[Bug 218339] kernel goes unresponsive if single-stepping over an instruction which writes to an address for which a hardware read/write watchpoint has been set

[bugzilla-daemon@kernel.org]

https://bugzilla.kernel.org/show_bug.cgi?id=218339

--- Comment #5 from Anthony L. Eden (anthony.louis.eden@gmail.com) ---
Actually upon closer inspection I'm seeing two distinct call stacks appear in
the core files.

#0  pv_native_set_debugreg (regno=7, val=0) at
arch/x86/include/asm/debugreg.h:92
#1  0xffffffff81a21533 in set_debugreg (reg=7, val=0) at
arch/x86/include/asm/paravirt.h:129
#2  local_db_save () at arch/x86/include/asm/debugreg.h:127
#3  exc_debug_kernel (dr6=0, regs=0xfffffe0000010f58) at
arch/x86/kernel/traps.c:1038
#4  exc_debug (regs=0xfffffe0000010f58) at arch/x86/kernel/traps.c:1175
#5  0xffffffff81c00c6a in asm_exc_debug () at
/build/reproducible-path/linux-6.1.66/arch/x86/include/asm/idtentry.h:606
#6  0x0000000000000000 in ?? ()

#0  pv_native_set_debugreg (regno=7, val=983554) at
arch/x86/include/asm/debugreg.h:92
#1  0xffffffff81a21509 in set_debugreg (reg=7, val=983554) at
arch/x86/include/asm/paravirt.h:129
#2  local_db_restore (dr7=983554) at arch/x86/include/asm/debugreg.h:147
#3  exc_debug_kernel (dr6=<optimized out>, regs=0xfffffe0000010f58) at
arch/x86/kernel/traps.c:1095
#4  exc_debug (regs=0xfffffe0000010f58) at arch/x86/kernel/traps.c:1175
#5  0xffffffff81c00c6a in asm_exc_debug () at
/build/reproducible-path/linux-6.1.66/arch/x86/include/asm/idtentry.h:606
#6  0x0000000000000000 in ?? ()


They are quite similar except in one of them frame #2 is local_db_save() and in
the other trace frame #2 is local_db_restore().

By the way this time I ran the VM under a different, newer version of
qemu-system-x86_64 (8.2.0), and it appears to have made no difference.


Also, concerning the VM in that tarball I linked to, if the run.sh is run as it
is you will be able to ssh into the running guest with 'ssh -p 10024
root@localhost', furthermore the path to the kernel image *with* debug info is
located at /usr/lib/debug/vmlinux-6.1.0-15-amd64.

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