Re: [PATCH 00/24] Fix reading and writing pseudo registers in non-current frames

Luis Machado
2023-11-08T11:58:12Z

Hi Simon,

On 11/8/23 05:00, Simon Marchi wrote:
> This series fixes reading/writing pseudo registers from/to non-current
> frames (that is, frames other than frame 0). Currently, we get this:
>
> (gdb) frame 0
> #0 break_here_asm () at /home/smarchi/src/binutils-gdb/gdb/testsuite/gdb.arch/amd64-pseudo-unwind-asm.S:38
> 38 pop %rbx
> (gdb) p/x $rbx
> $1 = 0x2021222324252627
> (gdb) p/x $ebx
> $2 = 0x24252627
> (gdb) frame 1
> #1 0x000055555555517d in caller () at /home/smarchi/src/binutils-gdb/gdb/testsuite/gdb.arch/amd64-pseudo-unwind-asm.S:58
> 58 call callee
> (gdb) p/x $rbx
> $3 = 0x1011121314151617
> (gdb) p/x $ebx
> $4 = 0x24252627
>
> This is a bit surprising, we would expect the last value to be
> 0x14151617, the bottom half of the rbx value from frame 1 (the currently
> selected frame at that point). Instead, we got the bottom half of the
> rbx value from frame 0. This is because pseudo registers are always
> read/written from/to the current thread's regcache.
>
> This series fixes this (as well as writing to pseudo registers) by
> making it so pseudo registers are read/written using a frame.
>
> Simon Marchi (24):
> gdb: don't handle i386 k registers as pseudo registers
> gdb: use reg_buffer_common throughout gdbsupport/common-regcache.h
> gdb: make store_integer take an array_view
> gdb: simplify conditions in
> regcache::{read,write,raw_collect,raw_supply}_part
> gdb: change regcache interface to use array_view
> gdb: fix bugs in {get,put}_frame_register_bytes
> gdb: make put_frame_register take an array_view
> gdb: change value_of_register and value_of_register_lazy to take the
> next frame
> gdb: remove frame_register
> gdb: make put_frame_register take the next frame
> gdb: make put_frame_register_bytes take the next frame
> gdb: make get_frame_register_bytes take the next frame
> gdb: add value::allocate_register
> gdb: read pseudo register through frame
> gdb: change parameter name in frame_unwind_register_unsigned
> declaration
> gdb: rename gdbarch_pseudo_register_write to
> gdbarch_deprecated_pseudo_register_write
> gdb: add gdbarch_pseudo_register_write that takes a frame
> gdb: migrate i386 and amd64 to the new gdbarch_pseudo_register_write
> gdb: make aarch64_za_offsets_from_regnum return za_offsets
> gdb: add missing raw register read in
> aarch64_sme_pseudo_register_write
> gdb: migrate aarch64 to new gdbarch_pseudo_register_write
> gdb: migrate arm to gdbarch_pseudo_register_read_value
> gdb: migrate arm to new gdbarch_pseudo_register_write
> gdb/testsuite: add tests for unwinding of pseudo registers
>
> gdb/aarch64-tdep.c | 297 +++++-----
> gdb/alpha-tdep.c | 11 +-
> gdb/amd64-tdep.c | 82 +--
> gdb/arch/arm-get-next-pcs.c | 6 +-
> gdb/arch/arm-get-next-pcs.h | 5 +-
> gdb/arch/arm.c | 2 +-
> gdb/arch/arm.h | 4 +-
> gdb/arm-linux-tdep.c | 11 +-
> gdb/arm-tdep.c | 145 +++--
> gdb/avr-tdep.c | 3 +-
> gdb/bfin-tdep.c | 3 +-
> gdb/csky-tdep.c | 4 +-
> gdb/defs.h | 39 +-
> gdb/dwarf2/expr.c | 22 +-
> gdb/dwarf2/frame.c | 5 +-
> gdb/eval.c | 3 +-
> gdb/findvar.c | 50 +-
