From fa5afbbc20ef3577c5338f9d0b24dad45cef59cd Mon Sep 17 00:00:00 2001 From: Jan Beulich Date: Fri, 4 Jun 2021 15:02:33 +0200 Subject: [PATCH] x86: make hypervisor build with gcc11 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Gcc 11 looks to make incorrect assumptions about valid ranges that pointers may be used for addressing when they are derived from e.g. a plain constant. See https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100680. Utilize RELOC_HIDE() to work around the issue, which for x86 manifests in at least - mpparse.c:efi_check_config(), - tboot.c:tboot_probe(), - tboot.c:tboot_gen_frametable_integrity(), - x86_emulate.c:x86_emulate() (at -O2 only). The last case is particularly odd not just because it only triggers at higher optimization levels, but also because it only affects one of at least three similar constructs. Various "note" diagnostics claim the valid index range to be [0, 2⁶³-1]. Signed-off-by: Jan Beulich Tested-by: Jason Andryuk Acked-by: Roger Pau Monné master commit: 722f59d38c710a940ab05e542a83020eb5546dea master date: 2021-05-27 14:40:29 +0200 --- tools/tests/x86_emulator/x86-emulate.c | 7 +++++++ xen/arch/x86/x86_emulate/x86_emulate.c | 2 +- xen/include/asm-x86/fixmap.h | 2 +- xen/include/xen/compiler.h | 6 ++++++ xen/include/xen/pdx.h | 2 +- 5 files changed, 16 insertions(+), 3 deletions(-) diff --git a/tools/tests/x86_emulator/x86-emulate.c b/tools/tests/x86_emulator/x86-emulate.c index 23dcbe4247..ecb4b6245e 100644 --- a/tools/tests/x86_emulator/x86-emulate.c +++ b/tools/tests/x86_emulator/x86-emulate.c @@ -2,6 +2,13 @@ #include +/* See gcc bug 100680, but here don't bother making this version dependent. */ +#define gcc11_wrap(x) ({ \ + unsigned long x_; \ + __asm__ ( "" : "=g" (x_) : "0" (x) ); \ + (typeof(x))x_; \ +}) + #define cpu_has_amd_erratum(nr) 0 #define cpu_has_mpx false #define read_bndcfgu() 0 diff --git a/xen/arch/x86/x86_emulate/x86_emulate.c b/xen/arch/x86/x86_emulate/x86_emulate.c index bba6dd0187..2dee940adb 100644 --- a/xen/arch/x86/x86_emulate/x86_emulate.c +++ b/xen/arch/x86/x86_emulate/x86_emulate.c @@ -723,7 +723,7 @@ union vex { #define copy_VEX(ptr, vex) ({ \ if ( !mode_64bit() ) \ (vex).reg |= 8; \ - (ptr)[0 - PFX_BYTES] = ext < ext_8f08 ? 0xc4 : 0x8f; \ + gcc11_wrap(ptr)[0 - PFX_BYTES] = ext < ext_8f08 ? 0xc4 : 0x8f; \ (ptr)[1 - PFX_BYTES] = (vex).raw[0]; \ (ptr)[2 - PFX_BYTES] = (vex).raw[1]; \ container_of((ptr) + 1 - PFX_BYTES, typeof(vex), raw[0]); \ diff --git a/xen/include/asm-x86/fixmap.h b/xen/include/asm-x86/fixmap.h index 9fb2f47946..b6b981b621 100644 --- a/xen/include/asm-x86/fixmap.h +++ b/xen/include/asm-x86/fixmap.h @@ -78,7 +78,7 @@ extern void __set_fixmap( #define clear_fixmap(idx) __set_fixmap(idx, 0, 0) -#define __fix_to_virt(x) (FIXADDR_TOP - ((x) << PAGE_SHIFT)) +#define __fix_to_virt(x) gcc11_wrap(FIXADDR_TOP - ((x) << PAGE_SHIFT)) #define __virt_to_fix(x) ((FIXADDR_TOP - ((x)&PAGE_MASK)) >> PAGE_SHIFT) #define fix_to_virt(x) ((void *)__fix_to_virt(x)) diff --git a/xen/include/xen/compiler.h b/xen/include/xen/compiler.h index ff6c0f5cdd..85cbd1ab00 100644 --- a/xen/include/xen/compiler.h +++ b/xen/include/xen/compiler.h @@ -99,6 +99,12 @@ __asm__ ("" : "=r"(__ptr) : "0"(ptr)); \ (typeof(ptr)) (__ptr + (off)); }) +#if CONFIG_GCC_VERSION >= 110000 /* See gcc bug 100680. */ +# define gcc11_wrap(x) RELOC_HIDE(x, 0) +#else +# define gcc11_wrap(x) (x) +#endif + #ifdef __GCC_ASM_FLAG_OUTPUTS__ # define ASM_FLAG_OUT(yes, no) yes #else diff --git a/xen/include/xen/pdx.h b/xen/include/xen/pdx.h index 770fadc06c..9fcfb0ce52 100644 --- a/xen/include/xen/pdx.h +++ b/xen/include/xen/pdx.h @@ -19,7 +19,7 @@ extern u64 pdx_region_mask(u64 base, u64 len); extern void set_pdx_range(unsigned long smfn, unsigned long emfn); #define page_to_pdx(pg) ((pg) - frame_table) -#define pdx_to_page(pdx) (frame_table + (pdx)) +#define pdx_to_page(pdx) gcc11_wrap(frame_table + (pdx)) bool __mfn_valid(unsigned long mfn);