Commit 8651ec01daed ("module: add support for symbol namespaces.")
broke linking for arm64 defconfig:
| lib/crypto/arc4.o: In function `__ksymtab_arc4_setkey':
| arc4.c:(___ksymtab+arc4_setkey+0x8): undefined reference to `no symbol'
| lib/crypto/arc4.o: In function `__ksymtab_arc4_crypt':
| arc4.c:(___ksymtab+arc4_crypt+0x8): undefined reference to `no symbol'
This is because the dummy initialisation of the 'namespace_offset' field
in 'struct kernel_symbol' when using EXPORT_SYMBOL on architectures with
support for PREL32 locations uses an offset from an absolute address (0)
in an effort to trick 'offset_to_pointer' into behaving as a NOP,
allowing non-namespaced symbols to be treated in the same way as those
belonging to a namespace.
Unfortunately, place-relative relocations require a symbol reference
rather than an absolute value and, although x86 appears to get away with
this due to placing the kernel text at the top of the address space, it
almost certainly results in a runtime failure if the kernel is relocated
dynamically as a result of KASLR.
Rework 'namespace_offset' so that a value of 0, which cannot occur for a
valid namespaced symbol, indicates that the corresponding symbol does
not belong to a namespace.
Cc: Matthias Maennich <[email protected]>
Cc: Jessica Yu <[email protected]>
Cc: Ard Biesheuvel <[email protected]>
Cc: Catalin Marinas <[email protected]>
Fixes: 8651ec01daed ("module: add support for symbol namespaces.")
Reported-by: kbuild test robot <[email protected]>
Signed-off-by: Will Deacon <[email protected]>
---
Please note that I've not been able to test this at LPC, but it's been
submitted to kernelci.
include/asm-generic/export.h | 2 +-
include/linux/export.h | 2 +-
kernel/module.c | 2 ++
3 files changed, 4 insertions(+), 2 deletions(-)
diff --git a/include/asm-generic/export.h b/include/asm-generic/export.h
index e2b5d0f569d3..d0912c7ac2fc 100644
--- a/include/asm-generic/export.h
+++ b/include/asm-generic/export.h
@@ -17,7 +17,7 @@
.macro __put, val, name
#ifdef CONFIG_HAVE_ARCH_PREL32_RELOCATIONS
- .long \val - ., \name - ., 0 - .
+ .long \val - ., \name - ., 0
#elif defined(CONFIG_64BIT)
.quad \val, \name, 0
#else
diff --git a/include/linux/export.h b/include/linux/export.h
index 2c5468d8ea9a..ef5d015d754a 100644
--- a/include/linux/export.h
+++ b/include/linux/export.h
@@ -68,7 +68,7 @@ extern struct module __this_module;
"__ksymtab_" #sym ": \n" \
" .long " #sym "- . \n" \
" .long __kstrtab_" #sym "- . \n" \
- " .long 0 - . \n" \
+ " .long 0 \n" \
" .previous \n")
struct kernel_symbol {
diff --git a/kernel/module.c b/kernel/module.c
index f76efcf2043e..7ab244c4e1ba 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -547,6 +547,8 @@ static const char *kernel_symbol_name(const struct kernel_symbol *sym)
static const char *kernel_symbol_namespace(const struct kernel_symbol *sym)
{
#ifdef CONFIG_HAVE_ARCH_PREL32_RELOCATIONS
+ if (!sym->namespace_offset)
+ return NULL;
return offset_to_ptr(&sym->namespace_offset);
#else
return sym->namespace;
--
2.23.0.162.g0b9fbb3734-goog
+++ Will Deacon [11/09/19 13:26 +0100]:
>Commit 8651ec01daed ("module: add support for symbol namespaces.")
>broke linking for arm64 defconfig:
>
> | lib/crypto/arc4.o: In function `__ksymtab_arc4_setkey':
> | arc4.c:(___ksymtab+arc4_setkey+0x8): undefined reference to `no symbol'
> | lib/crypto/arc4.o: In function `__ksymtab_arc4_crypt':
> | arc4.c:(___ksymtab+arc4_crypt+0x8): undefined reference to `no symbol'
>
>This is because the dummy initialisation of the 'namespace_offset' field
>in 'struct kernel_symbol' when using EXPORT_SYMBOL on architectures with
>support for PREL32 locations uses an offset from an absolute address (0)
>in an effort to trick 'offset_to_pointer' into behaving as a NOP,
>allowing non-namespaced symbols to be treated in the same way as those
>belonging to a namespace.
