From 047b9c8391765973fb9ee31c87e25e0f31a2dc04 Mon Sep 17 00:00:00 2001
From: Alan Modra <amodra@gmail.com>
Date: Wed, 22 Nov 2023 09:53:27 +0800
Subject: [PATCH] gdb: warn unused result for bfd IO functions

This fixes the compilation warnings introduced by my bfdio.c patch.

The removed bfd_seeks in coff_symfile_read date back to 1994, commit
7f4c859520, prior to which the file used stdio rather than bfd to read
symbols.  Since it now uses bfd to read the file there should be no
need to synchronise to bfd's idea of the file position.  I also fixed
a potential uninitialised memory access.

Approved-By: Andrew Burgess <aburgess@redhat.com>
---
 gdb/coff-pe-read.c | 114 +++++++++++++++++++++++++++++----------------
 gdb/coffread.c     |  27 ++---------
 gdb/dbxread.c      |   7 +--
 gdb/xcoffread.c    |   5 +-
 4 files changed, 85 insertions(+), 68 deletions(-)

diff --git a/gdb/coff-pe-read.c b/gdb/coff-pe-read.c
index 90b406f..ad197a8 100644
--- a/gdb/coff-pe-read.c
+++ b/gdb/coff-pe-read.c
@@ -291,23 +291,31 @@ read_pe_truncate_name (char *dll_name)
 
 /* Low-level support functions, direct from the ld module pe-dll.c.  */
 static unsigned int
-pe_get16 (bfd *abfd, int where)
+pe_get16 (bfd *abfd, int where, bool *fail)
 {
   unsigned char b[2];
 
-  bfd_seek (abfd, (file_ptr) where, SEEK_SET);
-  bfd_bread (b, (bfd_size_type) 2, abfd);
+  if (bfd_seek (abfd, where, SEEK_SET) != 0
+      || bfd_bread (b, 2, abfd) != 2)
+    {
+      *fail = true;
+      return 0;
+    }
   return b[0] + (b[1] << 8);
 }
 
 static unsigned int
-pe_get32 (bfd *abfd, int where)
+pe_get32 (bfd *abfd, int where, bool *fail)
 {
   unsigned char b[4];
 
-  bfd_seek (abfd, (file_ptr) where, SEEK_SET);
-  bfd_bread (b, (bfd_size_type) 4, abfd);
-  return b[0] + (b[1] << 8) + (b[2] << 16) + (b[3] << 24);
+  if (bfd_seek (abfd, where, SEEK_SET) != 0
+      || bfd_bread (b, 4, abfd) != 4)
+    {
+      *fail = true;
+      return 0;
+    }
+  return b[0] + (b[1] << 8) + (b[2] << 16) + ((unsigned) b[3] << 24);
 }
 
 static unsigned int
@@ -323,7 +331,7 @@ pe_as32 (void *ptr)
 {
   unsigned char *b = (unsigned char *) ptr;
 
-  return b[0] + (b[1] << 8) + (b[2] << 16) + (b[3] << 24);
+  return b[0] + (b[1] << 8) + (b[2] << 16) + ((unsigned) b[3] << 24);
 }
 
 /* Read the (non-debug) export symbol table from a portable
@@ -376,37 +384,50 @@ read_pe_exported_syms (minimal_symbol_reader &reader,
 	     || strcmp (target, "pei-i386") == 0
 	     || strcmp (target, "pe-arm-wince-little") == 0
 	     || strcmp (target, "pei-arm-wince-little") == 0);
+
+  /* Possibly print a debug message about DLL not having a valid format.  */
+  auto maybe_print_debug_msg = [&] () -> void {
+    if (debug_coff_pe_read)
+      fprintf_unfiltered (gdb_stdlog, _("%s doesn't appear to be a DLL\n"),
+		  bfd_get_filename (dll));
+  };
+
   if (!is_pe32 && !is_pe64)
-    {
-      /* This is not a recognized PE format file.  Abort now, because
-	 the code is untested on anything else.  *FIXME* test on
-	 further architectures and loosen or remove this test.  */
-      return;
-    }
+    return maybe_print_debug_msg ();
 
