diff mbox series

[v6,01/14] Rewrite abi-note.S in C.

Message ID 896f9afab21b31d0e168e61eb8781d477bf3a7dd.1593612309.git.szabolcs.nagy@arm.com
State Superseded
Headers
Series aarch64: branch protection support |

Commit Message

Szabolcs Nagy July 1, 2020, 2:37 p.m. UTC 
  Using C code allows the compiler to add target specific object file
markings based on CFLAGS.

The arm specific abi-note.S is removed and similar object file fix
up will be avoided on AArch64 with standard branch-prtection.
---
 csu/{abi-note.S => abi-note.c} | 23 +++++++++++++----------
 sysdeps/arm/abi-note.S         |  8 --------
 2 files changed, 13 insertions(+), 18 deletions(-)
 rename csu/{abi-note.S => abi-note.c} (90%)
 delete mode 100644 sysdeps/arm/abi-note.S

Comments

H.J. Lu July 1, 2020, 2:41 p.m. UTC | #1 
On Wed, Jul 1, 2020 at 7:38 AM Szabolcs Nagy <szabolcs.nagy@arm.com> wrote:
>
> Using C code allows the compiler to add target specific object file
> markings based on CFLAGS.
>
> The arm specific abi-note.S is removed and similar object file fix
> up will be avoided on AArch64 with standard branch-prtection.
> ---
>  csu/{abi-note.S => abi-note.c} | 23 +++++++++++++----------
>  sysdeps/arm/abi-note.S         |  8 --------
>  2 files changed, 13 insertions(+), 18 deletions(-)
>  rename csu/{abi-note.S => abi-note.c} (90%)
>  delete mode 100644 sysdeps/arm/abi-note.S
>
> diff --git a/csu/abi-note.S b/csu/abi-note.c
> similarity index 90%
> rename from csu/abi-note.S
> rename to csu/abi-note.c
> index 2b4b5f8824..db195c7ab7 100644
> --- a/csu/abi-note.S
> +++ b/csu/abi-note.c
> @@ -53,6 +53,8 @@ offset        length  contents
>     identify the earliest release of that OS that supports this ABI.
>     See abi-tags (top level) for details. */
>
> +#include <link.h>
> +#include <stdint.h>
>  #include <config.h>
>  #include <abi-tag.h>           /* OS-specific ABI tag value */
>
> @@ -60,13 +62,14 @@ offset      length  contents
>     name begins with `.note' and creates a PT_NOTE program header entry
>     pointing at it. */
>
> -       .section ".note.ABI-tag", "a"
> -       .p2align 2
> -       .long 1f - 0f           /* name length */
> -       .long 3f - 2f           /* data length */
> -       .long  1                /* note type */
> -0:     .asciz "GNU"            /* vendor name */
> -1:     .p2align 2
> -2:     .long __ABI_TAG_OS      /* note data: the ABI tag */
> -       .long __ABI_TAG_VERSION
> -3:     .p2align 2              /* pad out section */
> +__attribute__ ((used, aligned (4), section (".note.ABI-tag")))
> +static const struct
> +{
> +  ElfW(Nhdr) nhdr;
> +  char name[4];
> +  int32_t desc[4];
> +} __abi_tag = {
> +  { .n_namesz = 4, .n_descsz = 16, .n_type = 1 },

sizeof "GNU"? and sizeof desc?

