Thomas Weißschuh
c7a6bd2019
commit e242bbbb6d7ac7556aa1e358294dc7e3c82cc902 upstream. The syscall wrappers use the "a0" register for two different register variables, both the first argument and the return value. Here the "ret" variable is used as both input and output while the argument register is only used as input. Clang treats the conflicting input parameters as an undefined behaviour and optimizes away the argument assignment. The code seems to work by chance for the most part today but that may change in the future. Specifically clock_gettime_fallback() fails with clockids from 16 to 23, as implemented by the upcoming auxiliary clocks. Switch the "ret" register variable to a pure output, similar to the other architectures' vDSO code. This works in both clang and GCC. Link: https://lore.kernel.org/lkml/20250602102825-42aa84f0-23f1-4d10-89fc-e8bbaffd291a@linutronix.de/ Link: https://lore.kernel.org/lkml/20250519082042.742926976@linutronix.de/ Fixes:c6b99bed6b("LoongArch: Add VDSO and VSYSCALL support") Fixes:18efd0b10e("LoongArch: vDSO: Wire up getrandom() vDSO implementation") Cc: stable@vger.kernel.org Reviewed-by: Nathan Chancellor <nathan@kernel.org> Reviewed-by: Yanteng Si <si.yanteng@linux.dev> Reviewed-by: WANG Xuerui <git@xen0n.name> Reviewed-by: Xi Ruoyao <xry111@xry111.site> Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de> Signed-off-by: Huacai Chen <chenhuacai@loongson.cn> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
40 lines
1.0 KiB
C
40 lines
1.0 KiB
C
// SPDX-License-Identifier: GPL-2.0-only
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/*
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* Copyright (C) 2024 Xi Ruoyao <xry111@xry111.site>. All Rights Reserved.
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*/
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#ifndef __ASM_VDSO_GETRANDOM_H
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#define __ASM_VDSO_GETRANDOM_H
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#ifndef __ASSEMBLY__
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#include <asm/unistd.h>
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#include <asm/vdso/vdso.h>
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static __always_inline ssize_t getrandom_syscall(void *_buffer, size_t _len, unsigned int _flags)
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{
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register long ret asm("a0");
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register long nr asm("a7") = __NR_getrandom;
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register void *buffer asm("a0") = _buffer;
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register size_t len asm("a1") = _len;
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register unsigned int flags asm("a2") = _flags;
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asm volatile(
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" syscall 0\n"
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: "=r" (ret)
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: "r" (nr), "r" (buffer), "r" (len), "r" (flags)
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: "$t0", "$t1", "$t2", "$t3", "$t4", "$t5", "$t6", "$t7", "$t8",
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"memory");
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return ret;
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}
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static __always_inline const struct vdso_rng_data *__arch_get_vdso_rng_data(void)
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{
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return (const struct vdso_rng_data *)(get_vdso_data() + VVAR_LOONGARCH_PAGES_START *
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PAGE_SIZE + offsetof(struct loongarch_vdso_data, rng_data));
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}
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#endif /* !__ASSEMBLY__ */
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#endif /* __ASM_VDSO_GETRANDOM_H */
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