On Mon, 21 Oct 2024 17:46:19 +0100
Will Deacon [off-list ref] wrote:

On Wed, Oct 16, 2024 at 09:59:00AM +0900, Masami Hiramatsu (Google) wrote:

quoted

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

Add ftrace_partial_regs() which converts the ftrace_regs to pt_regs.
This is for the eBPF which needs this to keep the same pt_regs interface
to access registers.
Thus when replacing the pt_regs with ftrace_regs in fprobes (which is
used by kprobe_multi eBPF event), this will be used.

If the architecture defines its own ftrace_regs, this copies partial
registers to pt_regs and returns it. If not, ftrace_regs is the same as
pt_regs and ftrace_partial_regs() will return ftrace_regs::regs.

Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Acked-by: Florent Revest <redacted>
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: Paul Walmsley <redacted>
Cc: Palmer Dabbelt <palmer@dabbelt.com>
Cc: Albert Ou <aou@eecs.berkeley.edu>

---
 Changes in v14:
  - Add riscv change.
 Changes in v8:
  - Add the reason why this required in changelog.
 Changes from previous series: NOTHING, just forward ported.
---
 arch/arm64/include/asm/ftrace.h |   11 +++++++++++
 arch/riscv/include/asm/ftrace.h |   14 ++++++++++++++
 include/linux/ftrace.h          |   17 +++++++++++++++++
 3 files changed, 42 insertions(+)

diff --git a/arch/arm64/include/asm/ftrace.h b/arch/arm64/include/asm/ftrace.h
index b5fa57b61378..d344c69eb01e 100644
--- a/arch/arm64/include/asm/ftrace.h
+++ b/arch/arm64/include/asm/ftrace.h

@@ -135,6 +135,17 @@ ftrace_regs_get_frame_pointer(const struct ftrace_regs *fregs)
 	return arch_ftrace_regs(fregs)->fp;
 }
 
+static __always_inline struct pt_regs *
+ftrace_partial_regs(const struct ftrace_regs *fregs, struct pt_regs *regs)
+{
+	memcpy(regs->regs, arch_ftrace_regs(fregs)->regs, sizeof(u64) * 9);

Since ftrace_regs::regs is an 'unsigned long regs[9]' can we just use
sizeof() on that instead of hard-coding the length of the array here?

Good catch! I will update it.

Thank you!

Will

-- 
Masami Hiramatsu (Google) [off-list ref]