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Simon Marchi b3245ceff0 gdb: read pseudo register through frame
Change gdbarch_pseudo_register_read_value to take a frame instead of a
regcache.  The frame (and formerly the regcache) is used to read raw
registers needed to make up the pseudo register value.  The problem with
using the regcache is that it always provides raw register values for
the current frame (frame 0).

Let's say the user wants to read the ebx register on amd64.  ebx is a pseudo
register, obtained by reading the bottom half (bottom 4 bytes) of the
rbx register, which is a raw register.  If the currently selected frame
is frame 0, it works fine:

    (gdb) frame 0
    #0  break_here_asm () at /home/smarchi/src/binutils-gdb/gdb/testsuite/gdb.arch/amd64-pseudo-unwind-asm.S:36
    36      in /home/smarchi/src/binutils-gdb/gdb/testsuite/gdb.arch/amd64-pseudo-unwind-asm.S
    (gdb) p/x $ebx
    $1 = 0x24252627
    (gdb) p/x $rbx
    $2 = 0x2021222324252627

But if the user is looking at another frame, and the raw register behind
the pseudo register has been saved at some point in the call stack, then
we get a wrong answer:

    (gdb) frame 1
    #1  0x000055555555517d in caller () at /home/smarchi/src/binutils-gdb/gdb/testsuite/gdb.arch/amd64-pseudo-unwind-asm.S:56
    56      in /home/smarchi/src/binutils-gdb/gdb/testsuite/gdb.arch/amd64-pseudo-unwind-asm.S
    (gdb) p/x $ebx
    $3 = 0x24252627
    (gdb) p/x $rbx
    $4 = 0x1011121314151617

Here, the value of ebx was computed using the value of rbx in frame 0
(through the regcache), it should have been computed using the value of
rbx in frame 1.

In other to make this work properly, make the following changes:

 - Make dwarf2_frame_prev_register return nullptr if it doesn't know how
   to unwind a register and that register is a pseudo register.
   Previously, it returned `frame_unwind_got_register`, meaning, in our
   example, "the value of ebx in frame 1 is the same as the value of ebx
   in frame 0", which is obviously false.  Return nullptr as a way to
   say "I don't know".

 - In frame_unwind_register_value, when prev_register (for instance
   dwarf2_frame_prev_register) returns nullptr, and we are trying to
   read a pseudo register, try to get the register value through
   gdbarch_pseudo_register_read_value or gdbarch_pseudo_register_read.
   If using gdbarch_pseudo_register_read, the behavior is known to be
   broken.  Implementations should be migrated to use
   gdbarch_pseudo_register_read_value to fix that.

 - Change gdbarch_pseudo_register_read_value to take a frame_info
   instead of a regcache, update implementations (aarch64, amd64, i386).
   In i386-tdep.c, I made a copy of i386_mmx_regnum_to_fp_regnum that
   uses a frame instead of a regcache.  The version using the regcache
   is still used by i386_pseudo_register_write.  It will get removed in
   a subsequent patch.

 - Add some helpers in value.{c,h} to implement the common cases of
   pseudo registers: taking part of a raw register and concatenating
   multiple raw registers.

 - Update readable_regcache::{cooked_read,cooked_read_value} to pass the
   current frame to gdbarch_pseudo_register_read_value.  Passing the
   current frame will give the same behavior as before: for frame 0, raw
   registers will be read from the current thread's regcache.

Notes:

 - I do not plan on changing gdbarch_pseudo_register_read to receive a
   frame instead of a regcache. That method is considered deprecated.
   Instead, we should be working on migrating implementations to use
   gdbarch_pseudo_register_read_value instead.

 - In frame_unwind_register_value, we still ask the unwinder to try to
   unwind pseudo register values.  It's apparently possible for the
   debug info to provide information about [1] pseudo registers, so we
   want to try that first, before falling back to computing them
   ourselves.

[1] https://inbox.sourceware.org/gdb-patches/20180528174715.A954AD804AD@oc3748833570.ibm.com/