> gdb/frame-unwind.c | 3 +-
> gdb/frame.c | 174 +++---
> gdb/frame.h | 28 +-
> gdb/frv-tdep.c | 3 +-
> gdb/gdbarch-gen.h | 28 +-
> gdb/gdbarch.c | 40 +-
> gdb/gdbarch_components.py | 29 +-
> gdb/guile/scm-frame.c | 3 +-
> gdb/h8300-tdep.c | 3 +-
> gdb/i386-tdep.c | 380 ++++--------
> gdb/i386-tdep.h | 15 +-
> gdb/i387-tdep.c | 16 +-
> gdb/ia64-tdep.c | 18 +-
> gdb/infcmd.c | 6 +-
> gdb/loongarch-tdep.c | 3 +-
> gdb/m32c-tdep.c | 3 +-
> gdb/m68hc11-tdep.c | 3 +-
> gdb/m68k-tdep.c | 17 +-
> gdb/mep-tdep.c | 3 +-
> gdb/mi/mi-main.c | 3 +-
> gdb/mips-tdep.c | 29 +-
> gdb/msp430-tdep.c | 3 +-
> gdb/nat/aarch64-hw-point.c | 3 +-
> gdb/nat/aarch64-scalable-linux-ptrace.c | 20 +-
> gdb/nat/linux-btrace.c | 3 +-
> gdb/nds32-tdep.c | 8 +-
> gdb/python/py-frame.c | 3 +-
> gdb/python/py-unwind.c | 4 +-
> gdb/regcache.c | 548 +++++++++++-------
> gdb/regcache.h | 113 +++-
> gdb/riscv-tdep.c | 13 +-
> gdb/rl78-tdep.c | 3 +-
> gdb/rs6000-tdep.c | 21 +-
> gdb/s12z-tdep.c | 2 +-
> gdb/s390-tdep.c | 3 +-
> gdb/sh-tdep.c | 9 +-
> gdb/sparc-tdep.c | 3 +-
> gdb/sparc64-tdep.c | 3 +-
> gdb/std-regs.c | 11 +-
> .../gdb.arch/aarch64-pseudo-unwind-asm.S | 82 +++
> .../gdb.arch/aarch64-pseudo-unwind.c | 33 ++
> .../gdb.arch/aarch64-pseudo-unwind.exp | 90 +++
> .../gdb.arch/amd64-pseudo-unwind-asm.S | 66 +++
> gdb/testsuite/gdb.arch/amd64-pseudo-unwind.c | 33 ++
> .../gdb.arch/amd64-pseudo-unwind.exp | 91 +++
> .../gdb.arch/arm-pseudo-unwind-asm.S | 81 +++
> .../gdb.arch/arm-pseudo-unwind-legacy-asm.S | 84 +++
> .../gdb.arch/arm-pseudo-unwind-legacy.c | 33 ++
> .../gdb.arch/arm-pseudo-unwind-legacy.exp | 86 +++
> gdb/testsuite/gdb.arch/arm-pseudo-unwind.c | 33 ++
> gdb/testsuite/gdb.arch/arm-pseudo-unwind.exp | 88 +++
> gdb/valops.c | 31 +-
> gdb/value.c | 149 +++++
> gdb/value.h | 64 +-
> gdb/xtensa-tdep.c | 3 +-
> gdbserver/linux-arm-low.cc | 4 +-
> gdbserver/regcache.cc | 69 ++-
> gdbserver/regcache.h | 6 +-
> gdbsupport/common-regcache.cc | 2 +-
> gdbsupport/common-regcache.h | 58 +-
> gdbsupport/rsp-low.cc | 8 +
> gdbsupport/rsp-low.h | 2 +
> 79 files changed, 2324 insertions(+), 1144 deletions(-)
> create mode 100644 gdb/testsuite/gdb.arch/aarch64-pseudo-unwind-asm.S
> create mode 100644 gdb/testsuite/gdb.arch/aarch64-pseudo-unwind.c
> create mode 100644 gdb/testsuite/gdb.arch/aarch64-pseudo-unwind.exp
> create mode 100644 gdb/testsuite/gdb.arch/amd64-pseudo-unwind-asm.S
> create mode 100644 gdb/testsuite/gdb.arch/amd64-pseudo-unwind.c
> create mode 100644 gdb/testsuite/gdb.arch/amd64-pseudo-unwind.exp
> create mode 100644 gdb/testsuite/gdb.arch/arm-pseudo-unwind-asm.S
> create mode 100644 gdb/testsuite/gdb.arch/arm-pseudo-unwind-legacy-asm.S
> create mode 100644 gdb/testsuite/gdb.arch/arm-pseudo-unwind-legacy.c
> create mode 100644 gdb/testsuite/gdb.arch/arm-pseudo-unwind-legacy.exp
> create mode 100644 gdb/testsuite/gdb.arch/arm-pseudo-unwind.c
> create mode 100644 gdb/testsuite/gdb.arch/arm-pseudo-unwind.exp
>
>
> base-commit: 1185b5b79a12ba67eb60bee3f75babf7a222fde0

I haven't tracked the particular patch that causes this, but for aarch64 systems supporting SVE
(and probably SME as well) I'm seeing internal errors related to one assertion:

