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Date: Sat, 12 Feb 2022 01:23:02 +0000 From: Song Liu <songliubraving@...com> To: Jakub Kicinski <kuba@...nel.org> CC: Song Liu <song@...nel.org>, "bpf@...r.kernel.org" <bpf@...r.kernel.org>, "netdev@...r.kernel.org" <netdev@...r.kernel.org>, "ast@...nel.org" <ast@...nel.org>, "daniel@...earbox.net" <daniel@...earbox.net>, "andrii@...nel.org" <andrii@...nel.org>, Kernel Team <Kernel-team@...com>, "sfr@...b.auug.org.au" <sfr@...b.auug.org.au> Subject: Re: [PATCH bpf-next] bpf: fix bpf_prog_pack build for ppc64_defconfig > On Feb 11, 2022, at 3:54 PM, Jakub Kicinski <kuba@...nel.org> wrote: > > On Thu, 10 Feb 2022 17:49:15 -0800 Song Liu wrote: >> bpf_prog_pack causes build error with powerpc ppc64_defconfig: >> >> kernel/bpf/core.c:830:23: error: variably modified 'bitmap' at file scope >> 830 | unsigned long bitmap[BITS_TO_LONGS(BPF_PROG_CHUNK_COUNT)]; >> | ^~~~~~ > > No idea what this error means but... v2 (which has applied to bpf-next) has more information about this. Basically, BPF_PROG_CHUNK_COUNT contains a global variable for ppc. > >> Fix it by turning bitmap into a 0-length array. >> >> Fixes: 57631054fae6 ("bpf: Introduce bpf_prog_pack allocator") >> Reported-by: Stephen Rothwell <sfr@...b.auug.org.au> >> Signed-off-by: Song Liu <song@...nel.org> >> --- >> kernel/bpf/core.c | 4 ++-- >> 1 file changed, 2 insertions(+), 2 deletions(-) >> >> diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c >> index 42d96549a804..44623c9b5bb1 100644 >> --- a/kernel/bpf/core.c >> +++ b/kernel/bpf/core.c >> @@ -827,7 +827,7 @@ int bpf_jit_add_poke_descriptor(struct bpf_prog *prog, >> struct bpf_prog_pack { >> struct list_head list; >> void *ptr; >> - unsigned long bitmap[BITS_TO_LONGS(BPF_PROG_CHUNK_COUNT)]; >> + unsigned long bitmap[]; > > This is really asking to be DECLARE_BITMAP(), does that fix the issue? I am afraid DECLARE_BITMAP() will hit the same error here. > >> }; >> >> #define BPF_PROG_MAX_PACK_PROG_SIZE BPF_PROG_PACK_SIZE >> @@ -840,7 +840,7 @@ static struct bpf_prog_pack *alloc_new_pack(void) >> { >> struct bpf_prog_pack *pack; >> >> - pack = kzalloc(sizeof(*pack), GFP_KERNEL); >> + pack = kzalloc(sizeof(*pack) + BITS_TO_BYTES(BPF_PROG_CHUNK_COUNT), GFP_KERNEL); > > Otherwise you may want to use struct_size(pack, bitmap, BITS...). > One of the bots will soon send us a patch to do that. Since v2 has applied to bpf-next, I will send another follow-up patch to use struct_size, unless some bot get it first. Thanks, Song
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