diff mbox series

[1/4] Initial support for GNU_PROPERTY_1_NEEDED

Message ID 20210620233620.391576-2-hjl.tools@gmail.com
State Superseded
Headers
Series Implement single global definition marker |

Checks

Context Check Description
dj/TryBot-apply_patch success Patch applied to master at the time it was sent

Commit Message

H.J. Lu June 20, 2021, 11:36 p.m. UTC 
  1. Add GNU_PROPERTY_1_NEEDED:

 #define GNU_PROPERTY_1_NEEDED      GNU_PROPERTY_UINT32_OR_LO

to indicate the needed properties by the object file.
2. Add GNU_PROPERTY_1_NEEDED_SINGLE_GLOBAL_DEFINITION:

 #define GNU_PROPERTY_1_NEEDED_SINGLE_GLOBAL_DEFINITION  (1U << 0)

to indicate that the object file requires canonical function pointers and
cannot be used with copy relocation.
3. Scan GNU_PROPERTY_1_NEEDED property and store it in l_1_needed.
---
 elf/elf.h                  | 17 +++++++++++++++++
 sysdeps/generic/dl-prop.h  |  9 ++++++++-
 sysdeps/generic/link_map.h |  3 ++-
 sysdeps/x86/dl-prop.h      | 19 ++++++++++++++-----
 sysdeps/x86/link_map.h     |  2 ++
 5 files changed, 43 insertions(+), 7 deletions(-)

Comments

Florian Weimer June 21, 2021, 7:06 a.m. UTC | #1 
* H. J. Lu via Libc-alpha:

> diff --git a/elf/elf.h b/elf/elf.h
> index 2a62b98d4a..45b107fdcf 100644
> --- a/elf/elf.h
> +++ b/elf/elf.h
> @@ -1310,6 +1310,23 @@ typedef struct
>  /* No copy relocation on protected data symbol.  */
>  #define GNU_PROPERTY_NO_COPY_ON_PROTECTED	2
>  
> +/* A 4-byte unsigned integer property: A bit is set if it is set in all
> +   relocatable inputs.  */
> +#define GNU_PROPERTY_UINT32_AND_LO	0xb0000000
> +#define GNU_PROPERTY_UINT32_AND_HI	0xb0007fff
> +
> +/* A 4-byte unsigned integer property: A bit is set if it is set in any
> +   relocatable inputs.  */
> +#define GNU_PROPERTY_UINT32_OR_LO	0xb0008000
> +#define GNU_PROPERTY_UINT32_OR_HI	0xb000ffff
> +
> +/* The needed properties by the object file.  */
> +#define GNU_PROPERTY_1_NEEDED		GNU_PROPERTY_UINT32_OR_LO
> +
> +/* Set if the object file requires canonical function pointers and
> +   cannot be used with copy relocation.  */
> +#define GNU_PROPERTY_1_NEEDED_SINGLE_GLOBAL_DEFINITION	(1U << 0)
> +
>  /* Processor-specific semantics, lo */
>  #define GNU_PROPERTY_LOPROC			0xc0000000
>  /* Processor-specific semantics, hi */

Please add a stable link to the full specification.

I think we need more bits: one bit to indicate the status (in this
patch), and another bit to indicate linker support for this feature.
And perhaps yet another to indicate incompatibility with this feature.

