[PATCH v2 0/3] LoongArch: Add hardware breakpoints/watchpoints support

[Qing Zhang]

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:
- 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)
3. ptrace (PTRACE_SETREGSET, tid, ... , ...)

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

Changes v1 -> v2:
Suggested by Huacai:
- Use irqentry_enter()/irqentry_exit() instead of
  exception_enter()/exception_exit()
- Add ptrace interface to expose hw-breakpoints to debuggers
- Use 2022-2023.
- Some other changes.

Qing Zhang (3):
  LoongArch: Add hardware breakpoints/watchpoints support
  LoongArch: Add ptrace single step support
  LoongArch: ptrace: expose hardware breakpoints to debuggers

 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/include/uapi/asm/ptrace.h   |   9 +
 arch/loongarch/kernel/Makefile             |   1 +
 arch/loongarch/kernel/hw_breakpoint.c      | 540 +++++++++++++++++++++
 arch/loongarch/kernel/process.c            |   7 +
 arch/loongarch/kernel/ptrace.c             | 484 ++++++++++++++++++
 arch/loongarch/kernel/traps.c              |  27 +-
 include/uapi/linux/elf.h                   |   2 +
 13 files changed, 1241 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