>
>Unfortunately, place-relative relocations require a symbol reference
>rather than an absolute value and, although x86 appears to get away with
>this due to placing the kernel text at the top of the address space, it
>almost certainly results in a runtime failure if the kernel is relocated
>dynamically as a result of KASLR.
>
>Rework 'namespace_offset' so that a value of 0, which cannot occur for a
>valid namespaced symbol, indicates that the corresponding symbol does
>not belong to a namespace.
>
>Cc: Matthias Maennich <[email protected]>
>Cc: Jessica Yu <[email protected]>
>Cc: Ard Biesheuvel <[email protected]>
>Cc: Catalin Marinas <[email protected]>
>Fixes: 8651ec01daed ("module: add support for symbol namespaces.")
>Reported-by: kbuild test robot <[email protected]>
>Signed-off-by: Will Deacon <[email protected]>
>---
>
>Please note that I've not been able to test this at LPC, but it's been
>submitted to kernelci.
Thanks for fixing this so quickly. I can confirm that this fixes the
build for arm64 defconfig and x86 built fine for me as well. I'll wait
a bit and apply this at the end of the day in case Matthias or anybody
else would like to confirm/test.
Thanks,
Jessica
> include/asm-generic/export.h | 2 +-
> include/linux/export.h | 2 +-
> kernel/module.c | 2 ++
> 3 files changed, 4 insertions(+), 2 deletions(-)
>
>diff --git a/include/asm-generic/export.h b/include/asm-generic/export.h
>index e2b5d0f569d3..d0912c7ac2fc 100644
>--- a/include/asm-generic/export.h
>+++ b/include/asm-generic/export.h
>@@ -17,7 +17,7 @@
>
> .macro __put, val, name
> #ifdef CONFIG_HAVE_ARCH_PREL32_RELOCATIONS
>- .long \val - ., \name - ., 0 - .
>+ .long \val - ., \name - ., 0
> #elif defined(CONFIG_64BIT)
> .quad \val, \name, 0
> #else
>diff --git a/include/linux/export.h b/include/linux/export.h
>index 2c5468d8ea9a..ef5d015d754a 100644
>--- a/include/linux/export.h
>+++ b/include/linux/export.h
>@@ -68,7 +68,7 @@ extern struct module __this_module;
> "__ksymtab_" #sym ": \n" \
> " .long " #sym "- . \n" \
> " .long __kstrtab_" #sym "- . \n" \
>- " .long 0 - . \n" \
>+ " .long 0 \n" \
> " .previous \n")
>
> struct kernel_symbol {
>diff --git a/kernel/module.c b/kernel/module.c
>index f76efcf2043e..7ab244c4e1ba 100644
>--- a/kernel/module.c
>+++ b/kernel/module.c
>@@ -547,6 +547,8 @@ static const char *kernel_symbol_name(const struct kernel_symbol *sym)
> static const char *kernel_symbol_namespace(const struct kernel_symbol *sym)
> {
> #ifdef CONFIG_HAVE_ARCH_PREL32_RELOCATIONS
>+ if (!sym->namespace_offset)
>+ return NULL;
> return offset_to_ptr(&sym->namespace_offset);
> #else
> return sym->namespace;
>--
>2.23.0.162.g0b9fbb3734-goog
>
On Wed, Sep 11, 2019 at 03:35:06PM +0200, Jessica Yu wrote:
> +++ Will Deacon [11/09/19 13:26 +0100]:
> > Commit 8651ec01daed ("module: add support for symbol namespaces.")
> > broke linking for arm64 defconfig:
> >
> > | lib/crypto/arc4.o: In function `__ksymtab_arc4_setkey':
> > | arc4.c:(___ksymtab+arc4_setkey+0x8): undefined reference to `no symbol'
> > | lib/crypto/arc4.o: In function `__ksymtab_arc4_crypt':
> > | arc4.c:(___ksymtab+arc4_crypt+0x8): undefined reference to `no symbol'
> >
> > This is because the dummy initialisation of the 'namespace_offset' field
> > in 'struct kernel_symbol' when using EXPORT_SYMBOL on architectures with
> > support for PREL32 locations uses an offset from an absolute address (0)
> > in an effort to trick 'offset_to_pointer' into behaving as a NOP,
> > allowing non-namespaced symbols to be treated in the same way as those
> > belonging to a namespace.
