Networking defect for ARM¡¯bsp intcp_input().

[Joel Sherrill]

ray wrote:

>Hi
>In fact, the code only wrong when ENDIAN is considered
>If change the code :
>#if BYTE_ORDER == LITTLE_ENDIAN
>	u_int	th_x2:4,		/* (unused) */
>		th_off:4;		/* data offset */
>#endif
>#if BYTE_ORDER == BIG_ENDIAN
>	u_int	th_off:4,		/* data offset */
>		th_x2:4;		/* (unused) */
>#endif
>
>To:
>	u_int	th_x2:4,		/* (unused) */
>		th_off:4;		/* data offset */
>
>the code works fine
>
>It also interesting that I find that both the following code would not compile:
>A: only use little endian
>#if BYTE_ORDER == LITTLE_ENDIAN
>	u_int	th_x2:4,		/* (unused) */
>		th_off:4;		/* data offset */
>#endif
>
>B: only use big
>#if BYTE_ORDER == BIG_ENDIAN
>	u_int	th_off:4,		/* data offset */
>		th_x2:4;		/* (unused) */
>#endif
>Both instance can not find member: th_off
>
>
>The question is:
>1 why ¡°#if BYTE_ORDER¡±used here, byte order base on 8bit byte, not 4bit, am I right?
>2 The arm-gcc always generate little endian code by default, but why BYTE_ORDER == LITTLE_ENDIAN fails?
>
>  
>
Can you check if BYTE_ORDER, LITTLE_ENDIAN, and BIG_ENDIAN are defined 
as expected
based upon the header files included?

Maybe something isn't right -- incomplete .h files or something not 
tripped as expected.

---joel

>
>My gcc(downloaded from rtems.com) configuration is:
>$ arm-rtems-gcc -v
>Reading specs from /opt/rtems-4.6/lib/gcc-lib/arm-rtems/3.2.3/specs
>Configured with: ../gcc-3.2.3/configure --build=i686-pc-linux-gnu --host=i386-cygwin --target=ar
>m-rtems --with-gnu-as --with-gnu-ld --with-newlib --verbose --with-system-zlib --disable-nls --e
>nable-version-specific-runtime-libs --enable-threads=rtems --prefix=/opt/rtems-4.6 --enable-lang
>uages=c,c++
>Thread model: rtems
>gcc version 3.2.3 (OAR Corporation gcc-3.2.3-20040420/newlib-1.11.0-20030605-4)
>
>I check the latest Netbsd code, ¡°#if BYTE_ORDER¡± still remains, there should be a reason, but I can not figure out.
>
>
>Thanks & Best Regards !
>------------------
>ray
>2006-07-04
>
>-------------------------------------------------------------
>from£ºRalf Corsepius
>Date£º2006-07-04 17:19:59
>to£ºray
>CC£ºRTEMS Users
>Subject£ºRe: Networking defect for ARM¡¯bsp intcp_input().
>
>On Tue, 2006-07-04 at 00:13 +0800, ray wrote:
>  
>
>>Hi:
>>    
>>
>
>  
>
>>Seems we get the unused data instead of th_off.
>>    
>>
>
>If what you say is true, it should be reproducible with the code samples
>below. I don't "speak arm-asm", so I can't judge.
>
>Compile the code snippets with:
>arm-rtems4.7-gcc -o bla1.o --save-temps -c bla1.c
>arm-rtems4.7-gcc -o bla2.o --save-temps -c bla2.c
>
>and then diff the *.s:
>
># diff -u bla1.s bla2.s
>@@ -12,8 +12,8 @@
>        sub     sp, sp, #4
>        str     r0, [fp, #-16]
>        ldr     r3, [fp, #-16]
>-       ldrb    r3, [r3, #0]
>-       and     r3, r3, #15
>+       ldrb    r3, [r3, #0]    @ zero_extendqisi2
>+       mov     r3, r3, lsr #4
>        and     r3, r3, #255
>        mov     r0, r3
>        ldmfd   sp, {r3, fp, sp, pc}
>
>Is this code correct? Are the bitfields accessed correctly?
>
>Ralf
>
>
>
>
>  
>