[PATCH 0/8] Switch FreeBSD x86 to using register maps for GP registers

[John Baldwin]

On 7/14/21 7:07 AM, John Baldwin wrote:
> The x86 architectures in GDB provide existing helpers for parsing
> general-purpose register sets.  However, these helpers have some
> limitations, such as assuming that registers are always full size.  On
> FreeBSD/amd64 in particular, segment registers are stored as 16-bit
> quantities that in some cases are packed together.  GDB for historical
> reasons treats these 16-bit registers as 32 bits in size.  Using the
> more generic regcache_map_entry to describe the GP register sets
> permits supporting these registers as 16-bit values.  In addition, the
> FreeBSD x86 signal frames have included the base address of the FS and
> GS segments (equivalent to the fs_base and gs_base registers), but the
> existing signal context helpers were written before those registers
> were added to GDB.
> 
> Longer term my goal is to use regcache_map_entry-based register sets
> in FreeBSD gdbserver support to simplify the implementation.
> 
> Note that patch 4 fixes an issue in regcache_collect_regset where it
> didn't quite do what I thought it did.  I believe the change is ok,
> but it definitely warrants review.

Ping.  Patch 4 is the only one that isn't FreeBSD-specific.

> I have tested this on both FreeBSD/amd64 (32-bit and 64-bit processes)
> and FreeBSD/i386.
> 
> John Baldwin (8):
>    Remove vestigal FreeBSD/i386 3.x support.
>    Remove support for pre-5.0 FreeBSD/i386 signal trampolines.
>    FreeBSD x86: Remove fallback for detecting signal trampolines by
>      address.
>    regcache: Zero-extend small registers described by a register map.
>    Use register maps for gp regsets on FreeBSD/x86 core dumps.
>    FreeBSD x86: Use tramp-frame for signal frames.
>    fbsd-nat: Return a bool from fetch_register_set and
>      store_register_set.
>    FreeBSD x86 nat: Use register maps for GP register sets.
> 
>   gdb/amd64-bsd-nat.c   |  96 ---------
>   gdb/amd64-fbsd-nat.c  | 346 ++++++++++++++++++-------------
>   gdb/amd64-fbsd-tdep.c | 279 ++++++++++++++-----------
>   gdb/amd64-fbsd-tdep.h |  27 +++
>   gdb/amd64-tdep.h      |   5 -
>   gdb/configure.nat     |   4 +-
>   gdb/fbsd-nat.c        |   8 +-
>   gdb/fbsd-nat.h        |  21 +-
>   gdb/i386-bsd-nat.c    |  98 +--------
>   gdb/i386-fbsd-nat.c   | 255 +++++++++++++++++++----
>   gdb/i386-fbsd-tdep.c  | 461 ++++++++++++++++++------------------------
>   gdb/i386-fbsd-tdep.h  |   4 +
>   gdb/i386-tdep.h       |   4 -
>   gdb/regcache.c        |   7 +-
>   gdb/x86-bsd-nat.c     |   4 -
>   gdb/x86-bsd-nat.h     |   3 -
>   16 files changed, 844 insertions(+), 778 deletions(-)
>   create mode 100644 gdb/amd64-fbsd-tdep.h
> 


-- 
John Baldwin