[PATCH AUTOSEL 5.15 26/27] RISC-V: vdso: Do not add missing symbols to version section in linker script

[Sasha Levin <sashal@kernel.org>]

From: Nathan Chancellor <nathan@kernel.org>

[ Upstream commit fcae44fd36d052e956e69a64642fc03820968d78 ]

Recently, ld.lld moved from '--undefined-version' to
'--no-undefined-version' as the default, which breaks the compat vDSO
build:

  ld.lld: error: version script assignment of 'LINUX_4.15' to symbol '__vdso_gettimeofday' failed: symbol not defined
  ld.lld: error: version script assignment of 'LINUX_4.15' to symbol '__vdso_clock_gettime' failed: symbol not defined
  ld.lld: error: version script assignment of 'LINUX_4.15' to symbol '__vdso_clock_getres' failed: symbol not defined

These symbols are not present in the compat vDSO or the regular vDSO for
32-bit but they are unconditionally included in the version section of
the linker script, which is prohibited with '--no-undefined-version'.

Fix this issue by only including the symbols that are actually exported
in the version section of the linker script.

Link: https://github.com/ClangBuiltLinux/linux/issues/1756
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Tested-by: Conor Dooley <conor.dooley@microchip.com>
Link: https://lore.kernel.org/r/20221108171324.3377226-1-nathan@kernel.org/
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 arch/riscv/kernel/vdso/Makefile   | 3 +++
 arch/riscv/kernel/vdso/vdso.lds.S | 2 ++
 2 files changed, 5 insertions(+)

diff --git a/arch/riscv/kernel/vdso/Makefile b/arch/riscv/kernel/vdso/Makefile
index 84ac0fe612e7..db6548509bb3 100644
--- a/arch/riscv/kernel/vdso/Makefile
+++ b/arch/riscv/kernel/vdso/Makefile
@@ -28,6 +28,9 @@ obj-vdso := $(addprefix $(obj)/, $(obj-vdso))
 
 obj-y += vdso.o
 CPPFLAGS_vdso.lds += -P -C -U$(ARCH)
+ifneq ($(filter vgettimeofday, $(vdso-syms)),)
+CPPFLAGS_vdso.lds += -DHAS_VGETTIMEOFDAY
+endif
 
 # Disable -pg to prevent insert call site
 CFLAGS_REMOVE_vgettimeofday.o = $(CC_FLAGS_FTRACE)
diff --git a/arch/riscv/kernel/vdso/vdso.lds.S b/arch/riscv/kernel/vdso/vdso.lds.S
index e9111f700af0..3729cb28aac8 100644
--- a/arch/riscv/kernel/vdso/vdso.lds.S
+++ b/arch/riscv/kernel/vdso/vdso.lds.S
@@ -65,9 +65,11 @@ VERSION
 	LINUX_4.15 {
 	global:
 		__vdso_rt_sigreturn;
+#ifdef HAS_VGETTIMEOFDAY
 		__vdso_gettimeofday;
 		__vdso_clock_gettime;
 		__vdso_clock_getres;
+#endif
 		__vdso_getcpu;
 		__vdso_flush_icache;
 	local: *;
-- 
2.35.1