Re: linux-next: build warning after merge of the akpm tree

Re: linux-next: build warning after merge of the akpm tree

[Stephen Rothwell]

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Hi Stephen,

On Fri, 4 Dec 2020 21:00:00 +1100 Stephen Rothwell <sfr@canb.auug.org.au> wrote:
>
> Hi all,
> 
> After merging the akpm tree, today's linux-next build (powerpc
> allyesconfig) produced warnings like this:
> 
> ld: warning: orphan section `.data..Lubsan_data177' from `arch/powerpc/oprofile/op_model_pa6t.o' being placed in section `.data..Lubsan_data177'
> 
> (lots of these latter ones)

781584 of them today!

> I don't know what produced these, but it is in the akpm-current or
> akpm trees.

Presumably the result of commit

  186c3e18dba3 ("ubsan: enable for all*config builds")

from the akpm-current tree.

arch/powerpc/kernel/vmlinux.lds.S has:

#ifdef CONFIG_PPC32
        .data : AT(ADDR(.data) - LOAD_OFFSET) {
                DATA_DATA
#ifdef CONFIG_UBSAN
                *(.data..Lubsan_data*)
                *(.data..Lubsan_type*)
#endif
                *(.data.rel*)
                *(SDATA_MAIN)

added by commit

  beba24ac5913 ("powerpc/32: Add .data..Lubsan_data*/.data..Lubsan_type* sections explicitly")

in 2018, but no equivalent for 64 bit.

I will try the following patch tomorrow:

From: Stephen Rothwell <sfr@canb.auug.org.au>
Date: Tue, 8 Dec 2020 22:58:24 +1100
Subject: [PATCH] powerpc: Add .data..Lubsan_data*/.data..Lubsan_type* sections explicitly

Similarly to commit

  beba24ac5913 ("powerpc/32: Add .data..Lubsan_data*/.data..Lubsan_type* sections explicitly")

since CONFIG_UBSAN bits can now be enabled for all*config.

Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>
---
 arch/powerpc/kernel/vmlinux.lds.S | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/arch/powerpc/kernel/vmlinux.lds.S b/arch/powerpc/kernel/vmlinux.lds.S
index 3b4c26e94328..0318ba436f34 100644
--- a/arch/powerpc/kernel/vmlinux.lds.S
+++ b/arch/powerpc/kernel/vmlinux.lds.S
@@ -296,6 +296,10 @@ SECTIONS
 #else
 	.data : AT(ADDR(.data) - LOAD_OFFSET) {
 		DATA_DATA
+#ifdef CONFIG_UBSAN
+		*(.data..Lubsan_data*)
+		*(.data..Lubsan_type*)
+#endif
 		*(.data.rel*)
 		*(.toc1)
 		*(.branch_lt)
-- 
2.29.2

-- 
Cheers,
Stephen Rothwell

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Re: linux-next: build warning after merge of the akpm tree

[Michael Ellerman]

Stephen Rothwell <sfr@canb.auug.org.au> writes:
> Hi Stephen,
>
> On Fri, 4 Dec 2020 21:00:00 +1100 Stephen Rothwell <sfr@canb.auug.org.au> wrote:
>>
>> Hi all,
>> 
>> After merging the akpm tree, today's linux-next build (powerpc
>> allyesconfig) produced warnings like this:
>> 
>> ld: warning: orphan section `.data..Lubsan_data177' from `arch/powerpc/oprofile/op_model_pa6t.o' being placed in section `.data..Lubsan_data177'
>> 
>> (lots of these latter ones)
>
> 781584 of them today!
>
>> I don't know what produced these, but it is in the akpm-current or
>> akpm trees.
>
> Presumably the result of commit
>
>   186c3e18dba3 ("ubsan: enable for all*config builds")
>
> from the akpm-current tree.
>
> arch/powerpc/kernel/vmlinux.lds.S has:
>
> #ifdef CONFIG_PPC32
>         .data : AT(ADDR(.data) - LOAD_OFFSET) {
>                 DATA_DATA
> #ifdef CONFIG_UBSAN
>                 *(.data..Lubsan_data*)
>                 *(.data..Lubsan_type*)
> #endif
>                 *(.data.rel*)
>                 *(SDATA_MAIN)
>
> added by commit
>
>   beba24ac5913 ("powerpc/32: Add .data..Lubsan_data*/.data..Lubsan_type* sections explicitly")
>
> in 2018, but no equivalent for 64 bit.

They should really be in DATA_DATA or similar shouldn't they?

cheers

Re: linux-next: build warning after merge of the akpm tree

[Stephen Rothwell]

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Hi Michael,

On Wed, 09 Dec 2020 15:44:35 +1100 Michael Ellerman <mpe@ellerman.id.au> wrote:
>
> They should really be in DATA_DATA or similar shouldn't they?

No other architecture appears t need them ...

-- 
Cheers,
Stephen Rothwell

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Re: linux-next: build warning after merge of the akpm tree

[Stephen Rothwell]

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Hi all,

On Tue, 8 Dec 2020 23:01:57 +1100 Stephen Rothwell <sfr@canb.auug.org.au> wrote:
>
> I will try the following patch tomorrow:
> 
> From: Stephen Rothwell <sfr@canb.auug.org.au>
> Date: Tue, 8 Dec 2020 22:58:24 +1100
> Subject: [PATCH] powerpc: Add .data..Lubsan_data*/.data..Lubsan_type* sections explicitly
> 
> Similarly to commit
> 
>   beba24ac5913 ("powerpc/32: Add .data..Lubsan_data*/.data..Lubsan_type* sections explicitly")
> 
> since CONFIG_UBSAN bits can now be enabled for all*config.
> 
> Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>
> ---
>  arch/powerpc/kernel/vmlinux.lds.S | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/arch/powerpc/kernel/vmlinux.lds.S b/arch/powerpc/kernel/vmlinux.lds.S
> index 3b4c26e94328..0318ba436f34 100644
> --- a/arch/powerpc/kernel/vmlinux.lds.S
> +++ b/arch/powerpc/kernel/vmlinux.lds.S
> @@ -296,6 +296,10 @@ SECTIONS
>  #else
>  	.data : AT(ADDR(.data) - LOAD_OFFSET) {
>  		DATA_DATA
> +#ifdef CONFIG_UBSAN
> +		*(.data..Lubsan_data*)
> +		*(.data..Lubsan_type*)
> +#endif
>  		*(.data.rel*)
>  		*(.toc1)
>  		*(.branch_lt)
> -- 
> 2.29.2

This got rid of all the warnings.

