Re: [PATCH] nfp: bpf: improve handling for disabled BPF syscall
From: Arnd Bergmann
Date: Fri, 23 Sep 2016 22:23:59 +0200
> I stumbled over a new warning during randconfig testing,
> with CONFIG_BPF_SYSCALL disabled:
>
> drivers/net/ethernet/netronome/nfp/nfp_net_offload.c: In function
> 'nfp_net_bpf_offload':
> drivers/net/ethernet/netronome/nfp/nfp_net_offload.c:263:3: error: '*((void
> *)&res+4)' may be used uninitialized in this function
> [-Werror=maybe-uninitialized]
> drivers/net/ethernet/netronome/nfp/nfp_net_offload.c:263:3: error:
> 'res.n_instr' may be used uninitialized in this function
> [-Werror=maybe-uninitialized]
>
> As far as I can tell, this is a false positive caused by the compiler
> getting confused about a function that is partially inlined, but it's
> easy to avoid while improving the code:
>
> The nfp_bpf_jit() stub helper for that configuration is unusual as it
> is defined in a header file but not marked 'static inline'. By moving
> the compile-time check into the caller using the IS_ENABLED() macro,
> we can remove that stub and simplify the nfp_net_bpf_offload_prepare()
> function enough to unconfuse the compiler.
>
> Fixes: 7533fdc0f77f ("nfp: bpf: add hardware bpf offload")
> Signed-off-by: Arnd Bergmann
Applied, thanks.
Re: [PATCH] nfp: bpf: improve handling for disabled BPF syscall
On Fri, 23 Sep 2016 22:23:59 +0200, Arnd Bergmann wrote:
> I stumbled over a new warning during randconfig testing,
> with CONFIG_BPF_SYSCALL disabled:
>
> drivers/net/ethernet/netronome/nfp/nfp_net_offload.c: In function
> 'nfp_net_bpf_offload':
> drivers/net/ethernet/netronome/nfp/nfp_net_offload.c:263:3: error: '*((void
> *)&res+4)' may be used uninitialized in this function
> [-Werror=maybe-uninitialized]
> drivers/net/ethernet/netronome/nfp/nfp_net_offload.c:263:3: error:
> 'res.n_instr' may be used uninitialized in this function
> [-Werror=maybe-uninitialized]
>
> As far as I can tell, this is a false positive caused by the compiler
> getting confused about a function that is partially inlined, but it's
> easy to avoid while improving the code:
>
> The nfp_bpf_jit() stub helper for that configuration is unusual as it
> is defined in a header file but not marked 'static inline'. By moving
> the compile-time check into the caller using the IS_ENABLED() macro,
> we can remove that stub and simplify the nfp_net_bpf_offload_prepare()
> function enough to unconfuse the compiler.
>
> Fixes: 7533fdc0f77f ("nfp: bpf: add hardware bpf offload")
> Signed-off-by: Arnd Bergmann
Thanks Arnd! static inline definitely missing there but if we can
depend on dead code elimination to remove the symbol that's even cooler!
Acked-by: Jakub Kicinski
[PATCH] nfp: bpf: improve handling for disabled BPF syscall
I stumbled over a new warning during randconfig testing,
with CONFIG_BPF_SYSCALL disabled:
drivers/net/ethernet/netronome/nfp/nfp_net_offload.c: In function
'nfp_net_bpf_offload':
drivers/net/ethernet/netronome/nfp/nfp_net_offload.c:263:3: error: '*((void
*)&res+4)' may be used uninitialized in this function
[-Werror=maybe-uninitialized]
drivers/net/ethernet/netronome/nfp/nfp_net_offload.c:263:3: error:
'res.n_instr' may be used uninitialized in this function
[-Werror=maybe-uninitialized]
As far as I can tell, this is a false positive caused by the compiler
getting confused about a function that is partially inlined, but it's
easy to avoid while improving the code:
The nfp_bpf_jit() stub helper for that configuration is unusual as it
is defined in a header file but not marked 'static inline'. By moving
the compile-time check into the caller using the IS_ENABLED() macro,
we can remove that stub and simplify the nfp_net_bpf_offload_prepare()
function enough to unconfuse the compiler.
Fixes: 7533fdc0f77f ("nfp: bpf: add hardware bpf offload")
Signed-off-by: Arnd Bergmann
---
drivers/net/ethernet/netronome/nfp/nfp_bpf.h | 10 --
drivers/net/ethernet/netronome/nfp/nfp_net_offload.c | 3 +++
2 files changed, 3 insertions(+), 10 deletions(-)
diff --git a/drivers/net/ethernet/netronome/nfp/nfp_bpf.h
b/drivers/net/ethernet/netronome/nfp/nfp_bpf.h
index fc220cd04115..87aa8a3e9112 100644
--- a/drivers/net/ethernet/netronome/nfp/nfp_bpf.h
+++ b/drivers/net/ethernet/netronome/nfp/nfp_bpf.h
@@ -192,20 +192,10 @@ struct nfp_bpf_result {
bool dense_mode;
};
-#ifdef CONFIG_BPF_SYSCALL
int
nfp_bpf_jit(struct bpf_prog *filter, void *prog, enum nfp_bpf_action_type act,
unsigned int prog_start, unsigned int prog_done,
unsigned int prog_sz, struct nfp_bpf_result *res);
-#else
-int
-nfp_bpf_jit(struct bpf_prog *filter, void *prog, enum nfp_bpf_action_type act,
- unsigned int prog_start, unsigned int prog_done,
- unsigned int prog_sz, struct nfp_bpf_result *res)
-{
- return -ENOTSUPP;
-}
-#endif
int nfp_prog_verify(struct nfp_prog *nfp_prog, struct bpf_prog *prog);
diff --git a/drivers/net/ethernet/netronome/nfp/nfp_net_offload.c
b/drivers/net/ethernet/netronome/nfp/nfp_net_offload.c
index 43f42f842eda..8acfb631a0ea 100644
--- a/drivers/net/ethernet/netronome/nfp/nfp_net_offload.c
+++ b/drivers/net/ethernet/netronome/nfp/nfp_net_offload.c
@@ -148,6 +148,9 @@ nfp_net_bpf_offload_prepare(struct nfp_net *nn,
unsigned int max_mtu;
int ret;
+ if (!IS_ENABLED(CONFIG_BPF_SYSCALL))
+ return -ENOTSUPP;
+
ret = nfp_net_bpf_get_act(nn, cls_bpf);
if (ret < 0)
return ret;
--
2.9.0
