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powerpc: Fix build bug with binutils < 2.18 and GCC < 4.2 

binutils < 2.18 has a bug that makes it misbehave when taking an
ELF file with all segments at load address 0 as input.  This
happens when running "strip" on vmlinux, because of the AT() magic
in this linker script.  People using GCC >= 4.2 won't run into
this problem, because the "build-id" support will put some data
into the "notes" segment (at a non-zero load address).

To work around this, we force some data into both the "dummy"
segment and the kernel segment, so the dummy segment will get a
non-zero load address.  It's not enough to always create the
"notes" segment, since if nothing gets assigned to it, its load
address will be zero.

Signed-off-by: Segher Boessenkool <segher@kernel.crashing.org>
Tested-By: Milton Miller <miltonm@bga.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
hifive-unleashed-5.1
Segher Boessenkool 2008-07-22 09:03:45 +10:00 committed by Benjamin Herrenschmidt
parent f36c5227cd
commit c69cccc95f
1 changed files with 28 additions and 3 deletions
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31
arch/powerpc/kernel/vmlinux.lds.S
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@ -9,6 +9,25 @@
ENTRY(_stext)
PHDRS {
kernel PT_LOAD FLAGS(7); /* RWX */
notes PT_NOTE FLAGS(0);
dummy PT_NOTE FLAGS(0);
/* binutils < 2.18 has a bug that makes it misbehave when taking an
ELF file with all segments at load address 0 as input. This
happens when running "strip" on vmlinux, because of the AT() magic
in this linker script. People using GCC >= 4.2 won't run into
this problem, because the "build-id" support will put some data
into the "notes" segment (at a non-zero load address).
To work around this, we force some data into both the "dummy"
segment and the kernel segment, so the dummy segment will get a
non-zero load address. It's not enough to always create the
"notes" segment, since if nothing gets assigned to it, its load
address will be zero. */
}
#ifdef CONFIG_PPC64
OUTPUT_ARCH(powerpc:common64)
jiffies = jiffies_64;
@ -50,7 +69,7 @@ SECTIONS
. = ALIGN(PAGE_SIZE);
_etext = .;
PROVIDE32 (etext = .);
}
} :kernel
/* Read-only data */
RODATA
@ -62,7 +81,13 @@ SECTIONS
__stop___ex_table = .;
}
NOTES
NOTES :kernel :notes
/* The dummy segment contents for the bug workaround mentioned above
near PHDRS. */
.dummy : {
LONG(0xf177)
} :kernel :dummy
/*
* Init sections discarded at runtime
@ -74,7 +99,7 @@ SECTIONS
_sinittext = .;
INIT_TEXT
_einittext = .;
}
} :kernel
/* .exit.text is discarded at runtime, not link time,
* to deal with references from __bug_table