The gdb CSR xml file has registers in documentation order, not numerical
order, so we need a table to map the register numbers. This also adds
fairly standard gdb hooks to access xml specified registers.
notice:
The fpu xml from gdb 8.3 has unused register #, 65 and make first
csr register # become 69. We register extra register on gdb to correct
csr offset calculation
Signed-off-by: Jim Wilson <jimw@sifive.com>
Signed-off-by: Chih-Min Chao <chihmin.chao@sifive.com>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Signed-off-by: Palmer Dabbelt <palmer@sifive.com>
Previous CSR code uses csr_read_helper and csr_write_helper
to update CSR registers however this interface prevents
atomic read/modify/write CSR operations; in addition
there is no trap-free method to access to CSRs due
to the monolithic CSR functions call longjmp.
The current iCSR interface is not safe to be called by
target/riscv/gdbstub.c as privilege checks or missing CSRs
may call longjmp to generate exceptions. It needs to
indicate existence so traps can be generated in the
CSR instruction helpers.
This commit moves CSR access from the monolithic switch
statements in target/riscv/op_helper.c into modular
read/write functions in target/riscv/csr.c using a new
function pointer table for dispatch (which can later
be used to allow CPUs to hook up model specific CSRs).
A read/modify/write interface is added to support atomic
CSR operations and a non-trapping interface is added
to allow exception-free access to CSRs by the debugger.
The CSR functions and CSR dispatch table are ordered
to match The RISC-V Instruction Set Manual, Volume II:
Privileged Architecture Version 1.10, 2.2 CSR Listing.
An API is added to allow derived cpu instances to modify
or implement new CSR operations.
Signed-off-by: Michael Clark <mjc@sifive.com>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Palmer Dabbelt <palmer@sifive.com>
GDB Register read and write routines.
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Sagar Karandikar <sagark@eecs.berkeley.edu>
Signed-off-by: Michael Clark <mjc@sifive.com>
