On Fri, Jul 25, 2025 at 02:57:04PM +0200, Casey Connolly wrote: >Implement support for printing stack backtraces on ARM64, make >framepointer support configurable by the build system with >CONFIG_FRAMEPOINTER and teach U-Boot to walk the framepointers and >unwind the stack when an exception occurs. Also show all 64 bits of the >exception syndrom register (ESR). > >Additionally, a new global unwind_stack() function is added, this can >be called from anywhere to print a backtrace which can be useful when >debugging certain problems. > >In the future, stack unwinding with symbol support could be extended >to for example only emit log messages when a function is called in a >specific code path. This would allow for less noise when debugging hot >paths under certain conditions, but this feature is left as future work. > >=== Handling relocation === > >Since U-Boot relocates itself at runtime, and can be built to be >position independent in the first place (effectively "relocating" itself >when it first starts too), we can't really rely on gd->reloc_off. > >The approach taken here is to subtract CONFIG_TEXT_BASE from the address >of each symbol in the lookup table (while it's being generated), then >when decoding we just subtract the address of the _start label since it >is always correct pre and post relocation. This allows us to avoid all >the awkward maths since the symbols are always relative to 0x0 in the >lookup table. > >Example output: > >"Synchronous Abort" handler, esr 0x0000000096000004, far 0xfffffffffffff >elr: 000000009fc6f768 lr : 000000009fc6f710 (reloc) >elr: 00000001ffe49768 lr : 00000001ffe49710 >x0 : 000fffffffffffff x1 : 0000000000000009 >x2 : 00000001efdbadd0 x3 : 0000000000000000 >x4 : 00000001efd99a28 x5 : 00000001ffec7676 >x6 : 00000001efdbac70 x7 : 0000000000000000 >x8 : 0000000000000002 x9 : 0000000000000034 >x10: 000000000000000d x11: 0000000000000006 >x12: 0000000000001000 x13: 00000000c3400000 >x14: 00000000fffffff8 x15: 00000001efd99837 >x16: 00000001ffe146b8 x17: 0000000000000000 >x18: 00000001efdbac70 x19: 000000000a6f8800 >x20: 00000001efe06fd0 x21: 0000000000000001 >x22: 00000001ffef5b80 x23: 00000001ffee08c0 >x24: 0000000000000002 x25: 0000000000000000 >x26: 0000000000000000 x27: 0000000000000000 >x28: 00000001efe512c0 x29: 00000001efd99c80 > >Code: 2a010000 b9001260 d5033fbf 92fffe00 (39400001) > >CONFIG_TEXT_BASE : 0x9fc00000 >Relocated base addr: 0x1ffdda000 >Backtrace: > <0x000001ffe496d0> dwc3_qcom_glue_configure+0x40 > <0x000001ffe494a4> dwc3_glue_probe+0x10c > <0x000001ffe1757c> device_probe+0x254 > <0x000001ffe1757c> device_probe+0x114 > <0x000001ffe4ff70> usb_init+0x158 > <0x000001ffe00fe4> do_usb_start+0xc > <0x000001ffe01018> do_usb+0x78 > <0x000001ffe0dec4> cmd_process+0x140 > <0x000001ffe04e24> run_list_real+0x6f0 > <0x000001ffe05554> parse_stream_outer+0x148 > <0x000001ffe04d30> parse_string_outer+0x90 > <0x000001ffe0d148> run_command_list+0x50 > <0x000001ffe02be0> main_loop+0x28 > <0x000001ffe065c0> board_init_r+0x3c8 > <0x000001ffddd00c> relocation_return+0x4
Nit: If this address could be printed with pre-relocated address (built address in elf), it would be better. Regards Peng > >Resetting CPU ... > >--- >Changes in v2: >- Include calling function in backtrace (current LR) >- Implement support for runtime symbol lookup >- Use symbol lookup to print more informative backtraces when available >- Adjust backtrace format and print U-Boot base address >- Link to v1: >https://lore.kernel.org/u-boot/20250703051951.43372-1-heinrich.schucha...@canonical.com > >To: Tom Rini <tr...@konsulko.com> >To: Heinrich Schuchardt <heinrich.schucha...@canonical.com> >Cc: Simon Glass <s...@chromium.org> >Cc: Marek Vasut <marek.vasut+rene...@mailbox.org> >Cc: Ben Dooks <ben.do...@codethink.co.uk> >Cc: Rick Chen <r...@andestech.com> >Cc: Leo <ycli...@andestech.com> >Cc: Ilias Apalodimas <ilias.apalodi...@linaro.org> >Cc: u-boot@lists.denx.de > >--- >Casey Connolly (3): > drop unused kallsyms support > add support for symbol lookups > arm64: implement printing backtraces with symbols > >Heinrich Schuchardt (4): > cmd/exception: missing include string.h > Kconfig: make CONFIG_FRAMEPOINTER available on arm64 > arm64: initialize the frame pointer register > arm64: simplify interrupt code > > Kconfig | 25 ++ > Makefile | 24 +- > arch/arm/Makefile | 9 +- > arch/arm/lib/crt0_64.S | 1 + > arch/arm/lib/interrupts_64.c | 133 ++++++--- > arch/riscv/Kconfig | 21 -- > common/Makefile | 1 - > common/kallsyms.c | 42 --- > common/system_map.c | 8 - > include/exception.h | 1 + > include/symbols.h | 22 ++ > lib/Kconfig | 9 + > lib/symbols.c | 141 ++++++++++ > tools/Makefile | 3 + > tools/symbols.c | 646 +++++++++++++++++++++++++++++++++++++++++++ > 15 files changed, 965 insertions(+), 121 deletions(-) >--- >base-commit: f2f451d9d6d3756458d5037e3e5135e5211582d7 > >// Caleb (they/them) >
