[LTP] arch_prctl: add ARCH_GET_FS, ARCH_GET_GS tests

[linuxtestproject.agent@gmail.com]

Hi Dmitry,

On Fri Oct 9 2026, Dmitry Chestnykh wrote:
> arch_prctl: add ARCH_GET_FS, ARCH_GET_GS tests

> diff --git a/testcases/kernel/syscalls/arch_prctl/arch_prctl02.c b/testcases/kernel/syscalls/arch_prctl/arch_prctl02.c
> +static int arch_prctl_get(int code, unsigned long *out)
> +{
> +	return tst_syscall(__NR_arch_prctl, code, out);
> +}

High severity: x32 also defines __x86_64__ and passes .supported_archs,
but its unsigned long is four bytes. The raw getters still write eight
bytes, overrunning fs_prctl and gs_prctl; glibc's x32 arch_prctl wrapper
uses a uint64_t temporary for this reason. Use uint64_t or unsigned long
long consistently for the output pointer, result buffers and bases read
by the instructions.

> +	if (gs == 0) {
> +		unsigned long test_gs = 0xabababab;
> +		TST_EXP_PASS_SILENT(set_gs(test_gs));
> +		if (TST_PASS) {
> +			TEST_GS_BASE();
> +		}
> +	}

Low severity: the checkpatch stage of make check-arch_prctl02 fails on
declaration spacing, single-statement braces, a trailing blank line and
bare unsigned declarations. Add blank lines after declarations, remove
the unnecessary braces/blank line, and spell the types unsigned int;
make ignores checker errors, so its zero exit status does not mean this
check passed.

Verdict - Needs revision

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