   /* Get pe_header, optional header and numbers of export entries.  */
-  pe_header_offset = pe_get32 (dll, 0x3c);
+  bool fail = false;
+  pe_header_offset = pe_get32 (dll, 0x3c, &fail);
+  if (fail)
+    return maybe_print_debug_msg ();
   opthdr_ofs = pe_header_offset + 4 + 20;
   if (is_pe64)
-    num_entries = pe_get32 (dll, opthdr_ofs + 108);
+    num_entries = pe_get32 (dll, opthdr_ofs + 108, &fail);
   else
-    num_entries = pe_get32 (dll, opthdr_ofs + 92);
+    num_entries = pe_get32 (dll, opthdr_ofs + 92, &fail);
+  if (fail)
+    return maybe_print_debug_msg ();
 
   if (num_entries < 1)		/* No exports.  */
     return;
   if (is_pe64)
     {
-      export_opthdrrva = pe_get32 (dll, opthdr_ofs + 112);
-      export_opthdrsize = pe_get32 (dll, opthdr_ofs + 116);
+      export_opthdrrva = pe_get32 (dll, opthdr_ofs + 112, &fail);
+      export_opthdrsize = pe_get32 (dll, opthdr_ofs + 116, &fail);
     }
   else
     {
-      export_opthdrrva = pe_get32 (dll, opthdr_ofs + 96);
-      export_opthdrsize = pe_get32 (dll, opthdr_ofs + 100);
+      export_opthdrrva = pe_get32 (dll, opthdr_ofs + 96, &fail);
+      export_opthdrsize = pe_get32 (dll, opthdr_ofs + 100, &fail);
     }
-  nsections = pe_get16 (dll, pe_header_offset + 4 + 2);
+  if (fail)
+    return maybe_print_debug_msg ();
+
+  nsections = pe_get16 (dll, pe_header_offset + 4 + 2, &fail);
   secptr = (pe_header_offset + 4 + 20 +
-	    pe_get16 (dll, pe_header_offset + 4 + 16));
+	    pe_get16 (dll, pe_header_offset + 4 + 16, &fail));
+  if (fail)
+    return maybe_print_debug_msg ();
   expptr = 0;
   export_size = 0;
 
@@ -415,12 +436,13 @@ read_pe_exported_syms (minimal_symbol_reader &reader,
     {
       char sname[8];
       unsigned long secptr1 = secptr + 40 * i;
-      unsigned long vaddr = pe_get32 (dll, secptr1 + 12);
-      unsigned long vsize = pe_get32 (dll, secptr1 + 16);
-      unsigned long fptr = pe_get32 (dll, secptr1 + 20);
+      unsigned long vaddr = pe_get32 (dll, secptr1 + 12, &fail);
+      unsigned long vsize = pe_get32 (dll, secptr1 + 16, &fail);
+      unsigned long fptr = pe_get32 (dll, secptr1 + 20, &fail);
 
-      bfd_seek (dll, (file_ptr) secptr1, SEEK_SET);
-      bfd_bread (sname, (bfd_size_type) sizeof (sname), dll);
+      if (fail
+	  || bfd_seek (dll, secptr1, SEEK_SET) != 0
+	  || bfd_bread (sname, sizeof (sname), dll) != sizeof (sname))
 
       if ((strcmp (sname, ".edata") == 0)
 	  || (vaddr <= export_opthdrrva && export_opthdrrva < vaddr + vsize))
@@ -461,16 +483,18 @@ read_pe_exported_syms (minimal_symbol_reader &reader,
   for (i = 0; i < nsections; i++)
     {
       unsigned long secptr1 = secptr + 40 * i;
-      unsigned long vsize = pe_get32 (dll, secptr1 + 8);
-      unsigned long vaddr = pe_get32 (dll, secptr1 + 12);
-      unsigned long characteristics = pe_get32 (dll, secptr1 + 36);
+      unsigned long vsize = pe_get32 (dll, secptr1 + 8, &fail);
+      unsigned long vaddr = pe_get32 (dll, secptr1 + 12, &fail);
+      unsigned long characteristics = pe_get32 (dll, secptr1 + 36, &fail);
       char sec_name[SCNNMLEN + 1];
       int sectix;
       unsigned int bfd_section_index;
       asection *section;
 