> >
> > Unfortunately, place-relative relocations require a symbol reference
> > rather than an absolute value and, although x86 appears to get away with
> > this due to placing the kernel text at the top of the address space, it
> > almost certainly results in a runtime failure if the kernel is relocated
> > dynamically as a result of KASLR.
> >
> > Rework 'namespace_offset' so that a value of 0, which cannot occur for a
> > valid namespaced symbol, indicates that the corresponding symbol does
> > not belong to a namespace.
> >
> > Cc: Matthias Maennich <[email protected]>
> > Cc: Jessica Yu <[email protected]>
> > Cc: Ard Biesheuvel <[email protected]>
> > Cc: Catalin Marinas <[email protected]>
> > Fixes: 8651ec01daed ("module: add support for symbol namespaces.")
> > Reported-by: kbuild test robot <[email protected]>
> > Signed-off-by: Will Deacon <[email protected]>
> > ---
> >
> > Please note that I've not been able to test this at LPC, but it's been
> > submitted to kernelci.
>
> Thanks for fixing this so quickly. I can confirm that this fixes the
> build for arm64 defconfig and x86 built fine for me as well. I'll wait
> a bit and apply this at the end of the day in case Matthias or anybody
> else would like to confirm/test.
FWIW, I've managed to boot arm64 Debian under QEMU and load/unload
modules successfully with this patch applied on top of modules-next.
Will
On Wed, 11 Sep 2019 at 13:26, Will Deacon <[email protected]> wrote:
>
> Commit 8651ec01daed ("module: add support for symbol namespaces.")
> broke linking for arm64 defconfig:
>
> | lib/crypto/arc4.o: In function `__ksymtab_arc4_setkey':
> | arc4.c:(___ksymtab+arc4_setkey+0x8): undefined reference to `no symbol'
> | lib/crypto/arc4.o: In function `__ksymtab_arc4_crypt':
> | arc4.c:(___ksymtab+arc4_crypt+0x8): undefined reference to `no symbol'
>
> This is because the dummy initialisation of the 'namespace_offset' field
> in 'struct kernel_symbol' when using EXPORT_SYMBOL on architectures with
> support for PREL32 locations uses an offset from an absolute address (0)
> in an effort to trick 'offset_to_pointer' into behaving as a NOP,
> allowing non-namespaced symbols to be treated in the same way as those
> belonging to a namespace.
>
> Unfortunately, place-relative relocations require a symbol reference
> rather than an absolute value and, although x86 appears to get away with
> this due to placing the kernel text at the top of the address space, it
> almost certainly results in a runtime failure if the kernel is relocated
> dynamically as a result of KASLR.
>
> Rework 'namespace_offset' so that a value of 0, which cannot occur for a
> valid namespaced symbol, indicates that the corresponding symbol does
> not belong to a namespace.
>
> Cc: Matthias Maennich <[email protected]>
> Cc: Jessica Yu <[email protected]>
> Cc: Ard Biesheuvel <[email protected]>
> Cc: Catalin Marinas <[email protected]>
> Fixes: 8651ec01daed ("module: add support for symbol namespaces.")
> Reported-by: kbuild test robot <[email protected]>
> Signed-off-by: Will Deacon <[email protected]>
> ---
>
> Please note that I've not been able to test this at LPC, but it's been
> submitted to kernelci.
>
The build tests all passed, and the boot tests that have completed by
now all look fine, so
Acked-by: Ard Biesheuvel <[email protected]>
Tested-by: Ard Biesheuvel <[email protected]>
> include/asm-generic/export.h | 2 +-
> include/linux/export.h | 2 +-
> kernel/module.c | 2 ++
> 3 files changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/include/asm-generic/export.h b/include/asm-generic/export.h
> index e2b5d0f569d3..d0912c7ac2fc 100644
> --- a/include/asm-generic/export.h
> +++ b/include/asm-generic/export.h
> @@ -17,7 +17,7 @@
>
> .macro __put, val, name
> #ifdef CONFIG_HAVE_ARCH_PREL32_RELOCATIONS
> - .long \val - ., \name - ., 0 - .
