linux-kernel - Re: [PATCH v3 2/4] kernel/trace: Provide default impelentations defined in trace_probe

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Message-Id: <20221224002157.ce3caeee919d153fe4f56bc8@kernel.org>
Date:   Sat, 24 Dec 2022 00:21:57 +0900
From:   Masami Hiramatsu (Google) <mhiramat@...nel.org>
To:     Song Chen <chensong_2000@....cn>
Cc:     rostedt@...dmis.org, arnd@...db.de, linux-kernel@...r.kernel.org,
        linux-trace-kernel@...r.kernel.org, linux-arch@...r.kernel.org
Subject: Re: [PATCH v3 2/4] kernel/trace: Provide default impelentations
 defined in trace_probe_tmpl.h

Hi Song,

On Mon,  5 Dec 2022 16:29:54 +0800
Song Chen <chensong_2000@....cn> wrote:

> @@ -112,4 +112,133 @@ kern_fetch_store_string(unsigned long addr, void *dest, void *base)
>  	return ret;
>  }
>  
> +static nokprobe_inline int
> +probe_mem_read_user(void *dest, void *src, size_t size)
> +{
> +	const void __user *uaddr =  (__force const void __user *)src;
> +
> +	return copy_from_user_nofault(dest, uaddr, size);
> +}
> +
> +static nokprobe_inline int
> +probe_mem_read(void *dest, void *src, size_t size)
> +{
> +#ifdef CONFIG_ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE
> +	if ((unsigned long)src < TASK_SIZE)
> +		return probe_mem_read_user(dest, src, size);
> +#endif
> +	return copy_from_kernel_nofault(dest, src, size);
> +}
> +

So, the error which kernel build bot found has been introduced by this patch.
The easiest acceptable change will add

#ifdef CONFIG_HAVE_REGS_AND_STACK_ACCESS_API

here, and #endif after process_fetch_insn(). 

Thank you,

> +static nokprobe_inline unsigned long
> +get_event_field(struct fetch_insn *code, void *rec)
> +{
> +	struct ftrace_event_field *field = code->data;
> +	unsigned long val;
> +	void *addr;
> +
> +	addr = rec + field->offset;
> +
> +	if (is_string_field(field)) {
> +		switch (field->filter_type) {
> +		case FILTER_DYN_STRING:
> +			val = (unsigned long)(rec + (*(unsigned int *)addr & 0xffff));
> +			break;
> +		case FILTER_RDYN_STRING:
> +			val = (unsigned long)(addr + (*(unsigned int *)addr & 0xffff));
> +			break;
> +		case FILTER_STATIC_STRING:
> +			val = (unsigned long)addr;
> +			break;
> +		case FILTER_PTR_STRING:
> +			val = (unsigned long)(*(char *)addr);
> +			break;
> +		default:
> +			WARN_ON_ONCE(1);
> +			return 0;
> +		}
> +		return val;
> +	}
> +
> +	switch (field->size) {
> +	case 1:
> +		if (field->is_signed)
> +			val = *(char *)addr;
> +		else
> +			val = *(unsigned char *)addr;
> +		break;
> +	case 2:
> +		if (field->is_signed)
> +			val = *(short *)addr;
> +		else
> +			val = *(unsigned short *)addr;
> +		break;
> +	case 4:
> +		if (field->is_signed)
> +			val = *(int *)addr;
> +		else
> +			val = *(unsigned int *)addr;
> +		break;
> +	default:
> +		if (field->is_signed)
> +			val = *(long *)addr;
> +		else
> +			val = *(unsigned long *)addr;
> +		break;
> +	}
> +	return val;
> +}
> +
> +/* Note that we don't verify it, since the code does not come from user space */
> +static int
> +process_fetch_insn(struct fetch_insn *code, void *rec, void *dest,
> +		   void *base)
> +{
> +	struct pt_regs *regs = rec;
> +	unsigned long val;
> +
> +retry:
> +	/* 1st stage: get value from context */
> +	switch (code->op) {
> +	case FETCH_OP_REG:
> +		val = regs_get_register(regs, code->param);
> +		break;
> +	case FETCH_OP_STACK:
> +		val = regs_get_kernel_stack_nth(regs, code->param);
> +		break;
> +	case FETCH_OP_STACKP:
> +		val = kernel_stack_pointer(regs);
> +		break;
> +	case FETCH_OP_RETVAL:
> +		val = regs_return_value(regs);
> +		break;
> +	case FETCH_OP_IMM:
> +		val = code->immediate;
> +		break;
> +	case FETCH_OP_COMM:
> +		val = (unsigned long)current->comm;
> +		break;
> +	case FETCH_OP_DATA:
> +		val = (unsigned long)code->data;
> +		break;
> +#ifdef CONFIG_HAVE_FUNCTION_ARG_ACCESS_API
> +	case FETCH_OP_ARG:
> +		val = regs_get_kernel_argument(regs, code->param);
> +		break;
> +#endif
> +	case FETCH_NOP_SYMBOL:	/* Ignore a place holder */
> +		code++;
> +		goto retry;
> +	case FETCH_OP_TP_ARG:
> +		val = get_event_field(code, rec);
> +		break;
> +	default:
> +		return -EILSEQ;
> +	}
> +	code++;
> +
> +	return process_fetch_insn_bottom(code, val, dest, base);
> +}
> +NOKPROBE_SYMBOL(process_fetch_insn)
> +
>  #endif /* __TRACE_PROBE_KERNEL_H_ */
> -- 
> 2.25.1
> 


-- 
Masami Hiramatsu (Google) <mhiramat@...nel.org>