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8.13 Operating System Auxiliary Information

No value for GDBN provides interfaces to useful OS facilities that can help you debug your program.

When No value for GDBN runs on a Posix system (such as GNU or Unix machines), it interfaces with the inferior via the ptrace system call. The operating system creates a special sata structure, called struct user, for this interface. You can use the command info udot to display the contents of this data structure.

info udot

Display the contents of the struct user maintained by the OS kernel for the program being debugged. No value for GDBN displays the contents of struct user as a list of hex numbers, similar to the examine command.

Some operating systems supply an auxiliary vector to programs at startup. This is akin to the arguments and environment that you specify for a program, but contains a system-dependent variety of binary values that tell system libraries important details about the hardware, operating system, and process. Each value's purpose is identified by an integer tag; the meanings are well-known but system-specific. Depending on the configuration and operating system facilities, No value for GDBN may be able to show you this information. For remote targets, this functionality may further depend on the remote stub's support of the ‘qXfer:auxv:read’ packet, see qXfer auxiliary vector read.

info auxv

Display the auxiliary vector of the inferior, which can be either a live process or a core dump file. No value for GDBN prints each tag value numerically, and also shows names and text descriptions for recognized tags. Some values in the vector are numbers, some bit masks, and some pointers to strings or other data. No value for GDBN displays each value in the most appropriate form for a recognized tag, and in hexadecimal for an unrecognized tag.

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