Question

（编辑：根据当前＆＃34;第三个答案;＃34;似乎正在使用Atom处理器。但我希望一些gdb专家可以回答这是否是一个基本限制，或者是否添加支持其他处理器在路线图上？）

反向执行似乎在我的环境中正常工作：我可以反向继续，查看合理的记录日志，并在其中移动：

(gdb) start
...Temporary breakpoint 5 at 0x8048460: file bang.cpp, line 13.
Starting program: /home/thomasg/temp/./bang 

Temporary breakpoint 5, main () at bang.cpp:13
13    f(1000);
(gdb) record 
(gdb) continue 
Continuing.

Breakpoint 3, f (d=900) at bang.cpp:5
5     if(d) {
(gdb) info record 
Active record target: record-full
Record mode:
Lowest recorded instruction number is 1.
Highest recorded instruction number is 1005.
Log contains 1005 instructions.
Max logged instructions is 200000.
(gdb) reverse-continue 
Continuing.

Breakpoint 3, f (d=901) at bang.cpp:5
5     if(d) {
(gdb) record goto end
Go forward to insn number 1005
#0  f (d=900) at bang.cpp:5
5     if(d) {

然而，指令和功能历史不可用：

(gdb) record instruction-history 
You can't do that when your target is `record-full'
(gdb) record function-call-history 
You can't do that when your target is `record-full'

唯一可用的目标类型是完整的，另一个记录类型＆＃34; btrace＆＃34;失败，＆＃34; Target不支持分支跟踪。＆＃34;

很可能它只是不支持这个目标，但因为它是主流的现代目标（gdb 7.6.1-ubuntu，amd64 Linux Mint＆＃34; Petra＆＃34;运行＆＃34;英特尔（R）Core（TM）i5-3570＆＃34;）我希望我忽略了关键步骤或配置？

Answer 1

似乎除了支持它的CPU之外没有其他解决方案。

更准确地说，您的内核必须支持英特尔处理器跟踪（英特尔PT）。可以在Linux中使用以下命令检查：

grep intel_pt /proc/cpuinfo

另请参阅：https://unix.stackexchange.com/questions/43539/what-do-the-flags-in-proc-cpuinfo-mean

这些命令仅适用于record btrace模式。

在GDB源代码提交beab5d9中，nat/linux-btrace.c:kernel_supports_pt检查我们是否可以输入btrace。进行以下检查：

检查/sys/bus/event_source/devices/intel_pt/type是否存在并阅读type
使用阅读syscall (SYS_perf_event_open, &attr, child, -1, -1, 0);执行type，看看它是否返回>=0。 TODO：为什么不使用C包装器？

第一次检查对我失败：文件不存在。

内核方面

cd进入内核4.1源代码并且：

git grep '"intel_pt"'

我们找到设置该文件的arch/x86/kernel/cpu/perf_event_intel_pt.c。特别是，它确实：

if (!test_cpu_cap(&boot_cpu_data, X86_FEATURE_INTEL_PT))
    goto fail;

所以intel_pt是先决条件。

我如何找到kernel_supports_pt

首先是grep：

git grep 'Target does not support branch tracing.'

引导我们btrace.c:btrace_enable。经过快速调试后：

gdb -q -ex start -ex 'b btrace_enable' -ex c --args /home/ciro/git/binutils-gdb/install/bin/gdb --batch -ex start -ex 'record btrace' ./hello_world.out

虚拟框也不支持它：Extract execution log from gdb record in a VirtualBox VM

英特尔SDE

Intel SDE 7.21已经有了这个CPU功能，请查看：

./sde64 -- cpuid | grep 'Intel processor trace'

但我不确定是否可以在其上运行Linux内核：https://superuser.com/questions/950992/how-to-run-the-linux-kernel-on-intel-software-development-emulator-sde

其他GDB方法

更通用的问题，软件解决方案效率较低：

致电图：List of all function calls made in an application
指令跟踪：Displaying each assembly instruction executed in gdb

Answer 2

至少部分答案（对于“我做错了”方面） - 来自gdb-7.6.50.20140108/gdb/NEWS

* A new record target "record-btrace" has been added.  The new target
  uses hardware support to record the control-flow of a process.  It
  does not support replaying the execution, but it implements the
  below new commands for investigating the recorded execution log.
  This new recording method can be enabled using:

record btrace

  The "record-btrace" target is only available on Intel Atom processors
  and requires a Linux kernel 2.6.32 or later.

* Two new commands have been added for record/replay to give information
  about the recorded execution without having to replay the execution.
  The commands are only supported by "record btrace".

record instruction-history      prints the execution history at
                                instruction granularity

record function-call-history    prints the execution history at
                                function granularity

我常常羡慕Atom处理器的所有者;-)

我将编辑问题以重新关注解决方案或未来支持计划的问题。

如何在GDB中运行记录指令历史和函数调用历史记录？

2 个答案: