[Rpm-maint] [PATCH 3/5] debugedit: Refactor reading/writing of relocated values.

Mark Wielaard mark at klomp.org
Mon Jun 17 09:23:24 UTC 2019


This refactors the reading and writing of relocated values into seperate
helper functions (setup_relbuf and update_rela_data). It will be easier
to reuse this code in case we want to read/write relocated values in other
sections than DEBUG_INFO. The only functional change is that we explicitly
track whether the relocation data is updated, and only explicitly update
and write out the relocation data if so. In the case there were no strp
or stmt updates, there will also not be any relocation updates, even if
there is relocation data available.

All new debugedit testcases pass before and after this refactoring.
---
 tools/debugedit.c | 395 +++++++++++++++++++++++++++++-------------------------
 1 file changed, 216 insertions(+), 179 deletions(-)

diff --git a/tools/debugedit.c b/tools/debugedit.c
index 4be85b9..cf9cc3c 100644
--- a/tools/debugedit.c
+++ b/tools/debugedit.c
@@ -401,13 +401,18 @@ dwarf2_write_be32 (unsigned char *p, uint32_t v)
    relend). Might just update the addend. So relocations need to be
    updated at the end.  */
 
+static bool rel_updated;
+
 #define do_write_32_relocated(ptr,val) ({ \
   if (relptr && relptr < relend && relptr->ptr == ptr)	\
     {							\
       if (reltype == SHT_REL)				\
 	do_write_32 (ptr, val - relptr->addend);	\
       else						\
-	relptr->addend = val;				\
+	{						\
+	  relptr->addend = val;				\
+	  rel_updated = true;				\
+	}						\
     }							\
   else							\
     do_write_32 (ptr,val);				\
@@ -418,14 +423,18 @@ dwarf2_write_be32 (unsigned char *p, uint32_t v)
   ptr += 4;			       \
 })
 
-static struct
+typedef struct debug_section
   {
     const char *name;
     unsigned char *data;
     Elf_Data *elf_data;
     size_t size;
     int sec, relsec;
-  } debug_sections[] =
+    REL *relbuf;
+    REL *relend;
+  } debug_section;
+
+static debug_section debug_sections[] =
   {
 #define DEBUG_INFO	0
 #define DEBUG_ABBREV	1
@@ -458,6 +467,201 @@ static struct
     { NULL, NULL, NULL, 0, 0, 0 }
   };
 
