Messages in this thread | | | From | Arnd Bergmann <> | Subject | Re: [PATCH 1/9] ARM: ARMv7-M uses BE-8, not BE-32 | Date | Thu, 18 Feb 2016 17:12:13 +0100 |
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On Thursday 18 February 2016 11:06:08 Nicolas Pitre wrote: > On Thu, 18 Feb 2016, Arnd Bergmann wrote: > > > When configuring the kernel for big-endian, we set either BE-8 or BE-32 > > based on the CPU architecture level. Until linux-4.4, we did not have > > any ARMv7-M platform allowing big-endian builds, but now i.MX/Vybrid > > is in that category, adn we get a build error because of this: > > > > arch/arm/kernel/module-plts.c: In function 'get_module_plt': > > arch/arm/kernel/module-plts.c:60:46: error: implicit declaration of function '__opcode_to_mem_thumb32' [-Werror=implicit-function-declaration] > > > > This comes down to picking the wrong default, ARMv7-M uses BE8 > > like ARMv7-A does. Changing the default gets the kernel to compile > > and presumably works. > > Was it tested without BE8 when it was submitted upstream? I don't think > you can switch this freely on a given hardware platform and expect it to > still work. > >
mach-imx contains a number of different SoCs, and one SoC was recently tested successfully after a number of endianess bugs got fixed. This was an i.mx6 using a Cortex-A9 core, but we are now also able to build vybrid vf610 big-endian based on that selection. This SoC supports Linux running either on its Cortex-A5 or its Cortex-M3 (or M4?) cores.
I am rather sure nobody has ever run Linux in big-endian mode on the Cortex-M platform, specifically because it was always wrong and could not be enabled in Kconfig.
Arnd
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