[PATCH v2] riscv: vdso.lds.S: Do not export __vdso_getrandom when building a 32-bit vDSO

[Nathan Chancellor]

ld.lld defaults to '--no-undefined-version', which causes the compat
vDSO for 64-bit builds and the regular vDSO for 32-bit builds to break
after wiring up the vDSO getrandom() call because __vdso_getrandom is
unconditionally exported, even though it is not always present.

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

Move the export of __vdso_getrandom() under an ifdef to only include it
when CONFIG_VDSO_GETRANDOM is defined (to exclude 32-bit builds) and
COMPAT_VDSO is not defined (to exclude the 32-bit vDSO on 64-bit builds)
to resolve the error.

Fixes: 89079520cef6 ("RISC-V: vDSO: Wire up getrandom() vDSO implementation")
Reported-by: Linux Kernel Functional Testing <lkft at linaro.org>
Closes: https://lore.kernel.org/CA+G9fYtN2ie+YtK3H9mrQ5QqrSCFGGjVbtJcfiYX0oHMVWMn9w@mail.gmail.com/
Signed-off-by: Nathan Chancellor <nathan at kernel.org>
---
Changes in v2:
- Include a check for CONFIG_VDSO_GETRANDOM to fix breakage on
  rv32_defconfig. Include the tags for the report that helped highlight
  this issue.
- Link to v1: https://lore.kernel.org/r/20250423-riscv-fix-compat_vdso-lld-v1-1-820de5cad605@kernel.org
---
 arch/riscv/kernel/vdso/vdso.lds.S | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/arch/riscv/kernel/vdso/vdso.lds.S b/arch/riscv/kernel/vdso/vdso.lds.S
index abc69cda0445..7c15b0f4ee3b 100644
--- a/arch/riscv/kernel/vdso/vdso.lds.S
+++ b/arch/riscv/kernel/vdso/vdso.lds.S
@@ -80,7 +80,9 @@ VERSION
 #ifndef COMPAT_VDSO
 		__vdso_riscv_hwprobe;
 #endif
+#if defined(CONFIG_VDSO_GETRANDOM) && !defined(COMPAT_VDSO)
 		__vdso_getrandom;
+#endif
 	local: *;
 	};
 }

---
base-commit: bafa451a96d0f1404aa1a5a267f78767a55fac71
change-id: 20250423-riscv-fix-compat_vdso-lld-e1b80b324d97

Best regards,
-- 
Nathan Chancellor <nathan at kernel.org>