linux-kernel - Re: [PATCH -next v4 17/19] entry: Add syscall arch functions to use generic syscall for arm64

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Message-ID: <875xpc2in5.ffs@tglx>
Date: Mon, 28 Oct 2024 19:21:18 +0100
From: Thomas Gleixner <tglx@...utronix.de>
To: Jinjie Ruan <ruanjinjie@...wei.com>, oleg@...hat.com,
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Subject: Re: [PATCH -next v4 17/19] entry: Add syscall arch functions to use
 generic syscall for arm64

On Fri, Oct 25 2024 at 18:06, Jinjie Ruan wrote:

$Subject: Can you please make this simply:

    entry: Add arch_pre/post_report_syscall_entry/exit()

> Add some syscall arch functions to support arm64 to use generic syscall
> code, which do not affect existing architectures that use generic entry:
>
>  - arch_pre/post_report_syscall_entry/exit().

> Also make syscall_exit_work() not static and move report_single_step() to
> thread_info.h, which can be used by arm64 later.

This does way too many things which have nothing to do with the subject
line.

>  long syscall_trace_enter(struct pt_regs *regs, long syscall,
>  				unsigned long work)
>  {
> @@ -34,7 +77,9 @@ long syscall_trace_enter(struct pt_regs *regs, long syscall,
>  
>  	/* Handle ptrace */
>  	if (work & (SYSCALL_WORK_SYSCALL_TRACE | SYSCALL_WORK_SYSCALL_EMU)) {
> +		unsigned long saved_reg = arch_pre_report_syscall_entry(regs);

Lacks a new line between declaration and code.

>  		ret = ptrace_report_syscall_entry(regs);
> +		arch_post_report_syscall_entry(regs, saved_reg, ret);

Though I'm not sure whether these pre/post hooks buy anything. It's
probably simpler to do:

-  		ret = ptrace_report_syscall_entry(regs);
+		ret = arch_ptrace_report_syscall_entry(regs);

And have the default implementation as

        return ptrace_report_syscall_entry(regs);

and let ARM64 implement it's magic around it in the architecture
header. The actual ptrace_report_syscall_entry() is simple enough to be
in both places. That reduces the inflation of architecture specific
helpers and keeps the code tidy.

Thanks,

        tglx