On Sun, Jul 09, 2023 at 01:03:10AM -0400, Sasha Levin wrote: > This is a note to let you know that I've just added the patch titled > > drm/vmwgfx: Add unwind hints around RBP clobber > > to the 6.4-stable tree which can be found at: > http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary > > The filename of the patch is: > drm-vmwgfx-add-unwind-hints-around-rbp-clobber.patch > and it can be found in the queue-6.4 subdirectory. > > If you, or anyone else, feels it should not be added to the stable tree, > please let <stable@xxxxxxxxxxxxxxx> know about it. > > > > commit aeb6b7c6b6ef84ab496189cdbc698426092aa46c > Author: Josh Poimboeuf <jpoimboe@xxxxxxxxxx> > Date: Mon Jun 5 09:12:22 2023 -0700 > > drm/vmwgfx: Add unwind hints around RBP clobber > > [ Upstream commit a9da8247627eefc73f909bf945031a5431a53993 ] > > VMware high-bandwidth hypercalls take the RBP register as input. This > breaks basic frame pointer convention, as RBP should never be clobbered. > > So frame pointer unwinding is broken for the instructions surrounding > the hypercalls. Fortunately this doesn't break live patching with > CONFIG_FRAME_POINTER, as it only unwinds from blocking tasks, and stack > traces from preempted tasks are already marked unreliable anyway. > > However, for live patching with ORC, this could actually be a > theoretical problem if vmw_port_hb_{in,out}() were still compiled with a > frame pointer due to having an aligned stack. In practice that hasn't > seemed to be an issue since the objtool warnings have only been seen > with CONFIG_FRAME_POINTER. > > Add unwind hint annotations to tell the ORC unwinder to mark stack > traces as unreliable. > > Fixes the following warnings: > > vmlinux.o: warning: objtool: vmw_port_hb_in+0x1df: return with modified stack frame > vmlinux.o: warning: objtool: vmw_port_hb_out+0x1dd: return with modified stack frame > > Fixes: 89da76fde68d ("drm/vmwgfx: Add VMWare host messaging capability") > Reported-by: kernel test robot <lkp@xxxxxxxxx> > Link: https://lore.kernel.org/oe-kbuild-all/202305160135.97q0Elax-lkp@xxxxxxxxx/ > Link: https://lore.kernel.org/r/4c795f2d87bc0391cf6543bcb224fa540b55ce4b.1685981486.git.jpoimboe@xxxxxxxxxx > Signed-off-by: Josh Poimboeuf <jpoimboe@xxxxxxxxxx> > Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> > > diff --git a/arch/x86/include/asm/unwind_hints.h b/arch/x86/include/asm/unwind_hints.h > index 01cb9692b160a..85cc57cb65392 100644 > --- a/arch/x86/include/asm/unwind_hints.h > +++ b/arch/x86/include/asm/unwind_hints.h > @@ -76,9 +76,18 @@ > > #else > > +#define UNWIND_HINT_UNDEFINED \ > + UNWIND_HINT(UNWIND_HINT_TYPE_UNDEFINED, 0, 0, 0) > + > #define UNWIND_HINT_FUNC \ > UNWIND_HINT(UNWIND_HINT_TYPE_FUNC, ORC_REG_SP, 8, 0) > > +#define UNWIND_HINT_SAVE \ > + UNWIND_HINT(UNWIND_HINT_TYPE_SAVE, 0, 0, 0) > + > +#define UNWIND_HINT_RESTORE \ > + UNWIND_HINT(UNWIND_HINT_TYPE_RESTORE, 0, 0, 0) > + > #endif /* __ASSEMBLY__ */ > > #endif /* _ASM_X86_UNWIND_HINTS_H */ > diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_msg_x86.h b/drivers/gpu/drm/vmwgfx/vmwgfx_msg_x86.h > index 0b74ca2dfb7bd..23899d743a903 100644 > --- a/drivers/gpu/drm/vmwgfx/vmwgfx_msg_x86.h > +++ b/drivers/gpu/drm/vmwgfx/vmwgfx_msg_x86.h > @@ -105,10 +105,14 @@ > flags, magic, bp, \ > eax, ebx, ecx, edx, si, di) \ > ({ \ > - asm volatile ("push %%rbp;" \ > + asm volatile ( \ > + UNWIND_HINT_SAVE \ > + "push %%rbp;" \ > + UNWIND_HINT_UNDEFINED \ > "mov %12, %%rbp;" \ > VMWARE_HYPERCALL_HB_OUT \ > - "pop %%rbp;" : \ > + "pop %%rbp;" \ > + UNWIND_HINT_RESTORE : \ > "=a"(eax), \ > "=b"(ebx), \ > "=c"(ecx), \ > @@ -130,10 +134,14 @@ > flags, magic, bp, \ > eax, ebx, ecx, edx, si, di) \ > ({ \ > - asm volatile ("push %%rbp;" \ > + asm volatile ( \ > + UNWIND_HINT_SAVE \ > + "push %%rbp;" \ > + UNWIND_HINT_UNDEFINED \ > "mov %12, %%rbp;" \ > VMWARE_HYPERCALL_HB_IN \ > - "pop %%rbp" : \ > + "pop %%rbp;" \ > + UNWIND_HINT_RESTORE : \ > "=a"(eax), \ > "=b"(ebx), \ > "=c"(ecx), \ This adds build warnings to the build, so I am going to drop this one for now, sorry. greg k-h
