From f0abfb5eca6821fb58c09331d0fa3ec97f86e0bb Mon Sep 17 00:00:00 2001 From: Jan Beulich Date: Mon, 6 Dec 2021 14:16:37 +0100 Subject: [PATCH] EFI: drop copy-in from QueryVariableInfo()'s OUT-only variable bouncing While be12fcca8b78 ("efi: fix alignment of function parameters in compat mode") intentionally bounced them both ways to avoid any functional change so close to the release of 4.16, the bouncing-in shouldn't really be needed. In exchange the local variables need to gain initializers to avoid copying back prior stack contents. Signed-off-by: Jan Beulich Acked-by: Andrew Cooper Reviewed-by: Luca Fancellu --- xen/common/efi/runtime.c | 25 +++++++++---------------- 1 file changed, 9 insertions(+), 16 deletions(-) diff --git a/xen/common/efi/runtime.c b/xen/common/efi/runtime.c index d2fdc28df3..fcd5a9cada 100644 --- a/xen/common/efi/runtime.c +++ b/xen/common/efi/runtime.c @@ -608,7 +608,15 @@ int efi_runtime_call(struct xenpf_efi_runtime_call *op) case XEN_EFI_query_variable_info: { - uint64_t max_store_size, remain_store_size, max_size; + /* + * Put OUT variables on 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 compilers may validly complain. This is done regardless of + * whether called from the compat handler or not, as it's not worth + * the extra logic to differentiate. + */ + uint64_t max_store_size = 0, remain_store_size = 0, max_size = 0; if ( op->misc & ~XEN_EFI_VARINFO_BOOT_SNAPSHOT ) return -EINVAL; @@ -642,21 +650,6 @@ 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; -- 2.30.2