[PATCH 1/2] powerpc: fix EDEADLOCK redefinition error in uapi/asm/errno.h

[Michael Ellerman]

From: Tony Ambardar <tony.ambardar at gmail.com>

A few archs like powerpc have different errno.h values for macros
EDEADLOCK and EDEADLK. In code including both libc and linux versions of
errno.h, this can result in multiple definitions of EDEADLOCK in the
include chain. Definitions to the same value (e.g. seen with mips) do
not raise warnings, but on powerpc there are redefinitions changing the
value, which raise warnings and errors (if using "-Werror").

Guard against these redefinitions to avoid build errors like the following,
first seen cross-compiling libbpf v5.8.9 for powerpc using GCC 8.4.0 with
musl 1.1.24:

  In file included from ../../arch/powerpc/include/uapi/asm/errno.h:5,
                   from ../../include/linux/err.h:8,
                   from libbpf.c:29:
  ../../include/uapi/asm-generic/errno.h:40: error: "EDEADLOCK" redefined [-Werror]
   #define EDEADLOCK EDEADLK

  In file included from toolchain-powerpc_8540_gcc-8.4.0_musl/include/errno.h:10,
                   from libbpf.c:26:
  toolchain-powerpc_8540_gcc-8.4.0_musl/include/bits/errno.h:58: note: this is the location of the previous definition
   #define EDEADLOCK       58

  cc1: all warnings being treated as errors

Cc: Stable <stable at vger.kernel.org>
Reported-by: Rosen Penev <rosenp at gmail.com>
Signed-off-by: Tony Ambardar <Tony.Ambardar at gmail.com>
Signed-off-by: Michael Ellerman <mpe at ellerman.id.au>
Link: https://lore.kernel.org/r/20200917135437.1238787-1-Tony.Ambardar@gmail.com
---
 arch/powerpc/include/uapi/asm/errno.h | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/powerpc/include/uapi/asm/errno.h b/arch/powerpc/include/uapi/asm/errno.h
index cc79856896a1..4ba87de32be0 100644
--- a/arch/powerpc/include/uapi/asm/errno.h
+++ b/arch/powerpc/include/uapi/asm/errno.h
@@ -2,6 +2,7 @@
 #ifndef _ASM_POWERPC_ERRNO_H
 #define _ASM_POWERPC_ERRNO_H
 
+#undef	EDEADLOCK
 #include <asm-generic/errno.h>
 
 #undef	EDEADLOCK
-- 
2.25.1