Running gdb/testsuite/gdb.arch/aarch64-pseudo-unwind.exp ...
PASS: gdb.arch/aarch64-pseudo-unwind.exp: continue to breakpoint: continue to callee
PASS: gdb.arch/aarch64-pseudo-unwind.exp: callee, before change: p/x $v8.q.u
PASS: gdb.arch/aarch64-pseudo-unwind.exp: callee, before change: p/x $s8.u
FAIL: gdb.arch/aarch64-pseudo-unwind.exp: set $s8.u = 0x34353637 (GDB internal error)
FAIL: gdb.arch/aarch64-pseudo-unwind.exp: callee, after change: p/x $v8.q.u
FAIL: gdb.arch/aarch64-pseudo-unwind.exp: callee, after change: p/x $s8.u
PASS: gdb.arch/aarch64-pseudo-unwind.exp: up
PASS: gdb.arch/aarch64-pseudo-unwind.exp: caller, before change: p/x $v8.q.u
PASS: gdb.arch/aarch64-pseudo-unwind.exp: caller, before change: p/x $s8.u
FAIL: gdb.arch/aarch64-pseudo-unwind.exp: set $s8.u = 0x44454647 (GDB internal error)
FAIL: gdb.arch/aarch64-pseudo-unwind.exp: caller, after change: p/x $v8.q.u
FAIL: gdb.arch/aarch64-pseudo-unwind.exp: caller, after change: p/x $s8.u
PASS: gdb.arch/aarch64-pseudo-unwind.exp: down
FAIL: gdb.arch/aarch64-pseudo-unwind.exp: callee, after change in caller: p/x $v8.q.u
FAIL: gdb.arch/aarch64-pseudo-unwind.exp: callee, after change in caller: p/x $s8.u
PASS: gdb.arch/aarch64-pseudo-unwind.exp: continue to breakpoint: continue to break_here_c
FAIL: gdb.arch/aarch64-pseudo-unwind.exp: p/x value
Running gdb/testsuite/gdb.arch/aarch64-fp.exp ...
PASS: gdb.arch/aarch64-fp.exp: set the breakpoint after setting the fp registers
PASS: gdb.arch/aarch64-fp.exp: continue until breakpoint
PASS: gdb.arch/aarch64-fp.exp: check register q0 value
PASS: gdb.arch/aarch64-fp.exp: check register q1 value
PASS: gdb.arch/aarch64-fp.exp: check register v0 value
PASS: gdb.arch/aarch64-fp.exp: check register v1 value
PASS: gdb.arch/aarch64-fp.exp: check register fpsr value
PASS: gdb.arch/aarch64-fp.exp: check register fpcr value
FAIL: gdb.arch/aarch64-fp.exp: bfloat16: set h0.bf to 129 (GDB internal error)
FAIL: gdb.arch/aarch64-fp.exp: bfloat16: h0 fields are valid
FAIL: gdb.arch/aarch64-fp.exp: bfloat16: set v0.h.bf[0] to 0 (GDB internal error)
FAIL: gdb.arch/aarch64-fp.exp: bfloat16: v0.h.s[0] is 0
FAIL: gdb.arch/aarch64-fp.exp: bfloat16: set v0.h.bf[0] to 129 (GDB internal error)
FAIL: gdb.arch/aarch64-fp.exp: bfloat16: v0.h.s[0] is 129

The failure mode is:

