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| author | Josh Poimboeuf <jpoimboe@kernel.org> | 2023-06-02 09:40:35 -0700 |
|---|---|---|
| committer | Josh Poimboeuf <jpoimboe@kernel.org> | 2023-06-02 10:09:22 -0700 |
| commit | 39d2f3a3dfd5e8301aaf40e9450ac0773783596c (patch) | |
| tree | 0ed491a4d9a9e3273fb234be10e3341e2c142918 | |
| parent | 820c5b433f17c84e8761fb7465a8d319d706b1cf (diff) | |
| download | linux-vmware-rbp-breakage.tar.gz | |
drm/vmwgfx: Silence RBP clobber warningsvmware-rbp-breakage
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
preempted task unwinds 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 teach objtool how to interpret the code.
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@intel.com>
Link: https://lore.kernel.org/oe-kbuild-all/202305160135.97q0Elax-lkp@intel.com/
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
| -rw-r--r-- | arch/x86/include/asm/unwind_hints.h | 9 | ||||
| -rw-r--r-- | drivers/gpu/drm/vmwgfx/vmwgfx_msg_x86.h | 16 |
2 files changed, 21 insertions, 4 deletions
diff --git a/arch/x86/include/asm/unwind_hints.h b/arch/x86/include/asm/unwind_hints.h index 01cb9692b160a0..85cc57cb65392e 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 0b74ca2dfb7bd2..23899d743a9035 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), \ |