6.4 Image$$ execution region symbols
The linker generates Image$$
symbols for every execution region present in the image.
Table 6-1 Image$$ execution region symbols
Symbol | Description |
---|---|
Image$$ |
Execution address of the region. |
Image$$ |
Execution region length in bytes excluding ZI length. |
Image$$ |
Address of the byte beyond the end of the non-ZI part of the execution region. |
Image$$ |
Execution address of the RO output section in this region. |
Image$$ |
Length of the RO output section in bytes. |
Image$$ |
Address of the byte beyond the end of the RO output section in the execution region. |
Image$$ |
Execution address of the RW output section in this region. |
Image$$ |
Length of the RW output section in bytes. |
Image$$ |
Address of the byte beyond the end of the RW output section in the execution region. |
Image$$ |
Execution address of the XO output section in this region. |
Image$$ |
Length of the XO output section in bytes. |
Image$$ |
Address of the byte beyond the end of the XO output section in the execution region. |
Image$$ |
Execution address of the ZI output section in this region. |
Image$$ |
Length of the ZI output section in bytes. |
Image$$ |
Address of the byte beyond the end of the ZI output section in the execution region. |
6.5 Load$$ execution region symbols
The linker generates Load$$
symbols for every execution region present in the image.
Note
Load$$region_name
symbols apply only to execution regions. Load$$LR$$load_region_name
symbols apply only to load regions.Load$$
execution region present in the image. All the symbols refer to load addresses after the C library is initialized.Table 6-2 Load$$ execution region symbols
Symbol | Description |
---|---|
Load$$ |
Load address of the region. |
Load$$ |
Region length in bytes. |
Load$$ |
Address of the byte beyond the end of the execution region. |
Load$$ |
Address of the RO output section in this execution region. |
Load$$ |
Length of the RO output section in bytes. |
Load$$ |
Address of the byte beyond the end of the RO output section in the execution region. |
Load$$ |
Address of the RW output section in this execution region. |
Load$$ |
Length of the RW output section in bytes. |
Load$$ |
Address of the byte beyond the end of the RW output section in the execution region. |
Load$$ |
Address of the XO output section in this execution region. |
Load$$ |
Length of the XO output section in bytes. |
Load$$ |
Address of the byte beyond the end of the XO output section in the execution region. |
Load$$ |
Load address of the ZI output section in this execution region. |
Load$$ |
Load length of the ZI output section in bytes.
The Load Length of ZI is zero unless
region_name has the ZEROPAD scatter-loading keyword set. If ZEROPAD is set then:Load Length =
Image$$ |
Load$$ |
Load address of the byte beyond the end of the ZI output section in the execution region. |
-
The symbols are absolute because section-relative symbols can only have execution addresses.
-
The symbols take into account RW compression.
-
References to linker-defined symbols from RW compressed execution regions must be to symbols that are resolvable before RW compression is applied.
-
If the linker detects a relocation from an RW-compressed region to a linker-defined symbol that depends on RW compression, then the linker disables compression for that region.
-
Any Zero Initialized data that is written to the file is taken into account by the Limit and Length values. Zero Initialized data is written into the file when the
ZEROPAD
scatter-loading keyword is used.
6.6 Load$$LR$$ load region symbols
The linker generates Load$$LR$$
symbols for every load region present in the image.
Load$$LR$$
load region can contain many execution regions, so there are no separate $$RO
and $$RW
components.Note
Load$$LR$$load_region_name
symbols apply only to load regions. Load$$region_name
symbols apply only to execution regions.Load$$LR$$
load region present in the image.Table 6-3 Load$$LR$$ load region symbols
Symbol | Description |
---|---|
Load$$LR$$ |
Address of the load region. |
Load$$LR$$ |
Length of the load region. |
Load$$LR$$ |
Address of the byte beyond the end of the load region. |
6.7 Region name values when not scatter-loading
When scatter-loading is not used when linking, the linker uses default region name values.
-
ER_XO
, for an execute-only execution region, if present. -
ER_RO
, for the read-only execution region. -
ER_RW
, for the read-write execution region. -
ER_ZI
, for the zero-initialized execution region.
-
Image$$
execution region symbols. -
Load$$
execution region symbols.
Load$$ER_RO$$Base
.Note
-
The ZI output sections of an image are not created statically, but are automatically created dynamically at runtime. Therefore, there is no load address symbol for ZI output sections.
-
It is recommended that you use region-related symbols in preference to section-related symbols.
6.9 Methods of importing linker-defined symbols in C and C++
You can import linker-defined symbols into your C or C++ source code either by value or by reference.
- Import by value
-
extern unsigned int symbol_name;
- Import by reference
-
extern void *symbol_name;
int
, then you must use the address-of operator (&
) to obtain the correct value as shown in these examples:- Importing a linker-defined symbol
-
extern unsigned int Image$$ZI$$Limit; config.heap_base = (unsigned int) &Image$$ZI$$Limit;
- Importing symbols that define a ZI output section
-
extern unsigned int Image$$ZI$$Length; extern char Image$$ZI$$Base[]; memset(Image$$ZI$$Base,0,(unsigned int)&Image$$Length);
6.11 Section-related symbols
Section-related symbols are symbols generated by the linker when it creates an image without scatter-loading.
-
Image symbols, if you do not use scatter-loading to create a simple image. A simple image has up to four output sections (XO, RO, RW, and ZI) that produce the corresponding execution regions.
-
Input section symbols, for every input section present in the image.
.text
sections are placed in one contiguous block. A contiguous block of sections with the same attribute and name is known as a consolidated section.6.21 Steering file command summary
A summary of the commands you can use in a streering file.
Table 6-6 Steering file command summary
Command | Description |
---|---|
EXPORT |
Specifies that a symbol can be accessed by other shared objects or executables. |
HIDE |
Makes defined global symbols in the symbol table anonymous. |
IMPORT |
Specifies that a symbol is defined in a shared object at runtime. |
RENAME |
Renames defined and undefined global symbol names. |
REQUIRE |
Creates a DT_NEEDED tag in the dynamic array. DT_NEEDED tags specify dependencies to other shared objects used by the application, for example, a shared library. |
RESOLVE |
Matches specific undefined references to a defined global symbol. |
SHOW |
Makes global symbols visible. This command is useful if you want to make a specific symbol visible that is hidden using a HIDE command with a wildcard. |