From cfb381d8f4b64f3752c95b4bdd787be63ef84fb2 Mon Sep 17 00:00:00 2001
From: Romain Naour <romain.naour@gmail.com>
Date: Sat, 25 Jul 2020 11:46:01 +0200
Subject: [PATCH] mips: Do not include hi and lo in clobber list for R6
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

From [1]
"GCC 10 (PR 91233) won't silently allow registers that are not architecturally
available to be present in the clobber list anymore, resulting in build failure
for mips*r6 targets in form of:
...
.../sysdep.h:146:2: error: the register ‘lo’ cannot be clobbered in ‘asm’ for the current target
  146 |  __asm__ volatile (      \
      |  ^~~~~~~

This is because base R6 ISA doesn't define hi and lo registers w/o DSP extension.
This patch provides the alternative clobber list for r6 targets that won't include
those registers."

Since kernel 5.4 and mips support for generic vDSO [2], the kernel fail to build
for mips r6 cpus with gcc 10 for the same reason as glibc.

[1] https://sourceware.org/git/?p=glibc.git;a=commit;h=020b2a97bb15f807c0482f0faee2184ed05bcad8
[2] https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=24640f233b466051ad3a5d2786d2951e43026c9d

Signed-off-by: Romain Naour <romain.naour@gmail.com>
---
 arch/mips/include/asm/vdso/gettimeofday.h | 45 +++++++++++++++++++++++
 1 file changed, 45 insertions(+)

diff --git a/arch/mips/include/asm/vdso/gettimeofday.h b/arch/mips/include/asm/vdso/gettimeofday.h
index 0ae9b4cbc153..ea600e0ebfe7 100644
--- a/arch/mips/include/asm/vdso/gettimeofday.h
+++ b/arch/mips/include/asm/vdso/gettimeofday.h
@@ -36,12 +36,21 @@ static __always_inline long gettimeofday_fallback(
 	register long nr asm("v0") = __NR_gettimeofday;
 	register long error asm("a3");
 
+#if MIPS_ISA_REV >= 6
+	asm volatile(
+	"       syscall\n"
+	: "=r" (ret), "=r" (error)
+	: "r" (tv), "r" (tz), "r" (nr)
+	: "$1", "$3", "$8", "$9", "$10", "$11", "$12", "$13",
+	  "$14", "$15", "$24", "$25", "memory");
+#else
 	asm volatile(
 	"       syscall\n"
 	: "=r" (ret), "=r" (error)
 	: "r" (tv), "r" (tz), "r" (nr)
 	: "$1", "$3", "$8", "$9", "$10", "$11", "$12", "$13",
 	  "$14", "$15", "$24", "$25", "hi", "lo", "memory");
+#endif
 
 	return error ? -ret : ret;
 }
@@ -60,12 +69,21 @@ static __always_inline long clock_gettime_fallback(
 #endif
 	register long error asm("a3");
 
+#if MIPS_ISA_REV >= 6
+	asm volatile(
+	"       syscall\n"
+	: "=r" (ret), "=r" (error)
+	: "r" (clkid), "r" (ts), "r" (nr)
+	: "$1", "$3", "$8", "$9", "$10", "$11", "$12", "$13",
+	  "$14", "$15", "$24", "$25", "memory");
+#else
 	asm volatile(
 	"       syscall\n"
 	: "=r" (ret), "=r" (error)
 	: "r" (clkid), "r" (ts), "r" (nr)
 	: "$1", "$3", "$8", "$9", "$10", "$11", "$12", "$13",
 	  "$14", "$15", "$24", "$25", "hi", "lo", "memory");
+#endif
 
 	return error ? -ret : ret;
 }
@@ -84,12 +102,21 @@ static __always_inline int clock_getres_fallback(
 #endif
 	register long error asm("a3");
 
+#if MIPS_ISA_REV >= 6
+	asm volatile(
+	"       syscall\n"
+	: "=r" (ret), "=r" (error)
+	: "r" (clkid), "r" (ts), "r" (nr)
+	: "$1", "$3", "$8", "$9", "$10", "$11", "$12", "$13",
+	  "$14", "$15", "$24", "$25", "memory");
+#else
 	asm volatile(
 	"       syscall\n"
 	: "=r" (ret), "=r" (error)
 	: "r" (clkid), "r" (ts), "r" (nr)
 	: "$1", "$3", "$8", "$9", "$10", "$11", "$12", "$13",
 	  "$14", "$15", "$24", "$25", "hi", "lo", "memory");
+#endif
 
 	return error ? -ret : ret;
 }
@@ -108,12 +135,21 @@ static __always_inline long clock_gettime32_fallback(
 	register long nr asm("v0") = __NR_clock_gettime;
 	register long error asm("a3");
 
+#if MIPS_ISA_REV >= 6
+	asm volatile(
+	"       syscall\n"
+	: "=r" (ret), "=r" (error)
+	: "r" (clkid), "r" (ts), "r" (nr)
+	: "$1", "$3", "$8", "$9", "$10", "$11", "$12", "$13",
+	  "$14", "$15", "$24", "$25", "memory");
+#else
 	asm volatile(
 	"       syscall\n"
 	: "=r" (ret), "=r" (error)
 	: "r" (clkid), "r" (ts), "r" (nr)
 	: "$1", "$3", "$8", "$9", "$10", "$11", "$12", "$13",
 	  "$14", "$15", "$24", "$25", "hi", "lo", "memory");
+#endif
 
 	return error ? -ret : ret;
 }
@@ -128,12 +164,21 @@ static __always_inline int clock_getres32_fallback(
 	register long nr asm("v0") = __NR_clock_getres;
 	register long error asm("a3");
 
+#if MIPS_ISA_REV >= 6
+	asm volatile(
+	"       syscall\n"
+	: "=r" (ret), "=r" (error)
+	: "r" (clkid), "r" (ts), "r" (nr)
+	: "$1", "$3", "$8", "$9", "$10", "$11", "$12", "$13",
+	  "$14", "$15", "$24", "$25", "memory");
+#else
 	asm volatile(
 	"       syscall\n"
 	: "=r" (ret), "=r" (error)
 	: "r" (clkid), "r" (ts), "r" (nr)
 	: "$1", "$3", "$8", "$9", "$10", "$11", "$12", "$13",
 	  "$14", "$15", "$24", "$25", "hi", "lo", "memory");
+#endif
 
 	return error ? -ret : ret;
 }
-- 
2.25.4