gdb/riscv: Don't error when decoding a 6 or 8 byte instruction
Commit Message
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
Comments
On 6/4/19 4:50 AM, Andrew Burgess wrote:
> 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.
Looks good to me.
On Tue, 04 Jun 2019 04:50:54 PDT (-0700), andrew.burgess@embecosm.com wrote:
> 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 <http://www.gnu.org/licenses/>. */
> +
> + .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 <http://www.gnu.org/licenses/>. */
> +
> + .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 <http://www.gnu.org/licenses/>. */
> +
> +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 <http://www.gnu.org/licenses/>.
> +
> +# 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:.*"
> +}
Thanks!
On 6/4/19 12:50 PM, Andrew Burgess wrote:
> + 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
Tiny nit, but please avoid "I" in comments. Either just don't use a
pronoun, e.g.:
Since these long instructions are ISA extensions, use .byte
or use "we" instead.
Thanks,
Pedro Alves
@@ -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
new file mode 100644
@@ -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 <http://www.gnu.org/licenses/>. */
+
+ .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
new file mode 100644
@@ -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 <http://www.gnu.org/licenses/>. */
+
+ .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
new file mode 100644
@@ -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 <http://www.gnu.org/licenses/>. */
+
+extern void func (void);
+extern void bar (void);
+
+int
+main ()
+{
+ bar ();
+ func ();
+ return 0;
+}
new file mode 100644
@@ -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 <http://www.gnu.org/licenses/>.
+
+# 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:.*"
+}