linux-kernel - [PATCH 0/2] LoongArch: Add hardware breakpoints/watchpoints support

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Date:   Wed,  8 Feb 2023 18:08:35 +0800
From:   Qing Zhang <zhangqing@...ngson.cn>
To:     Huacai Chen <chenhuacai@...nel.org>,
        Oleg Nesterov <oleg@...hat.com>,
        WANG Xuerui <kernel@...0n.name>
Cc:     Jiaxun Yang <jiaxun.yang@...goat.com>, loongarch@...ts.linux.dev,
        linux-kernel@...r.kernel.org
Subject: [PATCH 0/2] LoongArch: Add hardware breakpoints/watchpoints support

Use perf framework to manage hardware instruction and data breakpoints.
LoongArch defines hardware watchpoint functions for instruction fetch
and load/store operations, after the software configures hardware watchpoints
for instruction fetch and load/store operations. The processor hardware will
monitor the access address of the instruction fetch and load/store operation,
and will trigger the exception of the watchpoint when it meets the conditions
set by the watchpoint.

The hardware monitoring points for instruction fetching and load/store operations
each have a register for the overall configuration of all monitoring points,
a register for recording the status of all monitoring points, and four registers
required for configuration of each watchpoint individually.

Watchpoint related control status register chapters:
https://github.com/loongson/LoongArch-Documentation/releases/download/2022.08.12/
LoongArch-Vol1-v1.02-CN.pdf

Initial version has the following limitations:
- userspace debug is not yet enabled: work on ptrace/gdb is in progress
- no support for virtualization

Can be tested: e.g.
1. see samples/hw_breakpoint and register_wide_hw_breakpoint.
2. ptrace(PTRACE_SINGLESTEP/..., pid, NULL, NULL)

TODO:
- Add hardware breakpoints/watchpoints for gdb, kgdb

Qing Zhang (2):
  LoongArch: Add hardware breakpoints/watchpoints support
  LoongArch: Add ptrace single step support

 arch/loongarch/Kconfig                     |   1 +
 arch/loongarch/include/asm/hw_breakpoint.h | 145 ++++++
 arch/loongarch/include/asm/loongarch.h     |  32 +-
 arch/loongarch/include/asm/processor.h     |  11 +-
 arch/loongarch/include/asm/ptrace.h        |   2 +
 arch/loongarch/include/asm/switch_to.h     |   1 +
 arch/loongarch/kernel/Makefile             |   1 +
 arch/loongarch/kernel/hw_breakpoint.c      | 525 +++++++++++++++++++++
 arch/loongarch/kernel/process.c            |   7 +
 arch/loongarch/kernel/ptrace.c             |  68 +++
 arch/loongarch/kernel/traps.c              |  31 +-
 11 files changed, 803 insertions(+), 21 deletions(-)
 create mode 100644 arch/loongarch/include/asm/hw_breakpoint.h
 create mode 100644 arch/loongarch/kernel/hw_breakpoint.c

-- 
2.36.0