> + .long \val - ., \name - ., 0
> #elif defined(CONFIG_64BIT)
> .quad \val, \name, 0
> #else
> diff --git a/include/linux/export.h b/include/linux/export.h
> index 2c5468d8ea9a..ef5d015d754a 100644
> --- a/include/linux/export.h
> +++ b/include/linux/export.h
> @@ -68,7 +68,7 @@ extern struct module __this_module;
> "__ksymtab_" #sym ": \n" \
> " .long " #sym "- . \n" \
> " .long __kstrtab_" #sym "- . \n" \
> - " .long 0 - . \n" \
> + " .long 0 \n" \
> " .previous \n")
>
> struct kernel_symbol {
> diff --git a/kernel/module.c b/kernel/module.c
> index f76efcf2043e..7ab244c4e1ba 100644
> --- a/kernel/module.c
> +++ b/kernel/module.c
> @@ -547,6 +547,8 @@ static const char *kernel_symbol_name(const struct kernel_symbol *sym)
> static const char *kernel_symbol_namespace(const struct kernel_symbol *sym)
> {
> #ifdef CONFIG_HAVE_ARCH_PREL32_RELOCATIONS
> + if (!sym->namespace_offset)
> + return NULL;
> return offset_to_ptr(&sym->namespace_offset);
> #else
> return sym->namespace;
> --
> 2.23.0.162.g0b9fbb3734-goog
>
On Wed, Sep 11, 2019 at 05:40:13PM +0100, Will Deacon wrote:
>On Wed, Sep 11, 2019 at 03:35:06PM +0200, Jessica Yu wrote:
>> +++ Will Deacon [11/09/19 13:26 +0100]:
>> > Commit 8651ec01daed ("module: add support for symbol namespaces.")
>> > broke linking for arm64 defconfig:
>> >
>> > | lib/crypto/arc4.o: In function `__ksymtab_arc4_setkey':
>> > | arc4.c:(___ksymtab+arc4_setkey+0x8): undefined reference to `no symbol'
>> > | lib/crypto/arc4.o: In function `__ksymtab_arc4_crypt':
>> > | arc4.c:(___ksymtab+arc4_crypt+0x8): undefined reference to `no symbol'
>> >
>> > This is because the dummy initialisation of the 'namespace_offset' field
>> > in 'struct kernel_symbol' when using EXPORT_SYMBOL on architectures with
>> > support for PREL32 locations uses an offset from an absolute address (0)
>> > in an effort to trick 'offset_to_pointer' into behaving as a NOP,
>> > allowing non-namespaced symbols to be treated in the same way as those
>> > belonging to a namespace.
>> >
>> > Unfortunately, place-relative relocations require a symbol reference
>> > rather than an absolute value and, although x86 appears to get away with
>> > this due to placing the kernel text at the top of the address space, it
>> > almost certainly results in a runtime failure if the kernel is relocated
>> > dynamically as a result of KASLR.
>> >
>> > Rework 'namespace_offset' so that a value of 0, which cannot occur for a
>> > valid namespaced symbol, indicates that the corresponding symbol does
>> > not belong to a namespace.
>> >
>> > Cc: Matthias Maennich <[email protected]>
>> > Cc: Jessica Yu <[email protected]>
>> > Cc: Ard Biesheuvel <[email protected]>
>> > Cc: Catalin Marinas <[email protected]>
>> > Fixes: 8651ec01daed ("module: add support for symbol namespaces.")
>> > Reported-by: kbuild test robot <[email protected]>
>> > Signed-off-by: Will Deacon <[email protected]>
>> > ---
>> >
>> > Please note that I've not been able to test this at LPC, but it's been
>> > submitted to kernelci.
>>
>> Thanks for fixing this so quickly. I can confirm that this fixes the
>> build for arm64 defconfig and x86 built fine for me as well. I'll wait
>> a bit and apply this at the end of the day in case Matthias or anybody
>> else would like to confirm/test.
>
>FWIW, I've managed to boot arm64 Debian under QEMU and load/unload
>modules successfully with this patch applied on top of modules-next.
