[Xen-devel] [PATCH for-4.13] clang: do not enable live-patching support

[Roger Pau Monne <roger.pau@xxxxxxxxxx>]

Live-patching requires unique symbols, and sadly the clang build
generates a lot of duplicate symbols:

Duplicate symbol 'asid.c#get_cpu_info' (ffff82d0803032c0 != ffff82d0802e0f50)
Duplicate symbol 'asid.c#get_cpu_info_from_stack' (ffff82d0802e1080 != 
ffff82d0803032f0)
Duplicate symbol 'ats.c#__list_add' (ffff82d080260a00 != ffff82d080267c70)
Duplicate symbol 'boot.c#constant_test_bit' (ffff82d08040ea60 != 
ffff82d0804372f0)
Duplicate symbol 'common.c#clear_bit' (ffff82d080332440 != ffff82d0802d33b0)
Duplicate symbol 'common.c#constant_test_bit' (ffff82d080332340 != 
ffff82d0802d2220)
Duplicate symbol 'common.c#cpumask_check' (ffff82d0802d3370 != ffff82d080337b60)
Duplicate symbol 'common.c#get_cpu_info' (ffff82d0802d22b0 != ffff82d080331590)
Duplicate symbol 'common.c#get_cpu_info_from_stack' (ffff82d0802d31c0 != 
ffff82d0803374b0)
Duplicate symbol 'common.c#pfn_to_pdx' (ffff82d0802d3270 != ffff82d080331e00)
Duplicate symbol 'common.c#test_and_set_bit' (ffff82d0802d3360 != 
ffff82d080332250)
Duplicate symbol 'common.c#variable_clear_bit' (ffff82d0802d2270 != 
ffff82d080337b50)
Duplicate symbol 'compat.c#get_cpu_info' (ffff82d08026eab0 != ffff82d080200460)
Duplicate symbol 'compat.c#get_cpu_info_from_stack' (ffff82d08026ebd0 != 
ffff82d080200f70)
Duplicate symbol 'cpu_idle.c#get_cpu_info' (ffff82d0802ccb00 != 
ffff82d08035fcc0)
[...]

For the time being disable live-patching when building with clang,
since duplicate symbols will trigger a build failure because
ENFORCE_UNIQUE_SYMBOLS is now also enabled by default in conjunction
with live-patching.

Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
---
Cc: Jürgen Groß <jgross@xxxxxxxx>
---
 Config.mk          | 2 ++
 xen/common/Kconfig | 6 +++++-
 2 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/Config.mk b/Config.mk
index d8f90d75b3..009abda225 100644
--- a/Config.mk
+++ b/Config.mk
@@ -157,6 +157,8 @@ ifndef XEN_HAS_CHECKPOLICY
     export XEN_HAS_CHECKPOLICY
 endif
 
+export XEN_BUILD_WITH_CLANG = $(clang)
+
 # as-insn: Check whether assembler supports an instruction.
 # Usage: cflags-y += $(call as-insn,CC FLAGS,"insn",option-yes,option-no)
 as-insn = $(if $(shell echo 'void _(void) { asm volatile ( $(2) ); }' \
diff --git a/xen/common/Kconfig b/xen/common/Kconfig
index f754741972..097996fc6c 100644
--- a/xen/common/Kconfig
+++ b/xen/common/Kconfig
@@ -80,6 +80,10 @@ config HAS_CHECKPOLICY
        string
        option env="XEN_HAS_CHECKPOLICY"
 
+config BUILD_WITH_CLANG
+       string
+       option env="XEN_BUILD_WITH_CLANG"
+
 menu "Speculative hardening"
 
 config SPECULATIVE_HARDEN_ARRAY
@@ -350,7 +354,7 @@ config CRYPTO
 config LIVEPATCH
        bool "Live patching support"
        default X86
-       depends on HAS_BUILD_ID = "y"
+       depends on HAS_BUILD_ID = "y" && BUILD_WITH_CLANG != "y"
        ---help---
          Allows a running Xen hypervisor to be dynamically patched using
          binary patches without rebooting. This is primarily used to binarily
-- 
2.24.0


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