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From be12fcca8b784e456df3adedbffe657d753c5ff9 Mon Sep 17 00:00:00 2001
From: Roger Pau Monne <roger.pau@citrix.com>
Date: Thu, 18 Nov 2021 09:28:06 +0100
Subject: [PATCH] efi: fix alignment of function parameters in compat mode
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
Currently the max_store_size, remain_store_size and max_size in
compat_pf_efi_runtime_call are 4 byte aligned, which makes clang
13.0.0 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@citrix.com>
Release-Acked-by: Ian Jackson <iwj@xenproject.org>
Reviewed-by: Ian Jackson <iwj@xenproject.org>
Signed-off-by: Ian Jackson <iwj@xenproject.org>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
---
Changes since v3:
- Remove hard tabs. Apply Jan's r-b as authorised in email.
Changes since v2:
- Adjust the commentary as per discussion.
Changes since v1:
- Copy back the results.
---
xen/common/efi/runtime.c | 31 +++++++++++++++++++++++++++----
1 file changed, 27 insertions(+), 4 deletions(-)
diff --git a/xen/common/efi/runtime.c b/xen/common/efi/runtime.c
index 375b94229e..d2fdc28df3 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 +641,36 @@ 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
+ * and compilers may validly complain.
+ *
+ * Note that while the function parameters are OUT only, copy the
+ * values here anyway just in case. This is done 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);
+
+ op->u.query_variable_info.max_store_size = max_store_size;
+ op->u.query_variable_info.remain_store_size = remain_store_size;
+ op->u.query_variable_info.max_size = max_size;
+
break;
+ }
case XEN_EFI_query_capsule_capabilities:
case XEN_EFI_update_capsule:
--
2.33.0
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