Re: [PATCH v2 2/3] binfmt: Normalize host CPU architecture

[Laurent Vivier <laurent@vivier.eu>]

Le 27/01/2025 à 19:29, Andrea Bolognani a écrit :
> Right now information regarding the family each CPU type belongs
> to is recorded in two places: the large data table at the top of
> the script, and the qemu_host_family() function.
> 
> We can make things better by mapping host CPU architecture to
> QEMU target in the few cases where the two don't already match
> and then using the data table to look up the family, same as
> we're already doing for the guest CPU architecture.
> 
> Being able to reason in terms of QEMU target regardless of
> whether we're looking at the host or guest CPU architecture will
> come in handy to implement upcoming changes.
> 
> A couple of entries are dropped in the process: BePC and Power
> Macintosh. I'm quite certain neither of those have ever been
> reported as CPU architectures by Linux. I believe many more of
> the entries that are carried forward could be dropped as well,
> but I don't have the same level of confidence there so I
> decided to play it safe just in case.
> 
> Signed-off-by: Andrea Bolognani <abologna@redhat.com>
> ---
>   scripts/qemu-binfmt-conf.sh | 44 +++++++++++++++++++++----------------
>   1 file changed, 25 insertions(+), 19 deletions(-)
> 
> diff --git a/scripts/qemu-binfmt-conf.sh b/scripts/qemu-binfmt-conf.sh
> index 426f075e31..8d9136a29f 100755
> --- a/scripts/qemu-binfmt-conf.sh
> +++ b/scripts/qemu-binfmt-conf.sh
> @@ -144,35 +144,35 @@ loongarch64_magic='\x7fELF\x02\x01\x01\x00\x00\x00\x00\x00\x00\x00\x00\x00\x02\x
>   loongarch64_mask='\xff\xff\xff\xff\xff\xff\xff\xfc\x00\xff\xff\xff\xff\xff\xff\xff\xfe\xff\xff\xff'
>   loongarch64_family=loongarch
>   
> -qemu_get_family() {
> -    cpu=${HOST_ARCH:-$(uname -m)}
> +# Converts the name of a host CPU architecture to the corresponding QEMU
> +# target.
> +#
> +# FIXME: This can probably be simplified a lot by dropping most entries.
> +#        Remember that the script is only used on Linux, so we only need to
> +#        handle the strings Linux uses to report the host CPU architecture.
> +qemu_normalize() {
> +    cpu="$1"
>       case "$cpu" in
> -    amd64|i386|i486|i586|i686|i86pc|BePC|x86_64)
> +    i[3-6]86)
>           echo "i386"
>           ;;
> -    mips*)
> -        echo "mips"
> +    amd64)
> +        echo "x86_64"
>           ;;
> -    "Power Macintosh"|ppc64|powerpc|ppc)

I don't know why we have "Power Macintosh" as a valid value for "uname -m".
I think it's a good idea to remove it.
It's here from the beginning
08785f48b73c ("updated so that PPC/ARM/SPARC executables are automatically launched when invoked")
Perhaps it's a value coming from the OpenFirmware or MkLinux.

> +    powerpc)
>           echo "ppc"
>           ;;
> -    ppc64el|ppc64le)
> -        echo "ppcle"
> +    ppc64el)
> +        echo "ppc64le"
>           ;;
> -    arm|armel|armhf|arm64|armv[4-9]*l|aarch64)
> +    armel|armhf|armv[4-9]*l)
>           echo "arm"
>           ;;
> -    armeb|armv[4-9]*b|aarch64_be)
> +    armv[4-9]*b)
>           echo "armeb"
>           ;;
> -    sparc*)
> -        echo "sparc"
> -        ;;
> -    riscv*)
> -        echo "riscv"
> -        ;;
> -    loongarch*)
> -        echo "loongarch"
> +    arm64)
> +        echo "aarch64"
>           ;;
>       *)
>           echo "$cpu"
> @@ -309,7 +309,13 @@ EOF
>   
>   qemu_set_binfmts() {
>       # probe cpu type
> -    host_family=$(qemu_get_family)
> +    host_cpu=$(qemu_normalize ${HOST_ARCH:-$(uname -m)})
> +    host_family=$(eval echo \$${host_cpu}_family)
> +
> +    if [ "$host_family" = "" ] ; then
> +        echo "INTERNAL ERROR: unknown host cpu $host_cpu" 1>&2
> +        exit 1
> +    fi
>   
>       # register the interpreter for each cpu except for the native one
>   

Reviewed-by: Laurent Vivier <laurent@vivier.eu>