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In collect_register() function of arc-linux-tdep.c, the "eret"
(exception return) register value was not being reported correctly.
This patch fixes that.
Background:
When asked for the "pc" value, we have to update the "eret" register
with GDB's STOP_PC. The "eret" instructs the kernel code where to
jump back when an instruction has stopped due to a breakpoint. This
is how collect_register() was doing so:
--------------8<--------------
if (regnum == gdbarch_pc_regnum (gdbarch))
regnum = ARC_ERET_REGNUM;
regcache->raw_collect (regnum, buf + arc_linux_core_reg_offsets[regnum]);
-------------->8--------------
Root cause:
Although this is using the correct offset (ERET register's), it is also
changing the REGNUM itself. Therefore, raw_collect (regnum, ...) is
not reading from "pc" anymore.
v2:
- Fix a copy/paste issue as rightfully addressed by Tom [1].
[1]
https://sourceware.org/pipermail/gdb-patches/2020-November/173208.html
gdb/ChangeLog:
* arc-linux-tdep.c (collect_register): Populate "eret" by
"pc" value from the regcache when asked for "pc" value.
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With the implemenations in this patch, ARC gdb can handle
coredump related matters. The binutils counter part of
this patch has already been pushed [1].
v2 [2]:
- arc_linux_collect_gregset: Use "reg <= ARC_LAST_REGNUM" instead of
"reg < ARC_LAST_REGNUM" for the condition check of the for-loop.
- arc-linux-tdep.c: Use "ARC_LAST_REGNUM < ARRAY_SIZE (...)" instead of
"ARC_LAST_REGNUM <= ARRAY_SIZE (...)" for the "asserts".
- Use "buf + arc_linux_core_reg_offsets[ARC_ERET_REGNUM]" instead of
"buf + REG_OFF (6)".
- Fix a few typos/indentation.
v3 [3]:
- Use gdb_assert_not_reached(text) instead of gdb_assert (!text).
- Remove unnecessary braces in the for loop.
[1] arc: Add support for ARC HS extra registers in core files
https://sourceware.org/git/?p=binutils-gdb.git;a=commit;h=2745674244d6aecddcf636475034bdb9c0a6b4a0
[2] First remarks
https://sourceware.org/pipermail/gdb-patches/2020-September/171912.html
[3] Second remarks
https://sourceware.org/pipermail/gdb-patches/2020-October/172302.html
gdb/ChangeLog:
* arc-linux-tdep.h: New file.
* arc-linux-tdep.c (arc_linux_core_reg_offsets,
arc_linux_supply_gregset, arc_linux_supply_v2_regset,
arc_linux_collect_gregset, arc_linux_collect_v2_regset,
arc_linux_gregset, arc_linux_v2_regset,
arc_linux_iterate_over_regset_sections,
arc_linux_core_read_description): Implement.
(arc_linux_init_osabi): Set iterate_over_regset_sections.
* arc-tdep.h (ARC_OFFSET_NO_REGISTER): Declare.
(arc_gdbarch_features_create): Add.
* arc-tdep.c (arc_gdbarch_features_create): Not static anymore.
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ARC Linux targets differences from baremetal:
- No support for hardware single instruction stepping.
- Different access rules to registers.
- Use of another instruction for breakpoints.
v2: Changes after Tom's remarks [1]
arc-linux-tdep.c
- Use true/false instead of TRUE/FALSE.
- arc_linux_sw_breakpoint_from_kind (): Break long lines into two.
- arc_linux_sw_breakpoint_from_kind (): Remove starting blank line.
- Use explicit number evaluation, e.g: if (a & b) -> if ((a & b) != 0)
arc-tdep.c
- Use explicit number evaluation, e.g: if (a & b) -> if ((a & b) != 0)
gdb/configure.tgt
- arc*-*-linux*): Remove "build_gdbserver=yes".
v3: Changes after Simon's remarks [2]
arc-linux-tdep.c
- Use "return trap_size" instead of cryptic "return 2".
- Removed unnecessary curly braces.
- Removed "void" from "_initialize_arc_linux_tdep (void)".
v5: Changes after Simon's remarks [3]
- Remove unnecessary empty lines.
- Replace "breakpoint uses" with "breakpoints use" in a comment.
- "return condition;" i.s.o. "if (condition) return true; else return false;"
[1] Tom's remarks
https://sourceware.org/pipermail/gdb-patches/2020-April/167887.html
[2] Simon's remarks on v2
https://sourceware.org/pipermail/gdb-patches/2020-May/168513.html
[3] Simon's remarks on v4
https://sourceware.org/pipermail/gdb-patches/2020-August/170994.html
gdb/ChangeLog:
2020-08-25 Anton Kolesov <anton.kolesov@synopsys.com>
* configure.tgt: ARC support for GNU/Linux.
* Makefile.in (ALL_TARGET_OBJS): Likewise.
* arc-linux-tdep.c: New file.
* arc-tdep.h (ARC_STATUS32_L_MASK, ARC_STATUS32_DE_MASK): Declare.
* arc-tdep.c (arc_write_pc): Use it.
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