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S390: Recognize special jumps in prologue parser

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Functions compiled with the gcc option `-mhotpatch' may start with a
branch-never BRCL instruction as a 6-byte NOP.  And functions compiled
with `-mstack-size' contain a BRC instruction in their prologue that is
actually a conditional trap.  Both of these special jumps cause the
prologue parser to stop and yield bad unwinding results.

This change makes the prologue analyzer recognize such special jumps and
ignore them.

gdb/ChangeLog:

	* s390-linux-tdep.c (s390_analyze_prologue): Ignore BRC and BRCL
	instructions that do nothing or are conditional traps.
This commit is contained in:
Andreas Arnez 2016-03-09 17:12:29 +01:00
parent 6d53bec88f
commit bc0e3f49c8
2 changed files with 19 additions and 2 deletions
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5
gdb/ChangeLog
View file

@ -1,3 +1,8 @@
2016-03-09 Andreas Arnez <arnez@linux.vnet.ibm.com>
* s390-linux-tdep.c (s390_analyze_prologue): Ignore BRC and BRCL
instructions that do nothing or are conditional traps.
2016-03-09 Andreas Arnez <arnez@linux.vnet.ibm.com>
* s390-linux-tdep.c (s390_prologue_frame_unwind_cache): Store

16
gdb/s390-linux-tdep.c
View file

@ -1567,13 +1567,25 @@ s390_analyze_prologue (struct gdbarch *gdbarch,
break;
}
/* BRC/BRCL -- branch relative on condition. Ignore "branch
never", branch to following instruction, and "conditional
trap" (BRC +2). Otherwise terminate search. */
else if (is_ri (insn, op1_brc, op2_brc, &r1, &i2))
{
if (r1 != 0 && i2 != 1 && i2 != 2)
break;
}
else if (is_ril (insn, op1_brcl, op2_brcl, &r1, &i2))
{
if (r1 != 0 && i2 != 3)
break;
}
/* Terminate search when hitting any other branch instruction. */
else if (is_rr (insn, op_basr, &r1, &r2)
|| is_rx (insn, op_bas, &r1, &d2, &x2, &b2)
|| is_rr (insn, op_bcr, &r1, &r2)
|| is_rx (insn, op_bc, &r1, &d2, &x2, &b2)
|| is_ri (insn, op1_brc, op2_brc, &r1, &i2)
|| is_ril (insn, op1_brcl, op2_brcl, &r1, &i2)
|| is_ril (insn, op1_brasl, op2_brasl, &r2, &i2))
break;