> +  "GNU",
> +  { __ABI_TAG_OS, __ABI_TAG_VERSION }
> +};
> diff --git a/sysdeps/arm/abi-note.S b/sysdeps/arm/abi-note.S
> deleted file mode 100644
> index 07bd4c4619..0000000000
> --- a/sysdeps/arm/abi-note.S
> +++ /dev/null
> @@ -1,8 +0,0 @@
> -/* Tag_ABI_align8_preserved: This code preserves 8-byte
> -   alignment in any callee.  */
> -       .eabi_attribute 25, 1
> -/* Tag_ABI_align8_needed: This code may require 8-byte alignment from
> -   the caller.  */
> -       .eabi_attribute 24, 1
> -
> -#include <csu/abi-note.S>
> --
> 2.17.1
>
Szabolcs Nagy July 1, 2020, 5:31 p.m. UTC | #2 
The 07/01/2020 07:41, H.J. Lu wrote:
> On Wed, Jul 1, 2020 at 7:38 AM Szabolcs Nagy <szabolcs.nagy@arm.com> wrote:
> > Using C code allows the compiler to add target specific object file
> > markings based on CFLAGS.
> >
> > The arm specific abi-note.S is removed and similar object file fix
> > up will be avoided on AArch64 with standard branch-prtection.
> > ---
> >  csu/{abi-note.S => abi-note.c} | 23 +++++++++++++----------
> >  sysdeps/arm/abi-note.S         |  8 --------
> >  2 files changed, 13 insertions(+), 18 deletions(-)
> >  rename csu/{abi-note.S => abi-note.c} (90%)
> >  delete mode 100644 sysdeps/arm/abi-note.S
> >
> > diff --git a/csu/abi-note.S b/csu/abi-note.c
> > similarity index 90%
> > rename from csu/abi-note.S
> > rename to csu/abi-note.c
> > index 2b4b5f8824..db195c7ab7 100644
> > --- a/csu/abi-note.S
> > +++ b/csu/abi-note.c
> > @@ -53,6 +53,8 @@ offset        length  contents
> >     identify the earliest release of that OS that supports this ABI.
> >     See abi-tags (top level) for details. */
> >
> > +#include <link.h>
> > +#include <stdint.h>
> >  #include <config.h>
> >  #include <abi-tag.h>           /* OS-specific ABI tag value */
> >
> > @@ -60,13 +62,14 @@ offset      length  contents
> >     name begins with `.note' and creates a PT_NOTE program header entry
> >     pointing at it. */
> >
> > -       .section ".note.ABI-tag", "a"
> > -       .p2align 2
> > -       .long 1f - 0f           /* name length */
> > -       .long 3f - 2f           /* data length */
> > -       .long  1                /* note type */
> > -0:     .asciz "GNU"            /* vendor name */
> > -1:     .p2align 2
> > -2:     .long __ABI_TAG_OS      /* note data: the ABI tag */
> > -       .long __ABI_TAG_VERSION
> > -3:     .p2align 2              /* pad out section */
> > +__attribute__ ((used, aligned (4), section (".note.ABI-tag")))
> > +static const struct
> > +{
> > +  ElfW(Nhdr) nhdr;
> > +  char name[4];
> > +  int32_t desc[4];
> > +} __abi_tag = {
> > +  { .n_namesz = 4, .n_descsz = 16, .n_type = 1 },
> 
> sizeof "GNU"? and sizeof desc?

i can do

  { .n_namesz = sizeof __abi_tag.name,
    .n_descsz = sizeof __abi_tag.desc,
    .n_type = 1 },

is that better? (for me the int literal looks
clear in the context and shorter. i don't like
sizeof "GNU" i think that's less clear.)

> > +  "GNU",
> > +  { __ABI_TAG_OS, __ABI_TAG_VERSION }
> > +};
> > diff --git a/sysdeps/arm/abi-note.S b/sysdeps/arm/abi-note.S
> > deleted file mode 100644
> > index 07bd4c4619..0000000000
> > --- a/sysdeps/arm/abi-note.S
> > +++ /dev/null
> > @@ -1,8 +0,0 @@
> > -/* Tag_ABI_align8_preserved: This code preserves 8-byte
> > -   alignment in any callee.  */
> > -       .eabi_attribute 25, 1
> > -/* Tag_ABI_align8_needed: This code may require 8-byte alignment from
> > -   the caller.  */
> > -       .eabi_attribute 24, 1
> > -
> > -#include <csu/abi-note.S>
> > --
> > 2.17.1
> >
> 
> 
> -- 
> H.J.
H.J. Lu July 1, 2020, 5:43 p.m. UTC | #3 
On Wed, Jul 1, 2020 at 10:31 AM Szabolcs Nagy <szabolcs.nagy@arm.com> wrote:
>
> The 07/01/2020 07:41, H.J. Lu wrote:
> > On Wed, Jul 1, 2020 at 7:38 AM Szabolcs Nagy <szabolcs.nagy@arm.com> wrote:
> > > Using C code allows the compiler to add target specific object file
> > > markings based on CFLAGS.
> > >
> > > The arm specific abi-note.S is removed and similar object file fix
> > > up will be avoided on AArch64 with standard branch-prtection.
> > > ---
> > >  csu/{abi-note.S => abi-note.c} | 23 +++++++++++++----------
> > >  sysdeps/arm/abi-note.S         |  8 --------
> > >  2 files changed, 13 insertions(+), 18 deletions(-)
> > >  rename csu/{abi-note.S => abi-note.c} (90%)
> > >  delete mode 100644 sysdeps/arm/abi-note.S
> > >
> > > diff --git a/csu/abi-note.S b/csu/abi-note.c
> > > similarity index 90%
> > > rename from csu/abi-note.S
> > > rename to csu/abi-note.c
> > > index 2b4b5f8824..db195c7ab7 100644
> > > --- a/csu/abi-note.S
> > > +++ b/csu/abi-note.c
> > > @@ -53,6 +53,8 @@ offset        length  contents
> > >     identify the earliest release of that OS that supports this ABI.
> > >     See abi-tags (top level) for details. */
> > >
> > > +#include <link.h>
> > > +#include <stdint.h>
> > >  #include <config.h>
> > >  #include <abi-tag.h>           /* OS-specific ABI tag value */
> > >
> > > @@ -60,13 +62,14 @@ offset      length  contents
> > >     name begins with `.note' and creates a PT_NOTE program header entry
> > >     pointing at it. */
> > >
> > > -       .section ".note.ABI-tag", "a"
> > > -       .p2align 2
> > > -       .long 1f - 0f           /* name length */
> > > -       .long 3f - 2f           /* data length */
> > > -       .long  1                /* note type */
> > > -0:     .asciz "GNU"            /* vendor name */
> > > -1:     .p2align 2
> > > -2:     .long __ABI_TAG_OS      /* note data: the ABI tag */
> > > -       .long __ABI_TAG_VERSION
> > > -3:     .p2align 2              /* pad out section */
> > > +__attribute__ ((used, aligned (4), section (".note.ABI-tag")))
> > > +static const struct
> > > +{
> > > +  ElfW(Nhdr) nhdr;
> > > +  char name[4];
> > > +  int32_t desc[4];
> > > +} __abi_tag = {
> > > +  { .n_namesz = 4, .n_descsz = 16, .n_type = 1 },
> >
> > sizeof "GNU"? and sizeof desc?
>
> i can do
>
>   { .n_namesz = sizeof __abi_tag.name,
>     .n_descsz = sizeof __abi_tag.desc,
>     .n_type = 1 },
>
> is that better? (for me the int literal looks
> clear in the context and shorter. i don't like
> sizeof "GNU" i think that's less clear.)

