On Thu, 17 Sep 2020 at 00:25, Nick Desaulniers <ndesaulniers@xxxxxxxxxx> wrote: > > On Wed, Sep 16, 2020 at 1:45 PM Ard Biesheuvel <ardb@xxxxxxxxxx> wrote: > > > > On Wed, 16 Sep 2020 at 22:53, Nick Desaulniers <ndesaulniers@xxxxxxxxxx> wrote: > > > > > > On Tue, Sep 15, 2020 at 10:55 PM Ard Biesheuvel <ardb@xxxxxxxxxx> wrote: > > > > > > > > On Wed, 16 Sep 2020 at 02:31, Nick Desaulniers <ndesaulniers@xxxxxxxxxx> wrote: > > > > > > > > > > On Tue, Sep 15, 2020 at 2:30 PM Ard Biesheuvel <ardb@xxxxxxxxxx> wrote: > > > > > > > > > > > > Excellent, thanks for testing. Do you have any coverage for Thumb2 > > > > > > builds as well? (CONFIG_THUMB2_KERNEL=y) > > > > > > > > > > Ah, right, manually testing ARCH=arm defconfig with > > > > > CONFIG_THUMB2_KERNEL enabled via menuconfig: > > > > > > > > > > Builds and boots for clang. > > > > > > > > > > (Also needed https://lore.kernel.org/lkml/20200915225751.274531-1-ndesaulniers@xxxxxxxxxx/T/#u > > > > > for an unrelated issue). > > > > > > > > > > For GCC, I observe: > > > > > > > > > > arch/arm/vfp/vfphw.o: in function `vfp_support_entry': > > > > > (.text+0xa): relocation truncated to fit: R_ARM_THM_JUMP19 against > > > > > symbol `vfp_kmode_exception' defined in .text.unlikely section in > > > > > arch/arm/vfp/vfpmodule.o > > > > > > > > > > > > > Interesting. And this is using ld.bfd ? > > > > > > $ arm-linux-gnueabihf-ld --version > > > GNU ld (GNU Binutils for Debian) 2.34 > > > > > > .text.unlikely reminds me of the sections created when profiling data > > > is present. That's obviously not the case here, so maybe there's > > > other ways this section can be created by GCC? I may have added a > > > patch recently for placing this section explicitly, which was a > > > prerequisite for Kees' series explicitly placing all sections. > > > https://lore.kernel.org/lkml/159896087937.20229.4955362311782724603.tip-bot2@tip-bot2/ > > > Maybe that can be improved? > > > > > > IIRC, LLD is able to emit range extension thunks for these cases, but > > > BFD does not. > > > > ld.bfd will usually emit veneers for branches that turn out to be out > > of range in the final link stage. > > > > Does the following help? > > > > diff --git a/arch/arm/vfp/vfphw.S b/arch/arm/vfp/vfphw.S > > index 4fcff9f59947..f1468702fbc9 100644 > > --- a/arch/arm/vfp/vfphw.S > > +++ b/arch/arm/vfp/vfphw.S > > @@ -82,6 +82,7 @@ ENTRY(vfp_support_entry) > > ldr r3, [sp, #S_PSR] @ Neither lazy restore nor FP exceptions > > and r3, r3, #MODE_MASK @ are supported in kernel mode > > teq r3, #USR_MODE > > +THUMB( it ne ) > > bne vfp_kmode_exception @ Returns through lr > > > > VFPFMRX r1, FPEXC @ Is the VFP enabled? > > Yes, it does! I'm curious why though? I've seen the "it prefixes" > before (is that what they're called?), but I don't recall what they're > for. How come that solves this issue? > It forces the use of an instruction encoding that has more space for an immediate. > (Feel free to use my tested by tag on a subsequent resulting patch > that uses that). That fix is irrespective of this series, so you > should send it maybe separately? > I will, thanks. > Also, it looks like the GCC build of milbeaut_m10v_defconfig fails to > boot for me in QEMU; so maybe not just a Clang bug (or maybe, more > than one bug). (or maybe one of my command line params to QEMU is > wrong). > I understand that this is actually an existing issue in -next, but in general, why would you expect to be able to boot milbeaut_m10v_defconfig on anything other than a Milbeaut MV10 machine? (whatever it is) Or does QEMU emulate a milbeaut machine? If not, better to stick with configs that are intended to boot on the QEMU machine emulation that you are using. Also, while I see the point of regression testing of -next, using it as a base to test arbitrary series and then report failures against it produces a lot of noise. -next is *not* a good base for development, because you get everybody else's half baked crap as well. When you test my stuff, please use a known good base so we're not off on a goose chase every time. > Stepping through