-- 
Cheers,
Stephen Rothwell

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Re: linux-next: build warning after merge of the akpm tree

[Kees Cook]

On Tue, Dec 08, 2020 at 11:01:57PM +1100, Stephen Rothwell wrote:
> Hi Stephen,
> 
> On Fri, 4 Dec 2020 21:00:00 +1100 Stephen Rothwell <sfr@canb.auug.org.au> wrote:
> >
> > Hi all,
> > 
> > After merging the akpm tree, today's linux-next build (powerpc
> > allyesconfig) produced warnings like this:
> > 
> > ld: warning: orphan section `.data..Lubsan_data177' from `arch/powerpc/oprofile/op_model_pa6t.o' being placed in section `.data..Lubsan_data177'
> > 
> > (lots of these latter ones)
> 
> 781584 of them today!
> 
> > I don't know what produced these, but it is in the akpm-current or
> > akpm trees.
> 
> Presumably the result of commit
> 
>   186c3e18dba3 ("ubsan: enable for all*config builds")
> 
> from the akpm-current tree.
> 
> arch/powerpc/kernel/vmlinux.lds.S has:
> 
> #ifdef CONFIG_PPC32
>         .data : AT(ADDR(.data) - LOAD_OFFSET) {
>                 DATA_DATA
> #ifdef CONFIG_UBSAN
>                 *(.data..Lubsan_data*)
>                 *(.data..Lubsan_type*)
> #endif
>                 *(.data.rel*)
>                 *(SDATA_MAIN)
> 
> added by commit
> 
>   beba24ac5913 ("powerpc/32: Add .data..Lubsan_data*/.data..Lubsan_type* sections explicitly")
> 
> in 2018, but no equivalent for 64 bit.
> 
> I will try the following patch tomorrow:
> 
> From: Stephen Rothwell <sfr@canb.auug.org.au>
> Date: Tue, 8 Dec 2020 22:58:24 +1100
> Subject: [PATCH] powerpc: Add .data..Lubsan_data*/.data..Lubsan_type* sections explicitly
> 
> Similarly to commit
> 
>   beba24ac5913 ("powerpc/32: Add .data..Lubsan_data*/.data..Lubsan_type* sections explicitly")
> 
> since CONFIG_UBSAN bits can now be enabled for all*config.
> 
> Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>
> ---
>  arch/powerpc/kernel/vmlinux.lds.S | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/arch/powerpc/kernel/vmlinux.lds.S b/arch/powerpc/kernel/vmlinux.lds.S
> index 3b4c26e94328..0318ba436f34 100644
> --- a/arch/powerpc/kernel/vmlinux.lds.S
> +++ b/arch/powerpc/kernel/vmlinux.lds.S
> @@ -296,6 +296,10 @@ SECTIONS
>  #else
>  	.data : AT(ADDR(.data) - LOAD_OFFSET) {
>  		DATA_DATA
> +#ifdef CONFIG_UBSAN
> +		*(.data..Lubsan_data*)
> +		*(.data..Lubsan_type*)
> +#endif
>  		*(.data.rel*)
>  		*(.toc1)
>  		*(.branch_lt)
> -- 
> 2.29.2
> 
> -- 
> Cheers,
> Stephen Rothwell

Reviewed-by: Kees Cook <keescook@chromium.org>

Thanks for figuring this one out. :) Andrew, can you add this to your
ubsan patch stack, or do you want me to resend it to you directly?


-- 
Kees Cook

Re: linux-next: build warning after merge of the akpm tree

[Michael Ellerman]

Stephen Rothwell <sfr@canb.auug.org.au> writes:
> Hi Michael,
>
> On Wed, 09 Dec 2020 15:44:35 +1100 Michael Ellerman <mpe@ellerman.id.au> wrote:
>>
>> They should really be in DATA_DATA or similar shouldn't they?
>
> No other architecture appears t need them ...

Any arch with orphan-handling=warn should see them I thought?

cheers

Re: linux-next: build warning after merge of the akpm tree

[Stephen Rothwell]

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Hi Michael,

On Thu, 10 Dec 2020 11:19:45 +1100 Michael Ellerman <mpe@ellerman.id.au> wrote:
>
> Stephen Rothwell <sfr@canb.auug.org.au> writes:
> >
> > On Wed, 09 Dec 2020 15:44:35 +1100 Michael Ellerman <mpe@ellerman.id.au> wrote:  
> >>
> >> They should really be in DATA_DATA or similar shouldn't they?  
> >
> > No other architecture appears t need them ...  
> 
> Any arch with orphan-handling=warn should see them I thought?

I did an x86_64 allyesconfig build (same compiler (more or less) and
same source) and it produces none of these sections.  The only
difference in UBSAN CONFIG_ options was that CONFIG_UBSAN_UNREACHABLE
is not set in the x86_64 build.

-- 
Cheers,
Stephen Rothwell

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