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[86.180.62.212]) by smtp.gmail.com with ESMTPSA id d17sm19260560wrx.9.2019.06.04.04.51.00 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Tue, 04 Jun 2019 04:51:00 -0700 (PDT) From: Andrew Burgess To: gdb-patches@sourceware.org Cc: Jim Wilson , Palmer Dabbelt , Andrew Burgess Subject: [PATCH] gdb/riscv: Don't error when decoding a 6 or 8 byte instruction Date: Tue, 4 Jun 2019 12:50:54 +0100 Message-Id: <20190604115054.25306-1-andrew.burgess@embecosm.com> X-IsSubscribed: yes If the RISC-V prologue scanner finds a 6 or 8 byte instruction we currently throw an internal error, which is not great for the user. A mechanism already exists in the prologue scanner to leave instructions marked as unknown so that we can stop the prologue scan without raising an error, this is used for all 2 and 4 byte instructions that are not part of the small set the prologue scanner actually understands. This commit changes GDB so that all 6 and 8 byte instructions are marked as unknown, rather than causing an error. gdb/ChangeLog: * riscv-tdep.c (riscv_insn::decode): Gracefully ignore instructions of lengths 6 or 8 bytes. gdb/testsuite/ChangeLog: * gdb.arch/riscv-unwind-long-insn-6.s: New file. * gdb.arch/riscv-unwind-long-insn-8.s: New file. * gdb.arch/riscv-unwind-long-insn.c: New file. * gdb.arch/riscv-unwind-long-insn.exp: New file. --- gdb/ChangeLog | 5 ++ gdb/riscv-tdep.c | 10 ++-- gdb/testsuite/ChangeLog | 7 +++ gdb/testsuite/gdb.arch/riscv-unwind-long-insn-6.s | 45 +++++++++++++++++ gdb/testsuite/gdb.arch/riscv-unwind-long-insn-8.s | 45 +++++++++++++++++ gdb/testsuite/gdb.arch/riscv-unwind-long-insn.c | 25 ++++++++++ gdb/testsuite/gdb.arch/riscv-unwind-long-insn.exp | 60 +++++++++++++++++++++++ 7 files changed, 193 insertions(+), 4 deletions(-) create mode 100644 gdb/testsuite/gdb.arch/riscv-unwind-long-insn-6.s create mode 100644 gdb/testsuite/gdb.arch/riscv-unwind-long-insn-8.s create mode 100644 gdb/testsuite/gdb.arch/riscv-unwind-long-insn.c create mode 100644 gdb/testsuite/gdb.arch/riscv-unwind-long-insn.exp diff --git a/gdb/riscv-tdep.c b/gdb/riscv-tdep.c index 3fc86ab825..bae987cf66 100644 --- a/gdb/riscv-tdep.c +++ b/gdb/riscv-tdep.c @@ -1385,10 +1385,12 @@ riscv_insn::decode (struct gdbarch *gdbarch, CORE_ADDR pc) m_opcode = OTHER; } else - internal_error (__FILE__, __LINE__, - _("unable to decode %d byte instructions in " - "prologue at %s"), m_length, - core_addr_to_string (pc)); + { + /* This must be a 6 or 8 byte instruction, we don't currently decode + any of these, so just ignore it. */ + gdb_assert (m_length == 6 || m_length == 8); + m_opcode = OTHER; + } } /* The prologue scanner. This is currently only used for skipping the diff --git a/gdb/testsuite/gdb.arch/riscv-unwind-long-insn-6.s b/gdb/testsuite/gdb.arch/riscv-unwind-long-insn-6.s new file mode 100644 index 0000000000..b21b1e10f3 --- /dev/null +++ b/gdb/testsuite/gdb.arch/riscv-unwind-long-insn-6.s @@ -0,0 +1,45 @@ +/* Copyright 2019 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 . */ + + .option nopic + .text + + .align 1 + .globl bar + .type bar, @function +bar: + tail 1f + .size bar, .-func + + .align 1 + .globl func + .type func, @function +func: + /* A fake 6 byte instruction. This is never executed, but the + prologue scanner will try to decode it. These long + instructions are ISA extensions, I use .byte rather than an + actual instruction mnemonic so that the test can be compiled + with a toolchain that doesn't include any long instruction + extensions. */ + .byte 0x1f, 0x00, 0x00, 0x00, 0x00, 0x00 +1: + addi sp,sp,-16 + sw s0,12(sp) + addi s0,sp,16 + nop + lw s0,12(sp) + addi sp,sp,16 + jr ra + .size func, .