[PATCH 4.19 27/41] um: allow not setting extra rpaths in the linux binary

[Sasha Levin <sashal@kernel.org>]

From: Johannes Berg <johannes.berg@intel.com>

[ Upstream commit 386093c68ba3e8bcfe7f46deba901e0e80713c29 ]

There doesn't seem to be any reason for the rpath being set in
the binaries, at on systems that I tested on. On the other hand,
setting rpath is actually harming binaries in some cases, e.g.
if using nix-based compilation environments where /lib & /lib64
are not part of the actual environment.

Add a new Kconfig option (under EXPERT, for less user confusion)
that allows disabling the rpath additions.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Richard Weinberger <richard@nod.at>
Stable-dep-of: 846cfbeed09b ("um: Fix adding '-no-pie' for clang")
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 arch/um/Kconfig      | 13 +++++++++++++
 arch/um/Makefile     |  3 ++-
 arch/x86/Makefile.um |  2 +-
 3 files changed, 16 insertions(+), 2 deletions(-)

diff --git a/arch/um/Kconfig b/arch/um/Kconfig
index 8f0cb28099392..251c77474e7b8 100644
--- a/arch/um/Kconfig
+++ b/arch/um/Kconfig
@@ -88,6 +88,19 @@ config LD_SCRIPT_DYN
 	depends on !LD_SCRIPT_STATIC
         select MODULE_REL_CRCS if MODVERSIONS
 
+config LD_SCRIPT_DYN_RPATH
+	bool "set rpath in the binary" if EXPERT
+	default y
+	depends on LD_SCRIPT_DYN
+	help
+	  Add /lib (and /lib64 for 64-bit) to the linux binary's rpath
+	  explicitly.
+
+	  You may need to turn this off if compiling for nix systems
+	  that have their libraries in random /nix directories and
+	  might otherwise unexpected use libraries from /lib or /lib64
+	  instead of the desired ones.
+
 config HOSTFS
 	tristate "Host filesystem"
 	help
diff --git a/arch/um/Makefile b/arch/um/Makefile
index ab1066c38944e..439edee0b2878 100644
--- a/arch/um/Makefile
+++ b/arch/um/Makefile
@@ -119,7 +119,8 @@ archheaders:
 archprepare: include/generated/user_constants.h
 
 LINK-$(CONFIG_LD_SCRIPT_STATIC) += -static
-LINK-$(CONFIG_LD_SCRIPT_DYN) += -Wl,-rpath,/lib $(call cc-option, -no-pie)
+LINK-$(CONFIG_LD_SCRIPT_DYN) += $(call cc-option, -no-pie)
+LINK-$(CONFIG_LD_SCRIPT_DYN_RPATH) += -Wl,-rpath,/lib
 
 CFLAGS_NO_HARDENING := $(call cc-option, -fno-PIC,) $(call cc-option, -fno-pic,) \
 	$(call cc-option, -fno-stack-protector,) \
diff --git a/arch/x86/Makefile.um b/arch/x86/Makefile.um
index 91085a08de6cb..8bc3d493d429a 100644
--- a/arch/x86/Makefile.um
+++ b/arch/x86/Makefile.um
@@ -51,7 +51,7 @@ ELF_FORMAT := elf64-x86-64
 
 # Not on all 64-bit distros /lib is a symlink to /lib64. PLD is an example.
 
-LINK-$(CONFIG_LD_SCRIPT_DYN) += -Wl,-rpath,/lib64
+LINK-$(CONFIG_LD_SCRIPT_DYN_RPATH) += -Wl,-rpath,/lib64
 LINK-y += -m64
 
 # Do unit-at-a-time unconditionally on x86_64, following the host
-- 
2.43.0