[PATCH] bpf: Added linker support for R_BPF_64_NODYLD32.

[PATCH] bpf: Added linker support for R_BPF_64_NODYLD32.

[Cupertino Miranda]

Hi everyone,

This patch is in context of Nick Cliftons request in thread:
  https://sourceware.org/pipermail/binutils/2023-October/130194.html
due to bug reported in:
  https://bugzilla.redhat.com/show_bug.cgi?id=2245296

For the time being the linker is not used in BPF infrastructure.
Considering that and without a proper way to validate the code, the
following patch is what I think is missing in order to add linker
support for the particular relocation.

Looking forward to your review.

Best regards,
Cupertino

This patch adds linker support to patch R_BPF_64_NODYLD32 relocations.
The implementation was based on comments and code in LLVM, as the GNU
toolchain does not uses this relocation type.
---
 bfd/elf64-bpf.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/bfd/elf64-bpf.c b/bfd/elf64-bpf.c
index aefad7da5ac..5820dd3d7d4 100644
--- a/bfd/elf64-bpf.c
+++ b/bfd/elf64-bpf.c
@@ -276,6 +276,7 @@ bpf_elf_relocate_section (bfd *output_bfd ATTRIBUTE_UNUSED,
           }
 	case R_BPF_64_ABS64:
 	case R_BPF_64_ABS32:
+	case R_BPF_64_NODYLD32:
 	  {
 	    addend = bfd_get (howto->bitsize, input_bfd, where);
 	    relocation += addend;
-- 
2.30.2

Re: [PATCH] bpf: Added linker support for R_BPF_64_NODYLD32.

[Jose E. Marchesi]

Hi Cuper.

> Hi everyone,
>
> This patch is in context of Nick Cliftons request in thread:
>   https://sourceware.org/pipermail/binutils/2023-October/130194.html
> due to bug reported in:
>   https://bugzilla.redhat.com/show_bug.cgi?id=2245296
>
> For the time being the linker is not used in BPF infrastructure.
> Considering that and without a proper way to validate the code, the
> following patch is what I think is missing in order to add linker
> support for the particular relocation.
>
> Looking forward to your review.
>
> Best regards,
> Cupertino
>
> This patch adds linker support to patch R_BPF_64_NODYLD32 relocations.
> The implementation was based on comments and code in LLVM, as the GNU
> toolchain does not uses this relocation type.
> ---
>  bfd/elf64-bpf.c | 1 +
>  1 file changed, 1 insertion(+)
>
> diff --git a/bfd/elf64-bpf.c b/bfd/elf64-bpf.c
> index aefad7da5ac..5820dd3d7d4 100644
> --- a/bfd/elf64-bpf.c
> +++ b/bfd/elf64-bpf.c
> @@ -276,6 +276,7 @@ bpf_elf_relocate_section (bfd *output_bfd ATTRIBUTE_UNUSED,
>            }
>  	case R_BPF_64_ABS64:
>  	case R_BPF_64_ABS32:
> +	case R_BPF_64_NODYLD32:

I would add here a comment explaining that R_BPF_64_NODYLD32 shall be
handled/resolved like R_BPF_64_ABS32 and that it differs from ABS32 only
in that the LLVM execution engine is not supposed to resolve it.

Given that, the patch is OK.
Thanks!

>  	  {
>  	    addend = bfd_get (howto->bitsize, input_bfd, where);
>  	    relocation += addend;

Re: [PATCH] bpf: Added linker support for R_BPF_64_NODYLD32.

[Cupertino Miranda]

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Hi Jose,

Thanks for your review.
I realized I missed to update the macro for the relocation where the
properties like size, overflow check, (etc.) are defined.
I have added the comment near the relocation macro definition.

Sending the patch for review once again.

Regards,
Cupertino


[-- Warning: decoded text below may be mangled, UTF-8 assumed --]
[-- Attachment #2: 0001-bpf-Added-linker-support-for-R_BPF_64_NODYLD32.patch --]
[-- Type: text/x-diff, Size: 2137 bytes --]

From bb8afde9a8f17d42393067c3a667bec1f08b252a Mon Sep 17 00:00:00 2001
From: Cupertino Miranda <cupertino.miranda@oracle.com>
Date: Wed, 20 Dec 2023 12:24:03 +0000
Subject: [PATCH] bpf: Added linker support for R_BPF_64_NODYLD32.

