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arc: Write correct "eret" value during register collection

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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.
This commit is contained in:
Shahab Vahedi 2020-11-12 12:50:33 +01:00
parent 1f2624a354
commit 10c19fadfd
2 changed files with 12 additions and 3 deletions
Download patch file Download diff file Expand all files Collapse all files

5
gdb/ChangeLog
View file

@ -1,3 +1,8 @@
2020-11-12 Shahab Vahedi <shahab@synopsys.com>
* arc-linux-tdep.c (collect_register): Populate "eret" by
"pc" value from the regcache when asked for "pc" value.
2020-11-12 Tom Tromey <tom@tromey.com> 2020-11-12 Tom Tromey <tom@tromey.com>
PR rust/26799: PR rust/26799:

10
gdb/arc-linux-tdep.c
View file

@ -319,8 +319,10 @@ static void
collect_register (const struct regcache *regcache, struct gdbarch *gdbarch, collect_register (const struct regcache *regcache, struct gdbarch *gdbarch,
int regnum, gdb_byte *buf) int regnum, gdb_byte *buf)
{ {
int offset;
/* Skip non-existing registers. */ /* Skip non-existing registers. */
if ((arc_linux_core_reg_offsets[regnum] == ARC_OFFSET_NO_REGISTER)) if (arc_linux_core_reg_offsets[regnum] == ARC_OFFSET_NO_REGISTER)
return; return;
/* The address where the execution has stopped is in pseudo-register /* The address where the execution has stopped is in pseudo-register
@ -332,8 +334,10 @@ collect_register (const struct regcache *regcache, struct gdbarch *gdbarch,
the program will continue at the address after the current instruction. the program will continue at the address after the current instruction.
*/ */
if (regnum == gdbarch_pc_regnum (gdbarch)) if (regnum == gdbarch_pc_regnum (gdbarch))
regnum = ARC_ERET_REGNUM; offset = arc_linux_core_reg_offsets[ARC_ERET_REGNUM];
regcache->raw_collect (regnum, buf + arc_linux_core_reg_offsets[regnum]); else
offset = arc_linux_core_reg_offsets[regnum];
regcache->raw_collect (regnum, buf + offset);
} }
void void