set $s8.u = 0x34353637^M
../../../repos/binutils-gdb/gdb/frame.c:1441: internal-error: put_frame_register: Assertion `buf.size () == size' failed.^M
A problem internal to GDB has been detected,^M
further debugging may prove unreliable.^M
----- Backtrace -----^M
FAIL: gdb.arch/aarch64-pseudo-unwind.exp: set $s8.u = 0x34353637 (GDB internal error)
Resyncing due to internal error.
0xaaaaabd6e08f gdb_internal_backtrace_1^M
../../../repos/binutils-gdb/gdb/bt-utils.c:122^M
0xaaaaabd6e08f _Z22gdb_internal_backtracev^M
../../../repos/binutils-gdb/gdb/bt-utils.c:168^M
0xaaaaac315307 internal_vproblem^M
../../../repos/binutils-gdb/gdb/utils.c:396^M
0xaaaaac31556f _Z15internal_verrorPKciS0_St9__va_list^M
../../../repos/binutils-gdb/gdb/utils.c:476^M
0xaaaaac8604e3 _Z18internal_error_locPKciS0_z^M
../../../repos/binutils-gdb/gdbsupport/errors.cc:58^M
0xaaaaabec89c7 _Z18put_frame_register14frame_info_ptriN3gdb10array_viewIKhEE^M
../../../repos/binutils-gdb/gdb/frame.c:1441^M
0xaaaaabc55243 aarch64_pseudo_write_1^M
../../../repos/binutils-gdb/gdb/aarch64-tdep.c:3316^M
0xaaaaabc5c943 aarch64_pseudo_write^M
../../../repos/binutils-gdb/gdb/aarch64-tdep.c:3414^M
0xaaaaabce0913 _Z29gdbarch_pseudo_register_writeP7gdbarch14frame_info_ptriN3gdb10array_viewIKhEE^M
../../../repos/binutils-gdb/gdb/gdbarch.c:1927^M
0xaaaaabec892f _Z18put_frame_register14frame_info_ptriN3gdb10array_viewIKhEE^M
../../../repos/binutils-gdb/gdb/frame.c:1462^M
0xaaaaabed0fa7 _Z24put_frame_register_bytes14frame_info_ptrimN3gdb10array_viewIKhEE^M
../../../repos/binutils-gdb/gdb/frame.c:1592^M
0xaaaaac33092b _Z12value_assignP5valueS0_^M
../../../repos/binutils-gdb/gdb/valops.c:1260^M
0xaaaaabe8fcdf _ZN10expression8evaluateEP4type6noside^M
../../../repos/binutils-gdb/gdb/eval.c:111^M
0xaaaaac0cba9f set_command^M
../../../repos/binutils-gdb/gdb/printcmd.c:1542^M
0xaaaaabd9d91b _Z8cmd_funcP16cmd_list_elementPKci^M
../../../repos/binutils-gdb/gdb/cli/cli-decode.c:2735^M
0xaaaaac2af583 _Z15execute_commandPKci^M
../../../repos/binutils-gdb/gdb/top.c:575^M
0xaaaaabe97413 _Z15command_handlerPKc^M
../../../repos/binutils-gdb/gdb/event-top.c:552^M
0xaaaaabe9869f _Z20command_line_handlerOSt10unique_ptrIcN3gdb13xfree_deleterIcEEE^M
../../../repos/binutils-gdb/gdb/event-top.c:788^M
0xaaaaabe97f17 gdb_rl_callback_handler^M
../../../repos/binutils-gdb/gdb/event-top.c:259^M
0xaaaaac3ce363 rl_callback_read_char^M
../../../../repos/binutils-gdb/readline/readline/callback.c:290^M
0xaaaaabe96e93 gdb_rl_callback_read_char_wrapper_noexcept^M
../../../repos/binutils-gdb/gdb/event-top.c:195^M
0xaaaaabe97d7b gdb_rl_callback_read_char_wrapper^M
../../../repos/binutils-gdb/gdb/event-top.c:234^M
0xaaaaac2ea1f7 stdin_event_handler^M
../../../repos/binutils-gdb/gdb/ui.c:155^M
0xaaaaac860ecf gdb_wait_for_event^M
../../../repos/binutils-gdb/gdbsupport/event-loop.cc:694^M
0xaaaaac8618af gdb_wait_for_event^M
../../../repos/binutils-gdb/gdbsupport/event-loop.cc:593^M
0xaaaaac8618af _Z16gdb_do_one_eventi^M
../../../repos/binutils-gdb/gdbsupport/event-loop.cc:264^M
0xaaaaabffe02f start_event_loop^M
../../../repos/binutils-gdb/gdb/main.c:407^M
0xaaaaabffe02f captured_command_loop^M
../../../repos/binutils-gdb/gdb/main.c:471^M
0xaaaaabfffc73 captured_main^M
../../../repos/binutils-gdb/gdb/main.c:1324^M
0xaaaaabfffc73 _Z8gdb_mainP18captured_main_args^M
../../../repos/binutils-gdb/gdb/main.c:1343^M
0xaaaaabc3b457 main^M
../../../repos/binutils-gdb/gdb/gdb.c:39^M

It is also worth noting that the v registers are *not* pseudo-registers when the aarch64-fpu feature is used. If SVE
is available though, then that means the v registers are pseudo-registers as well. You can tell them apart by their types.

Real register (no SVE support):

type = union aarch64v {
vnd d;
vns s;
vnh h;
vnb b;
vnq q;
}

Pseudo-register (SVE support):

union __gdb_builtin_type_vnv {
__gdb_builtin_type_vnd d;
__gdb_builtin_type_vns s;
__gdb_builtin_type_vnh h;
__gdb_builtin_type_vnb b;
__gdb_builtin_type_vnq q;
}

Please let me know if you want me to narrow this down or provide more info.