forked from Mirrors/opensbi
017a161788
When OpenSBI is built with a relatively new compiler (gcc-13 and greater) I observed that GDB is unable to produce proper backtraces and some variable values appear corrupted (even if the associated DWARF location descriptor is correct). Turns out that to properly work with debug information, debuggers often need to unwind the stack. They generally rely on Call Frame Information (CFI) records provided by the compiler to facilitate this task. Currently, the GCC compiler offers two mechanisms: - `.debug_frame` section (as described in the DWARF specification). - `.eh_frame` sections (as described in LSB documents). The latter (`.eh_frame`) supports stack unwinding at runtime, providing a framework for C++ exceptions or enabling backtrace generation using libraries like libunwind. However, the downside of this approach is that these sections should be part of loadable segments. The former (`.debug_frame`) is simply an ordinary debug section. Starting from GCC 13, Linux targets enable the `-fasynchronous-unwind-tables` and `-funwind-tables` flags by default. Relevant commit: https://github.com/gcc-mirror/gcc/commit/3cd08f7168 When these flags are active, the compiler generates `.eh_frame` sections instead of `.debug_frame`. Since OpenSBI is built using the **Linux toolchain**, this behavior applies to OpenSBI as well. The problem arises because the SBI build system uses `-Wl,--gc-sections`, which discards the `.eh_frame` section. Possible Fixes: 1. Enforce `.debug_frame` generation – Modify compiler flags to generate `.debug_frame` instead of `.eh_frame`. 2. Preserve `.eh_frame` in the linker script – Add `KEEP(*(.eh_frame))` to ensure the section is not discarded. I chose Option 1 because it avoids any runtime overhead. Signed-off-by: Parshintsev Anatoly <anatoly.parshintsev@syntacore.com> Reviewed-by: Anup Patel <anup@brainfault.org> Link: https://lore.kernel.org/r/20250421124729.36364-1-anatoly.parshintsev@syntacore.com Signed-off-by: Anup Patel <anup@brainfault.org>
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