It is better.
Szabolcs Nagy July 2, 2020, 8:39 a.m. UTC | #4 
The 07/01/2020 10:43, H.J. Lu wrote:
> On Wed, Jul 1, 2020 at 10:31 AM Szabolcs Nagy <szabolcs.nagy@arm.com> wrote:
> > The 07/01/2020 07:41, H.J. Lu wrote:
> > > sizeof "GNU"? and sizeof desc?
> >
> > i can do
> >
> >   { .n_namesz = sizeof __abi_tag.name,
> >     .n_descsz = sizeof __abi_tag.desc,
> >     .n_type = 1 },
> >
> > is that better? (for me the int literal looks
> > clear in the context and shorter. i don't like
> > sizeof "GNU" i think that's less clear.)
> 
> It is better.

fixed and force pushed into nsz/pacbti-v6.
diff mbox series

Patch

diff --git a/csu/abi-note.S b/csu/abi-note.c
similarity index 90%
rename from csu/abi-note.S
rename to csu/abi-note.c
index 2b4b5f8824..db195c7ab7 100644
--- a/csu/abi-note.S
+++ b/csu/abi-note.c
@@ -53,6 +53,8 @@  offset	length	contents
    identify the earliest release of that OS that supports this ABI.
    See abi-tags (top level) for details. */
 
+#include <link.h>
+#include <stdint.h>
 #include <config.h>
 #include <abi-tag.h>		/* OS-specific ABI tag value */
 
@@ -60,13 +62,14 @@  offset	length	contents
    name begins with `.note' and creates a PT_NOTE program header entry
    pointing at it. */
 
-	.section ".note.ABI-tag", "a"
-	.p2align 2
-	.long 1f - 0f		/* name length */
-	.long 3f - 2f		/* data length */
-	.long  1		/* note type */
-0:	.asciz "GNU"		/* vendor name */
-1:	.p2align 2
-2:	.long __ABI_TAG_OS	/* note data: the ABI tag */
-	.long __ABI_TAG_VERSION
-3:	.p2align 2		/* pad out section */
+__attribute__ ((used, aligned (4), section (".note.ABI-tag")))
+static const struct
+{
+  ElfW(Nhdr) nhdr;
+  char name[4];
+  int32_t desc[4];
+} __abi_tag = {
+  { .n_namesz = 4, .n_descsz = 16, .n_type = 1 },
+  "GNU",
+  { __ABI_TAG_OS, __ABI_TAG_VERSION }
+};
diff --git a/sysdeps/arm/abi-note.S b/sysdeps/arm/abi-note.S
deleted file mode 100644
index 07bd4c4619..0000000000
--- a/sysdeps/arm/abi-note.S
+++ /dev/null
@@ -1,8 +0,0 @@ 
-/* Tag_ABI_align8_preserved: This code preserves 8-byte
-   alignment in any callee.  */
-	.eabi_attribute 25, 1
-/* Tag_ABI_align8_needed: This code may require 8-byte alignment from
-   the caller.  */
-	.eabi_attribute 24, 1
-
-#include <csu/abi-note.S>