[PATCH 5/7] ftrace, PPC64: handle module trampolines for dyn ftrace

[Paul Mackerras]

Steven Rostedt writes:

> +	if (!rec->arch.mod) {
> +		if (!mod) {
> +			printk(KERN_ERR "No module loaded addr=%lx\n",
> +			       addr);
> +			return -EFAULT;
> +		}
> +		rec->arch.mod = mod;
> +	} else if (mod) {
> +		printk(KERN_ERR
> +		       "Record mod %p not equal to passed in mod %p\n",
> +		       rec->arch.mod, mod);
> +		return -EINVAL;

That looks wrong; surely you need an if (mod != rec->arch.mod)
somewhere here?

> +	/* Make sure that that this is still a 24bit jump */
> +	if ((*op & 0xff000000) != 0x48000000) {
> +		printk(KERN_ERR "Not expected bl: opcode is %x\n", *op);
> +		return -EINVAL;
> +	}

Needs to be

	if ((*op & 0xfc000003) != 0x48000001)

since the major opcode is the top 6 bits, and the bottom 2 bits are
the link bit and the absolute address bit.

> +	/* lets find where the pointer goes */
> +	offset = (*op & 0x03fffffc);
> +	/* make it signed */
> +	if (offset & 0x02000000)
> +		offset |= 0xfe000000;

but you got that right... :)

> +	/* get the address this jumps too */
> +	tramp = mod->arch.toc + offset + 32;

Why + 32?

Paul.