On Tue, 2022-08-02 at 11:10 +0000, YunQiang Su wrote:
> If we cannot get info from options and cpuinfo, we try to get from:
> 1. getauxval(AT_BASE_PLATFORM), introduced since Linux 5.7
> 2. _MIPS_ARCH from host compiler.
>
> This can fix the wrong loader usage on r5/r6 platform with
> -march=native.
/* snip */
> if (argc < 1)
> - return NULL;
> + goto fallback_cpu;
I don't think this should be changed, if argc < 1 it means the spec
(disambiguation: the thing printed by "gcc -dumpspecs", hard coded in
gnu-user.h) is wrong. It cannot happen with the built-in spec, but if a
user specifies a bad custom spec with "-spec", we shouldn't be tricked.
> arch = strcmp (argv[0], "arch") == 0;
> if (!arch && strcmp (argv[0], "tune"))
> - return NULL;
> + goto fallback_cpu;
Likewise.
> f = fopen ("/proc/cpuinfo", "r");
> if (f == NULL)
> - return NULL;
> + goto fallback_cpu;
OK.
> +fallback_cpu:
> +/*FIXME: how about other OSes, like FreeBSD? */
https://reviews.freebsd.org/D12743 added elf_aux_info as a counterpart
of getauxinfo, but it looks like FreeBSD does not have AT_BASE_PLATFORM.
> +#ifdef __linux__
> + /*Note: getauxval may return NULL as:
> + * AT_BASE_PLATFORM is supported since Linux 5.7
> + * Or from older version of qemu-user
> + * */
> + if (cpu == NULL)
> + cpu = (const char *) getauxval (AT_BASE_PLATFORM);
getauxval is added in Glibc-2.16 so it will fail to build on hosts with
old glibc or other libc implementation. Check if getauxval and
AT_BASE_PLATFORM are available (in gcc/configure.ac) instead of an
inaccurate "#ifdef __linux__".
> +#endif
> +
> if (cpu == NULL)
> +#if defined (_MIPS_ARCH)
> + cpu = _MIPS_ARCH;
> +#else
Ok.
> return NULL;
> +#endif
>
> return concat ("-m", argv[0], "=", cpu, NULL);
> }