-      bfd_seek (dll, (file_ptr) secptr1 + 0, SEEK_SET);
-      bfd_bread (sec_name, (bfd_size_type) SCNNMLEN, dll);
+      if (fail
+	  || bfd_seek (dll, secptr1 + 0, SEEK_SET) != 0
+	  || bfd_bread (sec_name, SCNNMLEN, dll) != SCNNMLEN)
+	return maybe_print_debug_msg ();
       sec_name[SCNNMLEN] = '\0';
 
       sectix = read_pe_section_index (sec_name);
@@ -509,8 +533,9 @@ read_pe_exported_syms (minimal_symbol_reader &reader,
   gdb::def_vector<unsigned char> expdata_storage (export_size);
   expdata = expdata_storage.data ();
 
-  bfd_seek (dll, (file_ptr) expptr, SEEK_SET);
-  bfd_bread (expdata, (bfd_size_type) export_size, dll);
+  if (bfd_seek (dll, expptr, SEEK_SET) != 0
+      || bfd_bread (expdata, export_size, dll) != export_size)
+    return maybe_print_debug_msg ();
   erva = expdata - export_rva;
 
   nexp = pe_as32 (expdata + 24);
@@ -658,20 +683,27 @@ pe_text_section_offset (struct bfd *abfd)
     }
 
   /* Get pe_header, optional header and numbers of sections.  */
-  pe_header_offset = pe_get32 (abfd, 0x3c);
-  nsections = pe_get16 (abfd, pe_header_offset + 4 + 2);
+  bool fail = false;
+  pe_header_offset = pe_get32 (abfd, 0x3c, &fail);
+  if (fail)
+    return DEFAULT_COFF_PE_TEXT_SECTION_OFFSET;
+  nsections = pe_get16 (abfd, pe_header_offset + 4 + 2, &fail);
   secptr = (pe_header_offset + 4 + 20 +
-	    pe_get16 (abfd, pe_header_offset + 4 + 16));
+	    pe_get16 (abfd, pe_header_offset + 4 + 16, &fail));
+  if (fail)
+    return DEFAULT_COFF_PE_TEXT_SECTION_OFFSET;
 
   /* Get the rva and size of the export section.  */
   for (i = 0; i < nsections; i++)
     {
       char sname[SCNNMLEN + 1];
       unsigned long secptr1 = secptr + 40 * i;
-      unsigned long vaddr = pe_get32 (abfd, secptr1 + 12);
+      unsigned long vaddr = pe_get32 (abfd, secptr1 + 12, &fail);
 
-      bfd_seek (abfd, (file_ptr) secptr1, SEEK_SET);
-      bfd_bread (sname, (bfd_size_type) SCNNMLEN, abfd);
+      if (fail
+	  || bfd_seek (abfd, secptr1, SEEK_SET) != 0
+	  || bfd_bread (sname, SCNNMLEN, abfd) != SCNNMLEN)
+	return DEFAULT_COFF_PE_TEXT_SECTION_OFFSET;
       sname[SCNNMLEN] = '\0';
       if (strcmp (sname, ".text") == 0)
 	return vaddr;
diff --git a/gdb/coffread.c b/gdb/coffread.c
index c02aad6..1a57c1e 100644
--- a/gdb/coffread.c
+++ b/gdb/coffread.c
@@ -691,8 +691,6 @@ coff_symfile_read (struct objfile *objfile, symfile_add_flags symfile_flags)
 
       /* FIXME: dubious.  Why can't we use something normal like
 	 bfd_get_section_contents?  */
-      bfd_seek (abfd, abfd->where, 0);
-
       stabstrsize = bfd_section_size (info->stabstrsect);
 
       coffstab_build_psymtabs (objfile,
@@ -782,22 +780,6 @@ coff_symtab_read (minimal_symbol_reader &reader,
 
   scoped_free_pendings free_pending;
 
