linux-kernel - [PATCH] MIPS: mark some functions as weak to avoid conflict with Octeon ones

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Date:   Wed, 25 Mar 2020 01:40:05 +0900
From:   Masahiro Yamada <masahiroy@...nel.org>
To:     Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
        linux-mips@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org,
        Masahiro Yamada <masahiroy@...nel.org>,
        Alexander Lobakin <alobakin@...nk.ru>,
        Paul Burton <paulburton@...nel.org>,
        clang-built-linux@...glegroups.com
Subject: [PATCH] MIPS: mark some functions as weak to avoid conflict with Octeon ones

MIPS provides multiple definitions for the following functions:

  fw_init_cmdline
  __delay
  __udelay
  __ndelay
  memmove
  __rmemcpy
  memcpy
  __copy_user

The generic ones are defined in lib-y objects, which are overridden by
the Octeon ones when CONFIG_CAVIUM_OCTEON_SOC is enabled.

The use of EXPORT_SYMBOL in static libraries potentially causes a
problem for the llvm linker [1]. So, I want to forcibly link lib-y
objects to vmlinux when CONFIG_MODULES=y.

As a groundwork, we must fix multiple definitions that have been
hidden by lib-y.

In this case, the generic implementations in arch/mips/lib/ are
weaker than the ones in arch/mips/cavium-octen/, so annotating __weak
is a straight-forward solution.

I also removed EXPORT_SYMBOL from the Octeon files to avoid the
'exported twice' warnings from modpost.

[1]: https://github.com/ClangBuiltLinux/linux/issues/515

Reported-by: kbuild test robot <lkp@...el.com>
Suggested-by: Nick Desaulniers <ndesaulniers@...gle.com>
Signed-off-by: Masahiro Yamada <masahiroy@...nel.org>
---

 arch/mips/cavium-octeon/csrc-octeon.c   | 4 ----
 arch/mips/cavium-octeon/octeon-memcpy.S | 3 ---
 arch/mips/fw/lib/cmdline.c              | 2 +-
 arch/mips/lib/delay.c                   | 6 +++---
 arch/mips/lib/memcpy.S                  | 5 +++++
 5 files changed, 9 insertions(+), 11 deletions(-)

diff --git a/arch/mips/cavium-octeon/csrc-octeon.c b/arch/mips/cavium-octeon/csrc-octeon.c
index 124817609ce0..fdc28fb5eda4 100644
--- a/arch/mips/cavium-octeon/csrc-octeon.c
+++ b/arch/mips/cavium-octeon/csrc-octeon.c
@@ -153,7 +153,6 @@ void __udelay(unsigned long us)
 	while (end > cur)
 		cur = read_c0_cvmcount();
 }
-EXPORT_SYMBOL(__udelay);
 
 void __ndelay(unsigned long ns)
 {
@@ -167,7 +166,6 @@ void __ndelay(unsigned long ns)
 	while (end > cur)
 		cur = read_c0_cvmcount();
 }
-EXPORT_SYMBOL(__ndelay);
 
 void __delay(unsigned long loops)
 {
@@ -179,8 +177,6 @@ void __delay(unsigned long loops)
 	while (end > cur)
 		cur = read_c0_cvmcount();
 }
-EXPORT_SYMBOL(__delay);
-
 
 /**
  * octeon_io_clk_delay - wait for a given number of io clock cycles to pass.
diff --git a/arch/mips/cavium-octeon/octeon-memcpy.S b/arch/mips/cavium-octeon/octeon-memcpy.S
index 0a7c9834b81c..3eb8d1a72d7f 100644
--- a/arch/mips/cavium-octeon/octeon-memcpy.S
+++ b/arch/mips/cavium-octeon/octeon-memcpy.S
@@ -147,11 +147,9 @@
  */
 	.align	5
 LEAF(memcpy)					/* a0=dst a1=src a2=len */
-EXPORT_SYMBOL(memcpy)
 	move	v0, dst				/* return value */
 __memcpy:
 FEXPORT(__copy_user)
-EXPORT_SYMBOL(__copy_user)
 	/*
 	 * Note: dst & src may be unaligned, len may be 0
 	 * Temps
@@ -438,7 +436,6 @@ s_exc:
 
 	.align	5
 LEAF(memmove)
-EXPORT_SYMBOL(memmove)
 	ADD	t0, a0, a2
 	ADD	t1, a1, a2
 	sltu	t0, a1, t0			# dst + len <= src -> memcpy
diff --git a/arch/mips/fw/lib/cmdline.c b/arch/mips/fw/lib/cmdline.c
index 6ecda64ad184..e1f9a0c23005 100644
--- a/arch/mips/fw/lib/cmdline.c
+++ b/arch/mips/fw/lib/cmdline.c
@@ -16,7 +16,7 @@ int fw_argc;
 int *_fw_argv;
 int *_fw_envp;
 
-void __init fw_init_cmdline(void)
+void __init __weak fw_init_cmdline(void)
 {
 	int i;
 
diff --git a/arch/mips/lib/delay.c b/arch/mips/lib/delay.c
index 68c495ed71e3..ba0ae7da5ced 100644
--- a/arch/mips/lib/delay.c
+++ b/arch/mips/lib/delay.c
@@ -24,7 +24,7 @@
 #define GCC_DADDI_IMM_ASM() "r"
 #endif
 
-void __delay(unsigned long loops)
+void __weak __delay(unsigned long loops)
 {
 	__asm__ __volatile__ (
 	"	.set	noreorder				\n"
@@ -48,7 +48,7 @@ EXPORT_SYMBOL(__delay);
  * a constant)
  */
 
-void __udelay(unsigned long us)
+void __weak __udelay(unsigned long us)
 {
 	unsigned int lpj = raw_current_cpu_data.udelay_val;
 
@@ -56,7 +56,7 @@ void __udelay(unsigned long us)
 }
 EXPORT_SYMBOL(__udelay);
 
-void __ndelay(unsigned long ns)
+void __weak __ndelay(unsigned long ns)
 {
 	unsigned int lpj = raw_current_cpu_data.udelay_val;
 
diff --git a/arch/mips/lib/memcpy.S b/arch/mips/lib/memcpy.S
index f7994d936505..f2f58326b927 100644
--- a/arch/mips/lib/memcpy.S
+++ b/arch/mips/lib/memcpy.S
@@ -598,6 +598,9 @@ SEXC(1)
 	 nop
 	.endm
 
+	.weak memmove
+	.weak __rmemcpy
+
 	.align	5
 LEAF(memmove)
 EXPORT_SYMBOL(memmove)
@@ -655,6 +658,8 @@ LEAF(__rmemcpy)					/* a0=dst a1=src a2=len */
  * the number of uncopied bytes.
  * memcpy sets v0 to dst.
  */
+	.weak memcpy
+	.weak __copy_user
 	.align	5
 LEAF(memcpy)					/* a0=dst a1=src a2=len */
 EXPORT_SYMBOL(memcpy)
-- 
2.17.1