PING: Re: [PATCH] gdb/riscv: Improve non-dwarf stack unwinding

[Andrew Burgess <andrew dot burgess at embecosm dot com>]

Ping!

Please could a global maintainer OK the testsuite changes.

Thanks,
Andrew


* Andrew Burgess <andrew.burgess@embecosm.com> [2018-09-19 17:41:38 +0100]:

> 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.
> ---
>  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
>