This patch adds linker support to patch R_BPF_64_NODYLD32 relocations.
The implementation was based on comments and code in LLVM, as the GNU
toolchain does not uses this relocation type.
---
 bfd/bpf-reloc.def | 17 ++++++++++-------
 bfd/elf64-bpf.c   |  1 +
 2 files changed, 11 insertions(+), 7 deletions(-)

diff --git a/bfd/bpf-reloc.def b/bfd/bpf-reloc.def
index 7e7497892fa..42ba1a169ea 100644
--- a/bfd/bpf-reloc.def
+++ b/bfd/bpf-reloc.def
@@ -90,17 +90,20 @@
 
   /* R_BPF_64_NODYLD32 is not used by GNU tools - but it is generated by LLVM.
      We provide an entry here so that tools like strip can safely handle BPF
-     binaries generated by other tools.  */
+     binaries generated by other tools.
+     R_BPF_64_NODYLD32 should be fixed at linker like a R_BPF_64_ABS32.
+     The difference to ABS32 is that LLVM execution engine does not resolve
+     R_BPF_64_NODYLD32 relocations.  */
   BPF_HOWTO (R_BPF_64_NODYLD32,	/* type */
 	 0,			/* rightshift */
-	 0,			/* size */
-	 0,			/* bitsize */
+	 4,			/* size */
+	 32,			/* bitsize */
 	 false,			/* pc_relative */
 	 0,			/* bitpos */
-	 complain_overflow_dont, /* complain_on_overflow */
+	 complain_overflow_bitfield, /* complain_on_overflow */
 	 bpf_elf_generic_reloc, /* special_function */
 	 "R_BPF_64_NODYLD32",	/* name */
 	 false,			/* partial_inplace */
-	 0,			/* src_mask */
-	 0,			/* dst_mask */
-	 false)			/* pcrel_offset */
+	 0xffffffff,		/* src_mask */
+	 0xffffffff,		/* dst_mask */
+	 true)			/* pcrel_offset */
diff --git a/bfd/elf64-bpf.c b/bfd/elf64-bpf.c
index c932a4024ba..0bffe2c5717 100644
--- a/bfd/elf64-bpf.c
+++ b/bfd/elf64-bpf.c
@@ -276,6 +276,7 @@ bpf_elf_relocate_section (bfd *output_bfd ATTRIBUTE_UNUSED,
           }
 	case R_BPF_64_ABS64:
 	case R_BPF_64_ABS32:
+	case R_BPF_64_NODYLD32:
 	  {
 	    addend = bfd_get (howto->bitsize, input_bfd, where);
 	    relocation += addend;
-- 
2.39.2


[-- Attachment #3: Type: text/plain, Size: 1559 bytes --]



Jose E. Marchesi writes:

> Hi Cuper.
>
>> Hi everyone,
>>
>> This patch is in context of Nick Cliftons request in thread:
>>   https://sourceware.org/pipermail/binutils/2023-October/130194.html
>> due to bug reported in:
>>   https://bugzilla.redhat.com/show_bug.cgi?id=2245296
>>
>> For the time being the linker is not used in BPF infrastructure.
>> Considering that and without a proper way to validate the code, the
>> following patch is what I think is missing in order to add linker
>> support for the particular relocation.
>>
>> Looking forward to your review.
>>
>> Best regards,
>> Cupertino
>>
>> This patch adds linker support to patch R_BPF_64_NODYLD32 relocations.
>> The implementation was based on comments and code in LLVM, as the GNU
>> toolchain does not uses this relocation type.
>> ---
>>  bfd/elf64-bpf.c | 1 +
>>  1 file changed, 1 insertion(+)
>>
>> diff --git a/bfd/elf64-bpf.c b/bfd/elf64-bpf.c
>> index aefad7da5ac..5820dd3d7d4 100644
>> --- a/bfd/elf64-bpf.c
>> +++ b/bfd/elf64-bpf.c
>> @@ -276,6 +276,7 @@ bpf_elf_relocate_section (bfd *output_bfd ATTRIBUTE_UNUSED,
>>            }
>>  	case R_BPF_64_ABS64:
>>  	case R_BPF_64_ABS32:
>> +	case R_BPF_64_NODYLD32:
>
> I would add here a comment explaining that R_BPF_64_NODYLD32 shall be
> handled/resolved like R_BPF_64_ABS32 and that it differs from ABS32 only
> in that the LLVM execution engine is not supposed to resolve it.
>
> Given that, the patch is OK.
> Thanks!
>
>>  	  {
>>  	    addend = bfd_get (howto->bitsize, input_bfd, where);
>>  	    relocation += addend;

