| Message ID | 20180510051659.15356-2-npiggin@gmail.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Thu, May 10, 2018 at 03:16:55PM +1000, Nicholas Piggin wrote: > The 64-bit toolchain uses the wrong ISA variant for compiling 32-bit > kernels, eve with -m32. Set -mcpu=powerpc which is the generic 32-bit > powerpc machine type and scheduling model. 32-bit platforms and CPUs > can override this with -mcpu= options that come later on the command > line. > > This fixes a lot of build failures due to incompatible assembly when > compiling 32-bit kernel with 64-bit toolchain. So what ISA is set for gas without this patch? With what GCC version? And, why is that wrong? Segher > +ifdef CONFIG_PPC32 > +# These options will be overridden by any -mcpu option that comes > +# later on the command line, but they are needed to set a sane > +# 32-bit cpu target for the 64-bit cross compiler. > +KBUILD_CFLAGS += -mcpu=powerpc > +KBUILD_AFLAGS += -mcpu=powerpc > +endif -- To unsubscribe from this list: send the line "unsubscribe linux-kbuild" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Thu, 10 May 2018 08:10:03 -0500 Segher Boessenkool <segher@kernel.crashing.org> wrote: > On Thu, May 10, 2018 at 03:16:55PM +1000, Nicholas Piggin wrote: > > The 64-bit toolchain uses the wrong ISA variant for compiling 32-bit > > kernels, eve with -m32. Set -mcpu=powerpc which is the generic 32-bit > > powerpc machine type and scheduling model. 32-bit platforms and CPUs > > can override this with -mcpu= options that come later on the command > > line. > > > > This fixes a lot of build failures due to incompatible assembly when > > compiling 32-bit kernel with 64-bit toolchain. > > So what ISA is set for gas without this patch? With what GCC version? I'm not sure, how do I find that out? > And, why is that wrong? Some 32-bit platforms and CPU types do not provide -mcpu, so I assume for 32-bit toolchains that must result in the "powerpc" machine. With 64-bit toolchains arch/powerpc/mm/hash_low_32.S:353: Error: missing operand Which is, tlbie r4 Is that v2.06? Thanks, Nick -- To unsubscribe from this list: send the line "unsubscribe linux-kbuild" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Thu, May 10, 2018 at 11:24:40PM +1000, Nicholas Piggin wrote: > On Thu, 10 May 2018 08:10:03 -0500 > Segher Boessenkool <segher@kernel.crashing.org> wrote: > > On Thu, May 10, 2018 at 03:16:55PM +1000, Nicholas Piggin wrote: > > > The 64-bit toolchain uses the wrong ISA variant for compiling 32-bit > > > kernels, eve with -m32. Set -mcpu=powerpc which is the generic 32-bit > > > powerpc machine type and scheduling model. 32-bit platforms and CPUs > > > can override this with -mcpu= options that come later on the command > > > line. > > > > > > This fixes a lot of build failures due to incompatible assembly when > > > compiling 32-bit kernel with 64-bit toolchain. > > > > So what ISA is set for gas without this patch? With what GCC version? > > I'm not sure, how do I find that out? gcc --version gcc -v <rest of command>, look at the command line options passed to as make something.s, look at what .machine is set (if any). > > And, why is that wrong? > > Some 32-bit platforms and CPU types do not provide -mcpu, so I assume > for 32-bit toolchains that must result in the "powerpc" machine. With It results in whatever is the default for that toolchain. Depends on many things. > 64-bit toolchains > > arch/powerpc/mm/hash_low_32.S:353: Error: missing operand > > Which is, > > tlbie r4 > > Is that v2.06? The original ISA did not have the L field, 2.xx does, for any xx even I think. Segher -- To unsubscribe from this list: send the line "unsubscribe linux-kbuild" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Thu, May 10, 2018 at 03:16:55PM +1000, Nicholas Piggin wrote: > The 64-bit toolchain uses the wrong ISA variant for compiling 32-bit > kernels, eve with -m32. Set -mcpu=powerpc which is the generic 32-bit > powerpc machine type and scheduling model. 32-bit platforms and CPUs > can override this with -mcpu= options that come later on the command > line. So it turns out your compiler was configured with --with-cpu=power8; it's not that GCC defaults are bad, but who built your compiler overrode the defaults. If the problem only happens in .S files, it might be better to put .machine directives in those. But your patch should work too, yes. Segher -- To unsubscribe from this list: send the line "unsubscribe linux-kbuild" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/arch/powerpc/Makefile b/arch/powerpc/Makefile index 95813df90801..7034b1ad50e0 100644 --- a/arch/powerpc/Makefile +++ b/arch/powerpc/Makefile @@ -27,6 +27,14 @@ KBUILD_ARFLAGS += --target=elf32-powerpc endif endif +ifdef CONFIG_PPC32 +# These options will be overridden by any -mcpu option that comes +# later on the command line, but they are needed to set a sane +# 32-bit cpu target for the 64-bit cross compiler. +KBUILD_CFLAGS += -mcpu=powerpc +KBUILD_AFLAGS += -mcpu=powerpc +endif + export CROSS32CC CROSS32AR ifeq ($(CROSS_COMPILE),)
The 64-bit toolchain uses the wrong ISA variant for compiling 32-bit kernels, eve with -m32. Set -mcpu=powerpc which is the generic 32-bit powerpc machine type and scheduling model. 32-bit platforms and CPUs can override this with -mcpu= options that come later on the command line. This fixes a lot of build failures due to incompatible assembly when compiling 32-bit kernel with 64-bit toolchain. Signed-off-by: Nicholas Piggin <npiggin@gmail.com> --- arch/powerpc/Makefile | 8 ++++++++ 1 file changed, 8 insertions(+)