path: root/arch/powerpc
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authorAnton Blanchard <anton@samba.org>2013-07-15 14:04:50 +1000
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2013-08-04 16:50:57 +0800
commit2b29b0d2f36f54034b7c038367f6b8e06bdc17ce (patch)
tree1e077ed8f51a613db63871898e20191cd88a1fc7 /arch/powerpc
parent85acabeb3c8170634eb69bee29ad58eec6d05482 (diff)
powerpc/modules: Module CRC relocation fix causes perf issues
commit 0e0ed6406e61434d3f38fb58aa8464ec4722b77e upstream. 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 <anton@samba.org> Acked-by: Rusty Russell <rusty@rustcorp.com.au> Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'arch/powerpc')
2 files changed, 2 insertions, 6 deletions
diff --git a/arch/powerpc/include/asm/module.h b/arch/powerpc/include/asm/module.h
index c1df590ec44..49fa55bfbac 100644
--- a/arch/powerpc/include/asm/module.h
+++ b/arch/powerpc/include/asm/module.h
@@ -82,10 +82,9 @@ struct exception_table_entry;
void sort_ex_table(struct exception_table_entry *start,
struct exception_table_entry *finish);
+#if defined(CONFIG_MODVERSIONS) && defined(CONFIG_PPC64)
-extern const unsigned long reloc_start[];
+#define reloc_start PHYSICAL_START
#endif /* __KERNEL__ */
#endif /* _ASM_POWERPC_MODULE_H */
diff --git a/arch/powerpc/kernel/vmlinux.lds.S b/arch/powerpc/kernel/vmlinux.lds.S
index 654e479802f..f096e72262f 100644
--- a/arch/powerpc/kernel/vmlinux.lds.S
+++ b/arch/powerpc/kernel/vmlinux.lds.S
@@ -38,9 +38,6 @@ jiffies = jiffies_64 + 4;
- . = 0;
- reloc_start = .;