[PATCH] xen/arm: Add workaround for Cortex-A53 erratum #843419

[Luca Fancellu <luca.fancellu@xxxxxxx>]

On the Cortex A53, when executing in AArch64 state, a load or store instruction
which uses the result of an ADRP instruction as a base register, or which uses
a base register written by an instruction immediately after an ADRP to the
same register, might access an incorrect address.

The workaround is to enable the linker flag --fix-cortex-a53-843419
if present, to check and fix the affected sequence. Otherwise print a warning
that Xen may be susceptible to this errata

Signed-off-by: Luca Fancellu <luca.fancellu@xxxxxxx>
---
 docs/misc/arm/silicon-errata.txt |  1 +
 xen/arch/arm/Kconfig             | 19 +++++++++++++++++++
 xen/arch/arm/Makefile            |  8 ++++++++
 xen/scripts/Kbuild.include       | 12 ++++++++++++
 4 files changed, 40 insertions(+)

diff --git a/docs/misc/arm/silicon-errata.txt b/docs/misc/arm/silicon-errata.txt
index 27bf957ebf..1925d8fd4e 100644
--- a/docs/misc/arm/silicon-errata.txt
+++ b/docs/misc/arm/silicon-errata.txt
@@ -45,6 +45,7 @@ stable hypervisors.
 | ARM            | Cortex-A53      | #827319         | ARM64_ERRATUM_827319    
|
 | ARM            | Cortex-A53      | #824069         | ARM64_ERRATUM_824069    
|
 | ARM            | Cortex-A53      | #819472         | ARM64_ERRATUM_819472    
|
+| ARM            | Cortex-A53      | #843419         | ARM64_ERRATUM_843419    
|
 | ARM            | Cortex-A55      | #1530923        | N/A                     
|
 | ARM            | Cortex-A57      | #852523         | N/A                     
|
 | ARM            | Cortex-A57      | #832075         | ARM64_ERRATUM_832075    
|
diff --git a/xen/arch/arm/Kconfig b/xen/arch/arm/Kconfig
index f5b1bcda03..41bde2f401 100644
--- a/xen/arch/arm/Kconfig
+++ b/xen/arch/arm/Kconfig
@@ -186,6 +186,25 @@ config ARM64_ERRATUM_819472
 
          If unsure, say Y.
 
+config ARM64_ERRATUM_843419
+       bool "Cortex-A53: 843419: A load or store might access an incorrect 
address"
+       default y
+       depends on ARM_64
+       help
+         This option adds an alternative code sequence to work around ARM
+         erratum 843419 on Cortex-A53 parts up to r0p4.
+
+         When executing in AArch64 state, a load or store instruction which 
uses
+         the result of an ADRP instruction as a base register, or which uses a
+         base register written by an instruction immediately after an ADRP to 
the
+         same register, might access an incorrect address.
+
+         The workaround enables the linker to check if the affected sequence is
+         produced and it will fix it with an alternative not affected sequence
+         that produce the same behavior.
+
+         If unsure, say Y.
+
 config ARM64_ERRATUM_832075
        bool "Cortex-A57: 832075: possible deadlock on mixing exclusive memory 
accesses with device loads"
        default y
diff --git a/xen/arch/arm/Makefile b/xen/arch/arm/Makefile
index 296c5e68bb..ad2d497c45 100644
--- a/xen/arch/arm/Makefile
+++ b/xen/arch/arm/Makefile
@@ -101,6 +101,14 @@ prelink.o: $(ALL_OBJS) FORCE
        $(call if_changed,ld)
 endif
 
+ifeq ($(CONFIG_ARM64_ERRATUM_843419),y)
+    ifeq ($(call ld-option, --fix-cortex-a53-843419),n)
+        $(warning ld does not support --fix-cortex-a53-843419; xen may be 
susceptible to erratum)
+    else
+        XEN_LDFLAGS += --fix-cortex-a53-843419
+    endif
+endif
+
 targets += prelink.o
 
 $(TARGET)-syms: prelink.o xen.lds
diff --git a/xen/scripts/Kbuild.include b/xen/scripts/Kbuild.include
index e62eddc365..83c7e1457b 100644
--- a/xen/scripts/Kbuild.include
+++ b/xen/scripts/Kbuild.include
@@ -43,6 +43,18 @@ define as-option-add-closure
     endif
 endef
 
+# $(if-success,<command>,<then>,<else>)
+# Return <then> if <command> exits with 0, <else> otherwise.
+if-success = $(shell { $(1); } >/dev/null 2>&1 && echo "$(2)" || echo "$(3)")
+
+# $(success,<command>)
+# Return y if <command> exits with 0, n otherwise
+success = $(call if-success,$(1),y,n)
+
+# $(ld-option,<flag>)
+# Return y if the linker supports <flag>, n otherwise
+ld-option = $(call success,$(LD) -v $(1))
+
 # cc-ifversion
 # Usage:  EXTRA_CFLAGS += $(call cc-ifversion, -lt, 0402, -O1)
 cc-ifversion = $(shell [ $(CONFIG_GCC_VERSION)0 $(1) $(2)000 ] && echo $(3) || 
echo $(4))
-- 
2.17.1