System for modifying relocatable object code files to monitor accesses to dynamically allocated memory

A computer implemented method for inserting new instructions into a relocatable object file having preexisting instructions, data, and linking and debugging auxiliary structures, a set of said preexisting instructions requiring new instructions, said method comprising the steps of:

• a) providing in a computer storage medium a set of tables, said tables being for storing items, wherein said items include instructions and data, said items having locations within said tables, said set of tables including
• i) an old object code table for storing said preexisting instructions and data;
• ii) a new object code table for storing new code blocks or preexisting instructions and new instructions,
• iii) an inter-item offset table for storing inter-item offsets, wherein inter-item offsets are referenced from a base and point to a target, and wherein said base and target are items in said old object code table,
• iv) a forward index table for storing locations of items within said new object code table, and
• v) a forward control index table for storing locations of new code blocks within said new object code table;
• b) copying said preexisting instructions and data of said relocatable object file into said old object code table;
• c) performing the following computer implemented steps for each item in said old object code table:
• i) storing a new code block into said new object code table, said new code block comprising said each item in said old object code table, and, for items in said set of said preexisting instructions requiring new instructions, said new code block additionally comprising new instructions;
• ii) storing said location within said new object code table of said each item in said old object code table into said forward index table;
• iii) storing said location of said new code block within said new object code table into said forward control index table;
• and
• iv) indicating, when said each item in said old object code table contains an inter-item offset, said locations within said old object code table of said target and base of said inter-item offset and of said offset in said new object code table;
• d) for each inter-item offset indicated in said inter-item offset table, determining a forward location for said base using said forward index table, determining a forward location for said target using said forward control index table when said target is a program control transfer destination and using said forward index table when said target is not a program control transfer destination, and updating said inter-item offset in said new object code table using said forward locations of said base and target;
• e) evaluating compliance of each inter-item offset indicated in said inter-item offset table with a maximum-byte offset constraint, using said forward locations of said base and target;
• f) updating offsets in said auxiliary structures;
• and
• g) creating anew relocatable object file comprising said new object code table and said updated auxiliary structures.

A computer implemented method for inserting new instructions into a relocatable object file having preexisting instructions, data, and auxiliary structures, said auxiliary structures having at least some offsets and comprising text relocation structures, data relocation structures, and symbol structures, wherein a set of said preexisting instructions requires new instructions, said method comprising the steps of:

• a) providing in a computer storage medium a set of tables, said tables being for storing items, wherein said times include instructions and data, said items having locations within said tables, said set of tables including
• i) an old object code table containing said preexisting instructions and data of said relocatable object file;
• ii) a new object code table for storing new code blocks of preexisting instructions and new instructions,
• iii) an inter-item offset table for storing inter-item offsets, wherein inter-item offsets are referenced from a base and point to a target, and wherein said base and target are items in said old object code table,
• iv) a forward index table for storing locations of items within said new object code table,
• v) a forward control index table for storing locations of new code blocks within said new object code table, and
• vi) an entry point table for storing function entry addresses;
• c) for each symbol structure associated with a function and having a function entry address, storing said function entry address in said entry point table, said entry address indicating in said old object code table a first instruction of said function, said function also having a last instruction, all items between said first instruction and said last instruction also being instructions of said function;
• d) performing the following computer implemented steps for each entry address stored in said entry point table;
• i) performing the following computer implemented steps for each preexisting instruction of said function indicated by said each entry address stored in said entry point table;
• 1) storing a new code block into said new object code table, said new code block comprising said each preexisting instruction of said indicated function, and, for preexisting instructions in said set of preexisting instructions requiring new instructions, said new code block additionally comprising new instructions;
• 2) storing, into said forward index table, said location within said new object code table of said each preexisting instruction of said indicated function;
• 3) storing said location of said new code block within said new object code table into said forward control index table;
• and
• 4) indicating, when said each item in said old object code table contains an inter-item offset, said locations within said old object code table of said target and base of said inter-item offset and of said offset in said new object code table;
• and
• ii) performing the following computer implemented steps for each function item in said old object code table after the last preexisting instruction of said function indicated by said entry address and before a closest next entry address;
• 1) copying said each function item into said new object code table;
• 2) storing said location of said each function item within said new object code table into said forward index table;
• e) for each inter-item offset indicated in said inter-item offset table, determining a forward location for said base using said forward index table, determining a forward location for said target using said forward control index table for targets which are program control transfer destinations and using said forward index table for targets which are not program control transfer destinations, and updating each inter-item offset in said new object code table using said forward locations of said base and target;
• f) updating offsets in said auxiliary structures;
• and
• g) creating a new relocatable object file comprising said new object code table and said updated auxiliary structures.

A computer implemented method for equipping a computer program with the ability to monitor most of its own memory accesses, wherein memory access types include read and write, said method comprising the steps of:

• performing the following computer implemented steps for substantially all relocatable object files for said program, said relocatable object files containing instruction items of preexisting object code, wherein instruction items include instructions and data, said instruction items having locations within said preexisting object code:
• a) providing in a computer storage medium a new object code table for storing instruction items;
• b) storing into said new object code table, for each preexisting instruction item in said preexisting object code, a new code block including said preexisting instruction item, said storing step comprising
• i) adding memory read monitoring code to said new code block, for preexisting read instruction items, for which performance involves a memory access of a read type;
• and
• ii) adding memory write monitoring code to said new code block, for preexisting write instruction items, for which performance involves a memory access of a write type;
• c) updating offsets in said new object code table;
• d) creating in a computer storage medium a new relocatable object film comprising instruction items from said new object code file.

In a computer, an executable computer programs capable of monitoring most of its own memory accesses, wherein memory access types include read and write, said computer program capable of accessing a set of memory regions, said computer program comprising

• a) status information maintenance computer code for causing the computer to maintain memory status information in a dedicated table having entries corresponding to memory addresses for at least most memory locations in said set of accessible memory regions, said status information indicating three states of dynamically allocated memory, said states being allocated-and-initialized, allocated-and-uninitialized, and unallocated, said allocated-and-initialized state corresponding to a memory location having been allocated to said computer program and having been initialized by having valid data for said computer program written thereto, said allocated-and-uninitialized state corresponding to a memory location having been allocated to said computer program but not having been initialized by having valid data for said computer program written thereto, and said unallocated state corresponding to a memory location not having been allocated to said computer program;
• b) write error signalling computer code for signalling an error if a memory location having unallocated status is accessed by a memory access of a write type;
• c) read error signalling computer code for signalling an error if a memory location having unallocated status is accessed by a memory access of a read type and if a memory location having allocated-and-uninitialized status is accessed by am memory access of a read type.