Messages in this thread | | | Date | Fri, 15 Mar 2019 10:24:28 -0700 | From | Stanislav Fomichev <> | Subject | Re: [PATCH] tcp: don't use __constant_cpu_to_be32 |
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On 03/15, Sergey Senozhatsky wrote: > On (03/14/19 05:42), Eric Dumazet wrote: > > > cpu_to_be32() is capable enough to detect __builtin_constant_p() > > > and to use an appropriate compile time ___constant_swahb32() > > > function. See my recent commit a0517a0f7ef23 ("selftests/bpf: use __bpf_constant_htons in test_prog.c") where compiler was not smart enough to figure it out (you can google similar issues for GCC < 4.8).
> > > > > > So we can use cpu_to_be32() instead of __constant_cpu_to_be32(). > > > > > > I dunno, this is uapi, this might break user space for some funky compiler ? > > I do not even know if cpu_to_be32() _is_ uapi. > > Hmm, excellent point. > > Looking at > > if_pppox.h:#define PTT_EOL __cpu_to_be16(0x0000) > if_pppox.h:#define PTT_SRV_NAME __cpu_to_be16(0x0101) > if_pppox.h:#define PTT_AC_NAME __cpu_to_be16(0x0102) > if_pppox.h:#define PTT_HOST_UNIQ __cpu_to_be16(0x0103) > if_pppox.h:#define PTT_AC_COOKIE __cpu_to_be16(0x0104) > if_pppox.h:#define PTT_VENDOR __cpu_to_be16(0x0105) > if_pppox.h:#define PTT_RELAY_SID __cpu_to_be16(0x0110) > if_pppox.h:#define PTT_SRV_ERR __cpu_to_be16(0x0201) > if_pppox.h:#define PTT_SYS_ERR __cpu_to_be16(0x0202) > if_pppox.h:#define PTT_GEN_ERR __cpu_to_be16(0x0203) > if_tunnel.h:#define GRE_CSUM __cpu_to_be16(0x8000) > if_tunnel.h:#define GRE_ROUTING __cpu_to_be16(0x4000) > if_tunnel.h:#define GRE_KEY __cpu_to_be16(0x2000) > if_tunnel.h:#define GRE_SEQ __cpu_to_be16(0x1000) > if_tunnel.h:#define GRE_STRICT __cpu_to_be16(0x0800) > if_tunnel.h:#define GRE_REC __cpu_to_be16(0x0700) > if_tunnel.h:#define GRE_ACK __cpu_to_be16(0x0080) > if_tunnel.h:#define GRE_FLAGS __cpu_to_be16(0x0078) > if_tunnel.h:#define GRE_VERSION __cpu_to_be16(0x0007) > if_tunnel.h:#define GRE_VERSION_0 __cpu_to_be16(0x0000) > if_tunnel.h:#define GRE_VERSION_1 __cpu_to_be16(0x0001) > if_tunnel.h:#define GRE_PROTO_PPP __cpu_to_be16(0x880b) > > You are right, probably would need __cpu_to_be32, which also does > the constant folding. > > =-=-=-=-= > > Subject: [PATCH] tcp: don't use __constant_cpu_to_be32 > > __cpu_to_be32() can detect __builtin_constant_p() at compile time. > So we can use __cpu_to_be32() instead of __constant_cpu_to_be32(). > > Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com> > --- > include/uapi/linux/tcp.h | 20 ++++++++++---------- > 1 file changed, 10 insertions(+), 10 deletions(-) > > diff --git a/include/uapi/linux/tcp.h b/include/uapi/linux/tcp.h > index 8bb6cc5f3235..cf9c246a59c8 100644 > --- a/include/uapi/linux/tcp.h > +++ b/include/uapi/linux/tcp.h > @@ -70,16 +70,16 @@ union tcp_word_hdr { > #define tcp_flag_word(tp) ( ((union tcp_word_hdr *)(tp))->words [3]) > > enum { > - TCP_FLAG_CWR = __constant_cpu_to_be32(0x00800000), > - TCP_FLAG_ECE = __constant_cpu_to_be32(0x00400000), > - TCP_FLAG_URG = __constant_cpu_to_be32(0x00200000), > - TCP_FLAG_ACK = __constant_cpu_to_be32(0x00100000), > - TCP_FLAG_PSH = __constant_cpu_to_be32(0x00080000), > - TCP_FLAG_RST = __constant_cpu_to_be32(0x00040000), > - TCP_FLAG_SYN = __constant_cpu_to_be32(0x00020000), > - TCP_FLAG_FIN = __constant_cpu_to_be32(0x00010000), > - TCP_RESERVED_BITS = __constant_cpu_to_be32(0x0F000000), > - TCP_DATA_OFFSET = __constant_cpu_to_be32(0xF0000000) > + TCP_FLAG_CWR = __cpu_to_be32(0x00800000), > + TCP_FLAG_ECE = __cpu_to_be32(0x00400000), > + TCP_FLAG_URG = __cpu_to_be32(0x00200000), > + TCP_FLAG_ACK = __cpu_to_be32(0x00100000), > + TCP_FLAG_PSH = __cpu_to_be32(0x00080000), > + TCP_FLAG_RST = __cpu_to_be32(0x00040000), > + TCP_FLAG_SYN = __cpu_to_be32(0x00020000), > + TCP_FLAG_FIN = __cpu_to_be32(0x00010000), > + TCP_RESERVED_BITS = __cpu_to_be32(0x0F000000), > + TCP_DATA_OFFSET = __cpu_to_be32(0xF0000000) > }; > > /* > -- > 2.21.0 >
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