[glibc] scripts/localplt.awk: Handle DT_JMPREL with empty PLT (for C-SKY)

[Florian Weimer <fw@sourceware.org>]

https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=77db67c56b24bba3c735aac34a6f796c909b68c0

commit 77db67c56b24bba3c735aac34a6f796c909b68c0
Author: Florian Weimer <fweimer@redhat.com>
Date:   Thu Oct 27 11:36:44 2022 +0200

    scripts/localplt.awk: Handle DT_JMPREL with empty PLT (for C-SKY)
    
    On csky-linux-gnuabiv2, binutils 2.33 produces a DT_JMPREL entry
    for the dynamic loader if it does not contain any PLT relocations:
    
    Dynamic section at offset 0x1df48 contains 19 entries:
      Tag        Type                         Name/Value
     0x0000000e (SONAME)                     Library soname: [ld-linux-cskyv2-hf.so.1]
     0x00000004 (HASH)                       0xd4
     0x6ffffef5 (GNU_HASH)                   0x1a8
     0x00000005 (STRTAB)                     0x4ac
     0x00000006 (SYMTAB)                     0x28c
     0x0000000a (STRSZ)                      527 (bytes)
     0x0000000b (SYMENT)                     16 (bytes)
     0x00000003 (PLTGOT)                     0x1f000
     0x00000002 (PLTRELSZ)                   0 (bytes)
     0x00000014 (PLTREL)                     RELA
     0x00000017 (JMPREL)                     0xaa4
     0x00000007 (RELA)                       0x75c
     0x00000008 (RELASZ)                     840 (bytes)
     0x00000009 (RELAENT)                    12 (bytes)
     0x6ffffffc (VERDEF)                     0x700
     0x6ffffffd (VERDEFNUM)                  3
     0x6ffffff0 (VERSYM)                     0x6bc
     0x6ffffff9 (RELACOUNT)                  68
     0x00000000 (NULL)                       0x0
    
    This confuses the script:
    
    Unexpected output from check-localplt: …/elf/ld.so.jmprel:
    *** DT_JMPREL does not match any section's address
    
    This commit changes the script to record the DT_PLTRELSZ value and
    reject DT_JMPREL values not a section boundary only if DT_PLTRELSZ
    is present with a non-zero value.
    
    Reviewed-by: Siddhesh Poyarekar <siddhesh@sourceware.org>

Diff:
---
 scripts/localplt.awk | 18 +++++++++++++++---
 1 file changed, 15 insertions(+), 3 deletions(-)

diff --git a/scripts/localplt.awk b/scripts/localplt.awk
index beaa342922..fe79ca01ab 100644
--- a/scripts/localplt.awk
+++ b/scripts/localplt.awk
@@ -4,17 +4,25 @@
 # It writes "NAME: SYMBOL" for each PLT entry in NAME that refers to a
 # symbol defined in the same object.
 
-BEGIN { result = 0 }
+BEGIN {
+  result = 0;
+  pltrelsize = -1;
+}
 
 FILENAME != lastfile {
   if (lastfile && jmprel_offset == 0 && rela_offset == 0 && rel_offset == 0) {
     print FILENAME ": *** failed to find expected output (readelf -WSdr)";
     result = 2;
   }
+  if (pltrelsz > 0 && jmprel_offset == -1) {
+    print FILENAME ": Could not find section for DT_JMPREL";
+    result = 2;
+  }
   lastfile = FILENAME;
   jmprel_offset = 0;
   rela_offset = 0;
   rel_offset = 0;
+  pltrelsz = -1;
   delete section_offset_by_address;
 }
 
@@ -82,12 +90,16 @@ $2 == "(JMPREL)" {
   if (jmprel_addr in section_offset_by_address) {
     jmprel_offset = section_offset_by_address[jmprel_addr];
   } else {
-    print FILENAME ": *** DT_JMPREL does not match any section's address";
-    result = 2;
+    jmprel_offset = -1
   }
   next
 }
 
+$2 == "(PLTRELSZ)" {
+  pltrelsz = strtonum($3);
+  next
+}
+
 $2 == "(RELA)" {
   rela_addr = strtonum($3);
   if (rela_addr in section_offset_by_address) {