From: Alistair Francis <alistair23@gmail.com>
To: Arnd Bergmann <arnd@arndb.de>, GNU C Library <libc-alpha@sourceware.org>
Cc: Alistair Francis <alistair.francis@wdc.com>,
Lukasz Majewski <lukma@denx.de>
Subject: 32-bit time_t inside itimerval
Date: Fri, 20 Dec 2019 14:28:46 -0800 [thread overview]
Message-ID: <CAKmqyKPki9K3JwYT4zn7JaAZHFW8UO7ztS2D=US3ccnTd-KAwA@mail.gmail.com> (raw)
Hey,
I just noticed something strange.
The setitimer syscall is not different for 32/64-bit time_t. So we use
this syscall for both 32/64 time_t [1]
SYSCALL_DEFINE3(setitimer, int, which, struct itimerval __user *, value,
struct itimerval __user *, ovalue)
Where struct itimerval __user *, value looks like this [2]:
struct itimerval {
struct timeval it_interval; /* timer interval */
struct timeval it_value; /* current value */
};
Which then uses this structure for timeval [3]:
struct timeval {
__kernel_old_time_t tv_sec; /* seconds */
__kernel_suseconds_t tv_usec; /* microseconds */
};
And __kernel_old_time_t is defined [4] as:
typedef __kernel_long_t __kernel_old_time_t;
typedef __kernel_long_t __kernel_time_t;
So __kernel_old_time_t and __kernel_time_t are both 32-bit values
inside the kernel. and the setiimer syscall expects a 32-bit time_t
for the values inside it.
This is different to the current glibc implementation where all time_t
values are treated as 64-bit for RISC-V [5].
What should we do here?
1. Change glibc to use a 32-bit time_t for some structures, such as
the timeval inside itimerval?
2. Convert the kernel time_t to be 64-bit for RV32?
Alistair
1: https://github.com/torvalds/linux/blob/ceb307474506f888e8f16dab183405ff01dffa08/kernel/time/itimer.c#L336
2: https://github.com/torvalds/linux/blob/b01d7cb41ff51b7779977de601a984406e2a5ba9/include/uapi/linux/time.h#L39
3: https://github.com/torvalds/linux/blob/b01d7cb41ff51b7779977de601a984406e2a5ba9/include/uapi/linux/time.h#L16
4: https://github.com/torvalds/linux/blob/b01d7cb41ff51b7779977de601a984406e2a5ba9/include/uapi/asm-generic/posix_types.h#L89
5: https://github.com/alistair23/glibc/commit/71faeb322c4f4a163d138893b6855920dad45e07
next reply other threads:[~2019-12-20 22:35 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-12-20 22:28 Alistair Francis [this message]
2019-12-21 13:31 ` 32-bit time_t inside itimerval Arnd Bergmann
2019-12-21 17:18 ` Alistair Francis
2019-12-30 10:02 ` Arnd Bergmann
2019-12-30 19:51 ` Alistair Francis
2019-12-30 20:11 ` Arnd Bergmann
2019-12-30 21:16 ` Alistair Francis
2019-12-30 22:11 ` Arnd Bergmann
2020-01-02 12:08 ` Lukasz Majewski
2020-01-02 12:28 ` Arnd Bergmann
2020-01-04 18:03 ` Alistair Francis
2020-01-05 16:07 ` Lukasz Majewski
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