Christophe Leroy <christophe.le...@csgroup.eu> writes: > Le 08/05/2021 à 08:46, Christophe Leroy a écrit : >> Le 06/05/2021 à 16:17, Arnd Bergmann a écrit : >>> On Thu, May 6, 2021 at 2:42 PM Christophe Leroy >>> <christophe.le...@csgroup.eu> wrote: >>>> >>>> Hello Arnd, >>>> >>>> May I ask you whether you plan to build cross compilers based on GCC 11.1 >>>> at >>>> https://mirrors.edge.kernel.org/pub/tools/crosstool/ ? >>> >>> Hi Christophe, >>> >>> I've built a snapshot a few days before the release, that one is >>> identical to 11.1 >>> except for the reported version number. I've tried to ask around for >>> help testing >>> this, but so far I have not heard from anyone. >>> >>> Building a new set of compilers takes around a day on my build box, so I >>> want >>> to make sure I don't have to do it more often than necessary. If you are >>> able >>> to give the binaries a spin, preferably on a ppc64le or arm64 host, please >>> let >>> me know how it goes and I'll rebuilt them on the release tag. >>> >> >> Hi Arnd, >> >> I don't have any ppc or arm host I can build on. >> I'm building on x86 for powerpc embedded boards. >> >> I have tried your GCC 11 snapshot, I get something booting but it crashes >> when launching init. >> >> [ 7.368410] init[1]: bad frame in sys_sigreturn: 7fb2fd60 nip 001083cc lr >> 001083c4 >> [ 7.376283] Kernel panic - not syncing: Attempted to kill init! >> exitcode=0x0000000b >> [ 7.383680] CPU: 0 PID: 1 Comm: init Not tainted >> 5.12.0-s3k-dev-16316-g9e799d5df185 #5054 >> [ 7.391767] Call Trace: >> [ 7.394174] [c9023db0] [c00211e8] panic+0x130/0x304 (unreliable) >> [ 7.400112] [c9023e10] [c0024e68] do_exit+0x874/0x910 >> [ 7.405104] [c9023e50] [c0024f80] do_group_exit+0x40/0xc4 >> [ 7.410440] [c9023e60] [c0033334] get_signal+0x1d8/0x93c >> [ 7.415689] [c9023ec0] [c0007f34] do_notify_resume+0x6c/0x314 >> [ 7.421369] [c9023f20] [c000d580] syscall_exit_prepare+0x120/0x184 >> [ 7.427479] [c9023f30] [c001101c] ret_from_syscall+0xc/0x28 >> >> Something is going wrong with asm goto output. I implemented get_user() >> helpers with asm goto this >> cycle (commit 5cd29b1fd3e8). I tested it with CLANG before submitting, it >> was working. >> >> Seems like there is something wrong with it with GCC11. When forcing >> CONFIG_CC_HAS_ASM_GOTO_OUTPUT >> to 'n', the kernel boots ok. >> > > I found the problem, that's due to r10 register being reused by GCC in the > copy loop below: > > 10: 7d 09 03 a6 mtctr r8 > 14: 80 ca 00 00 lwz r6,0(r10) > 18: 80 ea 00 04 lwz r7,4(r10) > 1c: 90 c9 00 08 stw r6,8(r9) > 20: 90 e9 00 0c stw r7,12(r9) > 24: 39 0a 00 08 addi r8,r10,8 > 28: 39 29 00 08 addi r9,r9,8 > =>2c: 81 4a 00 08 lwz r10,8(r10) > 30: 81 6a 00 0c lwz r11,12(r10) > 34: 91 49 00 08 stw r10,8(r9) > 38: 91 69 00 0c stw r11,12(r9) > 3c: 39 48 00 08 addi r10,r8,8 > 40: 39 29 00 08 addi r9,r9,8 > 44: 42 00 ff d0 bdnz 14 <__unsafe_restore_general_regs+0x14> > > earlyclobber modifier is missing in the CONFIG_CC_HAS_ASM_GOTO_OUTPUT version > of __get_user_asm2_goto().
Thanks for tracking that down. I hit it last week when testing Arnd's compilers but hadn't had time to find the root cause. cheers