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From: "gabriel at inconstante dot net.br" <sourceware-bugzilla@sourceware.org>
To: gdb-prs@sourceware.org
Subject: [Bug tdep/27525] New: powerpc: displaced stepping broken for
 breakpoint at lnia instruction
Date: Fri, 05 Mar 2021 15:41:18 +0000
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https://sourceware.org/bugzilla/show_bug.cgi?id=3D27525

            Bug ID: 27525
           Summary: powerpc: displaced stepping broken for breakpoint at
                    lnia instruction
           Product: gdb
           Version: unknown
            Status: NEW
          Severity: normal
          Priority: P2
         Component: tdep
          Assignee: unassigned at sourceware dot org
          Reporter: gabriel at inconstante dot net.br
                CC: pedromfc at linux dot ibm.com, rcardoso at linux dot vn=
et.ibm.com
  Target Milestone: ---

Consider the following function:

.global fn
.type fn,@function
fn:
    lnia   3
    blr

If I place a breakpoing at 'fn', then try to 'stepi', the result in 'r3' is=
 not
set to the address of the next instruction, as can be seen in the following
output snippet:

Breakpoint 1, 0x0000000010000680 in fn ()
>>> set displaced-stepping on
>>> x /i $pc
=3D> 0x10000680 <fn>:     lnia    r3
>>> stepi
0x0000000010000684 in fn ()
>>> info registers r3
r3             0x100004ac          268436652

However, pedromfc told me that disabling displaced stepping would probably =
fix
the problem, and it did, indeed:

Breakpoint 1, 0x0000000010000680 in fn ()
>>> set displaced-stepping off
>>> x /i $pc
=3D> 0x10000680 <fn>:     lnia    r3
>>> stepi
0x0000000010000684 in fn ()
>>> info registers r3
r3             0x10000684          268437124

Cheers,
Gabriel

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