[dpdk-dev] pmdinfogen issues: cross compilation for ARM fails with older host compiler

[Neil Horman]

On Tue, Nov 15, 2016 at 09:34:16AM +0000, Hemant Agrawal wrote:
> > On Mon, Nov 14, 2016 at 02:29:24AM +0530, Jerin Jacob wrote:
> > > On Fri, Nov 11, 2016 at 10:34:39AM +0000, Hemant Agrawal wrote:
> > > > Hi Neil,
> > > >                Pmdinfogen compiles with host compiler. It usages rte_byteorder.h
> > of the target platform.
> > > > However, if the host compiler is older than 4.8, it will be an issue during cross
> > compilation for some platforms.
> > > > e.g. if we are compiling on x86 host for ARM, x86 host compiler will not
> > understand the arm asm instructions.
> > > >
> > > > /* fix missing __builtin_bswap16 for gcc older then 4.8 */ #if
> > > > !(__GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 8)) static
> > > > inline uint16_t rte_arch_bswap16(uint16_t _x) {
> > > >                register uint16_t x = _x;
> > > >                asm volatile ("rev16 %0,%1"
> > > >                                     : "=r" (x)
> > > >                                     : "r" (x)
> > > >                                     );
> > > >                return x;
> > > > }
> > > > #endif
> > > >
> > > > One easy solution is that we add compiler platform check in this
> > > > code section of rte_byteorder.h e.g #if !(defined __arm__ || defined
> > > > __aarch64__) static inline uint16_t rte_arch_bswap16(uint16_t _x) {
> > > >                return (_x >> 8) | ((_x << 8) & 0xff00); } #else ….
> > > >
> > > > Is there a better way to fix it?
> > >
> > > IMO, It is a HOST build infrastructure issue. If a host app is using
> > > the dpdk service then it should compile and link against HOST
> > > target(in this specific case, build/x86_64-native-linuxapp-gcc). I
> > > think, introducing the HOSTTARGET kind of scheme is a clean solution.
> > >
> > > /Jerin
> > >
> > >
> > That would be accurate.  That is to say, pmdinfogen is a tool that should only be
> > run on the host doing the build, by the host doing the build, and so should be
> > compiled to run on the host, not on the target being built for.
> > 
> > Yeah, so what we need is a way to get to the host version of rte_byteorder.h
> > when building in a cross environment
> > 
> +1 
> 
> > Neil
> 

Give this a try, I've tested it on linux, but not BSD.  From what I read the
functions are not posix compliant, though they should exist on all BSD and Linux
systems in recent history.  There may be some fiddling needed for Net and
OpenBSD variants, but I think this is the right general direction.


diff --git a/buildtools/pmdinfogen/pmdinfogen.h b/buildtools/pmdinfogen/pmdinfogen.h
index 1da2966..c5ef89d 100644
--- a/buildtools/pmdinfogen/pmdinfogen.h
+++ b/buildtools/pmdinfogen/pmdinfogen.h
@@ -21,7 +21,6 @@
 #include <elf.h>
 #include <rte_config.h>
 #include <rte_pci.h>
-#include <rte_byteorder.h>
 
 /* On BSD-alike OSes elf.h defines these according to host's word size */
 #undef ELF_ST_BIND
@@ -75,9 +74,9 @@
 #define CONVERT_NATIVE(fend, width, x) ({ \
 typeof(x) ___x; \
 if ((fend) == ELFDATA2LSB) \
-	___x = rte_le_to_cpu_##width(x); \
+	___x = le##width##toh(x); \
 else \
-	___x = rte_be_to_cpu_##width(x); \
+	___x = be##width##toh(x); \
 	___x; \
 })