Re: [PATCH] bpf: Added linker support for R_BPF_64_NODYLD32.

[Jose E. Marchesi]

Hi Cuper.
OK, thanks.

> Hi Jose,
>
> Thanks for your review.
> I realized I missed to update the macro for the relocation where the
> properties like size, overflow check, (etc.) are defined.
> I have added the comment near the relocation macro definition.
>
> Sending the patch for review once again.
>
> Regards,
> Cupertino
>
> From bb8afde9a8f17d42393067c3a667bec1f08b252a Mon Sep 17 00:00:00 2001
> From: Cupertino Miranda <cupertino.miranda@oracle.com>
> Date: Wed, 20 Dec 2023 12:24:03 +0000
> Subject: [PATCH] bpf: Added linker support for R_BPF_64_NODYLD32.
>
> This patch adds linker support to patch R_BPF_64_NODYLD32 relocations.
> The implementation was based on comments and code in LLVM, as the GNU
> toolchain does not uses this relocation type.
> ---
>  bfd/bpf-reloc.def | 17 ++++++++++-------
>  bfd/elf64-bpf.c   |  1 +
>  2 files changed, 11 insertions(+), 7 deletions(-)
>
> diff --git a/bfd/bpf-reloc.def b/bfd/bpf-reloc.def
> index 7e7497892fa..42ba1a169ea 100644
> --- a/bfd/bpf-reloc.def
> +++ b/bfd/bpf-reloc.def
> @@ -90,17 +90,20 @@
>  
>    /* R_BPF_64_NODYLD32 is not used by GNU tools - but it is generated by LLVM.
>       We provide an entry here so that tools like strip can safely handle BPF
> -     binaries generated by other tools.  */
> +     binaries generated by other tools.
> +     R_BPF_64_NODYLD32 should be fixed at linker like a R_BPF_64_ABS32.
> +     The difference to ABS32 is that LLVM execution engine does not resolve
> +     R_BPF_64_NODYLD32 relocations.  */
>    BPF_HOWTO (R_BPF_64_NODYLD32,	/* type */
>  	 0,			/* rightshift */
> -	 0,			/* size */
> -	 0,			/* bitsize */
> +	 4,			/* size */
> +	 32,			/* bitsize */
>  	 false,			/* pc_relative */
>  	 0,			/* bitpos */
> -	 complain_overflow_dont, /* complain_on_overflow */
> +	 complain_overflow_bitfield, /* complain_on_overflow */
>  	 bpf_elf_generic_reloc, /* special_function */
>  	 "R_BPF_64_NODYLD32",	/* name */
>  	 false,			/* partial_inplace */
> -	 0,			/* src_mask */
> -	 0,			/* dst_mask */
> -	 false)			/* pcrel_offset */
> +	 0xffffffff,		/* src_mask */
> +	 0xffffffff,		/* dst_mask */
> +	 true)			/* pcrel_offset */
> diff --git a/bfd/elf64-bpf.c b/bfd/elf64-bpf.c
> index c932a4024ba..0bffe2c5717 100644
> --- a/bfd/elf64-bpf.c
> +++ b/bfd/elf64-bpf.c
> @@ -276,6 +276,7 @@ bpf_elf_relocate_section (bfd *output_bfd ATTRIBUTE_UNUSED,
>            }
>  	case R_BPF_64_ABS64:
>  	case R_BPF_64_ABS32:
> +	case R_BPF_64_NODYLD32:
>  	  {
>  	    addend = bfd_get (howto->bitsize, input_bfd, where);
>  	    relocation += addend;

Re: [PATCH] bpf: Added linker support for R_BPF_64_NODYLD32.

