| Message ID | 20201026210355.3885283-1-arnd@kernel.org (mailing list archive) |
|---|---|
| State | New, archived |
| Delegated to: | BPF |
| Headers | show |
| Series | bpf: fix incorrect initialization of bpf_ctx_convert_map | expand |
On Mon, Oct 26, 2020 at 2:04 PM Arnd Bergmann <arnd@kernel.org> wrote: > > From: Arnd Bergmann <arnd@arndb.de> > > gcc -Wextra points out that a field may get overridden in some > configurations such as x86 allmodconfig, when the next index after the one > that has been assigned last already had a value, in this case for index > BPF_PROG_TYPE_SK_LOOKUP, which comes after BPF_PROG_TYPE_LSM in the list: > > kernel/bpf/btf.c:4225:2: warning: initialized field overwritten [-Woverride-init] > 4225 | 0, /* avoid empty array */ > | ^ > kernel/bpf/btf.c:4225:2: note: (near initialization for 'bpf_ctx_convert_map[30]') > > Move the zero-initializer first instead. This avoids the warning since > nothing else uses index 0, and the last element does not have to be zero. Wouldn't it be cleaner and more explicit to add __MAX_BPF_PROG_TYPE to enum bpf_prog_type in include/uapi/linux/bpf.h, similarly to how we do it with enum bpf_attach_type? Then just specify the size of the array here explicitly? Unless we are trying to save a few bytes for more minimal configurations where some BPF program types are not used (but still defined in an enum)? > > Fixes: e9ddbb7707ff ("bpf: Introduce SK_LOOKUP program type with a dedicated attach point") > Fixes: 4c80c7bc583a ("bpf: Fix build in minimal configurations, again") > Signed-off-by: Arnd Bergmann <arnd@arndb.de> > --- > kernel/bpf/btf.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c > index ed7d02e8bc93..2a4a4aeeaac1 100644 > --- a/kernel/bpf/btf.c > +++ b/kernel/bpf/btf.c > @@ -4218,11 +4218,11 @@ enum { > __ctx_convert_unused, /* to avoid empty enum in extreme .config */ > }; > static u8 bpf_ctx_convert_map[] = { > + [0] = 0, /* avoid empty array */ > #define BPF_PROG_TYPE(_id, _name, prog_ctx_type, kern_ctx_type) \ > [_id] = __ctx_convert##_id, > #include <linux/bpf_types.h> > #undef BPF_PROG_TYPE > - 0, /* avoid empty array */ > }; > #undef BPF_MAP_TYPE > #undef BPF_LINK_TYPE > -- > 2.27.0 >
diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c index ed7d02e8bc93..2a4a4aeeaac1 100644 --- a/kernel/bpf/btf.c +++ b/kernel/bpf/btf.c @@ -4218,11 +4218,11 @@ enum { __ctx_convert_unused, /* to avoid empty enum in extreme .config */ }; static u8 bpf_ctx_convert_map[] = { + [0] = 0, /* avoid empty array */ #define BPF_PROG_TYPE(_id, _name, prog_ctx_type, kern_ctx_type) \ [_id] = __ctx_convert##_id, #include <linux/bpf_types.h> #undef BPF_PROG_TYPE - 0, /* avoid empty array */ }; #undef BPF_MAP_TYPE #undef BPF_LINK_TYPE