[glibc] x86: Check PT_GNU_PROPERTY early

[glibc] x86: Check PT_GNU_PROPERTY early

[H.J. Lu]

https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=4753e9286858a61d5fbe8742d48d8c9166143354

commit 4753e9286858a61d5fbe8742d48d8c9166143354
Author: H.J. Lu <hjl.tools@gmail.com>
Date:   Thu Dec 7 13:05:39 2023 -0800

    x86: Check PT_GNU_PROPERTY early
    
    The PT_GNU_PROPERTY segment is scanned before PT_NOTE.  For binaries
    with the PT_GNU_PROPERTY segment, we can check it to avoid scan of
    the PT_NOTE segment.
    Reviewed-by: Noah Goldstein <goldstein.w.n@gmail.com>

Diff:
---
 sysdeps/x86/dl-prop.h | 120 +++++++++++++++++++++++++++++++++-----------------
 1 file changed, 80 insertions(+), 40 deletions(-)

diff --git a/sysdeps/x86/dl-prop.h b/sysdeps/x86/dl-prop.h
index b2836f3009..d2c53c2182 100644
--- a/sysdeps/x86/dl-prop.h
+++ b/sysdeps/x86/dl-prop.h
@@ -81,6 +81,60 @@ _dl_open_check (struct link_map *m)
 #endif
 }
 
+/* Check the GNU property and return its value.  It returns:
+   -1: Skip this note.
+    0: Stop checking.
+    1: Continue to check.
+ */
+static inline int
+_dl_check_gnu_property (unsigned int type, unsigned int datasz,
+			void *ptr, unsigned int *feature_1_and,
+			unsigned int *needed_1,
+			unsigned int *isa_1_needed)
+{
+  if (type == GNU_PROPERTY_X86_FEATURE_1_AND
+      || 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
+	 note is ill-formed.  */
+      if (datasz != 4)
+	return -1;
+
+      /* 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)
+		       && (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_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;
+
+	  /* Keep searching for the next GNU property note
+	     generated by the older linker.  */
+	  return 0;
+	}
+    }
+  else if (type > GNU_PROPERTY_X86_ISA_1_NEEDED)
+    {
+      /* Stop the scan since property type is in ascending
+	 order.  */
+      return 0;
+    }
+
+  return 1;
+}
+
 static inline void __attribute__ ((unused))
 _dl_process_property_note (struct link_map *l, const ElfW(Nhdr) *note,
 			   const ElfW(Addr) size, const ElfW(Addr) align)
@@ -141,45 +195,14 @@ _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_1_NEEDED)
-		{
-		  /* The sizes of types which we are searching for are
-		     4 bytes.  There is no point to continue if this
-		     note is ill-formed.  */
-		  if (datasz != 4)
-		    return;
-
-		  /* 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)
-				   && (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_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;
-
-		      /* Keep searching for the next GNU property note
-			 generated by the older linker.  */
-		      break;
-		    }
-		}
-	      else if (type > GNU_PROPERTY_X86_ISA_1_NEEDED)
-		{
-		  /* Stop the scan since property type is in ascending
-		     order.  */
-		  break;
-		}
+	      int result = _dl_check_gnu_property (type, datasz, ptr,
+						   &feature_1_and,
+						   &needed_1,
+						   &isa_1_needed);
+	      if (result == -1)
+		return;		/* Skip this note.  */
+	      else if (result == 0)
+		break; /* Stop checking.  */
 
 	      /* Check the next property item.  */
 	      ptr += ALIGN_UP (datasz, sizeof (ElfW(Addr)));
@@ -217,7 +240,24 @@ 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;
+  /* This is called on each GNU property.  */
+  unsigned int needed_1 = 0;
+  unsigned int feature_1_and = 0;
+  unsigned int isa_1_needed = 0;
+  int result = _dl_check_gnu_property (type, datasz, data,
+				       &feature_1_and, &needed_1,
+				       &isa_1_needed);
+  if (needed_1 != 0)
+    l->l_1_needed = needed_1;
+  if (isa_1_needed != 0)
+    l->l_x86_isa_1_needed = isa_1_needed;
+  if (feature_1_and != 0)
+    l->l_x86_feature_1_and = feature_1_and;
+  if ((needed_1 | isa_1_needed | feature_1_and) != 0)
+    l->l_property = lc_property_valid;
+  else if (l->l_property == lc_property_unknown)
+    l->l_property = lc_property_none;
+  return result <= 0 ? 0 : result;
 }
 
 #endif /* _DL_PROP_H */