From be12fcca8b784e456df3adedbffe657d753c5ff9 Mon Sep 17 00:00:00 2001 From: Roger Pau Monne 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 Release-Acked-by: Ian Jackson Reviewed-by: Ian Jackson Signed-off-by: Ian Jackson Reviewed-by: Jan Beulich --- 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