Currently the max_store_size, remain_store_size and max_size in
compat_pf_efi_runtime_call are 4 byte aligned, which makes clang
complain with:
In file included from compat.c:30:
./runtime.c:646:13: error: passing 4-byte aligned argument to 8-byte aligned
parameter 2 of 'QueryVariableInfo' may result in an unaligned pointer access
[-Werror,-Walign-mismatch]
&op->u.query_variable_info.max_store_size,
^
./runtime.c:647:13: error: passing 4-byte aligned argument to 8-byte aligned
parameter 3 of 'QueryVariableInfo' may result in an unaligned pointer access
[-Werror,-Walign-mismatch]
&op->u.query_variable_info.remain_store_size,
^
./runtime.c:648:13: error: passing 4-byte aligned argument to 8-byte aligned
parameter 4 of 'QueryVariableInfo' may result in an unaligned pointer access
[-Werror,-Walign-mismatch]
&op->u.query_variable_info.max_size);
^
Fix this by bouncing the variables on the stack in order for them to
be 8 byte aligned.
Note this could be done in a more selective manner to only apply to
compat code calls, but given the overhead of making an EFI call doing
an extra copy of 3 variables doesn't seem to warrant the special
casing.
Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
---
Cc: Ian Jackson <iwj@xxxxxxxxxxxxxx>
Tagged for possible inclusion into the release, as it's a likely
candidate for backport. It shouldn't introduce any functional change
from a caller PoV. I think the risk is getting the patch wrong and not
passing the right parameters, or broken EFI implementations corrupting
data on our stack instead of doing it in xenpf_efi_runtime_call.
---
xen/common/efi/runtime.c | 24 ++++++++++++++++++++----
1 file changed, 20 insertions(+), 4 deletions(-)
diff --git a/xen/common/efi/runtime.c b/xen/common/efi/runtime.c
index 375b94229e..4462233798 100644
--- a/xen/common/efi/runtime.c
+++ b/xen/common/efi/runtime.c
@@ -607,6 +607,9 @@ int efi_runtime_call(struct xenpf_efi_runtime_call *op)
break;
case XEN_EFI_query_variable_info:
+ {
+ uint64_t max_store_size, remain_store_size, max_size;
+
if ( op->misc & ~XEN_EFI_VARINFO_BOOT_SNAPSHOT )
return -EINVAL;
@@ -638,16 +641,29 @@ int efi_runtime_call(struct xenpf_efi_runtime_call *op)
if ( !efi_enabled(EFI_RS) || (efi_rs->Hdr.Revision >> 16) < 2 )
return -EOPNOTSUPP;
+
+ /*
+ * Bounce the variables onto the stack to make them 8 byte aligned when
+ * called from the compat handler, as their placement in
+ * compat_pf_efi_runtime_call will make them 4 byte aligned instead and
+ * clang will complain.
+ *
+ * Note we do this regardless of whether called from the compat handler
+ * or not, as it's not worth the extra logic to differentiate.
+ */
+ max_store_size = op->u.query_variable_info.max_store_size;
+ remain_store_size = op->u.query_variable_info.remain_store_size;
+ max_size = op->u.query_variable_info.max_size;
+
state = efi_rs_enter();
if ( !state.cr3 )
return -EOPNOTSUPP;
status = efi_rs->QueryVariableInfo(
- op->u.query_variable_info.attr,
- &op->u.query_variable_info.max_store_size,
- &op->u.query_variable_info.remain_store_size,
- &op->u.query_variable_info.max_size);
+ op->u.query_variable_info.attr, &max_store_size,
&remain_store_size,
+ &max_size);
efi_rs_leave(&state);