Thanks,
Florian
H.J. Lu June 21, 2021, 12:57 p.m. UTC | #2 
On Mon, Jun 21, 2021 at 12:06 AM Florian Weimer <fweimer@redhat.com> wrote:
>
> * H. J. Lu via Libc-alpha:
>
> > diff --git a/elf/elf.h b/elf/elf.h
> > index 2a62b98d4a..45b107fdcf 100644
> > --- a/elf/elf.h
> > +++ b/elf/elf.h
> > @@ -1310,6 +1310,23 @@ typedef struct
> >  /* No copy relocation on protected data symbol.  */
> >  #define GNU_PROPERTY_NO_COPY_ON_PROTECTED    2
> >
> > +/* A 4-byte unsigned integer property: A bit is set if it is set in all
> > +   relocatable inputs.  */
> > +#define GNU_PROPERTY_UINT32_AND_LO   0xb0000000
> > +#define GNU_PROPERTY_UINT32_AND_HI   0xb0007fff
> > +
> > +/* A 4-byte unsigned integer property: A bit is set if it is set in any
> > +   relocatable inputs.  */
> > +#define GNU_PROPERTY_UINT32_OR_LO    0xb0008000
> > +#define GNU_PROPERTY_UINT32_OR_HI    0xb000ffff
> > +
> > +/* The needed properties by the object file.  */
> > +#define GNU_PROPERTY_1_NEEDED                GNU_PROPERTY_UINT32_OR_LO
> > +
> > +/* Set if the object file requires canonical function pointers and
> > +   cannot be used with copy relocation.  */
> > +#define GNU_PROPERTY_1_NEEDED_SINGLE_GLOBAL_DEFINITION       (1U << 0)
> > +
> >  /* Processor-specific semantics, lo */
> >  #define GNU_PROPERTY_LOPROC                  0xc0000000
> >  /* Processor-specific semantics, hi */
>
> Please add a stable link to the full specification.

I will work on it.

> I think we need more bits: one bit to indicate the status (in this
> patch), and another bit to indicate linker support for this feature.
> And perhaps yet another to indicate incompatibility with this feature.
>

There is

#define GNU_PROPERTY_1_NEEDED                GNU_PROPERTY_UINT32_OR_LO

Since the setting on output is ORed from inputs, one bit is
sufficient.
diff mbox series

Patch

diff --git a/elf/elf.h b/elf/elf.h
index 2a62b98d4a..45b107fdcf 100644
--- a/elf/elf.h
+++ b/elf/elf.h
@@ -1310,6 +1310,23 @@  typedef struct
 /* No copy relocation on protected data symbol.  */
 #define GNU_PROPERTY_NO_COPY_ON_PROTECTED	2
 
+/* A 4-byte unsigned integer property: A bit is set if it is set in all
+   relocatable inputs.  */
+#define GNU_PROPERTY_UINT32_AND_LO	0xb0000000
+#define GNU_PROPERTY_UINT32_AND_HI	0xb0007fff
+
+/* A 4-byte unsigned integer property: A bit is set if it is set in any
+   relocatable inputs.  */
+#define GNU_PROPERTY_UINT32_OR_LO	0xb0008000
+#define GNU_PROPERTY_UINT32_OR_HI	0xb000ffff
+
+/* The needed properties by the object file.  */
+#define GNU_PROPERTY_1_NEEDED		GNU_PROPERTY_UINT32_OR_LO
+
+/* Set if the object file requires canonical function pointers and
+   cannot be used with copy relocation.  */
+#define GNU_PROPERTY_1_NEEDED_SINGLE_GLOBAL_DEFINITION	(1U << 0)
+
 /* Processor-specific semantics, lo */
 #define GNU_PROPERTY_LOPROC			0xc0000000
 /* Processor-specific semantics, hi */
diff --git a/sysdeps/generic/dl-prop.h b/sysdeps/generic/dl-prop.h
index eaee8052b6..207aadb35d 100644
--- a/sysdeps/generic/dl-prop.h
+++ b/sysdeps/generic/dl-prop.h
@@ -47,7 +47,14 @@  static inline int __attribute__ ((always_inline))
 _dl_process_gnu_property (struct link_map *l, int fd, uint32_t type,
 			  uint32_t datasz, void *data)
 {
-  return 0;
+  /* Continue until GNU_PROPERTY_1_NEEDED is found.  */
+  if (type == GNU_PROPERTY_1_NEEDED)
+    {
+      if (datasz == 4)
+	l->l_1_needed = *(unsigned int *) data;
+      return 0;
+    }
+  return 1;
 }
 
