b717e68780
Add fixes for XSA-{395,398} and backport clang retpoline support from
unstable.
Sponsored by: Citrix Systems R&D
Approved by: bapt (implicit)
56 lines
2 KiB
Diff
56 lines
2 KiB
Diff
From 9412486707f8f1ca2eb31c2ef330c5e39c0a2f30 Mon Sep 17 00:00:00 2001
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From: Roger Pau Monne <roger.pau@citrix.com>
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Date: Fri, 18 Feb 2022 15:34:15 +0100
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Subject: [PATCH 2/2] x86/clang: add retpoline support
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MIME-Version: 1.0
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Content-Type: text/plain; charset=UTF-8
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Content-Transfer-Encoding: 8bit
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Detect whether the compiler supports clang retpoline option and enable
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by default if available, just like it's done for gcc.
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Note clang already disables jump tables when retpoline is enabled, so
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there's no need to also pass the fno-jump-tables parameter. Also clang
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already passes the return address in a register always on amd64, so
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there's no need for any equivalent mindirect-branch-register
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parameter.
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Reported-by: Andrew Cooper <andrew.cooper3@citrix.com>
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Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
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Acked-by: Andrew Cooper <andrew.cooper3@citrix.com>
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---
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xen/arch/x86/Kconfig | 3 ++-
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xen/arch/x86/arch.mk | 3 +++
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2 files changed, 5 insertions(+), 1 deletion(-)
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diff --git a/xen/arch/x86/Kconfig b/xen/arch/x86/Kconfig
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index fe89fa7274..1465874097 100644
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--- a/xen/arch/x86/Kconfig
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+++ b/xen/arch/x86/Kconfig
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@@ -33,7 +33,8 @@ config ARCH_DEFCONFIG
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default "arch/x86/configs/x86_64_defconfig"
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config CC_HAS_INDIRECT_THUNK
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- def_bool $(cc-option,-mindirect-branch-register)
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+ def_bool $(cc-option,-mindirect-branch-register) || \
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+ $(cc-option,-mretpoline-external-thunk)
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config INDIRECT_THUNK
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def_bool y
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diff --git a/xen/arch/x86/arch.mk b/xen/arch/x86/arch.mk
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index 15d0cbe487..edfc043dbb 100644
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--- a/xen/arch/x86/arch.mk
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+++ b/xen/arch/x86/arch.mk
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@@ -47,6 +47,9 @@ ifeq ($(CONFIG_INDIRECT_THUNK),y)
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CFLAGS-$(CONFIG_CC_IS_GCC) += -mindirect-branch=thunk-extern
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CFLAGS-$(CONFIG_CC_IS_GCC) += -mindirect-branch-register
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CFLAGS-$(CONFIG_CC_IS_GCC) += -fno-jump-tables
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+
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+# Enable clang retpoline support if available.
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+CFLAGS-$(CONFIG_CC_IS_CLANG) += -mretpoline-external-thunk
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endif
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# If supported by the compiler, reduce stack alignment to 8 bytes. But allow
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--
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2.35.1
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