On 4/19/2011 5:21 PM, Nicolas Pitre wrote:
Are you saying that your user space libc was reading at 0xffff0ff0 directly? I hope not, because if you did so, you clearly abused the interface and the contract between user space and the kernel. Here's what I wrote in the comment right above the related code: * These are segment of kernel provided user code reachable from user space * at a fixed address in kernel memory. This is used to provide user space * with some operations which require kernel help because of unimplemented * native feature and/or instructions in many ARM CPUs. The idea is for * this code to be executed directly in user mode for best efficiency but * which is too intimate with the kernel counter part to be left to user * libraries. In fact this code might even differ from one CPU to another * depending on the available instruction set and restrictions like on * SMP systems. In other words, the kernel reserves the right to change * this code as needed without warning. Only the entry points and their * results are guaranteed to be stable. This has been there since April 29th 2005 i.e. 6 years ago.
Yes, unfortunately Android appears to do this as an 'optimization' in the case of dynamically linked execs. That is, it skips the helper code all together.
Mike -- Employee of Qualcomm Innovation Center, Inc. Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum -- To unsubscribe from this list: send the line "unsubscribe linux-arm-msm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
