On Tue, 7 Feb 2023 at 17:51, Peter Maydell <peter.mayd...@linaro.org> wrote: > > On Tue, 7 Feb 2023 at 17:37, ~dreiss-meta <dreiss-m...@git.sr.ht> wrote: > > > > New in v4: Moved arm_v7m_mrs_control out of the `#ifdef > > CONFIG_USER_ONLY` block, unbreaking the user-only build. The downside > > is that this function is now taking up space in the user-only binary, > > but it can (presumably?) never be used because there are no user modes > > for v8m cores. Let me know if you'd prefer for me to wrap `#ifdef > > CONFIG_USER_ONLY` around the v8m registers in the gdb stub. Also, let > > me know if you'd prefer a separate commit for renaming and moving > > v7m_mrs_control. > > We do support the M-profile cores in the linux-user executables, > so this code is "live". The view that the guest program and > the debugger should see is that the core is always in > user mode (aka unprivileged, Thread mode).
Having looked more closely at the registers in the org.gnu.gdb.arm.secext set, I think the right answer here is that for CONFIG_USER_ONLY we should never expose the second org.gnu.gdb.arm.secext block. Because the guest is restricted to non-secure mode only, the registers in the org.gnu.gdb.arm.m-system block are sufficient to get all the interesting information, and the debugger shouldn't be confused by only seeing one of the two, because that's what it sees when talking to a CPU which doesn't have the security extension. The register state in the other block is OK. (I don't think the code as it stands will be broken as such, but it will let the debugger read a lot of confusing 0s, and it leaves the door open for us forgetting to prevent writes if we add system register write suport later, which would let gdb put QEMU into states it doesn't expect to be in.) That change is simple (couple of ifdefs in gdbstub.c, and then it lets us avoid moving the definition of the arm_v7m_get_sp_ptr() function). But Richard has just told me he has a rework of some of the gdbstub handling which he incorporated this patchset into, so I think the best thing is if he can post that series. thanks -- PMM
