[project @ 2004-12-08 12:05:51 by simonmar]

Fix bug #1073501: checkProddableBlock: invalid fixup in runtime linker

The bug manifested when trying to load an object with debugging info
(compiled with gcc -g) into GHCi.

The problem was that the object loader was ignoring the sections
containing debugging info, but then it was later trying to do
relocations for those sections, and its own sanity checking code
correctly detected that the relocations were in unknown parts of the
object file.

The fix is to ignore relocations whose target section isn't one of the
sections that we're interested in, using the same test in both cases
(the code to test section kind has been extracted).  The code could
probably benefit from more refactoring: it looks like the list of
sections we build up in the first phase isn't even used in the second
phase, instead we traverse the section table in the image again.  This
looks like cruft leftover from when the GC used to check whether an
address was in text or data space.

diff --git a/ghc/rts/Linker.c b/ghc/rts/Linker.c
index ef5697a..3902382 100644 (file)
--- a/ghc/rts/Linker.c
+++ b/ghc/rts/Linker.c
@@ -2450,10 +2450,10 @@ ocVerifyImage_ELF ( ObjectCode* oc )
    }
 
    if (ehdr->e_ident[EI_DATA] == ELFDATA2LSB) {
-       IF_DEBUG(linker,debugBelch( "Is little-endian" ));
+       IF_DEBUG(linker,debugBelch( "Is little-endian\n" ));
    } else
    if (ehdr->e_ident[EI_DATA] == ELFDATA2MSB) {
-       IF_DEBUG(linker,debugBelch( "Is big-endian" ));
+       IF_DEBUG(linker,debugBelch( "Is big-endian\n" ));
    } else {
        errorBelch("%s: unknown endiannness", oc->fileName);
        return 0;
@@ -2463,7 +2463,7 @@ ocVerifyImage_ELF ( ObjectCode* oc )
       errorBelch("%s: not a relocatable object (.o) file", oc->fileName);
       return 0;
    }
-   IF_DEBUG(linker, debugBelch( "Is a relocatable object (.o) file" ));
+   IF_DEBUG(linker, debugBelch( "Is a relocatable object (.o) file\n" ));
 
    IF_DEBUG(linker,debugBelch( "Architecture is " ));
    switch (ehdr->e_machine) {
@@ -2479,7 +2479,7 @@ ocVerifyImage_ELF ( ObjectCode* oc )
    }
 
    IF_DEBUG(linker,debugBelch(
-             "\nSection header table: start %d, n_entries %d, ent_size %d",
+             "\nSection header table: start %d, n_entries %d, ent_size %d\n",
              ehdr->e_shoff, ehdr->e_shnum, ehdr->e_shentsize  ));
 
    ASSERT (ehdr->e_shentsize == sizeof(Elf_Shdr));
@@ -2490,7 +2490,7 @@ ocVerifyImage_ELF ( ObjectCode* oc )
       errorBelch("%s: no section header string table", oc->fileName);
       return 0;
    } else {
-      IF_DEBUG(linker,debugBelch( "Section header string table is section %d",
+      IF_DEBUG(linker,debugBelch( "Section header string table is section %d\n",
                           ehdr->e_shstrndx));
       sh_strtab = ehdrC + shdr[ehdr->e_shstrndx].sh_offset;
    }
@@ -2541,11 +2541,11 @@ ocVerifyImage_ELF ( ObjectCode* oc )
    IF_DEBUG(linker,debugBelch( "\nSymbol tables" ));
    for (i = 0; i < ehdr->e_shnum; i++) {
       if (shdr[i].sh_type != SHT_SYMTAB) continue;
-      IF_DEBUG(linker,debugBelch( "section %d is a symbol table", i ));
+      IF_DEBUG(linker,debugBelch( "section %d is a symbol table\n", i ));
       nsymtabs++;
       stab = (Elf_Sym*) (ehdrC + shdr[i].sh_offset);
       nent = shdr[i].sh_size / sizeof(Elf_Sym);
-      IF_DEBUG(linker,debugBelch( "   number of entries is apparently %d (%d rem)",
+      IF_DEBUG(linker,debugBelch( "   number of entries is apparently %d (%d rem)\n",
                nent,
                shdr[i].sh_size % sizeof(Elf_Sym)
              ));
@@ -2592,6 +2592,38 @@ ocVerifyImage_ELF ( ObjectCode* oc )
    return 1;
 }
 
