On Mon, Aug 7, 2023 at 8:49 AM Masami Hiramatsu (Google)
<mhiramat@xxxxxxxxxx> wrote:
>
> From: Masami Hiramatsu (Google) <mhiramat@xxxxxxxxxx>
>
> Add ftrace_partial_regs() which converts the ftrace_regas to pt_regs.
ftrace_regs*
> 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@xxxxxxxxxx>
> ---
> arch/arm64/include/asm/ftrace.h | 11 +++++++++++
> include/linux/ftrace.h | 11 +++++++++++
> 2 files changed, 22 insertions(+)
>
> diff --git a/arch/arm64/include/asm/ftrace.h b/arch/arm64/include/asm/ftrace.h
> index ab158196480c..b108cd6718cf 100644
> --- a/arch/arm64/include/asm/ftrace.h
> +++ b/arch/arm64/include/asm/ftrace.h
> @@ -137,6 +137,17 @@ ftrace_override_function_with_return(struct ftrace_regs *fregs)
> fregs->pc = fregs->lr;
> }
>
> +static __always_inline struct pt_regs *
> +ftrace_partial_regs(const struct ftrace_regs *fregs, struct pt_regs *regs)
> +{
> + memcpy(regs->regs, fregs->regs, sizeof(u64) * 10);
Are you intentionally copying that tenth value (fregs.direct_tramp)
into pt_regs.regs[9] ? This seems wrong and it looks like it will bite
us back one day. Isn't it one of these cases where we can simply use
sizeof(fregs->regs) ?
> + regs->sp = fregs->sp;
> + regs->pc = fregs->pc;
> + regs->x[29] = fregs->fp;
> + regs->x[30] = fregs->lr;
> + return regs;
> +}
> +
> int ftrace_regs_query_register_offset(const char *name);
>
> int ftrace_init_nop(struct module *mod, struct dyn_ftrace *rec);
> diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
> index 3fb94a1a2461..7f45654441b7 100644
> --- a/include/linux/ftrace.h
> +++ b/include/linux/ftrace.h
> @@ -155,6 +155,17 @@ static __always_inline struct pt_regs *ftrace_get_regs(struct ftrace_regs *fregs
> return arch_ftrace_get_regs(fregs);
> }
>
> +#if !defined(CONFIG_HAVE_DYNAMIC_FTRACE_WITH_ARGS) || \
> + defined(CONFIG_HAVE_PT_REGS_COMPAT_FTRACE_REGS)
> +
> +static __always_inline struct pt_regs *
> +ftrace_partial_regs(const struct ftrace_regs *fregs, struct pt_regs *regs)
> +{
> + return arch_ftrace_get_regs((struct ftrace_regs *)fregs);
> +}
I don't think this works. Suppose you are on x86, WITH_ARGS, and with
HAVE_PT_REGS_COMPAT_FTRACE_REGS. If you register to ftrace without
FTRACE_OPS_FL_SAVE_REGS you will receive a ftrace_regs from the light
ftrace pre-trampoline that has a CS register equal to 0 and
arch_ftrace_get_regs will return NULL here, which should never happen.
Have you tested your series without registering as FTRACE_OPS_FL_SAVE_REGS ?