 #endif /* _DL_PROP_H */
diff --git a/sysdeps/generic/link_map.h b/sysdeps/generic/link_map.h
index a056184690..9f482b8c20 100644
--- a/sysdeps/generic/link_map.h
+++ b/sysdeps/generic/link_map.h
@@ -1 +1,2 @@ 
-/* No architecture specific definitions.  */
+/* GNU_PROPERTY_1_NEEDED of this object.  */
+unsigned int l_1_needed;
diff --git a/sysdeps/x86/dl-prop.h b/sysdeps/x86/dl-prop.h
index 56bd020b3c..385548fad3 100644
--- a/sysdeps/x86/dl-prop.h
+++ b/sysdeps/x86/dl-prop.h
@@ -97,6 +97,7 @@  _dl_process_property_note (struct link_map *l, const ElfW(Nhdr) *note,
 
   const ElfW(Addr) start = (ElfW(Addr)) note;
 
+  unsigned int needed_1 = 0;
   unsigned int feature_1_and = 0;
   unsigned int isa_1_needed = 0;
   unsigned int last_type = 0;
@@ -141,7 +142,8 @@  _dl_process_property_note (struct link_map *l, const ElfW(Nhdr) *note,
 	      last_type = type;
 
 	      if (type == GNU_PROPERTY_X86_FEATURE_1_AND
-		  || type == GNU_PROPERTY_X86_ISA_1_NEEDED)
+		  || type == GNU_PROPERTY_X86_ISA_1_NEEDED
+		  || type == GNU_PROPERTY_1_NEEDED)
 		{
 		  /* The sizes of types which we are searching for are
 		     4 bytes.  There is no point to continue if this
@@ -151,12 +153,18 @@  _dl_process_property_note (struct link_map *l, const ElfW(Nhdr) *note,
 
 		  /* NB: Stop the scan only after seeing all types which
 		     we are searching for.  */
-		  _Static_assert ((GNU_PROPERTY_X86_ISA_1_NEEDED >
-				   GNU_PROPERTY_X86_FEATURE_1_AND),
+		  _Static_assert (((GNU_PROPERTY_X86_ISA_1_NEEDED
+				    > GNU_PROPERTY_X86_FEATURE_1_AND)
+				   && (GNU_PROPERTY_X86_FEATURE_1_AND
+				       > GNU_PROPERTY_1_NEEDED)),
 				  "GNU_PROPERTY_X86_ISA_1_NEEDED > "
-				  "GNU_PROPERTY_X86_FEATURE_1_AND");
+				  "GNU_PROPERTY_X86_FEATURE_1_AND && "
+				  "GNU_PROPERTY_X86_FEATURE_1_AND > "
+				  "GNU_PROPERTY_1_NEEDED");
 		  if (type == GNU_PROPERTY_X86_FEATURE_1_AND)
 		    feature_1_and = *(unsigned int *) ptr;
+		  else if (type == GNU_PROPERTY_1_NEEDED)
+		    needed_1 = *(unsigned int *) ptr;
 		  else
 		    {
 		      isa_1_needed = *(unsigned int *) ptr;
@@ -187,9 +195,10 @@  _dl_process_property_note (struct link_map *l, const ElfW(Nhdr) *note,
     }
 
   /* We get here only if there is one or no GNU property note.  */
-  if (isa_1_needed != 0 || feature_1_and != 0)
+  if (needed_1 != 0 || isa_1_needed != 0 || feature_1_and != 0)
     {
       l->l_property = lc_property_valid;
+      l->l_1_needed = needed_1;
       l->l_x86_isa_1_needed = isa_1_needed;
       l->l_x86_feature_1_and = feature_1_and;
     }
diff --git a/sysdeps/x86/link_map.h b/sysdeps/x86/link_map.h
index 4c46a25f83..0c7e25dc96 100644
--- a/sysdeps/x86/link_map.h
+++ b/sysdeps/x86/link_map.h
@@ -29,3 +29,5 @@  unsigned int l_x86_feature_1_and;
 
 /* GNU_PROPERTY_X86_ISA_1_NEEDED of this object.  */
 unsigned int l_x86_isa_1_needed;
+
+#include <sysdeps/generic/link_map.h>