Hi Dirk, We found that the issue was at the early stages of Barebox (a.k.a U-BOOT v2). Our implementation of putc_ll (on debug_ll) was writing into the UART Tx FIFO without checking if the FIFO is full. Once the fifo got full it caused this SError probably because the UART IP generated an apberror signal. Now the Linux is running and doesn't report the SError again but now we face another issue. We see that the PC is getting into a "report_bug" function. The Linux doesn't print anything to the UART (probably since it hasn't got to the point where the console is configured?). Since our debug means are limited it can take some time to find the root cause. I will keep you posted and update our findings. Love to hear your thoughts, Cheers, Lior. > -----Original Message----- > From: Dirk Behme <dirk.behme@xxxxxxxxx> > Sent: Tuesday, December 19, 2023 3:37 PM > To: Lior Weintraub <liorw@xxxxxxxxxx>; linux-embedded@xxxxxxxxxxxxxxx > Subject: Re: Debugging early SError exception > > [You don't often get email from dirk.behme@xxxxxxxxx. Learn why this is > important at https://aka.ms/LearnAboutSenderIdentification ] > > CAUTION: External Sender > > Am 19.12.23 um 14:23 schrieb Lior Weintraub: > > Thanks Dirk, > > Welcome :) > > In case you find the root cause it would be nice to get some generic > description of it so that we can learn something :) > > Best regards > > Dirk > > > >> -----Original Message----- > >> From: Dirk Behme <dirk.behme@xxxxxxxxx> > >> Sent: Tuesday, December 19, 2023 9:09 AM > >> To: Lior Weintraub <liorw@xxxxxxxxxx>; linux-embedded@xxxxxxxxxxxxxxx > >> Subject: Re: Debugging early SError exception > >> > >> [You don't often get email from dirk.behme@xxxxxxxxx. Learn why this is > >> important at https://aka.ms/LearnAboutSenderIdentification ] > >> > >> CAUTION: External Sender > >> > >> Am 17.12.23 um 22:32 schrieb Lior Weintraub: > >>> Hi, > >>> > >>> We have a new SoC with eLinux porting (kernel v6.5). > >>> This SoC is ARM64 (A53) single core based device. > >>> It runs correctly on QEMU but fails with SError on emulation platform > >> (Synopsys Zebu running our SoC model). > >>> There is no debugger connected to this emulation but there are several > >> debug capabilities we can use: > >>> 1. Generating wave dump of CPU signals > >>> 2. Generate a Tarmac log > >>> 3. UART > >>> > >>> Since the SError happens at early stages of Linux boot the UART is not > >> enabled yet. > >>> From the Tarmac log we can see: > >>> 3824884521 ps ES (ffff800080760888:d65f03c0) O el1h_ns: ret > >> (parse_early_param) > >>> 3824884522 ps ES (ffff800080763a60:d2801800) O el1h_ns: mov > x0, > >> #0xc0 // #192 (setup_arch) > >>> R X0 (AARCH64) 00000000 000000c0 > >>> 3824884523 ps ES (ffff800080763a64:d51b4220) O el1h_ns: msr > >> daif, x0 (setup_arch) > >>> R CPSR 600000c5 > >>> 3824884529 ps ES System Error (Abort) > >>> EXC [0x380] SError/vSError Current EL with SP_ELx > >>> R ESR_EL1 (AARCH64) bf000002 > >>> R CPSR 600003c5 > >>> R SPSR_EL1 (AARCH64) 600000c5 > >>> R ELR_EL1 (AARCH64) ffff8000 80763a68 > >>> 3824884925 ps ES (ffff800080010b80:d10543ff) O el1h_ns: sub > sp, > >> sp, #0x150 (vectors) > >>> R SP_EL1 (AARCH64) ffff8000 808f3c50 > >>> 3824884925 ps ES (ffff800080010b84:8b2063ff) O el1h_ns: add > sp, > >> sp, x0 (vectors) > >>> R SP_EL1 (AARCH64) ffff8000 808f3d10 > >>> 3824884926 ps ES (ffff800080010b88:cb2063e0) O el1h_ns: sub > x0, > >> sp, x0 (vectors) > >>> R X0 (AARCH64) ffff8000 808f3c50 > >>> 3824884927 ps ES (ffff800080010b8c:37700080) O el1h_ns: tbnz > w0, > >> #14, ffff800080010b9c <vectors+0x39c> (vectors) > >>> 3824884935 ps ES (ffff800080010b90:cb2063e0) O el1h_ns: sub > x0, > >> sp, x0 (vectors) > >>> R X0 (AARCH64) 00000000 000000c0 > >>> 3824884937 ps ES (ffff800080010b94:cb2063ff) O el1h_ns: sub sp, > >> sp, x0 (vectors) > >>> R SP_EL1 (AARCH64) ffff8000 808f3c50 > >>> 3824884938 ps ES (ffff800080010b98:140001ef) O el1h_ns: b > >> ffff800080011354 <el1h_64_error> (vectors) > >>> > >>> If I understand correctly, the exception happened sometime earlier and > only > >> now Linux boot code (setup_arch) opened the exception handling and as a > >> result we immediately jump to the SError exception handler. > >> > >> > >> Yes, that sounds reasonable. If I understood correctly, you are > >> running something "quite new" on some software (QEMU) and hardware > >> (Synopsis) simulators. > >> > >> That would mean that you have new hardware with e.g. new memory map > >> not used before. What you describe might sound like in the code before > >> Linux (boot loader) there is anything resulting in the SError. This > >> might be an access to non-existing or non-enabled hardware. I.e. it > >> might be that you try to access (read/write) an address what is not > >> available, yet (or just invalid). It's hard to debug that. In case you > >> are able to modify the code before Linux (the boot loader?) you might > >> try to enable SError exceptions, there, too. To get it earlier and > >> with that make the search window smaller. I'm not that familiar with > >> QEMU, but could you try to trace which (all?) hardware accesses your > >> code does. And with that analyse all accesses and with that check if > >> all these accesses are valid even on the hardware (Synopsis) emulation > >> system? That should be checked from valid address and from hardware > >> subsystem enablement point of view. > >> > >> Hth, > >> > >> Dirk > >> > >> > >>> From the Linux source: > >>> parse_early_param(); > >>> > >>> dynamic_scs_init(); > >>> > >>> /* > >>> * Unmask asynchronous aborts and fiq after bringing up possible > >>> * earlycon. (Report possible System Errors once we can report this > >>> * occurred). > >>> */ > >>> local_daif_restore(DAIF_PROCCTX_NOIRQ); <---- This is when we get > the > >> exception. > >>> > >>> After some kernel hacking (replacing printk) we could extract the logs: > >>> 6Booting Linux on physical CPU 0x0000000000 [0x410fd034] > >>> 5Linux version 6.5.0 (pliops@dev-liorw) (aarch64-buildroot-linux-gnu- > >> gcc.br_real (Buildroot 2023.02.1-95-g8391404e23) 11.3.0, GNU ld (GNU > >> Binutils) 2.38) #101 SMP Sun Dec 17 20:09:06 IST 2023 > >>> 6Machine model: Pliops Spider MK-I EVK > >>> 2SError Interrupt on CPU0, code 0x00000000bf000002 -- SError > >>> CPU: 0 PID: 0 Comm: swapper Not tainted 6.5.0 #101 > >>> Hardware name: Pliops Spider MK-I EVK (DT) > >>> pstate: 600000c5 (nZCv daIF -PAN -UAO -TCO -DIT -SSBS BTYPE=--) > >>> pc : setup_arch+0x13c/0x5ac > >>> lr : setup_arch+0x134/0x5ac > >>> sp : ffff8000808f3da0 > >>> x29: ffff8000808f3da0c x28: 0000000008758074c x27: > >> 0000000005e31b58c > >>> x26: 0000000000000001c x25: 0000000007e5f728c x24: > >> ffff8000808f8000c > >>> x23: ffff8000808f8600c x22: ffff8000807b6000c x21: > ffff800080010000c > >>> x20: ffff800080a1e000c x19: fffffbfffddfe190c x18: 000000002266684ac > >>> x17: 00000000fcad60bbc x16: 0000000000001800c x15: > >> 0000000000000008c > >>> x14: ffffffffffffffffc x13: 0000000000000000c x12: 0000000000000003c > >>> x11: 0101010101010101c x10: ffffffffffee87dfc x9 : > 0000000000000038c > >>> x8 : 0101010101010101c x7 : 7f7f7f7f7f7f7f7fc x6 : > 0000000000000001c > >>> x5 : 0000000000000000c x4 : 8000000000000000c x3 : > >> 0000000000000065c > >>> x2 : 0000000000000000c x1 : 0000000000000000c x0 : > >> 00000000000000c0c > >>> 0Kernel panic - not syncing: Asynchronous SError Interrupt > >>> CPU: 0 PID: 0 Comm: swapper Not tainted 6.5.0 #101 > >>> Hardware name: Pliops Spider MK-I EVK (DT) > >>> Call trace: > >>> dump_backtrace+0x9c/0xd0 > >>> show_stack+0x14/0x1c > >>> dump_stack_lvl+0x44/0x58 > >>> dump_stack+0x14/0x1c > >>> panic+0x2e0/0x33c > >>> nmi_panic+0x68/0x6c > >>> arm64_serror_panic+0x68/0x78 > >>> do_serror+0x24/0x54 > >>> el1h_64_error_handler+0x2c/0x40 > >>> el1h_64_error+0x64/0x68 > >>> setup_arch+0x13c/0x5ac > >>> start_kernel+0x5c/0x5b8 > >>> __primary_switched+0xb4/0xbc > >>> 0---[ end Kernel panic - not syncing: Asynchronous SError Interrupt ]--- > >>> > >>> Can you please advice how to proceed with debugging? > >>> > >>> Thanks in advanced, > >>> Cheers, > >>> Lior. > >>> > >>> > >> > >
