linux-kernel - [PATCH] powerpc/vdso32: Add missing _restgpr_31

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Date:   Tue,  9 Mar 2021 06:19:30 +0000 (UTC)
From:   Christophe Leroy <christophe.leroy@...roup.eu>
To:     Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        segher@...nel.crashing.org
Cc:     linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org
Subject: [PATCH] powerpc/vdso32: Add missing _restgpr_31_x to fix build
 failure

With some defconfig including CONFIG_CC_OPTIMIZE_FOR_SIZE,
(for instance mvme5100_defconfig and ps3_defconfig), gcc 5
generates a call to _restgpr_31_x.

Until recently it went unnoticed, but
commit 42ed6d56ade2 ("powerpc/vdso: Block R_PPC_REL24 relocations")
made it rise to the surface.

Provide that function (copied from lib/crtsavres.S) in
gettimeofday.S

Fixes: ab037dd87a2f ("powerpc/vdso: Switch VDSO to generic C implementation.")
Signed-off-by: Christophe Leroy <christophe.leroy@...roup.eu>
---
I don't know if there is a way to tell GCC not to emit that call, because at the end we get more instructions than needed.
---
 arch/powerpc/kernel/vdso32/gettimeofday.S | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/arch/powerpc/kernel/vdso32/gettimeofday.S b/arch/powerpc/kernel/vdso32/gettimeofday.S
index a6e29f880e0e..d21d08140a5e 100644
--- a/arch/powerpc/kernel/vdso32/gettimeofday.S
+++ b/arch/powerpc/kernel/vdso32/gettimeofday.S
@@ -65,3 +65,14 @@ V_FUNCTION_END(__kernel_clock_getres)
 V_FUNCTION_BEGIN(__kernel_time)
 	cvdso_call_time __c_kernel_time
 V_FUNCTION_END(__kernel_time)
+
+/* Routines for restoring integer registers, called by the compiler.  */
+/* Called with r11 pointing to the stack header word of the caller of the */
+/* function, just beyond the end of the integer restore area.  */
+_GLOBAL(_restgpr_31_x)
+_GLOBAL(_rest32gpr_31_x)
+	lwz	r0,4(r11)
+	lwz	r31,-4(r11)
+	mtlr	r0
+	mr	r1,r11
+	blr
-- 
2.25.0