-  /* Work around a stdio bug in SunOS4.1.1 (this makes me nervous....
-     it's hard to know I've really worked around it.  The fix should
-     be harmless, anyway).  The symptom of the bug is that the first
-     fread (in read_one_sym), will (in my example) actually get data
-     from file offset 268, when the fseek was to 264 (and ftell shows
-     264).  This causes all hell to break loose.  I was unable to
-     reproduce this on a short test program which operated on the same
-     file, performing (I think) the same sequence of operations.
-
-     It stopped happening when I put in this (former) rewind().
-
-     FIXME: Find out if this has been reported to Sun, whether it has
-     been fixed in a later release, etc.  */
-
-  bfd_seek (objfile->obfd, 0, 0);
-
   /* Position to read the symbol table.  */
   val = bfd_seek (objfile->obfd, symtab_offset, 0);
   if (val < 0)
@@ -1287,12 +1269,13 @@ init_stringtab (bfd *abfd, file_ptr offset, gdb::unique_xmalloc_ptr<char> *stora
   if (bfd_seek (abfd, offset, 0) < 0)
     return -1;
 
-  val = bfd_bread ((char *) lengthbuf, sizeof lengthbuf, abfd);
-  length = bfd_h_get_32 (symfile_bfd, lengthbuf);
-
+  val = bfd_bread (lengthbuf, sizeof lengthbuf, abfd);
   /* If no string table is needed, then the file may end immediately
      after the symbols.  Just return with `stringtab' set to null.  */
-  if (val != sizeof lengthbuf || length < sizeof lengthbuf)
+  if (val != sizeof lengthbuf)
+    return 0;
+  length = bfd_h_get_32 (symfile_bfd, lengthbuf);
+  if (length < sizeof lengthbuf)
     return 0;
 
   storage->reset ((char *) xmalloc (length));
diff --git a/gdb/dbxread.c b/gdb/dbxread.c
index cf35880..1c2fb36 100644
--- a/gdb/dbxread.c
+++ b/gdb/dbxread.c
@@ -812,7 +812,8 @@ stabs_seek (int sym_offset)
       symbuf_left -= sym_offset;
     }
   else
-    bfd_seek (symfile_bfd, sym_offset, SEEK_CUR);
+    if (bfd_seek (symfile_bfd, sym_offset, SEEK_CUR) != 0)
+      perror_with_name (bfd_get_filename (symfile_bfd));
 }
 
 #define INTERNALIZE_SYMBOL(intern, extern, abfd)			\
@@ -2095,8 +2096,8 @@ dbx_expand_psymtab (legacy_psymtab *pst, struct objfile *objfile)
       symbol_size = SYMBOL_SIZE (pst);
 
       /* Read in this file's symbols.  */
-      bfd_seek (objfile->obfd, SYMBOL_OFFSET (pst), SEEK_SET);
-      read_ofile_symtab (objfile, pst);
+      if (bfd_seek (objfile->obfd, SYMBOL_OFFSET (pst), SEEK_SET) == 0)
+	read_ofile_symtab (objfile, pst);
     }
 
   pst->readin = true;
diff --git a/gdb/xcoffread.c b/gdb/xcoffread.c
index a854d4d..6d380b1 100644
--- a/gdb/xcoffread.c
+++ b/gdb/xcoffread.c
@@ -865,8 +865,9 @@ enter_line_range (struct subfile *subfile, unsigned beginoffset,
 
   while (curoffset <= limit_offset)
     {
-      bfd_seek (abfd, curoffset, SEEK_SET);
-      bfd_bread (ext_lnno, linesz, abfd);
+      if (bfd_seek (abfd, curoffset, SEEK_SET) != 0
+	  || bfd_bread (ext_lnno, linesz, abfd) != linesz)
+	return;
       bfd_coff_swap_lineno_in (abfd, ext_lnno, &int_lnno);
 
       /* Find the address this line represents.  */
-- 
2.33.0