Automatic placement of __at sections

• The __at address lies within the execution region base and limit, where limit is the base address + maximum size of execution region. If no maximum size is set, the linker sets the limit for placing __at sections as the current size of the execution region without __at sections plus a constant. The default value of this constant is 10240 bytes, but you can change the value using the --max_er_extension command-line option.
• The execution region meets at least one of the following conditions:
  • It has a selector that matches the __at section by the standard scatter-loading rules.
  • It has at least one section of the same type (RO, RW or ZI) as the __at section.
  • It does not have the EMPTY attribute.

    Note

    The linker considers an __at section with type RW compatible with RO.

Example

// place the RO variable in a section called .ARM.__at_0x00000000
const int baz __attribute__((at(0x0000))) = 100;
// place the RW variable in a section called .ARM.__at_0x00002000
int foo __attribute__((at(0x2000))) = 100;
// place the ZI variable in a section called .ARM.__at_0x00004000
int bar __attribute__((at(0x4000), zero_init));
// place the ZI variable in a section called .ARM.__at_0x00008000
int variable __attribute__((at(0x8000), zero_init));

LR1 0x0
{
    ER_RO 0x0 0x2000
    {
        *(+RO)      ; .ARM.__at_0x00000000 lies within the bounds of ER_RO
    }
    ER_RW 0x2000 0x2000
    {
        *(+RW)      ; .ARM.__at_0x00002000 lies within the bounds of ER_RW
    }
    ER_ZI 0x4000 0x2000
    {
        *(+ZI)      ; .ARM.__at_0x00004000 lies within the bounds of ER_ZI
    }
}
; The linker creates a load and execution region for the __at section
; .ARM.__at_0x00008000 because it lies outside all candidate regions.