[Xen-devel] [PATCH 2/2] build/clang: fix XSM dummy policy when using clang 4.0

[Roger Pau Monne <roger.pau@xxxxxxxxxx>]

There seems to be some weird bug in clang 4.0 that prevents xsm_pmu_op from
working as expected, and vpmu.o ends up with a reference to
__xsm_action_mismatch_detected which makes the build fail:

[...]
ld    -melf_x86_64_fbsd  -T xen.lds -N prelink.o  \
    xen/common/symbols-dummy.o -o xen/.xen-syms.0
prelink.o: In function `xsm_default_action':
xen/include/xsm/dummy.h:80: undefined reference to 
`__xsm_action_mismatch_detected'
xen/xen/include/xsm/dummy.h:80: relocation truncated to fit: R_X86_64_PC32 
against undefined symbol `__xsm_action_mismatch_detected'
ld: xen/xen/.xen-syms.0: hidden symbol `__xsm_action_mismatch_detected' isn't 
defined

Then doing a search in the objects files:

# find xen/ -type f -name '*.o' -print0 | xargs -0 bash -c \
  'for filename; do nm "$filename" | \
  grep -q __xsm_action_mismatch_detected && echo "$filename"; done' bash
xen/arch/x86/prelink.o
xen/arch/x86/cpu/vpmu.o
xen/arch/x86/cpu/built_in.o
xen/arch/x86/built_in.o

The current patch is the only way I've found to fix this so far, by simply
moving the XSM_PRIV check into the default case in xsm_pmu_op. This also fixes
the behavior of do_xenpmu_op, which will now return -EINVAL for unknown
XENPMU_* operations, instead of -EPERM when called by a privileged domain.

Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
---
Cc: Daniel De Graaf <dgdegra@xxxxxxxxxxxxx>
---
 xen/include/xsm/dummy.h | 7 +------
 1 file changed, 1 insertion(+), 6 deletions(-)

diff --git a/xen/include/xsm/dummy.h b/xen/include/xsm/dummy.h
index 4b27ae7..ff73039 100644
--- a/xen/include/xsm/dummy.h
+++ b/xen/include/xsm/dummy.h
@@ -682,18 +682,13 @@ static XSM_INLINE int xsm_pmu_op (XSM_DEFAULT_ARG struct 
domain *d, unsigned int
     XSM_ASSERT_ACTION(XSM_OTHER);
     switch ( op )
     {
-    case XENPMU_mode_set:
-    case XENPMU_mode_get:
-    case XENPMU_feature_set:
-    case XENPMU_feature_get:
-        return xsm_default_action(XSM_PRIV, d, current->domain);
     case XENPMU_init:
     case XENPMU_finish:
     case XENPMU_lvtpc_set:
     case XENPMU_flush:
         return xsm_default_action(XSM_HOOK, d, current->domain);
     default:
-        return -EPERM;
+        return xsm_default_action(XSM_PRIV, d, current->domain);
     }
 }
 
-- 
2.10.1 (Apple Git-78)


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