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From: "Ozkan Sezer (sezeroz AT gmail DOT com) [via djgpp AT delorie DOT com]" <djgpp AT delorie DOT com>
Date: Fri, 28 Apr 2017 22:20:39 +0300
Message-ID: <CAA2C=vC3EtQJmndPY7NRN_cSnDLbNpJPPM2FV6H4E9DcLoWgTg@mail.gmail.com>
Subject: Re: dxe3gen does not handle relocs > 65535
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On 4/28/17, Ozkan Sezer <sezeroz AT gmail DOT com> wrote:
> On 4/28/17, Ozkan Sezer <sezeroz AT gmail DOT com> wrote:
>> On 4/28/17, Ozkan Sezer <sezeroz AT gmail DOT com> wrote:
>>> dxe3gen does not handle extended relocations, i.e. STYP_NRELOC_OVFL
>>> set in hdr->s_flags: it still takes hdr->s_nreloc as number of relocs
>>> and ends up generating a broken dxe which leads to bad crashes when
>>> loaded.  We have one such c++ project where s_nreloc does overflow.
>>>
>>> I will be trying a few things with this, but I'd appreciate help or
>>> advice or links too:  How should I read the actual number of relocs?
>>> Would our current dlopen() still work with this?
>>
>> Here is a dirty draft (to be tested yet). Comments?
[...]
>
> Just tested the above patch by generating out dxe and loading
> and running with it: works fine for me.
>

Here is a somewhat cleaned-up patch with a changelog entry:

dxe3gen.c: handle extended relocations. bump version to 1.0.4.

Index: src/docs/kb/wc206.txi
===================================================================
RCS file: /cvs/djgpp/djgpp/src/docs/kb/wc206.txi,v
retrieving revision 1.3
diff -u -p -r1.3 wc206.txi
--- src/docs/kb/wc206.txi	26 Apr 2017 11:46:19 -0000	1.3
+++ src/docs/kb/wc206.txi	28 Apr 2017 18:11:10 -0000
@@ -3,6 +3,9 @@

 Here is a list of changes from DJGPP V2.05 to DJGPP V2.06

+@cindex dxe3gen and extended coff relocations
+dxe3gen now handles extended coff relocations (more than 65535 relocs.)
+
 @cindex Update of DXE linker script
 The dxe linker script, dxe.ld, now handles @code{.gnu.linkonce.b.*} and
 @code{.bss.*} sections.
Index: src/dxe/dxe3gen.c
===================================================================
RCS file: /cvs/djgpp/djgpp/src/dxe/dxe3gen.c,v
retrieving revision 1.23
diff -u -p -r1.23 dxe3gen.c
--- src/dxe/dxe3gen.c	4 Oct 2015 10:27:26 -0000	1.23
+++ src/dxe/dxe3gen.c	28 Apr 2017 18:11:10 -0000
@@ -193,7 +193,7 @@
 #include "../../include/sys/dxe.h"
 #include "../../include/coff.h"

-#define VERSION  "1.0.3"
+#define VERSION  "1.0.4"

 #define TEMP_BASE    "dxe_tmp"       /* 7 chars, 1 char suffix */
 #define TEMP_O_FILE  TEMP_BASE".o"
@@ -937,6 +937,7 @@ static int write_dxe(FILE *inf, FILE *ou
   char *strings;
   RELOC *relocs;
   unsigned int i, j, errcount;
+  ULONG32 real_nrelocs;
   size_t hdrsize;

   /* Exported symbols table */
@@ -985,9 +986,18 @@ static int write_dxe(FILE *inf, FILE *ou
   strings[0] = 0;

   /* Read the relocation table */
-  relocs = (RELOC *)malloc(sc.s_nreloc * sizeof(RELOC));
   fseek(inf, sc.s_relptr, SEEK_SET);
-  fread(relocs, RELSZ, sc.s_nreloc, inf);
+  if (sc.s_flags & STYP_NRELOC_OVFL) {
+    fread(&real_nrelocs, 4, 1, inf); /* read r_vaddr */
+    fseek(inf, RELSZ - 4, SEEK_CUR); /* skip the rest */
+    dh.nrelocs = --real_nrelocs; /* lose the '+1' */
+    if (opt.verbose)
+      printf("%s: real nrelocs: %lu\n", progname, (unsigned long)real_nrelocs);
+  } else {
+    real_nrelocs = dh.nrelocs;
+  }
+  relocs = (RELOC *)malloc(real_nrelocs * sizeof(RELOC));
+  fread(relocs, RELSZ, real_nrelocs, inf);

   /* Close input file */
   fclose(inf);
@@ -1042,7 +1052,7 @@ static int write_dxe(FILE *inf, FILE *ou
       int n_abs_relocs = 0, n_rel_relocs = 0;

       /* count the amount of relocations pointing to this symbol */
-      for (j = 0; j < sc.s_nreloc; j++)
+      for (j = 0; j < real_nrelocs; j++)
       {
         if (relocs[j].r_symndx == i)
         {
@@ -1101,7 +1111,7 @@ static int write_dxe(FILE *inf, FILE *ou

       unres_size = newsize;

-      for (j = 0; j < sc.s_nreloc; j++)
+      for (j = 0; j < real_nrelocs; j++)
       {
         if (relocs[j].r_symndx == i)
         {
@@ -1202,7 +1212,7 @@ static int write_dxe(FILE *inf, FILE *ou

   /* Compute the amount of valid relocations */
   DEBUG_PRINT_RELOCATION_DIRECTIVE_PROLOG();
-  for (i = 0; i < sc.s_nreloc; i++)
+  for (i = 0; i < real_nrelocs; i++)
   {
     DEBUG_PRINT_RELOCATION_DIRECTIVE(i, relocs);
     if (!VALID_RELOC(relocs[i]))
@@ -1278,7 +1288,7 @@ static int write_dxe(FILE *inf, FILE *ou
   free(data);

   /* Output the relocations */
-  for (i = 0; i < sc.s_nreloc; i++)
+  for (i = 0; i < real_nrelocs; i++)
   {
     if (VALID_RELOC(relocs[i]))
       fwrite(&relocs[i].r_vaddr, 1, sizeof(relocs[0].r_vaddr), outf);


Any gotchas anyone can notice? Any comments and/or suggestions?
Should apply to CVS?

--
O.S.