Change-Id: Id6ef1c64e19090a183dec050e4034d8c2394e7ca
Reviewed-by: John Baldwin <jhb@FreeBSD.org>
2023-12-14 16:04:49 +00:00
bfd Automatic date update in version.in 2023-12-14 00:00:23 +00:00
binutils PR31096, nm shows 32bit addresses as 64bit addresses 2023-12-06 12:23:05 +10:30
config libiberty: Disable hwcaps for sha1.o 2023-11-30 10:14:30 +01:00
contrib Import mklog.py from gcc repo 2020-09-25 10:24:44 -04:00
cpu sim --enable-cgen-maint 2023-08-19 12:41:32 +09:30
elfcpp MIPS: Change all E_MIPS_* to EF_MIPS_* 2023-11-10 14:03:17 +00:00
etc Update year range in gprofng copyright notices 2023-01-01 23:26:30 +10:30
gas RISC-V: Fix the wrong encoding and operand of the XTheadFmv extension. 2023-12-14 09:54:19 +01:00
gdb gdb: read pseudo register through frame 2023-12-14 16:04:49 +00:00
gdbserver gdb: change regcache interface to use array_view 2023-12-14 16:04:49 +00:00
gdbsupport gdb: change regcache interface to use array_view 2023-12-14 16:04:49 +00:00
gnulib gnulib: mark configure +x 2023-11-28 12:55:29 -05:00
gold R_MICROMIPS_GPREL7_S2 2023-12-11 10:42:59 +10:30
gprof Finalized intl-update patches 2023-11-15 12:53:04 +00:00
gprofng gprofng: support GNU option syntax in gp-display-html, plus various fixes 2023-11-29 10:18:35 -08:00
include RISC-V: Fix the wrong encoding and operand of the XTheadFmv extension. 2023-12-14 09:54:19 +01:00
ld Update Make const_1_mode print $1 in AT&T syntax 2023-12-13 09:19:47 -08:00
libbacktrace regen config 2023-08-12 10:27:57 +09:30
libctf libctf: adding CU mappings should be idempotent 2023-11-20 12:31:41 +00:00
libdecnumber regen config 2023-08-12 10:27:57 +09:30
libiberty libiberty: Fix build with GCC < 7 2023-12-05 23:34:01 +01:00
libsframe regen config 2023-08-12 10:27:57 +09:30
opcodes RISC-V: Fix the wrong encoding and operand of the XTheadFmv extension. 2023-12-14 09:54:19 +01:00
readline [readline] Fix double free in _rl_scxt_dispose 2023-05-28 10:17:57 +02:00
sim Improve performance of the H8 simulator 2023-12-10 13:26:03 -07:00
texinfo
zlib regen config 2023-08-12 10:27:57 +09:30
.cvsignore
.editorconfig Add top-level .editorconfig file 2022-01-28 08:25:42 -05:00
.gitattributes binutils-gdb/git: highlight whitespace errors in source files 2022-07-25 14:35:41 +01:00
.gitignore Finalized intl-update patches 2023-11-15 12:53:04 +00:00
ar-lib Bump to autoconf 2.69 and automake 1.15.1 2018-06-19 16:55:06 -04:00
ChangeLog Finalized intl-update patches 2023-11-15 12:53:04 +00:00
compile
config-ml.in MSP430: Add -fno-exceptions multilib 2023-08-12 10:24:26 +09:30
config.guess kvx: New port. 2023-08-16 14:22:54 +01:00
config.rpath
config.sub kvx: New port. 2023-08-16 14:22:54 +01:00
configure Finalized intl-update patches 2023-11-15 12:53:04 +00:00
configure.ac Finalized intl-update patches 2023-11-15 12:53:04 +00:00
COPYING
COPYING.LIB
COPYING.LIBGLOSS
COPYING.NEWLIB
COPYING3
COPYING3.LIB
depcomp
djunpack.bat
install-sh
libtool.m4 FDPIC: Handle arm*-*-uclinuxfdpiceabi in configure scripts 2023-08-12 10:25:06 +09:30
ltgcc.m4
ltmain.sh Do not use HAVE_DOS_BASED_FILE_SYSTEM for Cygwin. 2023-08-12 10:25:06 +09:30
ltoptions.m4
ltsugar.m4
ltversion.m4
lt~obsolete.m4
MAINTAINERS MAINTAINERS: Update path to readline config.{sub,guess} files 2021-05-24 18:11:49 +02:00
Makefile.def Finalized intl-update patches 2023-11-15 12:53:04 +00:00
Makefile.in Finalized intl-update patches 2023-11-15 12:53:04 +00:00
Makefile.tpl toplevel: Substitute GDCFLAGS instead of using CFLAGS 2023-08-12 10:27:44 +09:30
makefile.vms
missing
mkdep
mkinstalldirs
move-if-change
multilib.am Merge autoconf / automake update changes from GCC. 2018-10-31 17:10:56 +00:00
README
README-maintainer-mode Note that at least dejagnu version 1.5.3 is required in order to be ale to run the testsuites. 2022-10-04 10:54:19 +01:00
SECURITY.txt Add a SECURITY.txt file describing the GNU Binutils' project's stance on security related bugs. 2023-04-20 16:52:11 +01:00
setup.com
src-release.sh Finalized intl-update patches 2023-11-15 12:53:04 +00:00
symlink-tree
test-driver Bump to autoconf 2.69 and automake 1.15.1 2018-06-19 16:55:06 -04:00
ylwrap

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