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21.3.2 ARM

GDB provides the following ARM-specific commands:

set arm disassembler

This commands selects from a list of disassembly styles. The "std" style is the standard style.

show arm disassembler

Show the current disassembly style.

set arm apcs32

This command toggles ARM operation mode between 32-bit and 26-bit.

show arm apcs32

Display the current usage of the ARM 32-bit mode.

set arm fpu fputype

This command sets the ARM floating-point unit (FPU) type. The argument fputype can be one of these:


Determine the FPU type by querying the OS ABI.


Software FPU, with mixed-endian doubles on little-endian ARM processors.


GCC-compiled FPA co-processor.


Software FPU with pure-endian doubles.


VFP co-processor.

show arm fpu

Show the current type of the FPU.

set arm abi

This command forces GDB to use the specified ABI.

show arm abi

Show the currently used ABI.

set arm fallback-mode (arm|thumb|auto)

GDB uses the symbol table, when available, to determine whether instructions are ARM or Thumb. This command controls GDB’s default behavior when the symbol table is not available. The default is ‘auto’, which causes GDB to use the current execution mode (from the T bit in the CPSR register).

show arm fallback-mode

Show the current fallback instruction mode.

set arm force-mode (arm|thumb|auto)

This command overrides use of the symbol table to determine whether instructions are ARM or Thumb. The default is ‘auto’, which causes GDB to use the symbol table and then the setting of ‘set arm fallback-mode’.

show arm force-mode

Show the current forced instruction mode.

set arm unwind-secure-frames

This command enables unwinding from Non-secure to Secure mode on Cortex-M with Security extension. This can trigger security exceptions when unwinding the exception stack. It is enabled by default.

show arm unwind-secure-frames

Show whether unwinding from Non-secure to Secure mode is enabled.

set debug arm

Toggle whether to display ARM-specific debugging messages from the ARM target support subsystem.

show debug arm

Show whether ARM-specific debugging messages are enabled.

target sim [simargs]

The GDB ARM simulator accepts the following optional arguments.


Tell the simulator which SWI interfaces to support. The argument type may be a comma separated list of the following values. The default value is all.


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