+static int getSectionKind_ELF( Elf_Shdr *hdr, int *is_bss )
+{
+    *is_bss = FALSE;
+
+    if (hdr->sh_type == SHT_PROGBITS
+       && (hdr->sh_flags & SHF_ALLOC) && (hdr->sh_flags & SHF_EXECINSTR)) {
+       /* .text-style section */
+       return SECTIONKIND_CODE_OR_RODATA;
+    }
+
+    if (hdr->sh_type == SHT_PROGBITS
+           && (hdr->sh_flags & SHF_ALLOC) && (hdr->sh_flags & SHF_WRITE)) {
+           /* .data-style section */
+           return SECTIONKIND_RWDATA;
+    }
+
+    if (hdr->sh_type == SHT_PROGBITS
+       && (hdr->sh_flags & SHF_ALLOC) && !(hdr->sh_flags & SHF_WRITE)) {
+       /* .rodata-style section */
+       return SECTIONKIND_CODE_OR_RODATA;
+    }
+
+    if (hdr->sh_type == SHT_NOBITS
+       && (hdr->sh_flags & SHF_ALLOC) && (hdr->sh_flags & SHF_WRITE)) {
+       /* .bss-style section */
+       *is_bss = TRUE;
+       return SECTIONKIND_RWDATA;
+    }
+
+    return SECTIONKIND_OTHER;
+}
+
 
 static int
 ocGetNames_ELF ( ObjectCode* oc )
@@ -2616,34 +2648,8 @@ ocGetNames_ELF ( ObjectCode* oc )
       /* Figure out what kind of section it is.  Logic derived from
          Figure 1.14 ("Special Sections") of the ELF document
          ("Portable Formats Specification, Version 1.1"). */
-      Elf_Shdr    hdr    = shdr[i];
-      SectionKind kind   = SECTIONKIND_OTHER;
       int         is_bss = FALSE;
-
-      if (hdr.sh_type == SHT_PROGBITS
-          && (hdr.sh_flags & SHF_ALLOC) && (hdr.sh_flags & SHF_EXECINSTR)) {
-         /* .text-style section */
-         kind = SECTIONKIND_CODE_OR_RODATA;
-      }
-      else
-      if (hdr.sh_type == SHT_PROGBITS
-          && (hdr.sh_flags & SHF_ALLOC) && (hdr.sh_flags & SHF_WRITE)) {
-         /* .data-style section */
-         kind = SECTIONKIND_RWDATA;
-      }
-      else
-      if (hdr.sh_type == SHT_PROGBITS
-          && (hdr.sh_flags & SHF_ALLOC) && !(hdr.sh_flags & SHF_WRITE)) {
-         /* .rodata-style section */
-         kind = SECTIONKIND_CODE_OR_RODATA;
-      }
-      else
-      if (hdr.sh_type == SHT_NOBITS
-          && (hdr.sh_flags & SHF_ALLOC) && (hdr.sh_flags & SHF_WRITE)) {
-         /* .bss-style section */
-         kind = SECTIONKIND_RWDATA;
-         is_bss = TRUE;
-      }
+      SectionKind kind   = getSectionKind_ELF(&shdr[i], &is_bss);
 
       if (is_bss && shdr[i].sh_size > 0) {
          /* This is a non-empty .bss section.  Allocate zeroed space for
@@ -2748,7 +2754,7 @@ ocGetNames_ELF ( ObjectCode* oc )
             }
          } else {
             /* Skip. */
-            IF_DEBUG(linker,debugBelch( "skipping `%s'",
+            IF_DEBUG(linker,debugBelch( "skipping `%s'\n",
                                    strtab + stab[j].st_name ));
             /*
             debugBelch(
@@ -2785,9 +2791,19 @@ do_Elf_Rel_relocations ( ObjectCode* oc, char* ehdrC,
 