[Cupertino Miranda]

Thanks! Committed.

Jose E. Marchesi writes:

> Hi Cuper.
> OK, thanks.
>
>> Hi Jose,
>>
>> Thanks for your review.
>> I realized I missed to update the macro for the relocation where the
>> properties like size, overflow check, (etc.) are defined.
>> I have added the comment near the relocation macro definition.
>>
>> Sending the patch for review once again.
>>
>> Regards,
>> Cupertino
>>
>> From bb8afde9a8f17d42393067c3a667bec1f08b252a Mon Sep 17 00:00:00 2001
>> From: Cupertino Miranda <cupertino.miranda@oracle.com>
>> Date: Wed, 20 Dec 2023 12:24:03 +0000
>> Subject: [PATCH] bpf: Added linker support for R_BPF_64_NODYLD32.
>>
>> This patch adds linker support to patch R_BPF_64_NODYLD32 relocations.
>> The implementation was based on comments and code in LLVM, as the GNU
>> toolchain does not uses this relocation type.
>> ---
>>  bfd/bpf-reloc.def | 17 ++++++++++-------
>>  bfd/elf64-bpf.c   |  1 +
>>  2 files changed, 11 insertions(+), 7 deletions(-)
>>
>> diff --git a/bfd/bpf-reloc.def b/bfd/bpf-reloc.def
>> index 7e7497892fa..42ba1a169ea 100644
>> --- a/bfd/bpf-reloc.def
>> +++ b/bfd/bpf-reloc.def
>> @@ -90,17 +90,20 @@
>>
>>    /* R_BPF_64_NODYLD32 is not used by GNU tools - but it is generated by LLVM.
>>       We provide an entry here so that tools like strip can safely handle BPF
>> -     binaries generated by other tools.  */
>> +     binaries generated by other tools.
>> +     R_BPF_64_NODYLD32 should be fixed at linker like a R_BPF_64_ABS32.
>> +     The difference to ABS32 is that LLVM execution engine does not resolve
>> +     R_BPF_64_NODYLD32 relocations.  */
>>    BPF_HOWTO (R_BPF_64_NODYLD32,	/* type */
>>  	 0,			/* rightshift */
>> -	 0,			/* size */
>> -	 0,			/* bitsize */
>> +	 4,			/* size */
>> +	 32,			/* bitsize */
>>  	 false,			/* pc_relative */
>>  	 0,			/* bitpos */
>> -	 complain_overflow_dont, /* complain_on_overflow */
>> +	 complain_overflow_bitfield, /* complain_on_overflow */
>>  	 bpf_elf_generic_reloc, /* special_function */
>>  	 "R_BPF_64_NODYLD32",	/* name */
>>  	 false,			/* partial_inplace */
>> -	 0,			/* src_mask */
>> -	 0,			/* dst_mask */
>> -	 false)			/* pcrel_offset */
>> +	 0xffffffff,		/* src_mask */
>> +	 0xffffffff,		/* dst_mask */
>> +	 true)			/* pcrel_offset */
>> diff --git a/bfd/elf64-bpf.c b/bfd/elf64-bpf.c
>> index c932a4024ba..0bffe2c5717 100644
>> --- a/bfd/elf64-bpf.c
>> +++ b/bfd/elf64-bpf.c
>> @@ -276,6 +276,7 @@ bpf_elf_relocate_section (bfd *output_bfd ATTRIBUTE_UNUSED,
>>            }
>>  	case R_BPF_64_ABS64:
>>  	case R_BPF_64_ABS32:
>> +	case R_BPF_64_NODYLD32:
>>  	  {
>>  	    addend = bfd_get (howto->bitsize, input_bfd, where);
>>  	    relocation += addend;