From 9bf449a90ed81f0058d96613a7ecaec0ca68061e Mon Sep 17 00:00:00 2001
From: Henny Sipma <hennysipma@mac.com>
Date: Wed, 25 Feb 2026 22:19:38 -0800
Subject: [PATCH] CHB:ELF: enable retrieval of last n bytes from section

---
 CodeHawk/CHB/bchlib/bCHVersion.ml      |  4 ++--
 CodeHawk/CHB/bchlibelf/bCHELFHeader.ml | 10 ++++++++--
 CodeHawk/CHB/bchlibelf/bCHELFTypes.mli | 22 +++++++++++++++++++++-
 3 files changed, 31 insertions(+), 5 deletions(-)

diff --git a/CodeHawk/CHB/bchlib/bCHVersion.ml b/CodeHawk/CHB/bchlib/bCHVersion.ml
index 383958b1..fef02570 100644
--- a/CodeHawk/CHB/bchlib/bCHVersion.ml
+++ b/CodeHawk/CHB/bchlib/bCHVersion.ml
@@ -95,8 +95,8 @@ end
 
 
 let version = new version_info_t 
-  ~version:"0.6.0_20260122"
-  ~date:"2026-01-22"
+  ~version:"0.6.0_20260225"
+  ~date:"2026-02-25"
   ~licensee: None
   ~maxfilesize: None
   ()
diff --git a/CodeHawk/CHB/bchlibelf/bCHELFHeader.ml b/CodeHawk/CHB/bchlibelf/bCHELFHeader.ml
index b244eff2..b7b3c1fc 100644
--- a/CodeHawk/CHB/bchlibelf/bCHELFHeader.ml
+++ b/CodeHawk/CHB/bchlibelf/bCHELFHeader.ml
@@ -6,7 +6,7 @@
 
    Copyright (c) 2005-2020 Kestrel Technology LLC
    Copyright (c) 2020      Henny Sipma
-   Copyright (c) 2021-2025 Aarno Labs LLC
+   Copyright (c) 2021-2026 Aarno Labs LLC
 
    Permission is hereby granted, free of charge, to any person obtaining a copy
    of this software and associated documentation files (the "Software"), to deal
@@ -808,12 +808,18 @@ object(self)
     match self#get_containing_section a with
     | Some s ->
        let diff = a#subtract_to_int s#get_vaddr in
+       (* In some cases the <= check may be problematic. If the section is the
+          last one in the file, or perhaps if there is a gap between this
+          section and the next, the check may succeed, but the retrieval of
+          the corresponding bytes may fail. However, a < check may result in
+          missing the last library stub in a plt section.*)
        if Result.is_ok diff then
-         (TR.tget_ok diff) + size < s#get_size
+         (TR.tget_ok diff) + size <= s#get_size
        else
          raise
            (BCH_failure
               (LBLOCK [
+                   STR __FILE__; STR ":"; INT __LINE__;
                    STR "ELFHeader:has_xsubstring: interal error: ";
                    STR "subtraction"]))
   | _ -> false
diff --git a/CodeHawk/CHB/bchlibelf/bCHELFTypes.mli b/CodeHawk/CHB/bchlibelf/bCHELFTypes.mli
index 71d69580..907bfc40 100644
--- a/CodeHawk/CHB/bchlibelf/bCHELFTypes.mli
+++ b/CodeHawk/CHB/bchlibelf/bCHELFTypes.mli
@@ -6,7 +6,7 @@
 
    Copyright (c) 2005-2020 Kestrel Technology LLC
    Copyright (c) 2020      Henny Sipma
-   Copyright (c) 2021-2024 Aarno Labs LLC
+   Copyright (c) 2021-2026 Aarno Labs LLC
 
    Permission is hereby granted, free of charge, to any person obtaining a copy
    of this software and associated documentation files (the "Software"), to deal
@@ -807,6 +807,11 @@ object
   method get_executable_sections: (elf_section_header_int * string) list
   method get_executable_segments: (elf_program_header_int * string) list
   method get_string_at_address: doubleword_int -> string option
+
+  (** [get_xsubstring addr size] returns the string of bytes starting at
+      virtual address [addr] with length size bytes.
+      Note: see comment for has_xsubstring below
+   *)
   method get_xsubstring: doubleword_int -> int -> string
   method get_relocation: doubleword_int -> string option
   method get_containing_section: doubleword_int -> elf_raw_section_int option
@@ -832,6 +837,21 @@ object
 
   method is_uninitialized_data_address: doubleword_int -> bool
   method is_global_offset_table_address: doubleword_int -> bool
+
+  (** [has_xsubstring addr size] returns true if the section that contains
+      virtual address [addr] has at least [size] bytes starting from address
+      [addr].
+
+      Note: the check performed is
+         [addr - section_start_address) + size <= section_size]
+      In some cases the less than equal check may be problematic: if the
+      section is the last section of the file, or perhaps if there is a
+      gap between this section and the next, the equal sign may make the
+      check succeed, but the retrieval of the corresponding bytes, by calling
+      [get_xsubstring] with the same arguments, may fail.
+      However, if a less-than check is used the last library stub in a plt
+      may be missed.
+   *)
   method has_xsubstring: doubleword_int -> int -> bool
   method has_debug_info: bool
   method has_debug_abbrev: bool