From bc0e3f49c84055034cae31bba169100d107b28f4 Mon Sep 17 00:00:00 2001 From: Andreas Arnez Date: Wed, 9 Mar 2016 17:12:29 +0100 Subject: [PATCH] S390: Recognize special jumps in prologue parser 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. --- gdb/ChangeLog | 5 +++++ gdb/s390-linux-tdep.c | 16 ++++++++++++++-- 2 files changed, 19 insertions(+), 2 deletions(-) diff --git a/gdb/ChangeLog b/gdb/ChangeLog index 0674836fb28..6c33877d9d2 100644 --- a/gdb/ChangeLog +++ b/gdb/ChangeLog @@ -1,3 +1,8 @@ +2016-03-09 Andreas Arnez + + * s390-linux-tdep.c (s390_analyze_prologue): Ignore BRC and BRCL + instructions that do nothing or are conditional traps. + 2016-03-09 Andreas Arnez * s390-linux-tdep.c (s390_prologue_frame_unwind_cache): Store diff --git a/gdb/s390-linux-tdep.c b/gdb/s390-linux-tdep.c index 155bc66bd7c..950696ea328 100644 --- a/gdb/s390-linux-tdep.c +++ b/gdb/s390-linux-tdep.c @@ -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; -- 2.30.2