    stab  = (Elf_Sym*) (ehdrC + shdr[ symtab_shndx ].sh_offset);
    targ  = (Elf_Word*)(ehdrC + shdr[ target_shndx ].sh_offset);
-   IF_DEBUG(linker,debugBelch( "relocations for section %d using symtab %d",
+   IF_DEBUG(linker,debugBelch( "relocations for section %d using symtab %d\n",
                           target_shndx, symtab_shndx ));
 
+   /* Skip sections that we're not interested in. */
+   {
+       int is_bss;
+       SectionKind kind = getSectionKind_ELF(&shdr[target_shndx], &is_bss);
+       if (kind == SECTIONKIND_OTHER) {
+          IF_DEBUG(linker,debugBelch( "skipping (target section not loaded)"));
+          return 1;
+       }
+   }
+
    for (j = 0; j < nent; j++) {
       Elf_Addr offset = rtab[j].r_offset;
       Elf_Addr info   = rtab[j].r_info;
@@ -2825,10 +2841,10 @@ do_Elf_Rel_relocations ( ObjectCode* oc, char* ehdrC,
             errorBelch("%s: unknown symbol `%s'", oc->fileName, symbol);
            return 0;
          }
-         IF_DEBUG(linker,debugBelch( "`%s' resolves to %p", symbol, (void*)S ));
+         IF_DEBUG(linker,debugBelch( "`%s' resolves to %p\n", symbol, (void*)S ));
       }
 
-      IF_DEBUG(linker,debugBelch( "Reloc: P = %p   S = %p   A = %p",
+      IF_DEBUG(linker,debugBelch( "Reloc: P = %p   S = %p   A = %p\n",
                             (void*)P, (void*)S, (void*)A ));
       checkProddableBlock ( oc, pP );
 
@@ -2866,7 +2882,7 @@ do_Elf_Rela_relocations ( ObjectCode* oc, char* ehdrC,
 
    stab  = (Elf_Sym*) (ehdrC + shdr[ symtab_shndx ].sh_offset);
    targ  = (Elf_Addr) (ehdrC + shdr[ target_shndx ].sh_offset);
-   IF_DEBUG(linker,debugBelch( "relocations for section %d using symtab %d",
+   IF_DEBUG(linker,debugBelch( "relocations for section %d using symtab %d\n",
                           target_shndx, symtab_shndx ));
 
    for (j = 0; j < nent; j++) {
@@ -3065,7 +3081,6 @@ ocResolve_ELF ( ObjectCode* oc )
    char*     ehdrC = (char*)(oc->image);
    Elf_Ehdr* ehdr  = (Elf_Ehdr*) ehdrC;
    Elf_Shdr* shdr  = (Elf_Shdr*) (ehdrC + ehdr->e_shoff);
-   char* sh_strtab = ehdrC + shdr[ehdr->e_shstrndx].sh_offset;
 
    /* first find "the" symbol table */
    stab = (Elf_Sym*) findElfSection ( ehdrC, SHT_SYMTAB );
@@ -3080,15 +3095,7 @@ ocResolve_ELF ( ObjectCode* oc )
 
    /* Process the relocation sections. */
    for (shnum = 0; shnum < ehdr->e_shnum; shnum++) {
-
-      /* Skip sections called ".rel.stab".  These appear to contain
-         relocation entries that, when done, make the stabs debugging
-         info point at the right places.  We ain't interested in all
-         dat jazz, mun. */
-      if (0 == memcmp(".rel.stab", sh_strtab + shdr[shnum].sh_name, 9))
-         continue;
-
-      if (shdr[shnum].sh_type == SHT_REL ) {
+      if (shdr[shnum].sh_type == SHT_REL) {
          ok = do_Elf_Rel_relocations ( oc, ehdrC, shdr,
                                        shnum, stab, strtab );
          if (!ok) return ok;