start_kernel(), the call to setup_arch() seems to > hang in qemu. For both GCC and Clang builds. A breakpoint in panic() > never gets hit. Looks like the deepest I can get is: > > Looks like: > #0 memblock_alloc_try_nid (size=108, align=4, min_addr=0, max_addr=0, > nid=-1) at mm/memblock.c:1601 > #1 0xc060f0b4 in memblock_alloc (size=<optimized out>, > align=<optimized out>) at ./include/linux/memblock.h:409 > #2 cma_init_reserved_mem (base=1543503872, size=67108864, > order_per_bit=0, name=0xc04b9240 "reserved", res_cma=0xc07ccbdc > <dma_contiguous_default_area>) at mm/cma.c:190 > #3 0xc060f2c0 in cma_declare_contiguous_nid (base=1543503872, > size=67108864, limit=1610612736, alignment=8388608, order_per_bit=0, > fixed=false, name=0xc04b9240 "reserved", > res_cma=0xc07ccbdc <dma_contiguous_default_area>, nid=-1) at mm/cma.c:352 > #4 0xc0608cb6 in cma_declare_contiguous (alignment=<optimized out>, > order_per_bit=<optimized out>, name=<optimized out>, > res_cma=<optimized out>, fixed=<optimized out>, > limit=<optimized out>, size=<optimized out>, base=<optimized out>) > at ./include/linux/cma.h:28 > #5 dma_contiguous_reserve_area (size=<optimized out>, base=<optimized > out>, limit=<optimized out>, res_cma=0xc07ccbdc > <dma_contiguous_default_area>, fixed=false) > at kernel/dma/contiguous.c:201 > #6 0xc0608d22 in dma_contiguous_reserve (limit=<optimized out>) at > kernel/dma/contiguous.c:171 > #7 0xc0604584 in arm_memblock_init (mdesc=0xc061bfe8 > <__mach_desc_GENERIC_DT.35641>) at arch/arm/mm/init.c:230 > #8 0xc060302c in setup_arch (cmdline_p=<optimized out>) at > arch/arm/kernel/setup.c:1132 > #9 0xc06007d2 in start_kernel () at init/main.c:857 > > there's a call to memset that seems to hang. I wonder if memset() was > defined in terms of __builtin_memset, which oft can result in infinite > loops? (IIRC there's an AEABI related memset; this kind of thing has > hit android userspace before). > > (gdb) layout asm > > shows that the source call to memset is transformed into a call to mmioset. > > (gdb) bt > #0 mmioset () at arch/arm/lib/memset.S:19 > #1 0xc060e2dc in memblock_alloc_try_nid (size=108, align=<optimized > out>, min_addr=0, max_addr=0, nid=-1) at mm/memblock.c:1602 > #2 0xc060f0b4 in memblock_alloc (size=<optimized out>, > align=<optimized out>) at ./include/linux/memblock.h:409 > #3 cma_init_reserved_mem (base=1543503872, size=67108864, > order_per_bit=0, name=0xc04b9240 "reserved", res_cma=0xc07ccbdc > <dma_contiguous_default_area>) at mm/cma.c:190 > #4 0xc060f2c0 in cma_declare_contiguous_nid (base=1543503872, > size=67108864, limit=1610612736, alignment=8388608, order_per_bit=0, > fixed=false, name=0xc04b9240 "reserved", > res_cma=0xc07ccbdc <dma_contiguous_default_area>, nid=-1) at mm/cma.c:352 > #5 0xc0608cb6 in cma_declare_contiguous (alignment=<optimized out>, > order_per_bit=<optimized out>, name=<optimized out>, > res_cma=<optimized out>, fixed=<optimized out>, > limit=<optimized out>, size=<optimized out>, base=<optimized out>) > at ./include/linux/cma.h:28 > #6 dma_contiguous_reserve_area (size=<optimized out>, base=<optimized > out>, limit=<optimized out>, res_cma=0xc07ccbdc > <dma_contiguous_default_area>, fixed=false) > at kernel/dma/contiguous.c:201 > #7 0xc0608d22 in dma_contiguous_reserve (limit=<optimized out>) at > kernel/dma/contiguous.c:171 > #8 0xc0604584 in arm_memblock_init (mdesc=0xc061bfe8 > <__mach_desc_GENERIC_DT.35641>) at arch/arm/mm/init.c:230 > #9 0xc060302c in setup_arch (cmdline_p=<optimized out>) at > arch/arm/kernel/setup.c:1132 > #10 0xc06007d2 in start_kernel () at init/main.c:857 > > Using `si` in gdb, it looks like we maybe hit an exception vector? > x 1202 .section .vectors, "ax", %progbits > > x > x 1203 .L__vectors_start: > > x > x 1204 W(b) vector_rst > > x > x 1205 W(b) vector_und > > x > x 1206 W(ldr) pc, .L__vectors_start + 0x1000 > > x > x >1207 W(b) vector_pabt > > Is the last thing I see, then `si` stops working. Not sure if `pabt` > is a recognizable acronym to anyone more familiar with ARM? > > Happens regardless of your series, FWIW. > -- > Thanks, > ~Nick Desaulniers