+static int
+rel_cmp (const void *a, const void *b)
+{
+  REL *rela = (REL *) a, *relb = (REL *) b;
+
+  if (rela->ptr < relb->ptr)
+    return -1;
+
+  if (rela->ptr > relb->ptr)
+    return 1;
+
+  return 0;
+}
+
+/* Returns a malloced REL array, or NULL when there are no relocations
+   for this section.  When there are relocations, will setup relend,
+   as the last REL, and reltype, as SHT_REL or SHT_RELA.  */
+static void
+setup_relbuf (DSO *dso, debug_section *sec, int *reltype)
+{
+  int ndx, maxndx;
+  GElf_Rel rel;
+  GElf_Rela rela;
+  GElf_Sym sym;
+  GElf_Addr base = dso->shdr[sec->sec].sh_addr;
+  Elf_Data *symdata = NULL;
+  int rtype;
+  REL *relbuf;
+  Elf_Scn *scn;
+  Elf_Data *data;
+  int i = sec->relsec;
+
+  /* No relocations, or did we do this already? */
+  if (i == 0 || sec->relbuf != NULL)
+    {
+      relptr = sec->relbuf;
+      relend = sec->relend;
+      return;
+    }
+
+  scn = dso->scn[i];
+  data = elf_getdata (scn, NULL);
+  assert (data != NULL && data->d_buf != NULL);
+  assert (elf_getdata (scn, data) == NULL);
+  assert (data->d_off == 0);
+  assert (data->d_size == dso->shdr[i].sh_size);
+  maxndx = dso->shdr[i].sh_size / dso->shdr[i].sh_entsize;
+  relbuf = malloc (maxndx * sizeof (REL));
+  *reltype = dso->shdr[i].sh_type;
+  if (relbuf == NULL)
+    error (1, errno, "%s: Could not allocate memory", dso->filename);
+
+  symdata = elf_getdata (dso->scn[dso->shdr[i].sh_link], NULL);
+  assert (symdata != NULL && symdata->d_buf != NULL);
+  assert (elf_getdata (dso->scn[dso->shdr[i].sh_link], symdata) == NULL);
+  assert (symdata->d_off == 0);
+  assert (symdata->d_size == dso->shdr[dso->shdr[i].sh_link].sh_size);
+
+  for (ndx = 0, relend = relbuf; ndx < maxndx; ++ndx)
+    {
+      if (dso->shdr[i].sh_type == SHT_REL)
+	{
+	  gelf_getrel (data, ndx, &rel);
+	  rela.r_offset = rel.r_offset;
+	  rela.r_info = rel.r_info;
+	  rela.r_addend = 0;
+	}
+      else
+	gelf_getrela (data, ndx, &rela);
+      gelf_getsym (symdata, ELF64_R_SYM (rela.r_info), &sym);
+      /* Relocations against section symbols are uninteresting in REL.  */
+      if (dso->shdr[i].sh_type == SHT_REL && sym.st_value == 0)
+	continue;
+      /* Only consider relocations against .debug_str, .debug_line
+	 and .debug_abbrev.  */
+      if (sym.st_shndx != debug_sections[DEBUG_STR].sec
+	  && sym.st_shndx != debug_sections[DEBUG_LINE].sec
+	  && sym.st_shndx != debug_sections[DEBUG_ABBREV].sec)
+	continue;
+      rela.r_addend += sym.st_value;
+      rtype = ELF64_R_TYPE (rela.r_info);
+      switch (dso->ehdr.e_machine)
+	{
+	case EM_SPARC:
+	case EM_SPARC32PLUS:
+	case EM_SPARCV9:
+	  if (rtype != R_SPARC_32 && rtype != R_SPARC_UA32)
+	    goto fail;
+	  break;
+	case EM_386:
+	  if (rtype != R_386_32)
+	    goto fail;
+	  break;
+	case EM_PPC:
+	case EM_PPC64:
+	  if (rtype != R_PPC_ADDR32 && rtype != R_PPC_UADDR32)
+	    goto fail;
+	  break;
+	case EM_S390:
+	  if (rtype != R_390_32)
+	    goto fail;
+	  break;
+	case EM_IA_64:
+	  if (rtype != R_IA64_SECREL32LSB)
+	    goto fail;
+	  break;
+	case EM_X86_64:
+	  if (rtype != R_X86_64_32)
+	    goto fail;
+	  break;
+	case EM_ALPHA:
+	  if (rtype != R_ALPHA_REFLONG)
+	    goto fail;
+	  break;
+#if defined(EM_AARCH64) && defined(R_AARCH64_ABS32)
+	case EM_AARCH64:
+	  if (rtype != R_AARCH64_ABS32)
+	    goto fail;
+	  break;
+#endif
+	case EM_68K:
+	  if (rtype != R_68K_32)
+	    goto fail;
+	  break;
+#if defined(EM_RISCV) && defined(R_RISCV_32)
+	case EM_RISCV:
+	  if (rtype != R_RISCV_32)
+	    goto fail;
+	  break;
+#endif
+	default:
+	fail:
+	  error (1, 0, "%s: Unhandled relocation %d in %s section",
+		 dso->filename, rtype, sec->name);
+	}
+      relend->ptr = sec->data
+	+ (rela.r_offset - base);
+      relend->addend = rela.r_addend;
+      relend->ndx = ndx;
+      ++(relend);
+    }
+  if (relbuf == relend)
+    {
+      free (relbuf);
+      relbuf = NULL;
+      relend = NULL;
+    }
+  else
+    qsort (relbuf, relend - relbuf, sizeof (REL), rel_cmp);
+
+  sec->relbuf = relbuf;
+  sec->relend = relend;
+  relptr = relbuf;
+}
+
+/* Updates SHT_RELA section associated with the given section based on
+   the relbuf data. The relbuf data is freed at the end.  */
+static void
+update_rela_data (DSO *dso, struct debug_section *sec)
+{
+  Elf_Data *symdata;
+  int relsec_ndx = sec->relsec;
+  Elf_Data *data = elf_getdata (dso->scn[relsec_ndx], NULL);
+  symdata = elf_getdata (dso->scn[dso->shdr[relsec_ndx].sh_link],
+			 NULL);
+
+  relptr = sec->relbuf;
+  relend = sec->relend;
+  while (relptr < relend)
+    {
+      GElf_Sym sym;
+      GElf_Rela rela;
+      int ndx = relptr->ndx;
+
+      if (gelf_getrela (data, ndx, &rela) == NULL)
+	error (1, 0, "Couldn't get relocation: %s",
+	       elf_errmsg (-1));
+
+      if (gelf_getsym (symdata, GELF_R_SYM (rela.r_info),
+		       &sym) == NULL)
+	error (1, 0, "Couldn't get symbol: %s", elf_errmsg (-1));
+
+      rela.r_addend = relptr->addend - sym.st_value;
+
+      if (gelf_update_rela (data, ndx, &rela) == 0)
+	error (1, 0, "Couldn't update relocations: %s",
+	       elf_errmsg (-1));
+
+      ++relptr;
+    }
+  elf_flagdata (data, ELF_C_SET, ELF_F_DIRTY);
+
+  free (sec->relbuf);
+}
+
 struct abbrev_attr
   {
     unsigned int attr;
@@ -1744,20 +1948,6 @@ edit_attributes (DSO *dso, unsigned char *ptr, struct abbrev_tag *t, int phase)
 }
 
