From 6eb61b1a9dfe23ca443f977799cafb22770708a0 Mon Sep 17 00:00:00 2001 From: =?utf8?q?Roger=20Pau=20Monn=C3=A9?= Date: Tue, 2 Jun 2020 13:36:41 +0200 Subject: [PATCH] x86/mm: do not attempt to convert _PAGE_GNTTAB to a boolean MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit Clang 10 complains with: mm.c:1239:10: error: converting the result of '<<' to a boolean always evaluates to true [-Werror,-Wtautological-constant-compare] if ( _PAGE_GNTTAB && (l1e_get_flags(l1e) & _PAGE_GNTTAB) && ^ xen/include/asm/x86_64/page.h:161:25: note: expanded from macro '_PAGE_GNTTAB' #define _PAGE_GNTTAB (1U<<22) ^ Remove the conversion of _PAGE_GNTTAB to a boolean and instead use a preprocessor conditional to check if _PAGE_GNTTAB is defined. Signed-off-by: Roger Pau Monné Acked-by: Jan Beulich Release-acked-by: Paul Durrant --- xen/arch/x86/mm.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) diff --git a/xen/arch/x86/mm.c b/xen/arch/x86/mm.c index 53e3dcb2d4..e376fc7e8f 100644 --- a/xen/arch/x86/mm.c +++ b/xen/arch/x86/mm.c @@ -1235,8 +1235,14 @@ void put_page_from_l1e(l1_pgentry_t l1e, struct domain *l1e_owner) * * (Note that the undestroyable active grants are not a security hole in * Xen. All active grants can safely be cleaned up when the domain dies.) + * + * NB: the preprocessor conditional is required in order to prevent clang's + * -Wtautological-constant-compare complaining about converting the result + * of a << into a bool is always true if it's evaluated directly in the if + * condition. */ - if ( _PAGE_GNTTAB && (l1e_get_flags(l1e) & _PAGE_GNTTAB) && +#if _PAGE_GNTTAB + if ( (l1e_get_flags(l1e) & _PAGE_GNTTAB) && !l1e_owner->is_shutting_down && !l1e_owner->is_dying ) { gdprintk(XENLOG_WARNING, @@ -1244,6 +1250,7 @@ void put_page_from_l1e(l1_pgentry_t l1e, struct domain *l1e_owner) l1e_get_intpte(l1e)); domain_crash(l1e_owner); } +#endif /* * Remember we didn't take a type-count of foreign writable mappings -- 2.39.5