f37bc8b13c
RISC-V supports instructions of varying lengths. Standard existing instructions in the base ISA are 4 bytes in length, but the 'C' extension adds support for compressed, 2 byte instructions. RISC-V supports two different breakpoint instructions: EBREAK is a 4 byte instruction in the base ISA, and C.EBREAK is a 2 byte instruction only available on processors implementing the 'C' extension. Using EBREAK to set breakpoints on compressed instructions causes problems as the second half of EBREAK will overwrite the first 2 bytes of the following instruction breaking other threads in the process if their PC is the following instruction. Thus, breakpoints on compressed instructions need to use C.EBREAK instead of EBREAK. Previously, the riscv architecture checked the MISA register to determine if the 'C' extension was available. If so, it used C.EBREAK for all breakpoints. However, the MISA register is not necessarily available to supervisor mode operating systems. While native targets could provide a fake MISA register value, this patch instead examines the existing instruction at a breakpoint target to determine which breakpoint instruction to use. If the existing instruction is a compressed instruction, C.EBREAK is used, otherwise EBREAK is used. gdb/ChangeLog: * disasm-selftests.c (print_one_insn_test): Add bfd_arch_riscv to case with explicit breakpoint kind. * riscv-tdep.c (show_use_compressed_breakpoints): Remove 'additional_info' and related logic. (riscv_debug_breakpoints): New variable. (riscv_breakpoint_kind_from_pc): Use the length of the existing instruction to determine the breakpoint kind. (_initialize_riscv_tdep): Add 'set/show debug riscv breakpoints' flag. Update description of 'set/show riscv use-compressed-breakpoints' flag. |
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README
README for GNU development tools This directory contains various GNU compilers, assemblers, linkers, debuggers, etc., plus their support routines, definitions, and documentation. If you are receiving this as part of a GDB release, see the file gdb/README. If with a binutils release, see binutils/README; if with a libg++ release, see libg++/README, etc. That'll give you info about this package -- supported targets, how to use it, how to report bugs, etc. It is now possible to automatically configure and build a variety of tools with one command. To build all of the tools contained herein, run the ``configure'' script here, e.g.: ./configure make To install them (by default in /usr/local/bin, /usr/local/lib, etc), then do: make install (If the configure script can't determine your type of computer, give it the name as an argument, for instance ``./configure sun4''. You can use the script ``config.sub'' to test whether a name is recognized; if it is, config.sub translates it to a triplet specifying CPU, vendor, and OS.) If you have more than one compiler on your system, it is often best to explicitly set CC in the environment before running configure, and to also set CC when running make. For example (assuming sh/bash/ksh): CC=gcc ./configure make A similar example using csh: setenv CC gcc ./configure make Much of the code and documentation enclosed is copyright by the Free Software Foundation, Inc. See the file COPYING or COPYING.LIB in the various directories, for a description of the GNU General Public License terms under which you can copy the files. REPORTING BUGS: Again, see gdb/README, binutils/README, etc., for info on where and how to report problems.