 static int
-rel_cmp (const void *a, const void *b)
-{
-  REL *rela = (REL *) a, *relb = (REL *) b;
-
-  if (rela->ptr < relb->ptr)
-    return -1;
-
-  if (rela->ptr > relb->ptr)
-    return 1;
-
-  return 0;
-}
-
-static int
 line_rel_cmp (const void *a, const void *b)
 {
   LINE_REL *rela = (LINE_REL *) a, *relb = (LINE_REL *) b;
@@ -1871,132 +2061,7 @@ edit_dwarf2 (DSO *dso)
       htab_t abbrev;
       struct abbrev_tag tag, *t;
       int phase;
-      REL *relbuf = NULL;
-
-      if (debug_sections[DEBUG_INFO].relsec)
-	{
-	  int ndx, maxndx;
-	  GElf_Rel rel;
-	  GElf_Rela rela;
-	  GElf_Sym sym;
-	  GElf_Addr base = dso->shdr[debug_sections[DEBUG_INFO].sec].sh_addr;
-	  Elf_Data *symdata = NULL;
-	  int rtype;
-
-	  i = debug_sections[DEBUG_INFO].relsec;
-	  scn = dso->scn[i];
-	  data = elf_getdata (scn, NULL);
-	  assert (data != NULL && data->d_buf != NULL);
-	  assert (elf_getdata (scn, data) == NULL);
-	  assert (data->d_off == 0);
-	  assert (data->d_size == dso->shdr[i].sh_size);
-	  maxndx = dso->shdr[i].sh_size / dso->shdr[i].sh_entsize;
-	  relbuf = malloc (maxndx * sizeof (REL));
-	  reltype = dso->shdr[i].sh_type;
-	  if (relbuf == NULL)
-	    error (1, errno, "%s: Could not allocate memory", dso->filename);
-
-	  symdata = elf_getdata (dso->scn[dso->shdr[i].sh_link], NULL);
-	  assert (symdata != NULL && symdata->d_buf != NULL);
-	  assert (elf_getdata (dso->scn[dso->shdr[i].sh_link], symdata)
-		  == NULL);
-	  assert (symdata->d_off == 0);
-	  assert (symdata->d_size
-		  == dso->shdr[dso->shdr[i].sh_link].sh_size);
-
-	  for (ndx = 0, relend = relbuf; ndx < maxndx; ++ndx)
-	    {
-	      if (dso->shdr[i].sh_type == SHT_REL)
-		{
-		  gelf_getrel (data, ndx, &rel);
-		  rela.r_offset = rel.r_offset;
-		  rela.r_info = rel.r_info;
-		  rela.r_addend = 0;
-		}
-	      else
-		gelf_getrela (data, ndx, &rela);
-	      gelf_getsym (symdata, ELF64_R_SYM (rela.r_info), &sym);
-	      /* Relocations against section symbols are uninteresting
-		 in REL.  */
-	      if (dso->shdr[i].sh_type == SHT_REL && sym.st_value == 0)
-		continue;
-	      /* Only consider relocations against .debug_str, .debug_line
-		 and .debug_abbrev.  */
-	      if (sym.st_shndx != debug_sections[DEBUG_STR].sec
-		  && sym.st_shndx != debug_sections[DEBUG_LINE].sec
-		  && sym.st_shndx != debug_sections[DEBUG_ABBREV].sec)
-		continue;
-	      rela.r_addend += sym.st_value;
-	      rtype = ELF64_R_TYPE (rela.r_info);
-	      switch (dso->ehdr.e_machine)
-		{
-		case EM_SPARC:
-		case EM_SPARC32PLUS:
-		case EM_SPARCV9:
-		  if (rtype != R_SPARC_32 && rtype != R_SPARC_UA32)
-		    goto fail;
-		  break;
-		case EM_386:
-		  if (rtype != R_386_32)
-		    goto fail;
-		  break;
-		case EM_PPC:
-		case EM_PPC64:
-		  if (rtype != R_PPC_ADDR32 && rtype != R_PPC_UADDR32)
-		    goto fail;
-		  break;
-		case EM_S390:
-		  if (rtype != R_390_32)
-		    goto fail;
-		  break;
-		case EM_IA_64:
-		  if (rtype != R_IA64_SECREL32LSB)
-		    goto fail;
-		  break;
-		case EM_X86_64:
-		  if (rtype != R_X86_64_32)
-		    goto fail;
-		  break;
-		case EM_ALPHA:
-		  if (rtype != R_ALPHA_REFLONG)
-		    goto fail;
-		  break;
-#if defined(EM_AARCH64) && defined(R_AARCH64_ABS32)
-		case EM_AARCH64:
-		  if (rtype != R_AARCH64_ABS32)
-		    goto fail;
-		  break;
-#endif
-		case EM_68K:
-		  if (rtype != R_68K_32)
-		    goto fail;
-		  break;
-#if defined(EM_RISCV) && defined(R_RISCV_32)
-		case EM_RISCV:
-		  if (rtype != R_RISCV_32)
-		    goto fail;
-		  break;
-#endif
-		default:
-		fail:
-		  error (1, 0, "%s: Unhandled relocation %d in .debug_info section",
-			 dso->filename, rtype);
-		}
-	      relend->ptr = debug_sections[DEBUG_INFO].data
-			    + (rela.r_offset - base);
-	      relend->addend = rela.r_addend;
-	      relend->ndx = ndx;
-	      ++relend;
-	    }
-	  if (relbuf == relend)
-	    {
-	      free (relbuf);
-	      relbuf = NULL;
-	      relend = NULL;
-	    }
-	  else
-	    qsort (relbuf, relend - relbuf, sizeof (REL), rel_cmp);
-	}
+      bool info_rel_updated = false;
 
