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Chapter 5 Notes on Debugging
Page 5-10
4. Note the following with regard to SWI instructions.
* Do not use SWI 0x123456 or SWI 0xab. The Angel debugging monitor uses these SWIs
to support C library semihosting requests.
* The application must restore registers to their states before the SWI instruction.
* If the application program uses SWI instructions, modify it to chain its SWI handler to the
Angel debugging monitor's SWI handler. The procedure is the same as that under 3.
above.
See also 5. below for a description of the Angel debugging monitor exception vector table.
5. The Angel debugging monitor uses the following exception vector table.
Address Description
0x0 ldr pc, 0x20 ; RESET
0x4 ldr pc, 0x24 ; Undefined opcode
0x8 ldr pc, 0x28 ; SWI
0xc ldr pc, 0x2c ; Prefetch abort
0x10 ldr pc, 0x30 ; Data abort
0x14 ldr pc, 0x34 ; Reserved
0x18 ldr pc. 0x38 ; IRQ
0x1c ldr pc, 0x3c ; FIQ
0x20 Reset handler (32-bit) address
0x24 Undefined opcode handler (32-bit) address
0x28 SWI handler (32-bit) address
0x2C Prefetch abort handler (32-bit) address
0x30 Data abort handler (32-bit) address
0x34 Reserved
0x38 IRQ handler (32-bit) address
0x3c FIQ handler (32-bit) address
Using this table
Consider the entry for 0x18, for example.
This instruction loads the program counter with the 32-bit address stored at the address
0x38, producing a branch to that handler.