Re: [PATCH v2 08/14] docs/system: clarify limits of using gdbstub in system emulation

It seems some users will try and use the gdbstub to debug userspace inside a system emulation. While possible clarify the limitations of this approach and direct the users to a less head scratching way of debugging user-space. Signed-off-by: Alex Bennée <alex.bennee(a)linaro.org&gt; Clarifies: https://gitlab.com/qemu-project/qemu/-/issues/1274 --- docs/system/gdb.rst | 13 ++++++++++++- 1 file changed, 12 insertions(+), 1 deletion(-) diff --git a/docs/system/gdb.rst b/docs/system/gdb.rst index 9906991b84..c0cc0c9c7e 100644 --- a/docs/system/gdb.rst +++ b/docs/system/gdb.rst @@ -60,7 +60,7 @@ As TCG cannot track all memory accesses in user-mode there is no support for watchpoints. Relocating code ---------------- +=============== On modern kernels confusion can be caused by code being relocated by features such as address space layout randomisation. To avoid @@ -68,6 +68,17 @@ confusion when debugging such things you either need to update gdb's view of where things are in memory or perhaps more trivially disable ASLR when booting the system. +Debugging user-space in system emulation +======================================== + +While technically possible to debug a user-space program running

+inside a system image it does present challenges. Kernel preemption

+and execution mode changes between kernel and user mode can make it +hard to follow whats going on. Unless you are specifically trying to

+debug some interaction between kernel and user-space you are better +off running your guest program with gdb either in the guest or using +a gdbserver exposed via a port to the outside world. + Debugging multicore machines ============================