Tag Archives: gcc

Linaro on Arch Linux

In order to use the Linaro ARM cross-toolchain on Arch Linux, some 32-Bit Libraries need to be available. Arch Linux supports multiarch too, just enable the packages in your /etc/pacman.conf:

Include = /etc/pacman.d/mirrorlist

Update your packages

pacman -Sy
:: Synchronizing package databases...
 core is up to date
 extra is up to date
 community is up to date
 multilib 104.5 KiB 148K/s 00:01 [##################################] 100%

Unlike in Debian based distribution the GNU C Library package is called lib32-glibc. Additionally needed libraries by GCC (such as libstdc++6) are included in the package lib32-gcc-libs.

pacman -S lib32-glibc lib32-gcc-libs lib32-zlib

Cortex-M3 supervisor call (SVC) using GCC

The Cortex-M3 has a new assembler instruction SVC to call the supervisor (usually the operating system). The ARM7TDMI used to call this interrupt SWI, but since this interrupt works differently on Cortex-M3, ARM renamed the instruction to make sure people recognize the difference and implement those calls correctly. The machine opcode however is still the same (bits 0-23 are user defined, bits 24-27 are ones).

On the Cortex-M3, other interrupts can interrupt the processor during state saving of the SVC interrupt (late arrival interrupt handling). Those late arriving interrupts most certainly leave the registers corrupted after execution. Therefor we cannot read the parameters form registers r0 to r4 directly as we could on the ARM7TDMI using SWI interrupts. Fortunately, the Cortex-M3 saves all registers used in standard C procedure call specification (ABI) on the stack. So the SVC handler can get the parameters directly from the stack.

Cortex-M3 stack frame

Cortex-M3 stack frame

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Linaro embedded toolchain on Ubuntu 64-Bit

Linaro provides a specialized toolchain for embedded (bare metal) development. But after installing, I could not execute the binary:

$ gcc-arm-none-eabi-4_7-2012q4/bin/arm-none-eabi-gcc
-bash: gcc-arm-none-eabi-4_7-2012q4/bin/arm-none-eabi-gcc: No such file or directory

Also ldd claims its not dynamically linked:

$ ldd gcc-arm-none-eabi-4_7-2012q4/bin/arm-none-eabi-gcc
 not a dynamic executable

The truth is: it is dynamically linked, but against 32-Bit libraries. And since I have not yet installed any 32-Bit library, ldd doesn’t work properly. According to the readme, you should install the 32-Bit variant of libc and libncurses. Since Ubuntu is Multi-Arch, you can easily install those libs:

sudo apt-get install libc6:i386 libncurses5:i386

Now you should be able to run the Linaro toolchain on 64-Bit variants of Ubuntu.