On Sat, Oct 26, 2024 at 01:35:30PM +0900, Masami Hiramatsu (Google) wrote:

From: Masami Hiramatsu (Google) <mhiramat@kernel.org>

Pass ftrace_regs to the fgraph_ops::entryfunc(). If ftrace_regs is not
available, it passes a NULL instead. User callback function can access
some registers (including return address) via this ftrace_regs.

Note that the ftrace_regs can be NULL when the arch does NOT define:
HAVE_DYNAMIC_FTRACE_WITH_ARGS or HAVE_DYNAMIC_FTRACE_WITH_REGS.
More specifically, if HAVE_DYNAMIC_FTRACE_WITH_REGS is defined but
not the HAVE_DYNAMIC_FTRACE_WITH_ARGS, and the ftrace ops used to
register the function callback does not set FTRACE_OPS_FL_SAVE_REGS.
In this case, ftrace_regs can be NULL in user callback.

Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>
Cc: Huacai Chen <chenhuacai@kernel.org>
Cc: WANG Xuerui <kernel@xen0n.name>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Christophe Leroy <redacted>
Cc: Naveen N Rao <naveen@kernel.org>
Cc: Madhavan Srinivasan <maddy@linux.ibm.com>
Cc: Paul Walmsley <redacted>
Cc: Palmer Dabbelt <palmer@dabbelt.com>
Cc: Albert Ou <aou@eecs.berkeley.edu>
Cc: Thomas Gleixner <redacted>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: x86@kernel.org
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

---
 Changes in v18:
  - Remove unclear comment about `regs->fp` access on arm64.
 Changes in v16:
  - Add a note when the ftrace_regs can be NULL.
  - Update against for the latest kernel.
 Changes in v11:
  - Update for the latest for-next branch.
 Changes in v8:
  - Just pass ftrace_regs to the handler instead of adding a new
    entryregfunc.
  - Update riscv ftrace_graph_func().
 Changes in v3:
  - Update for new multiple fgraph.
---
 arch/arm64/kernel/ftrace.c               |   15 ++++++++-

For the arm64 bits:

Acked-by: Will Deacon <will@kernel.org>

Will