dwarf: fixup x86 register mapping logic
dwarf: change the register context update to update in-place instead of copying
debug: always print the unwind error type
This change enhances stack trace output to include a note that debug info was missing,
and therefore the stack trace may not be accurate. For example, if the user is using a libc
compiled with -fomit-frame-pointer and doesn't have debug symbols installed, any traces
that begin in a libc function may not unwind correctly. This allows the user to notice this and
potentially install debug symbols to improve the output.
Some DWARF5 subprograms have non-contiguous instruction ranges. An example of such
a function is `puts` in Ubuntu's libc. This change fixes name lookups for functions that use
DW_AT_range in their DIE.
- Fix unwindFrame using the previous FDE row instead of the current one
- Handle unwinding through noreturn functions
- Add x86-linux getcontext
- Fixup x86_64-linux getcontext not restoring the fp env
- Fix start_addr filtering on x86-windows
- .eh_frame_hdr contains a binary-searchable data structure for finding an FDE. If present, we can use this
section to avoid having to parse the entire FDE/CIE list in the binary, instead only entries that are actually
required for unwinding are read.
- rework the inputs pc-relative pointer decoding to support both already-mapped sections as well as sections
mapped from a file
- store the VirtualMachine on UnwindContext so the allocations can be reused
Most of this migration was performed automatically with `zig fmt`. There
were a few exceptions which I had to manually fix:
* `@alignCast` and `@addrSpaceCast` cannot be automatically rewritten
* `@truncate`'s fixup is incorrect for vectors
* Test cases are not formatted, and their error locations change
This data changed quite significantly between DWARF 4 and 5. Some
systems are shipping DWARF 5 libraries (Void Linux on musl libc seems to
use it for crt1 etc), which meant when printing stack traces, a random
compile unit might be incorrectly identified as containing an address,
resulting in incorrect location information.
I was consistently experiencing this issue with compiler stack traces,
and this change fixed it.
