syscall or from eBPF program */
static int queue_stack_map_update_elem(struct bpf_map *map, void *key,
void *value, u64 flags)
static long queue_stack_map_update_elem(struct bpf_map *map, void *key,
void *value, u64 flags)
{
return -EINVAL;
}
/* Called from syscall or from eBPF program */
static int queue_stack_map_delete_elem(struct bpf_map *map, void *key)
static long queue_stack_map_delete_elem(struct bpf_map *map, void *key)
{
return -EINVAL;
}