69 lines
2.3 KiB
Text
69 lines
2.3 KiB
Text
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python
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import os, subprocess
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kdir = os.environ['KERNELDIR']
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mdir = os.environ['MODULEDIR'] or '/lib/modules'
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gdb.execute(f'add-auto-load-safe-path {kdir}/scripts/gdb/')
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cwd=os.getcwd()
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gdb.execute(f'cd {kdir}')
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gdb.execute(f'source {kdir}/vmlinux-gdb.py')
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p = subprocess.run([f'./linux', '--version'], capture_output=True)
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ver = p.stdout.strip().decode('ascii')
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gdb.execute(f'cd {cwd}')
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end
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break os_early_checks
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commands
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silent
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python
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gdb.execute(f'cd {kdir}')
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gdb.execute(f'lx-symbols {mdir}/{ver}/')
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gdb.execute(f'cd {cwd}')
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end
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# only once
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del 1
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continue
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end
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handle 11 nostop noprint pass
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#
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# So ... this is complicated. When gdb installs a regular breakpoint
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# on some place, it writes there a breakpoint instruction (which is
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# a single 0xCC byte on x86). This breaks out into the debugger and
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# it can then restart/simulate the correct instruction when continuing
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# across the breakpoint.
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#
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# Additionally, gdb (correctly) removes these breakpoint instructions
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# from forked children when detaching from them. This also seems fine.
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#
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# However, due to how user-mode-linux works, this causes issues with
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# kernel modules. These are loaded into the vmalloc area, and even if
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# that isn't quite part of physmem, it's still mapped as MAP_SHARED.
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#
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# Unfortunately, this means that gdb deletes breakpoints in modules
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# when a new userspace process is started, since that causes a new
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# process to be created by clone() and gdb has to detach from it.
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#
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# The other thing to know is that when gdb hits a breakpoint it will
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# restore all the code to normal, and reinstall breakpoints when we
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# continue.
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#
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# Thus we can use that behaviour to work around the module issue:
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# simply put a breakpoint on init_new_ldt which happens just after
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# the clone() for a new userspace process, and do nothing there but
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# continue, which reinstalls all breakpoints, including the ones in
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# modules.
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#
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break init_new_ldt
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commands
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silent
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continue
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end
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echo \n
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echo Welcome to hwsim kernel debugging\n
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echo ---------------------------------\n\n
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echo You can install breakpoints in modules, they're treated\n
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echo as shared libraries, so just say 'y' if asked to make the\n
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echo breakpoint pending on future load.\n\n
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echo Do NOT, however, delete the breakpoint on 'init_new_ldt'!\n\n
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echo Now enter 'run' to start the run.\n\n
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echo Have fun!\n\n
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