gdb - TechWrites

近期用gdb调试coredump文件时发现会有warning：

warning: Unexpected size of section `.reg-xstate/13997' in core file.

起初以为是core文件有问题，后发现其实是低版本gdb（8.0版本）无法识别CPU的某些寄存器而做出的提示。

如果CPU支持Intel MPX技术，则会有几个额外的寄存器，而低版本的gdb无法识别这些寄存器，因此提示warning。

可以通过以下命令确定CPU是否支持MPX：

$ grep mpx /proc/cpuinfo 
flags           : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush mmx fxsr sse sse2 ss ht syscall nx pdpe1gb rdtscp lm constant_tsc rep_good nopl nonstop_tsc eagerfpu pni pclmulqdq ssse3 fma cx16 pcid sse4_1 sse4_2 x2apic movbe popcnt tsc_deadline_timer aes xsave avx f16c rdrand hypervisor lahf_lm abm 3dnowprefetch invpcid_single fsgsbase bmi1 hle avx2 smep bmi2 erms invpcid rtm mpx avx512f avx512dq rdseed adx smap clflushopt clwb avx512cd avx512bw avx512vl xsaveopt xsavec xgetbv1 arat avx512_vnni

更换高版本（10.0版本）的gdb后，warning消失，且通过gdb命令info all-registers也确实可以查看到MPX相关的几个寄存器：

(gdb) info all-registers
bndcfgu        {raw = 0x0, config = {base = 0x0, reserved = 0x0, preserved = 0x0, enabled = 0x0}} {raw = 0x0, config = {base = 0, reserved = 0, preserved = 0, enabl--Type &lt;RET> for more, q to quit, c to continue without paging--
ed = 0}}
bndstatus      {raw = 0x0, status = {bde = 0x0, error = 0x0}} {raw = 0x0, status = {bde = 0, error = 0}}
bnd0           {lbound = 0x0, ubound = 0xffffffffffffffff} : size -1 {lbound = 0x0, ubound = 0xffffffffffffffff} : size -1
bnd1           {lbound = 0x0, ubound = 0xffffffffffffffff} : size -1 {lbound = 0x0, ubound = 0xffffffffffffffff} : size -1
bnd2           {lbound = 0x0, ubound = 0xffffffffffffffff} : size -1 {lbound = 0x0, ubound = 0xffffffffffffffff} : size -1
bnd3           {lbound = 0x0, ubound = 0xffffffffffffffff} : size -1 {lbound = 0x0, ubound = 0xffffffffffffffff} : size -1

标签： gdb

深究一次常见的CoreDump问题

GDB调试时遇到的寄存器识别问题——Unexpected size of section `.reg-xstate’