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From: Sasha Levin <sashal@kernel.org>
To: stable@vger.kernel.org, linux-kernel@vger.kernel.org
Cc: Joel Stanley <joel@jms.id.au>,
	Michael Ellerman <mpe@ellerman.id.au>,
	Sasha Levin <sashal@kernel.org>
Subject: [PATCH AUTOSEL 4.9 15/21] powerpc/boot: Ensure _zimage_start is a weak symbol
Date: Sun,  4 Nov 2018 08:53:49 -0500	[thread overview]
Message-ID: <20181104135355.88602-15-sashal@kernel.org> (raw)
In-Reply-To: <20181104135355.88602-1-sashal@kernel.org>

From: Joel Stanley <joel@jms.id.au>

[ Upstream commit ee9d21b3b3583712029a0db65a4b7c081d08d3b3 ]

When building with clang crt0's _zimage_start is not marked weak, which
breaks the build when linking the kernel image:

 $ objdump -t arch/powerpc/boot/crt0.o |grep _zimage_start$
 0000000000000058 g       .text  0000000000000000 _zimage_start

 ld: arch/powerpc/boot/wrapper.a(crt0.o): in function '_zimage_start':
 (.text+0x58): multiple definition of '_zimage_start';
 arch/powerpc/boot/pseries-head.o:(.text+0x0): first defined here

Clang requires the .weak directive to appear after the symbol is
declared. The binutils manual says:

 This directive sets the weak attribute on the comma separated list of
 symbol names. If the symbols do not already exist, they will be
 created.

So it appears this is different with clang. The only reference I could
see for this was an OpenBSD mailing list post[1].

Changing it to be after the declaration fixes building with Clang, and
still works with GCC.

 $ objdump -t arch/powerpc/boot/crt0.o |grep _zimage_start$
 0000000000000058  w      .text	0000000000000000 _zimage_start

Reported to clang as https://bugs.llvm.org/show_bug.cgi?id=38921

[1] https://groups.google.com/forum/#!topic/fa.openbsd.tech/PAgKKen2YCY

Signed-off-by: Joel Stanley <joel@jms.id.au>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 arch/powerpc/boot/crt0.S | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/arch/powerpc/boot/crt0.S b/arch/powerpc/boot/crt0.S
index 12866ccb5694..5c2199857aa8 100644
--- a/arch/powerpc/boot/crt0.S
+++ b/arch/powerpc/boot/crt0.S
@@ -47,8 +47,10 @@ p_end:		.long	_end
 p_pstack:	.long	_platform_stack_top
 #endif
 
-	.weak	_zimage_start
 	.globl	_zimage_start
+	/* Clang appears to require the .weak directive to be after the symbol
+	 * is defined. See https://bugs.llvm.org/show_bug.cgi?id=38921  */
+	.weak	_zimage_start
 _zimage_start:
 	.globl	_zimage_start_lib
 _zimage_start_lib:
-- 
2.17.1


  parent reply	other threads:[~2018-11-04 13:57 UTC|newest]

Thread overview: 21+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-11-04 13:53 [PATCH AUTOSEL 4.9 01/21] mm/vmstat.c: assert that vmstat_text is in sync with stat_items_size Sasha Levin
2018-11-04 13:53 ` [PATCH AUTOSEL 4.9 02/21] userfaultfd: allow get_mempolicy(MPOL_F_NODE|MPOL_F_ADDR) to trigger userfaults Sasha Levin
2018-11-04 13:53 ` [PATCH AUTOSEL 4.9 03/21] mm: don't warn about large allocations for slab Sasha Levin
2018-11-04 13:53 ` [PATCH AUTOSEL 4.9 04/21] powerpc/eeh: Fix possible null deref in eeh_dump_dev_log() Sasha Levin
2018-11-04 13:53 ` [PATCH AUTOSEL 4.9 05/21] tty: check name length in tty_find_polling_driver() Sasha Levin
2018-11-04 13:53 ` [PATCH AUTOSEL 4.9 06/21] ARM: imx_v6_v7_defconfig: Select CONFIG_TMPFS_POSIX_ACL Sasha Levin
2018-11-04 13:53 ` [PATCH AUTOSEL 4.9 07/21] powerpc/nohash: fix undefined behaviour when testing page size support Sasha Levin
2018-11-04 13:53 ` [PATCH AUTOSEL 4.9 08/21] watchdog: lantiq: update register names to better match spec Sasha Levin
2018-11-04 13:53 ` [PATCH AUTOSEL 4.9 09/21] drm/omap: fix memory barrier bug in DMM driver Sasha Levin
2018-11-04 13:53 ` [PATCH AUTOSEL 4.9 10/21] iio: adc: at91: fix wrong channel number in triggered buffer mode Sasha Levin
2018-11-04 13:53 ` [PATCH AUTOSEL 4.9 11/21] iio: adc: at91: fix acking DRDY irq on simple conversions Sasha Levin
2018-11-04 13:53 ` [PATCH AUTOSEL 4.9 12/21] media: pci: cx23885: handle adding to list failure Sasha Levin
2018-11-04 13:53 ` [PATCH AUTOSEL 4.9 13/21] iio: adc: imx25-gcq: Fix leak of device_node in mx25_gcq_setup_cfgs() Sasha Levin
2018-11-04 13:53 ` [PATCH AUTOSEL 4.9 14/21] MIPS: kexec: Mark CPU offline before disabling local IRQ Sasha Levin
2018-11-04 13:53 ` Sasha Levin [this message]
2018-11-04 13:53 ` [PATCH AUTOSEL 4.9 16/21] MIPS/PCI: Call pcie_bus_configure_settings() to set MPS/MRRS Sasha Levin
2018-11-04 13:53 ` [PATCH AUTOSEL 4.9 17/21] sc16is7xx: Fix for multi-channel stall Sasha Levin
2018-11-04 13:53 ` [PATCH AUTOSEL 4.9 18/21] media: tvp5150: fix width alignment during set_selection() Sasha Levin
2018-11-04 13:53 ` [PATCH AUTOSEL 4.9 19/21] powerpc/selftests: Wait all threads to join Sasha Levin
2018-11-04 13:53 ` [PATCH AUTOSEL 4.9 20/21] 9p locks: fix glock.client_id leak in do_lock Sasha Levin
2018-11-04 13:53 ` [PATCH AUTOSEL 4.9 21/21] 9p: clear dangling pointers in p9stat_free Sasha Levin

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