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Re: [PATCH] gdb/riscv: Improve non-dwarf stack unwinding
* Joel Brobecker <brobecker@adacore.com> [2018-09-26 06:49:16 -0700]:
> Hi Andrew,
>
> > This commit improves the prologue scanning stack unwinder, to better
> > support AUIPC, LUI, and more variants of ADD and ADDI.
> >
> > This allows unwinding over frames containing large local variables,
> > where the frame size does not fit into a single instruction immediate,
> > and is first loaded into a temporary register, before being added to
> > the stack pointer.
> >
> > A new test is added that tests this behaviour. As there's nothing
> > truely RiscV specific about this test I've added it into gdb.base, but
> > as this depends on target specific code to perform the unwind it is
> > possible that some targets might fail this new test.
> >
> > gdb/ChangeLog:
> >
> > * riscv-tdep.c (riscv_insn::decode): Decode c.lui.
> > (riscv_scan_prologue): Split handling of AUIPC, LUI, ADD, ADDI,
> > and NOP.
> >
> > gdb/testsuite/ChangeLog:
> >
> > * gdb.base/large-frame-1.c: New file.
> > * gdb.base/large-frame-2.c: New file.
> > * gdb.base/large-frame.exp: New file.
> > * gdb.base/large-frame.h: New file.
>
> I am OK with the patch.
>
> Are you sure you want to assert on the register number? What if
> the instruction was malformed and the register number ended up
> being larger than RISCV_NUM_INTEGER_REGS; is that possible?
Well, it shouldn't happen in the sense that, for a given instruction,
if it operates on integer registers then the space in the encoding
should only allow for up to RISCV_NUM_INTEGER_REGS registers (some
encodings allow for less registers).
Right now I can't imagine a situation where one of those asserts could
fire and it's not either a bug in GDB, or a bug in the libopcode field
extraction code - hence an assert rather than an error.
Thanks,
Andrew
>
>
> > ---
> > gdb/ChangeLog | 6 ++++
> > gdb/riscv-tdep.c | 59 ++++++++++++++++++++++------------
> > gdb/testsuite/ChangeLog | 7 ++++
> > gdb/testsuite/gdb.base/large-frame-1.c | 32 ++++++++++++++++++
> > gdb/testsuite/gdb.base/large-frame-2.c | 25 ++++++++++++++
> > gdb/testsuite/gdb.base/large-frame.exp | 57 ++++++++++++++++++++++++++++++++
> > gdb/testsuite/gdb.base/large-frame.h | 24 ++++++++++++++
> > 7 files changed, 189 insertions(+), 21 deletions(-)
> > create mode 100644 gdb/testsuite/gdb.base/large-frame-1.c
> > create mode 100644 gdb/testsuite/gdb.base/large-frame-2.c
> > create mode 100644 gdb/testsuite/gdb.base/large-frame.exp
> > create mode 100644 gdb/testsuite/gdb.base/large-frame.h
> >
> > diff --git a/gdb/riscv-tdep.c b/gdb/riscv-tdep.c
> > index 254914c9c7e..163c8ec231d 100644
> > --- a/gdb/riscv-tdep.c
> > +++ b/gdb/riscv-tdep.c
> > @@ -1227,7 +1227,11 @@ riscv_insn::decode (struct gdbarch *gdbarch, CORE_ADDR pc)
> > m_imm.s = EXTRACT_RVC_ADDI4SPN_IMM (ival);
> > }
> > else if (is_c_lui_insn (ival))
> > - m_opcode = OTHER;
> > + {
> > + m_opcode = LUI;
> > + m_rd = decode_register_index (ival, OP_SH_CRS1S);
> > + m_imm.s = EXTRACT_RVC_LUI_IMM (ival);
> > + }
> > /* C_SD and C_FSW have the same opcode. C_SD is RV64 and RV128 only,
> > and C_FSW is RV32 only. */
> > else if (xlen != 4 && is_c_sd_insn (ival))
> > @@ -1359,28 +1363,41 @@ riscv_scan_prologue (struct gdbarch *gdbarch,
> > gdb_assert (insn.rs1 () < RISCV_NUM_INTEGER_REGS);
> > regs[insn.rd ()] = pv_add_constant (regs[insn.rs1 ()], 0);
> > }
> > - else if ((insn.rd () == RISCV_GP_REGNUM
> > - && (insn.opcode () == riscv_insn::AUIPC
> > - || insn.opcode () == riscv_insn::LUI
