linux-kernel - [PATCH 0/2] riscv: ftrace: make stack walk more robust.

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Message-Id: <20240328184020.34278-1-puranjay12@gmail.com>
Date: Thu, 28 Mar 2024 18:40:18 +0000
From: Puranjay Mohan <puranjay12@...il.com>
To: Paul Walmsley <paul.walmsley@...ive.com>,
	Palmer Dabbelt <palmer@...belt.com>,
	Albert Ou <aou@...s.berkeley.edu>,
	linux-riscv@...ts.infradead.org,
	linux-kernel@...r.kernel.org,
	Björn Töpel <bjorn@...osinc.com>
Cc: puranjay12@...il.com
Subject: [PATCH 0/2] riscv: ftrace: make stack walk more robust.

The current stack walker in riscv implemented in walk_stackframe() provides
the PC to a callback function when it unwinds the stacks. This doesn't
allow implementing stack walkers that need access to more information like
the frame pointer, etc.

This series makes walk_stackframe() provide a unwinde_state structure to
callback functions. This structure has all the information that
walk_stackframe() can provide.

Currently, there are four users of walk_stackframe(): return_address(),
perf_callchain_kernel(), dump_backtrace(), and __get_wchan(). All of these
have been converted to use arch_stack_walk() rather than calling
walk_stackframe() directly.

We need this to implement arch_bpf_stack_walk() that provides a callback
that needs the FP, SP, and PC. This will be needed for implementing BFP
exceptions for RISCV.

There are no functional changes in this series.

I have tested this by crashing the kernel and looking at the stack trace
with and without CONFIG_FRAME_POINTER

Puranjay Mohan (2):
  riscv: stacktrace: use arch_stack_walk() in place of walk_stackframe
  riscv: stacktrace: make walk_stackframe() more robust

 arch/riscv/include/asm/stacktrace.h |  2 -
 arch/riscv/kernel/perf_callchain.c  |  2 +-
 arch/riscv/kernel/stacktrace.c      | 75 +++++++++++++++++++++++------
 3 files changed, 61 insertions(+), 18 deletions(-)

-- 
2.40.1