On Tue, 5 Mar 2024 at 17:13, Alex Bennée <alex.ben...@linaro.org> wrote: > > QEMU's handling of the program counter is special in so far as the > translator avoids setting it whenever possible. As the PC is available > at translation time lets avoid confusion by just filtering the program > counter from the list of available registers. > > Update the documentation with some notes about the register access and > calling out the behaviour of the PC. > > Resolves: https://gitlab.com/qemu-project/qemu/-/issues/2208 > Signed-off-by: Alex Bennée <alex.ben...@linaro.org> > --- > docs/devel/tcg-plugins.rst | 15 +++++++++++++++ > plugins/api.c | 5 +++++ > 2 files changed, 20 insertions(+) > > diff --git a/docs/devel/tcg-plugins.rst b/docs/devel/tcg-plugins.rst > index 9cc09d8c3da..656df012e77 100644 > --- a/docs/devel/tcg-plugins.rst > +++ b/docs/devel/tcg-plugins.rst > @@ -151,6 +151,21 @@ Unsuccessful operations (i.e. faults) will not be > visible to memory > instrumentation although the execution side effects can be observed > (e.g. entering a exception handler). > > +Register Values > ++++++++++++++++ > + > +Callbacks registered with the ``QEMU_PLUGIN_CB_R_REGS`` flags can read > +the current register values of the system. The plugin need to request > +the list of available registers after a vcpu has initialised by > +calling ``qemu_plugin_get_registers`` and using the supplied handle to > +query the values when executing the callback. > + > +.. Note:: the program counter (PC) is not available through this > + interface but can be queried at translation time by using > + the ``qemu_plugin_insn_vaddr`` and > + ``qemu_plugin_insn_haddr`` on the instruction handle. > + > + > System Idle and Resume States > +++++++++++++++++++++++++++++ > > diff --git a/plugins/api.c b/plugins/api.c > index 8fa5a600ac3..fc3477acf2d 100644 > --- a/plugins/api.c > +++ b/plugins/api.c > @@ -448,6 +448,11 @@ static GArray *create_register_handles(GArray > *gdbstub_regs) > continue; > } > > + /* skip the program counter */ > + if (g_ascii_strncasecmp(grd->name, "pc", 2) == 0) { > + continue; > + }
Is the program counter always named "pc"? For instance gdb-xml/microblaze-core.xml suggests it's named "rpc" there. And on x86-64 I think from the gdb protocol point of view it is named "rip" and the gdb "$pc" alias is handled on the gdb side, but maybe I'm wrong. Does the same problem apply to other registers whose value we fix up after-the-fact via the restore_state_to_opc hook, like the SPARC npc register, or the 32-bit Arm Thumb IT bits in the CPSR? thanks -- PMM