> > - || (insn.opcode () == riscv_insn::ADDI
> > - && insn.rs1 () == RISCV_GP_REGNUM)
> > - || (insn.opcode () == riscv_insn::ADD
> > - && (insn.rs1 () == RISCV_GP_REGNUM
> > - || insn.rs2 () == RISCV_GP_REGNUM))))
> > - || (insn.opcode () == riscv_insn::ADDI
> > - && insn.rd () == RISCV_ZERO_REGNUM
> > - && insn.rs1 () == RISCV_ZERO_REGNUM
> > - && insn.imm_signed () == 0))
> > + else if ((insn.opcode () == riscv_insn::ADDI
> > + && insn.rd () == RISCV_ZERO_REGNUM
> > + && insn.rs1 () == RISCV_ZERO_REGNUM
> > + && insn.imm_signed () == 0))
> > {
> > - /* Handle: auipc gp, n
> > - or: addi gp, gp, n
> > - or: add gp, gp, reg
> > - or: add gp, reg, gp
> > - or: lui gp, n
> > - or: add x0, x0, 0 (NOP) */
> > - /* These instructions are part of the prologue, but we don't need
> > - to do anything special to handle them. */
> > + /* Handle: add x0, x0, 0 (NOP) */
> > }
> > + else if (insn.opcode () == riscv_insn::AUIPC)
> > + {
> > + gdb_assert (insn.rd () < RISCV_NUM_INTEGER_REGS);
> > + regs[insn.rd ()] = pv_constant (cur_pc + insn.imm_signed ());
> > + }
> > + else if (insn.opcode () == riscv_insn::LUI)
> > + {
> > + /* Handle: lui REG, n
> > + Where REG is not gp register. */
> > + gdb_assert (insn.rd () < RISCV_NUM_INTEGER_REGS);
> > + regs[insn.rd ()] = pv_constant (insn.imm_signed ());
> > + }
> > + else if (insn.opcode () == riscv_insn::ADDI)
> > + {
> > + /* Handle: addi REG1, REG2, IMM */
> > + gdb_assert (insn.rd () < RISCV_NUM_INTEGER_REGS);
> > + gdb_assert (insn.rs1 () < RISCV_NUM_INTEGER_REGS);
> > + regs[insn.rd ()]
> > + = pv_add_constant (regs[insn.rs1 ()], insn.imm_signed ());
> > + }
> > + else if (insn.opcode () == riscv_insn::ADD)
> > + {
> > + /* Handle: addi REG1, REG2, IMM */
> > + gdb_assert (insn.rd () < RISCV_NUM_INTEGER_REGS);
> > + gdb_assert (insn.rs1 () < RISCV_NUM_INTEGER_REGS);
> > + gdb_assert (insn.rs2 () < RISCV_NUM_INTEGER_REGS);
> > + regs[insn.rd ()] = pv_add (regs[insn.rs1 ()], regs[insn.rs2 ()]);
> > + }
> > else
> > {
> > end_prologue_addr = cur_pc;
> > diff --git a/gdb/testsuite/gdb.base/large-frame-1.c b/gdb/testsuite/gdb.base/large-frame-1.c
> > new file mode 100644
> > index 00000000000..cd9c5ccdd0a
> > --- /dev/null
> > +++ b/gdb/testsuite/gdb.base/large-frame-1.c
> > @@ -0,0 +1,32 @@
> > +/* This file is part of GDB, the GNU debugger.
> > +
> > + Copyright 2018 Free Software Foundation, Inc.
> > +
> > + This program is free software; you can redistribute it and/or modify
> > + it under the terms of the GNU General Public License as published by
> > + the Free Software Foundation; either version 3 of the License, or
> > + (at your option) any later version.
> > +
> > + This program is distributed in the hope that it will be useful,
> > + but WITHOUT ANY WARRANTY; without even the implied warranty of
> > + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
> > + GNU General Public License for more details.
> > +
> > + You should have received a copy of the GNU General Public License
> > + along with this program. If not, see <http://www.gnu.org/licenses/>. */
> > +
> > +#include "large-frame.h"
> > +
> > +__attribute__ ((noinline)) void
> > +blah (int *a)
> > +{
> > + asm ("" :: "m" (a) : "memory");
> > +}
> > +
> > +int
> > +main ()
> > +{
> > + func ();
> > +
> > + return 0;
> > +}
> > diff --git a/gdb/testsuite/gdb.base/large-frame-2.c b/gdb/testsuite/gdb.base/large-frame-2.c
> > new file mode 100644
> > index 00000000000..2491c347292
> > --- /dev/null
> > +++ b/gdb/testsuite/gdb.base/large-frame-2.c
> > @@ -0,0 +1,25 @@
> > +/* This file is part of GDB, the GNU debugger.
