![]() The p expr or print expr prints the expression value.Įxample: Dump 3 instructions at the current instruction pointer: ![]() Use the xp command in the QEMU monitor and the x command in GDB to inspect memory at corresponding physical and virtual addresses and make sure you see the same data. To access the QEMU monitor, press Ctrl-a c in the terminal (the same binding returns to the serial console), or Ctrl-Alt-2 in the VGA window ( Ctrl-Alt-1 returns to the VGA console). You may wish to review the QEMU monitor commands, especially the xp command, which lets you inspect physical memory. While GDB can only access QEMU's memory by virtual address, it's often useful to be able to inspect physical memory while setting up virtual memory. This reference contains a list of commands that can be used with the QEMU monitor. Once at a breakpoint, you can continue execution using the c and si commands: c causes QEMU to continue execution until the next breakpoint (or until you press Ctrl-C, in GDB), and si N steps through the instructions N at a time. For example,ī *0x7c00 sets a breakpoint at address 0x7C00. GDB can only access QEMU's memory and set breakpoints by virtual address. You can set address breakpoints in GDB with the b command. Is GDB's disassembly of the first instruction to be executed The target architecture is assumed to be i8086 This GDB was configured as "i486-linux-gnu". There is NO WARRANTY, to the extent permitted by law. This is free software: you are free to change and redistribute it. License GPLv3+: GNU GPL version 3 or later You should see something like this,Ĭopyright (C) 2008 Free Software Foundation, Inc. In the second terminal, from the same directory where you ran make, run gdb. This starts up QEMU, but QEMU stops just before the processor executes the first instruction and waits for a debugging connection from GDB. In your CS372H/lab/ directory, open two terminal windows. ![]() The command make qemu executes QEMU, supplying the file obj/kern/kernel.img as the contents of the emulated PC's "virtual hard disk", andĭirects serial port output to the terminal. While QEMU's built-in monitor provides only limited debugging support, QEMU can act as a remote debugging target for the GNU debugger (GDB). CS372H Spring 2010: QEMU and GDB reference CS372H Spring 2010: QEMU and GDB referenceįor Lab 6, we are using the QEMU Emulator, a modern and relatively fast emulator.
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