linux.git/arch/powerpc/kernel/vmlinux.lds.S, branch v3.17

powerpc/modules: Module CRC relocation fix causes perf issues

2013-07-24T04:18:43+00:00

Module CRCs are implemented as absolute symbols that get resolved by
a linker script. We build an intermediate .o that contains an
unresolved symbol for each CRC. genksysms parses this .o, calculates
the CRCs and writes a linker script that "resolves" the symbols to
the calculated CRC.

Unfortunately the ppc64 relocatable kernel sees these CRCs as symbols
that need relocating and relocates them at boot. Commit d4703aef
(module: handle ppc64 relocating kcrctabs when CONFIG_RELOCATABLE=y)
added a hook to reverse the bogus relocations. Part of this patch
created a symbol at 0x0:

# head -2 /proc/kallsyms
0000000000000000 T reloc_start
c000000000000000 T .__start

This reloc_start symbol is causing lots of confusion to perf. It
thinks reloc_start is a massive function that stretches from 0x0 to
0xc000000000000000 and we get various cryptic errors out of perf,
including:

problem incrementing symbol count, skipping event

This patch removes the  reloc_start linker script label and instead
defines it as PHYSICAL_START. We also need to wrap it with
CONFIG_PPC64 because the ppc32 kernel can set a non zero
PHYSICAL_START at compile time and we wouldn't want to subtract
it from the CRCs in that case.

Signed-off-by: Anton Blanchard 
Cc: 
Acked-by: Rusty Russell 
Signed-off-by: Benjamin Herrenschmidt

powerpc: Relocate prom_init.c on 64bit

2013-01-10T06:00:25+00:00

The ppc64 kernel can get loaded at any address which means
our very early init code in prom_init.c must be relocatable. We do
this with a pretty nasty RELOC() macro that we wrap accesses of
variables with. It is very fragile and sometimes we forget to add a
RELOC() to an uncommon path or sometimes a compiler change breaks it.

32bit has a much more elegant solution where we build prom_init.c
with -mrelocatable and then process the relocations manually.
Unfortunately we can't do the equivalent on 64bit and we would
have to build the entire kernel relocatable (-pie), resulting in a
large increase in kernel footprint (megabytes of relocation data).
The relocation data will be marked __initdata but it still creates
more pressure on our already tight memory layout at boot.

Alan Modra pointed out that the 64bit ABI is relocatable even
if we don't build with -pie, we just need to relocate the TOC.
This patch implements that idea and relocates the TOC entries of
prom_init.c. An added bonus is there are very few relocations to
process which helps keep boot times on simulators down.

gcc does not put 64bit integer constants into the TOC but to be
safe we may want a build time script which passes through the
prom_init.c TOC entries to make sure everything looks reasonable.

Signed-off-by: Anton Blanchard 
Signed-off-by: Benjamin Herrenschmidt

powerpc: Remove legacy iSeries bits from assembly files

2012-03-08T23:54:59+00:00

This removes the various bits of assembly in the kernel entry,
exception handling and SLB management code that were specific
to running under the legacy iSeries hypervisor which is no
longer supported.

Signed-off-by: Benjamin Herrenschmidt

powerpc: Process dynamic relocations for kernel

2011-12-20T15:21:08+00:00

The following patch implements the dynamic relocation processing for
PPC32 kernel. relocate() accepts the target virtual address and relocates
 the kernel image to the same.

Currently the following relocation types are handled :

	R_PPC_RELATIVE
	R_PPC_ADDR16_LO
	R_PPC_ADDR16_HI
	R_PPC_ADDR16_HA

The last 3 relocations in the above list depends on value of Symbol indexed
whose index is encoded in the Relocation entry. Hence we need the Symbol
Table for processing such relocations.

Note: The GNU ld for ppc32 produces buggy relocations for relocation types
that depend on symbols. The value of the symbols with STB_LOCAL scope
should be assumed to be zero. - Alan Modra

Signed-off-by: Suzuki K. Poulose 
Signed-off-by: Josh Poimboeuf 
Cc: Paul Mackerras 
Cc: Benjamin Herrenschmidt 
Cc: Alan Modra 
Cc: Kumar Gala 
Cc: linuxppc-dev 
Signed-off-by: Josh Boyer

percpu: Always align percpu output section to PAGE_SIZE

2011-03-24T17:50:09+00:00

Percpu allocator honors alignment request upto PAGE_SIZE and both the
percpu addresses in the percpu address space and the translated kernel
addresses should be aligned accordingly.  The calculation of the
former depends on the alignment of percpu output section in the kernel
image.

The linker script macros PERCPU_VADDR() and PERCPU() are used to
define this output section and the latter takes @align parameter.
Several architectures are using @align smaller than PAGE_SIZE breaking
percpu memory alignment.

This patch removes @align parameter from PERCPU(), renames it to
PERCPU_SECTION() and makes it always align to PAGE_SIZE.  While at it,
add PCPU_SETUP_BUG_ON() checks such that alignment problems are
reliably detected and remove percpu alignment comment recently added
in workqueue.c as the condition would trigger BUG way before reaching
there.

For um, this patch raises the alignment of percpu area.  As the area
is in .init, there shouldn't be any noticeable difference.

This problem was discovered by David Howells while debugging boot
failure on mn10300.

Signed-off-by: Tejun Heo 
Acked-by: Mike Frysinger 
Cc: uclinux-dist-devel@blackfin.uclinux.org
Cc: David Howells 
Cc: Jeff Dike 
Cc: user-mode-linux-devel@lists.sourceforge.net

percpu: align percpu readmostly subsection to cacheline

2011-01-25T13:26:50+00:00

Currently percpu readmostly subsection may share cachelines with other
percpu subsections which may result in unnecessary cacheline bounce
and performance degradation.

This patch adds @cacheline parameter to PERCPU() and PERCPU_VADDR()
linker macros, makes each arch linker scripts specify its cacheline
size and use it to align percpu subsections.

This is based on Shaohua's x86 only patch.

Signed-off-by: Tejun Heo 
Cc: Shaohua Li

Rename .data.read_mostly to .data..read_mostly.

2010-03-03T10:26:00+00:00

Signed-off-by: Denys Vlasenko 
Signed-off-by: Michal Marek

Rename .data.page_aligned to .data..page_aligned.

2010-03-03T10:25:59+00:00

Signed-off-by: Tim Abbott 
Cc: Sam Ravnborg 
Signed-off-by: Denys Vlasenko 
Signed-off-by: Michal Marek

Rename .data.init_task to .data..init_task.

2010-03-03T10:25:58+00:00

Signed-off-by: Tim Abbott 
Cc: Sam Ravnborg 
Signed-off-by: Denys Vlasenko 
Signed-off-by: Michal Marek

Rename .data.cacheline_aligned to .data..cacheline_aligned.

2010-03-03T10:25:58+00:00

Signed-off-by: Tim Abbott 
Cc: Sam Ravnborg 
Signed-off-by: Denys Vlasenko 
Signed-off-by: Michal Marek