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SubjectRe: [patch 4/5] x86/vdso/32: Use 32bit syscall fallback
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On 28/07/2019 14:12, Thomas Gleixner wrote:
> The generic VDSO implementation uses the Y2038 safe clock_gettime64() and
> clock_getres_time64() syscalls as fallback for 32bit VDSO. This breaks
> seccomp setups because these syscalls might be not (yet) allowed.
>
> Implement the 32bit variants which use the legacy syscalls and select the
> variant in the core library.
>
> The 64bit time variants are not removed because they are required for the
> time64 based vdso accessors.
>

Reviewed-by: Vincenzo Frascino <vincenzo.frascino@arm.com>

> Reported-by: Sean Christopherson <sean.j.christopherson@intel.com>
> Reported-by: Paul Bolle <pebolle@tiscali.nl>
> Suggested-by: Andy Lutomirski <luto@kernel.org>
> Fixes: 7ac870747988 ("x86/vdso: Switch to generic vDSO implementation")
> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
> ---
> arch/x86/include/asm/vdso/gettimeofday.h | 36 +++++++++++++++++++++++++++++++
> 1 file changed, 36 insertions(+)
>
> --- a/arch/x86/include/asm/vdso/gettimeofday.h
> +++ b/arch/x86/include/asm/vdso/gettimeofday.h
> @@ -96,6 +96,8 @@ long clock_getres_fallback(clockid_t _cl
>
> #else
>
> +#define VDSO_HAS_32BIT_FALLBACK 1
> +
> static __always_inline
> long clock_gettime_fallback(clockid_t _clkid, struct __kernel_timespec *_ts)
> {
> @@ -114,6 +116,23 @@ long clock_gettime_fallback(clockid_t _c
> }
>
> static __always_inline
> +long clock_gettime32_fallback(clockid_t _clkid, struct old_timespec32 *_ts)
> +{
> + long ret;
> +
> + asm (
> + "mov %%ebx, %%edx \n"
> + "mov %[clock], %%ebx \n"
> + "call __kernel_vsyscall \n"
> + "mov %%edx, %%ebx \n"
> + : "=a" (ret), "=m" (*_ts)
> + : "0" (__NR_clock_gettime), [clock] "g" (_clkid), "c" (_ts)
> + : "edx");
> +
> + return ret;
> +}
> +
> +static __always_inline
> long gettimeofday_fallback(struct __kernel_old_timeval *_tv,
> struct timezone *_tz)
> {
> @@ -146,6 +165,23 @@ clock_getres_fallback(clockid_t _clkid,
> : "edx");
>
> return ret;
> +}
> +
> +static __always_inline
> +long clock_getres32_fallback(clockid_t _clkid, struct old_timespec32 *_ts)
> +{
> + long ret;
> +
> + asm (
> + "mov %%ebx, %%edx \n"
> + "mov %[clock], %%ebx \n"
> + "call __kernel_vsyscall \n"
> + "mov %%edx, %%ebx \n"
> + : "=a" (ret), "=m" (*_ts)
> + : "0" (__NR_clock_getres), [clock] "g" (_clkid), "c" (_ts)
> + : "edx");
> +
> + return ret;
> }
>
> #endif
>
>

--
Regards,
Vincenzo

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