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hwclock: fix musl breakage of settimeofday(tz)

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function                                             old     new   delta
set_kernel_timezone_and_clock                          -     119    +119
set_kernel_tz                                          -      28     +28
hwclock_main                                         480     301    -179
------------------------------------------------------------------------------
(add/remove: 2/0 grow/shrink: 0/1 up/down: 147/-179)          Total: -32 bytes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
This commit is contained in:
Denys Vlasenko 2020-12-16 13:49:10 +01:00
parent a97a795dcb
commit 9e262f13c2
1 changed files with 75 additions and 53 deletions
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128
util-linux/hwclock.c
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@ -36,6 +36,19 @@
#include <sys/utsname.h>
#include "rtc_.h"
//musl has no __MUSL__ or similar define to check for,
//but its <sys/types.h> has these lines:
// #define __NEED_fsblkcnt_t
// #define __NEED_fsfilcnt_t
#if defined(__linux__) && defined(__NEED_fsblkcnt_t) && defined(__NEED_fsfilcnt_t)
# define LIBC_IS_MUSL 1
# include <sys/syscall.h>
#else
# define LIBC_IS_MUSL 0
#endif
/* diff code is disabled: it's not sys/hw clock diff, it's some useless
* "time between hwclock was started and we saw CMOS tick" quantity.
* It's useless since hwclock is started at a random moment,
@ -116,26 +129,73 @@ static void show_clock(const char **pp_rtcname, int utc)
#endif
}
static void set_kernel_tz(const struct timezone *tz)
{
#if LIBC_IS_MUSL
/* musl libc does not pass tz argument to syscall
* because "it's deprecated by POSIX, therefore it's fine
* if we gratuitously break stuff" :(
*/
#if !defined(SYS_settimeofday) && defined(SYS_settimeofday_time32)
# define SYS_settimeofday SYS_settimeofday_time32
#endif
int ret = syscall(SYS_settimeofday, NULL, tz);
#else
int ret = settimeofday(NULL, tz);
#endif
if (ret)
bb_simple_perror_msg_and_die("settimeofday");
}
/*
* At system boot, kernel may set system time from RTC,
* but it knows nothing about timezones. If RTC is in local time,
* then system time is wrong - it is offset by timezone.
* --systz option corrects system time if RTC is in local time,
* and (always) sets in-kernel timezone.
*
* This is an alternate option to --hctosys that does not read the
* hardware clock.
*
* util-linux's code has this comment:
* RTC | settimeofday calls
* ------|-------------------------------------------------
* Local | 1) warps system time*, sets PCIL* and kernel tz
* UTC | 1st) locks warp_clock 2nd) sets kernel tz
* * only on first call after boot
* (PCIL is "persistent_clock_is_local" kernel internal flag,
* it makes kernel save RTC in local time, not UTC.)
*/
static void set_kernel_timezone_and_clock(int utc, const struct timeval *hctosys)
{
time_t cur;
struct tm *broken;
struct timezone tz = { 0 };
/* if --utc, prevent kernel's warp_clock() with a dummy call */
if (utc)
set_kernel_tz(&tz);
/* Set kernel's timezone offset based on userspace one */
cur = time(NULL);
broken = localtime(&cur);
tz.tz_minuteswest = -broken->tm_gmtoff / 60;
/*tz.tz_dsttime = 0; already is */
set_kernel_tz(&tz); /* MIGHT warp_clock() if 1st call since boot */
if (hctosys) { /* it's --hctosys: set time too */
if (settimeofday(hctosys, NULL))
bb_simple_perror_msg_and_die("settimeofday");
}
}
static void to_sys_clock(const char **pp_rtcname, int utc)
{
struct timeval tv;
struct timezone tz;
tz.tz_minuteswest = timezone / 60;
/* ^^^ used to also subtract 60*daylight, but it's wrong:
* daylight!=0 means "this timezone has some DST
* during the year", not "DST is in effect now".
*/
tz.tz_dsttime = 0;
/* glibc v2.31+ returns an error if both args are non-NULL */
if (settimeofday(NULL, &tz))
bb_simple_perror_msg_and_die("settimeofday");
tv.tv_sec = read_rtc(pp_rtcname, NULL, utc);
tv.tv_usec = 0;
if (settimeofday(&tv, NULL))
bb_simple_perror_msg_and_die("settimeofday");
return set_kernel_timezone_and_clock(utc, &tv);
}
static void from_sys_clock(const char **pp_rtcname, int utc)
@ -261,39 +321,6 @@ static void from_sys_clock(const char **pp_rtcname, int utc)
close(rtc);
}
/*
* At system boot, kernel may set system time from RTC,
* but it knows nothing about timezones. If RTC is in local time,
* then system time is wrong - it is offset by timezone.
* This option corrects system time if RTC is in local time,
* and (always) sets in-kernel timezone.
*
* This is an alternate option to --hctosys that does not read the
* hardware clock.
*/
static void set_system_clock_timezone(int utc)
{
struct timeval tv;
struct tm *broken;
struct timezone tz;
gettimeofday(&tv, NULL);
broken = localtime(&tv.tv_sec);
tz.tz_minuteswest = timezone / 60;
if (broken->tm_isdst > 0)
tz.tz_minuteswest -= 60;
tz.tz_dsttime = 0;
gettimeofday(&tv, NULL);
if (!utc)
tv.tv_sec += tz.tz_minuteswest * 60;
/* glibc v2.31+ returns an error if both args are non-NULL */
if (settimeofday(NULL, &tz))
bb_simple_perror_msg_and_die("settimeofday");
if (settimeofday(&tv, NULL))
bb_simple_perror_msg_and_die("settimeofday");
}
//usage:#define hwclock_trivial_usage
//usage: IF_LONG_OPTS(
//usage: "[-swu] [--systz] [--localtime] [-f FILE]"
@ -333,7 +360,6 @@ int hwclock_main(int argc UNUSED_PARAM, char **argv)
const char *rtcname = NULL;
unsigned opt;
int utc;
#if ENABLE_LONG_OPTS
static const char hwclock_longopts[] ALIGN1 =
"localtime\0" No_argument "l" /* short opt is non-standard */
@ -345,10 +371,6 @@ int hwclock_main(int argc UNUSED_PARAM, char **argv)
"rtc\0" Required_argument "f"
;
#endif
/* Initialize "timezone" (libc global variable) */
tzset();
opt = getopt32long(argv,
"^lurswtf:" "\0" "r--wst:w--rst:s--wrt:t--rsw:l--u:u--l",
hwclock_longopts,
@ -366,7 +388,7 @@ int hwclock_main(int argc UNUSED_PARAM, char **argv)
else if (opt & HWCLOCK_OPT_SYSTOHC)
from_sys_clock(&rtcname, utc);
else if (opt & HWCLOCK_OPT_SYSTZ)
set_system_clock_timezone(utc);
set_kernel_timezone_and_clock(utc, NULL);
else
/* default HWCLOCK_OPT_SHOW */
show_clock(&rtcname, utc);