Extend local PLT reference check

On x86, linker in binutils 2.26 and newer consolidates R_*_JUMP_SLOT with
R_*_GLOB_DAT relocation against the same symbol.  This patch extends
local PLT reference check to support alternate relocations.

	[BZ #18078]
	* scripts/check-localplt.awk: Support alternate relocations.
	* scripts/localplt.awk: Also check relocations in DT_RELA/DT_REL
	sections.
	* sysdeps/unix/sysv/linux/i386/localplt.data: Mark free and
	malloc entries with + REL R_386_GLOB_DAT.
	* sysdeps/x86_64/localplt.data: New file.

scripts/check-localplt.awk

@@ -3,9 +3,14 @@
 # Each line is either a comment starting with # or it looks like:
 #	libfoo.so: function
 # or
+#	libfoo.so: function + {RELA|REL} RELOC
+# or
 #	libfoo.so: function ?
-# The latter means that a PLT entry for function is optional in libfoo.so.
-# The former means one is required.
+# The first entry means that one is required.
+# The second entry means that one is required and relocation may also be
+# {RELA|REL} RELOC.
+# The third entry means that a PLT entry for function is optional in
+# libfoo.so.
 # The second file argument is - and this (stdin) receives the output
 # of the check-localplt program.
 
@@ -14,7 +19,10 @@ BEGIN { result = 0 }
 FILENAME != "-" && /^#/ { next }
 
 FILENAME != "-" {
-  if (NF != 2 && !(NF == 3 && $3 == "?")) {
+  if (NF == 5 && $3 == "+" && ($4 == "RELA" || $4 == "REL")) {
+    accept_type[$1 " " $2] = $4;
+    accept_reloc[$1 " " $2] = $5;
+  } else if (NF != 2 && !(NF == 3 && $3 == "?")) {
     printf "%s:%d: bad data line: %s\n", FILENAME, FNR, $0 > "/dev/stderr";
     result = 2;
   } else {
@@ -23,7 +31,7 @@ FILENAME != "-" {
   next;
 }
 
-NF != 2 {
+NF != 2 && !(NF == 4 && ($3 == "RELA" || $3 == "REL")) {
   print "Unexpected output from check-localplt:", $0 > "/dev/stderr";
   result = 2;
   next
@@ -31,7 +39,23 @@ NF != 2 {
 
 {
   key = $1 " " $2
-  if (key in accept) {
+  if ($3 == "RELA" || $3 == "REL") {
+    # Entries like:
+    # libc.so: free + RELA R_X86_64_GLOB_DAT
+    # may be ignored.
+    if (key in accept_type && accept_type[key] == $3 && accept_reloc[key] == $4) {
+      # Match
+      # libc.so: free + RELA R_X86_64_GLOB_DAT
+      delete accept_type[key]
+    }
+  } else if (NF == 2 && key in accept_reloc) {
+    # Match
+    # libc.so: free
+    # against
+    # libc.so: free + RELA R_X86_64_GLOB_DAT
+    if (key in accept_type)
+      delete accept_type[key]
+  } else if (key in accept) {
     delete accept[key]
   } else {
     print "Extra PLT reference:", $0;
@@ -49,5 +73,11 @@ END {
     }
   }
 
+  for (key in accept_type) {
+    # It's mandatory.
+    print "Missing required PLT or " accept_reloc[key] " reference:", key;
+    result = 1;
+  }
+
   exit(result);
 }

scripts/localplt.awk

@@ -13,6 +13,8 @@ FILENAME != lastfile {
   }
   lastfile = FILENAME;
   jmprel_offset = 0;
+  rela_offset = 0;
+  rel_offset = 0;
   delete section_offset_by_address;
 }
 
@@ -43,6 +45,30 @@ in_relocs && relocs_offset == jmprel_offset && NF >= 5 {
   }
 }
 
+in_relocs && relocs_offset == rela_offset && NF >= 5 {
+  # Relocations against GNU_IFUNC symbols are not shown as an hexadecimal
+  # value, but rather as the resolver symbol followed by ().
+  if ($4 ~ /\(\)/) {
+    print whatfile, gensub(/@.*/, "", "g", $5), "RELA", $3
+  } else {
+    symval = strtonum("0x" $4);
+    if (symval != 0)
+      print whatfile, gensub(/@.*/, "", "g", $5), "RELA", $3
+  }
+}
+
+in_relocs && relocs_offset == rel_offset && NF >= 5 {
+  # Relocations against GNU_IFUNC symbols are not shown as an hexadecimal
+  # value, but rather as the resolver symbol followed by ().
+  if ($4 ~ /\(\)/) {
+    print whatfile, gensub(/@.*/, "", "g", $5), "REL", $3
+  } else {
+    symval = strtonum("0x" $4);
+    if (symval != 0)
+      print whatfile, gensub(/@.*/, "", "g", $5), "REL", $3
+  }
+}
+
 in_relocs { next }
 
 $1 == "Relocation" && $2 == "section" && $5 == "offset" {
@@ -62,4 +88,25 @@ $2 == "(JMPREL)" {
   next
 }
 
+$2 == "(RELA)" {
+  rela_addr = strtonum($3);
+  if (rela_addr in section_offset_by_address) {
+    rela_offset = section_offset_by_address[rela_addr];
+  } else {
+    print FILENAME ": *** DT_RELA does not match any section's address";
+    result = 2;
+  }
+  next
+}
+
+$2 == "(REL)" {
+  rel_addr = strtonum($3);
+  if (rel_addr in section_offset_by_address) {
+    rel_offset = section_offset_by_address[rel_addr];
+  } else {
+    print FILENAME ": *** DT_REL does not match any section's address";
+    result = 2;
+  }
+  next
+}
 END { exit(result) }