写入端口0cf8h失败，出现segfault [英] Write to port 0cf8h fails with segfault

问题描述

我有一个e2-2000模型的AMD处理器.这是家庭0fh. 根据0fh BKDG系列，我有以下代码可以读取设备和供应商ID:

I have an AMD processor of e2-2000 model. THis is family 0fh. According to family 0fh BKDG I have this code to read device and vendor ID:

ReadPCIConfiguration:
movq    $0x80000100, %rax
movq    $0x0cf8, %rdx
outl    %eax, %dx          # sigsegv caught here
movq    $0x0cfc, %rdx
inl     %dx, %eax
ret

据我所知，读写PCI配置的算法如下:

As far as I know the algorithm to read/write PCI configuration is as follows:

• 将目标总线号，设备号功能号和偏移量或寄存器号写入配置地址端口
• 从/到配置数据端口执行1字节，2字节或4字节的读/写操作

端口0xcf8..0xcfb-配置地址端口(双字)

Ports 0xcf8..0xcfb - configuration address port (doubleword)

位含义:

• 31-EnReg-启用交易(读/写)
• 24..31-保留(R/O)
• 16..23-BusNum(R/W)
• 11..15-DevNum(R/W)
• 8..10-FuncNum(R/W)
• 2..7-RegNum(R/W)
• 0..1-保留(R/O)

所以，我写到bus-0，dev-0，func-1，reg-00

So, I write to bus - 0, dev - 0, func - 1, reg - 00

我做错什么了吗?

(我从用户空间GNU/Debian"Wheezy" Linux 3.11.6运行已编译和链接的应用程序)

(I run the compiled and linked application from userspace, GNU/Debian "Wheezy" Linux 3.11.6)

推荐答案

Linux默认情况下不允许用户区代码写入I/O端口. (从安全角度来看，这样做非常危险.)如果您希望Linux允许您的进程访问I/O端口，则有两种选择:

Linux does not, by default, allow userland code to write to I/O ports. (Doing so can be quite dangerous from a security perspective.) If you’d like Linux to give your process access to the I/O ports, you have two options:

1. 您可以使用ioperm系统调用.但是，ioperm已经过时了一段时间，Josh Triplett最近推出了补丁程序允许用户将其从内核中删除.如果您希望代码在可预见的将来继续工作，请避免使用ioperm.

1. You can use the ioperm system call. However, ioperm has been deprecated for some time, and Josh Triplett recently pushed a patch that allows users to remove it from the kernel. Avoid ioperm if you want your code to continue working for the forseeable future.

您可以读写/dev/port.参见 mem(4).显然，您的进程将需要对/dev/mem的读写权限；在Wheezy上，这意味着它需要以root用户身份运行，除非您更改设备的权限.

You can read from and write to /dev/port. See mem(4). Your process will, obviously, need read and write permissions for /dev/mem; on Wheezy, that means it needs to run as root, unless you change the permissions on the device.

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