Thanks Will for fixing this so quickly! The patch looks good to me.
Feel free to add
Reviewed-by: Matthias Maennich <[email protected]>
Tested-by: Matthias Maennich <[email protected]>
Cheers,
Matthias
+++ Will Deacon [11/09/19 13:26 +0100]:
>Commit 8651ec01daed ("module: add support for symbol namespaces.")
>broke linking for arm64 defconfig:
>
> | lib/crypto/arc4.o: In function `__ksymtab_arc4_setkey':
> | arc4.c:(___ksymtab+arc4_setkey+0x8): undefined reference to `no symbol'
> | lib/crypto/arc4.o: In function `__ksymtab_arc4_crypt':
> | arc4.c:(___ksymtab+arc4_crypt+0x8): undefined reference to `no symbol'
>
>This is because the dummy initialisation of the 'namespace_offset' field
>in 'struct kernel_symbol' when using EXPORT_SYMBOL on architectures with
>support for PREL32 locations uses an offset from an absolute address (0)
>in an effort to trick 'offset_to_pointer' into behaving as a NOP,
>allowing non-namespaced symbols to be treated in the same way as those
>belonging to a namespace.
>
>Unfortunately, place-relative relocations require a symbol reference
>rather than an absolute value and, although x86 appears to get away with
>this due to placing the kernel text at the top of the address space, it
>almost certainly results in a runtime failure if the kernel is relocated
>dynamically as a result of KASLR.
>
>Rework 'namespace_offset' so that a value of 0, which cannot occur for a
>valid namespaced symbol, indicates that the corresponding symbol does
>not belong to a namespace.
>
>Cc: Matthias Maennich <[email protected]>
>Cc: Jessica Yu <[email protected]>
>Cc: Ard Biesheuvel <[email protected]>
>Cc: Catalin Marinas <[email protected]>
>Fixes: 8651ec01daed ("module: add support for symbol namespaces.")
>Reported-by: kbuild test robot <[email protected]>
>Signed-off-by: Will Deacon <[email protected]>
Applied, thanks everyone!
Jessica
>---
>
>Please note that I've not been able to test this at LPC, but it's been
>submitted to kernelci.
>
> include/asm-generic/export.h | 2 +-
> include/linux/export.h | 2 +-
> kernel/module.c | 2 ++
> 3 files changed, 4 insertions(+), 2 deletions(-)
>
>diff --git a/include/asm-generic/export.h b/include/asm-generic/export.h
>index e2b5d0f569d3..d0912c7ac2fc 100644
>--- a/include/asm-generic/export.h
>+++ b/include/asm-generic/export.h
>@@ -17,7 +17,7 @@
>
> .macro __put, val, name
> #ifdef CONFIG_HAVE_ARCH_PREL32_RELOCATIONS
>- .long \val - ., \name - ., 0 - .
>+ .long \val - ., \name - ., 0
> #elif defined(CONFIG_64BIT)
> .quad \val, \name, 0
> #else
>diff --git a/include/linux/export.h b/include/linux/export.h
>index 2c5468d8ea9a..ef5d015d754a 100644
>--- a/include/linux/export.h
>+++ b/include/linux/export.h
>@@ -68,7 +68,7 @@ extern struct module __this_module;
> "__ksymtab_" #sym ": \n" \
> " .long " #sym "- . \n" \
> " .long __kstrtab_" #sym "- . \n" \
>- " .long 0 - . \n" \
>+ " .long 0 \n" \
> " .previous \n")
>
> struct kernel_symbol {
>diff --git a/kernel/module.c b/kernel/module.c
>index f76efcf2043e..7ab244c4e1ba 100644
>--- a/kernel/module.c
>+++ b/kernel/module.c
>@@ -547,6 +547,8 @@ static const char *kernel_symbol_name(const struct kernel_symbol *sym)
> static const char *kernel_symbol_namespace(const struct kernel_symbol *sym)
> {
> #ifdef CONFIG_HAVE_ARCH_PREL32_RELOCATIONS
>+ if (!sym->namespace_offset)
>+ return NULL;
> return offset_to_ptr(&sym->namespace_offset);
> #else
> return sym->namespace;
>--
>2.23.0.162.g0b9fbb3734-goog
>