> > +
> > + Copyright 2018 Free Software Foundation, Inc.
> > +
> > + This program is free software; you can redistribute it and/or modify
> > + it under the terms of the GNU General Public License as published by
> > + the Free Software Foundation; either version 3 of the License, or
> > + (at your option) any later version.
> > +
> > + This program is distributed in the hope that it will be useful,
> > + but WITHOUT ANY WARRANTY; without even the implied warranty of
> > + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
> > + GNU General Public License for more details.
> > +
> > + You should have received a copy of the GNU General Public License
> > + along with this program. If not, see <http://www.gnu.org/licenses/>. */
> > +
> > +#include "large-frame.h"
> > +
> > +__attribute__ ((noinline)) int
> > +func (void)
> > +{
> > + int a[4096];
> > + blah (a);
> > +}
> > diff --git a/gdb/testsuite/gdb.base/large-frame.exp b/gdb/testsuite/gdb.base/large-frame.exp
> > new file mode 100644
> > index 00000000000..00090da795e
> > --- /dev/null
> > +++ b/gdb/testsuite/gdb.base/large-frame.exp
> > @@ -0,0 +1,57 @@
> > +# Copyright 2018 Free Software Foundation, Inc.
> > +#
> > +# This program is free software; you can redistribute it and/or modify
> > +# it under the terms of the GNU General Public License as published by
> > +# the Free Software Foundation; either version 3 of the License, or
> > +# (at your option) any later version.
> > +#
> > +# This program is distributed in the hope that it will be useful,
> > +# but WITHOUT ANY WARRANTY; without even the implied warranty of
> > +# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
> > +# GNU General Public License for more details.
> > +#
> > +# You should have received a copy of the GNU General Public License
> > +# along with this program. If not, see <http://www.gnu.org/licenses/>.
> > +#
> > +# This file is part of the gdb testsuite.
> > +
> > +# This test was added to test GDB's ability to backtrace over a large
> > +# stack frame for which there is no debug information. This should
> > +# test the non-DWARF stack unwinder.
> > +#
> > +# The test was originally added for Risc-V where this case caused a
> > +# problem at one point, however, there's nothing Risc-V specific in
> > +# the test.
> > +
> > +proc run_test { opt_level } {
> > + global srcfile srcfile2 binfile hex
> > +
> > + standard_testfile large-frame-1.c large-frame-2.c
> > +
> > + if {[prepare_for_testing_full "failed to prepare" \
> > + [list ${binfile}-${opt_level} debug \
> > + $srcfile [list debug] \
> > + $srcfile2 [list nodebug optimize=-$opt_level]]]} {
> > + return
> > + }
> > +
> > + if { ![runto_main] } then {
> > + unsupported "runto main"
> > + return
> > + }
> > +
> > + gdb_breakpoint "blah"
> > + gdb_continue_to_breakpoint "blah"
> > +
> > + gdb_test "backtrace" [multi_line \
> > + "#0 blah \[^\n\r\]+" \
> > + "#1 $hex in func \[^\n\r\]+" \
> > + "#2 $hex in main \[^\n\r\]+"]
> > +}
> > +
> > +foreach opt { O0 O1 O2 } {
> > + with_test_prefix "optimize=-$opt" {
> > + run_test $opt
> > + }
> > +}
> > +
> > diff --git a/gdb/testsuite/gdb.base/large-frame.h b/gdb/testsuite/gdb.base/large-frame.h
> > new file mode 100644
> > index 00000000000..17058a5efd2
> > --- /dev/null
> > +++ b/gdb/testsuite/gdb.base/large-frame.h
> > @@ -0,0 +1,24 @@
> > +/* This file is part of GDB, the GNU debugger.
> > +
> > + Copyright 2018 Free Software Foundation, Inc.
> > +
> > + This program is free software; you can redistribute it and/or modify
> > + it under the terms of the GNU General Public License as published by
> > + the Free Software Foundation; either version 3 of the License, or
> > + (at your option) any later version.
> > +
> > + This program is distributed in the hope that it will be useful,
> > + but WITHOUT ANY WARRANTY; without even the implied warranty of
> > + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
> > + GNU General Public License for more details.
> > +
> > + You should have received a copy of the GNU General Public License
> > + along with this program. If not, see <http://www.gnu.org/licenses/>. */
> > +
> > +#ifndef LARGE_FRAME_H
> > +#define LARGE_FRAME_H
> > +
> > +extern void blah (int *);
> > +extern int func (void);
> > +
> > +#endif /* LARGE_FRAME_H */
> > --
> > 2.14.4
>
> --
> Joel