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Subject[PATCH 50/52] module: handle ppc64 relocating kcrctabs when CONFIG_RELOCATABLE=y
Date
From: Rusty Russell <rusty@rustcorp.com.au>

commit d4703aefdbc8f9f347f6dcefcddd791294314eb7 upstream.

powerpc applies relocations to the kcrctab. They're absolute symbols,
but it's not completely unreasonable: other archs may too, but the
relocation is often 0.

http://lists.ozlabs.org/pipermail/linuxppc-dev/2009-November/077972.html

Inspired-by: Neil Horman <nhorman@tuxdriver.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Tested-by: Neil Horman <nhorman@tuxdriver.com>
Acked-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
---
arch/powerpc/include/asm/module.h | 5 +++++
arch/powerpc/kernel/vmlinux.lds.S | 3 +++
kernel/module.c | 28 +++++++++++++++++++++-------
3 files changed, 29 insertions(+), 7 deletions(-)
diff --git a/arch/powerpc/include/asm/module.h b/arch/powerpc/include/asm/module.h
index 0845488..0192a4e 100644
--- a/arch/powerpc/include/asm/module.h
+++ b/arch/powerpc/include/asm/module.h
@@ -87,5 +87,10 @@ struct exception_table_entry;
void sort_ex_table(struct exception_table_entry *start,
struct exception_table_entry *finish);

+#ifdef CONFIG_MODVERSIONS
+#define ARCH_RELOCATES_KCRCTAB
+
+extern const unsigned long reloc_start[];
+#endif
#endif /* __KERNEL__ */
#endif /* _ASM_POWERPC_MODULE_H */
diff --git a/arch/powerpc/kernel/vmlinux.lds.S b/arch/powerpc/kernel/vmlinux.lds.S
index 27735a7..dcd01c8 100644
--- a/arch/powerpc/kernel/vmlinux.lds.S
+++ b/arch/powerpc/kernel/vmlinux.lds.S
@@ -38,6 +38,9 @@ jiffies = jiffies_64 + 4;
#endif
SECTIONS
{
+ . = 0;
+ reloc_start = .;
+
. = KERNELBASE;

/*
diff --git a/kernel/module.c b/kernel/module.c
index 37caef0..dfa33e8 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -1030,11 +1030,23 @@ static int try_to_force_load(struct module *mod, const char *reason)
}

#ifdef CONFIG_MODVERSIONS
+/* If the arch applies (non-zero) relocations to kernel kcrctab, unapply it. */
+static unsigned long maybe_relocated(unsigned long crc,
+ const struct module *crc_owner)
+{
+#ifdef ARCH_RELOCATES_KCRCTAB
+ if (crc_owner == NULL)
+ return crc - (unsigned long)reloc_start;
+#endif
+ return crc;
+}
+
static int check_version(Elf_Shdr *sechdrs,
unsigned int versindex,
const char *symname,
struct module *mod,
- const unsigned long *crc)
+ const unsigned long *crc,
+ const struct module *crc_owner)
{
unsigned int i, num_versions;
struct modversion_info *versions;
@@ -1055,10 +1067,10 @@ static int check_version(Elf_Shdr *sechdrs,
if (strcmp(versions[i].name, symname) != 0)
continue;

- if (versions[i].crc == *crc)
+ if (versions[i].crc == maybe_relocated(*crc, crc_owner))
return 1;
DEBUGP("Found checksum %lX vs module %lX\n",
- *crc, versions[i].crc);
+ maybe_relocated(*crc, crc_owner), versions[i].crc);
goto bad_version;
}

@@ -1081,7 +1093,8 @@ static inline int check_modstruct_version(Elf_Shdr *sechdrs,
if (!find_symbol(MODULE_SYMBOL_PREFIX "module_layout", NULL,
&crc, true, false))
BUG();
- return check_version(sechdrs, versindex, "module_layout", mod, crc);
+ return check_version(sechdrs, versindex, "module_layout", mod, crc,
+ NULL);
}

/* First part is kernel version, which we ignore if module has crcs. */
@@ -1099,7 +1112,8 @@ static inline int check_version(Elf_Shdr *sechdrs,
unsigned int versindex,
const char *symname,
struct module *mod,
- const unsigned long *crc)
+ const unsigned long *crc,
+ const struct module *crc_owner)
{
return 1;
}
@@ -1134,8 +1148,8 @@ static const struct kernel_symbol *resolve_symbol(Elf_Shdr *sechdrs,
/* use_module can fail due to OOM,
or module initialization or unloading */
if (sym) {
- if (!check_version(sechdrs, versindex, name, mod, crc) ||
- !use_module(mod, owner))
+ if (!check_version(sechdrs, versindex, name, mod, crc, owner)
+ || !use_module(mod, owner))
sym = NULL;
}
return sym;
--
1.6.6


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