bpf: Fix build in minimal configurations, again

Message ID 20191210203553.2941035-1-arnd@arndb.de
State Accepted
Commit 4c80c7bc583a87ded5f61906f81256b57c795806
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Series
  • bpf: Fix build in minimal configurations, again
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Commit Message

Arnd Bergmann Dec. 10, 2019, 8:35 p.m.
Building with -Werror showed another failure:

kernel/bpf/btf.c: In function 'btf_get_prog_ctx_type.isra.31':
kernel/bpf/btf.c:3508:63: error: array subscript 0 is above array bounds of 'u8[0]' {aka 'unsigned char[0]'} [-Werror=array-bounds]
  ctx_type = btf_type_member(conv_struct) + bpf_ctx_convert_map[prog_type] * 2;

I don't actually understand why the array is empty, but a similar
fix has addressed a related problem, so I suppose we can do the
same thing here.

Fixes: ce27709b8162 ("bpf: Fix build in minimal configurations")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>

---
 kernel/bpf/btf.c | 1 +
 1 file changed, 1 insertion(+)

-- 
2.20.0

Comments

Martin Lau Dec. 10, 2019, 11:34 p.m. | #1
On Tue, Dec 10, 2019 at 09:35:46PM +0100, Arnd Bergmann wrote:
> Building with -Werror showed another failure:

> 

> kernel/bpf/btf.c: In function 'btf_get_prog_ctx_type.isra.31':

> kernel/bpf/btf.c:3508:63: error: array subscript 0 is above array bounds of 'u8[0]' {aka 'unsigned char[0]'} [-Werror=array-bounds]

>   ctx_type = btf_type_member(conv_struct) + bpf_ctx_convert_map[prog_type] * 2;

> 

> I don't actually understand why the array is empty, but a similar

> fix has addressed a related problem, so I suppose we can do the

> same thing here.

> 

> Fixes: ce27709b8162 ("bpf: Fix build in minimal configurations")

> Signed-off-by: Arnd Bergmann <arnd@arndb.de>

> ---

>  kernel/bpf/btf.c | 1 +

>  1 file changed, 1 insertion(+)

> 

> diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c

> index 7d40da240891..ed2075884724 100644

> --- a/kernel/bpf/btf.c

> +++ b/kernel/bpf/btf.c

> @@ -3470,6 +3470,7 @@ static u8 bpf_ctx_convert_map[] = {

>  	[_id] = __ctx_convert##_id,

>  #include <linux/bpf_types.h>

>  #undef BPF_PROG_TYPE

> +	0, /* avoid empty array */

If bpf_types.h is empty, the prog should have already failed
earlier in find_prog_type() in syscall.c, so 0 here should
be fine.

Acked-by: Martin KaFai Lau <kafai@fb.com>
Daniel Borkmann Dec. 11, 2019, 1 p.m. | #2
On Tue, Dec 10, 2019 at 09:35:46PM +0100, Arnd Bergmann wrote:
> Building with -Werror showed another failure:

> 

> kernel/bpf/btf.c: In function 'btf_get_prog_ctx_type.isra.31':

> kernel/bpf/btf.c:3508:63: error: array subscript 0 is above array bounds of 'u8[0]' {aka 'unsigned char[0]'} [-Werror=array-bounds]

>   ctx_type = btf_type_member(conv_struct) + bpf_ctx_convert_map[prog_type] * 2;

> 

> I don't actually understand why the array is empty, but a similar

> fix has addressed a related problem, so I suppose we can do the

> same thing here.

> 

> Fixes: ce27709b8162 ("bpf: Fix build in minimal configurations")

> Signed-off-by: Arnd Bergmann <arnd@arndb.de>


Applied, thanks!

Patch

diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
index 7d40da240891..ed2075884724 100644
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -3470,6 +3470,7 @@  static u8 bpf_ctx_convert_map[] = {
 	[_id] = __ctx_convert##_id,
 #include <linux/bpf_types.h>
 #undef BPF_PROG_TYPE
+	0, /* avoid empty array */
 };
 #undef BPF_MAP_TYPE