-func diff --git a/gdb/testsuite/gdb.arch/riscv-unwind-long-insn-8.s b/gdb/testsuite/gdb.arch/riscv-unwind-long-insn-8.s new file mode 100644 index 0000000000..3fad07b59d --- /dev/null +++ b/gdb/testsuite/gdb.arch/riscv-unwind-long-insn-8.s @@ -0,0 +1,45 @@ +/* Copyright 2019 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 . */ + + .option nopic + .text + + .align 1 + .globl bar + .type bar, @function +bar: + tail 1f + .size bar, .-func + + .align 1 + .globl func + .type func, @function +func: + /* A fake 8 byte instruction. This is never executed, but the + prologue scanner will try to decode it. These long + instructions are ISA extensions, I use .byte rather than an + actual instruction mnemonic so that the test can be compiled + with a toolchain that doesn't include any long instruction + extensions. */ + .byte 0x3f, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00 +1: + addi sp,sp,-16 + sw s0,12(sp) + addi s0,sp,16 + nop + lw s0,12(sp) + addi sp,sp,16 + jr ra + .size func, .-func diff --git a/gdb/testsuite/gdb.arch/riscv-unwind-long-insn.c b/gdb/testsuite/gdb.arch/riscv-unwind-long-insn.c new file mode 100644 index 0000000000..d601e2d3d8 --- /dev/null +++ b/gdb/testsuite/gdb.arch/riscv-unwind-long-insn.c @@ -0,0 +1,25 @@ +/* Copyright 2019 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 . */ + +extern void func (void); +extern void bar (void); + +int +main () +{ + bar (); + func (); + return 0; +} diff --git a/gdb/testsuite/gdb.arch/riscv-unwind-long-insn.exp b/gdb/testsuite/gdb.arch/riscv-unwind-long-insn.exp new file mode 100644 index 0000000000..e4bc489720 --- /dev/null +++ b/gdb/testsuite/gdb.arch/riscv-unwind-long-insn.exp @@ -0,0 +1,60 @@ +# Copyright 2019 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 . + +# This tests GDB's ability to handle 6 and 8 byte instructions in the +# RISC-V prologue scanner. These instruction should be ignored, but +# should not result in an error that interrupts the debug session. +# +# Each of the files riscv-unwind-long-insn-*.s include a function +# (func) that contains a fake long instruction (6 or 8 bytes) in the +# prologue. We trick GDB into parsing the fake instruction by tail +# calling from a different function, 'bar' to the middle of 'func'. + +if {![istarget "riscv*-*-*"]} { + verbose "Skipping ${gdb_test_file_name}." + return +} + +foreach_with_prefix {insn_size} {6 8} { + standard_testfile riscv-unwind-long-insn.c \ + riscv-unwind-long-insn-${insn_size}.s + + if {[prepare_for_testing "failed to prepare" $testfile \ + "$srcfile $srcfile2" debug]} { + return -1 + } + + if ![runto_main] then { + fail "can't run to main" + return 0 + } + + gdb_breakpoint "bar" + gdb_continue_to_breakpoint "bar" + + # This next single instruction step takes us through a tail-call + # from 'bar' into 'func'. + gdb_test "si" "func \(\).*" + + # Now check that we have a sane backtrace. + gdb_test "bt" \ + [multi_line \ + "#0\[ \t\]*func \\\(\\\) at .*$srcfile2:\[0-9\]+" \ + "#1\[ \t\]*$hex in main \\\(\\\) at .*$srcfile:\[0-9\]+"] \ + "Backtrace to the main frame" + + # Finally finish, and we should end up back in main. + gdb_test "finish" "main \\\(\\\) at .*$srcfile:.*" +}