       for (phase = 0; phase < 2; phase++)
 	{
@@ -2008,7 +2073,8 @@ edit_dwarf2 (DSO *dso)
 	    break;
 
 	  ptr = debug_sections[DEBUG_INFO].data;
-	  relptr = relbuf;
+	  setup_relbuf(dso, &debug_sections[DEBUG_INFO], &reltype);
+	  rel_updated = false;
 	  endsec = ptr + debug_sections[DEBUG_INFO].size;
 	  while (ptr < endsec)
 	    {
@@ -2096,6 +2162,10 @@ edit_dwarf2 (DSO *dso)
 	      htab_delete (abbrev);
 	    }
 
+	  /* Remember whether any .debug_info relocations might need
+	     to be updated. */
+	  info_rel_updated = rel_updated;
+
 	  /* We might have to recalculate/rewrite the debug_line
 	     section.  We need to do that before going into phase one
 	     so we have all new offsets.  We do this separately from
@@ -2240,41 +2310,8 @@ edit_dwarf2 (DSO *dso)
 	dirty_section (DEBUG_INFO);
 
       /* Update any debug_info relocations addends we might have touched. */
-      if (relbuf != NULL && reltype == SHT_RELA)
-	{
-	  Elf_Data *symdata;
-          int relsec_ndx = debug_sections[DEBUG_INFO].relsec;
-          data = elf_getdata (dso->scn[relsec_ndx], NULL);
-	  symdata = elf_getdata (dso->scn[dso->shdr[relsec_ndx].sh_link],
-				 NULL);
-
-	  relptr = relbuf;
-	  while (relptr < relend)
-	    {
-	      GElf_Sym sym;
-	      GElf_Rela rela;
-	      int ndx = relptr->ndx;
-
-	      if (gelf_getrela (data, ndx, &rela) == NULL)
-		error (1, 0, "Couldn't get relocation: %s",
-		       elf_errmsg (-1));
-
-	      if (gelf_getsym (symdata, GELF_R_SYM (rela.r_info),
-			       &sym) == NULL)
-		error (1, 0, "Couldn't get symbol: %s", elf_errmsg (-1));
-
-	      rela.r_addend = relptr->addend - sym.st_value;
-
-	      if (gelf_update_rela (data, ndx, &rela) == 0)
-		error (1, 0, "Couldn't update relocations: %s",
-		       elf_errmsg (-1));
-
-	      ++relptr;
-	    }
-	  elf_flagdata (data, ELF_C_SET, ELF_F_DIRTY);
-	}
-
-      free (relbuf);
+      if (info_rel_updated)
+	update_rela_data (dso, &debug_sections[DEBUG_INFO]);
     }
 
   return 0;
-- 
1.8.3.1



More information about the Rpm-maint mailing list