| Message ID | 20220125024712.6626-1-dirty@apple.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | linux-user: Implement starttime field in self stat emulation | expand |
Le 25/01/2022 à 03:47, Cameron Esfahani a écrit : > Instead of always returning 0, return actual starttime. > > Signed-off-by: Cameron Esfahani <dirty@apple.com> > --- > linux-user/syscall.c | 28 ++++++++++++++++++++++++++++ > 1 file changed, 28 insertions(+) > > diff --git a/linux-user/syscall.c b/linux-user/syscall.c > index 5950222a77..59265ab986 100644 > --- a/linux-user/syscall.c > +++ b/linux-user/syscall.c > @@ -8107,6 +8107,34 @@ static int open_self_stat(void *cpu_env, int fd) > } else if (i == 3) { > /* ppid */ > g_string_printf(buf, FMT_pid " ", getppid()); > + } else if (i == 21) { > + /* starttime */ > + FILE *fp = NULL; > + char *line = NULL; > + char *skipped_comm = NULL; > + size_t n = 0; > + unsigned long long starttime = 0; > + > + fp = fopen("/proc/self/stat", "r"); > + if (fp) { > + if (getdelim(&line, &n, '\0', fp) != -1) { > + /* Find end of comm field */ > + skipped_comm = strrchr(line, ')'); > + if (skipped_comm != NULL) { > + /* Skip over parenthesis and space */ > + skipped_comm += 2; > + /* Scan starttime (field 20 after pid and comm) */ > + (void) sscanf(skipped_comm, "%*c %*d %*d %*d %*d %*d " > + "%*u %*u %*u %*u %*u %*u %*u %*d " > + "%*d %*d %*d %*d %*d %llu", > + &starttime); > + } > + free(line); > + } > + fclose(fp); > + } > + > + g_string_printf(buf, "%llu ", starttime); According to the kernel code: start_time = nsec_to_clock_t(timens_add_boottime_ns(task->start_boottime)); (timens_add_boottime_ns() is to adjust time offset according to the namespace) (nsec_to_clock_t() is "div_u64(x, NSEC_PER_SEC / USER_HZ);") and p->start_boottime = ktime_get_boottime_ns(); ... static inline u64 ktime_get_boottime_ns(void) { return ktime_to_ns(ktime_get_boottime()); } ... /** * ktime_get_boottime - Returns monotonic time since boot in ktime_t format * * This is similar to CLOCK_MONTONIC/ktime_get, but also includes the * time spent in suspend. */ static inline ktime_t ktime_get_boottime(void) { return ktime_get_with_offset(TK_OFFS_BOOT); } So I think rather than scanning /proc/self/stat you could use clock_gettime(CLOCK_BOOTTIME, ...) to get the value. https://linux.die.net/man/2/clock_gettime CLOCK_BOOTTIME (since Linux 2.6.39; Linux-specific) Identical to CLOCK_MONOTONIC, except it also includes any time that the system is suspended. This allows applications to get a suspend-aware monotonic clock without having to deal with the complications of CLOCK_REALTIME, which may have discontinuities if the time is changed using settimeofday(2). https://man7.org/linux/man-pages/man5/proc.5.html /proc/[pid]/stat ... (22) starttime %llu The time the process started after system boot. In kernels before Linux 2.6, this value was expressed in jiffies. Since Linux 2.6, the value is expressed in clock ticks (divide by sysconf(_SC_CLK_TCK)). The format for this field was %lu before Linux 2.6. > } else if (i == 27) { > /* stack bottom */ > g_string_printf(buf, TARGET_ABI_FMT_ld " ", ts->info->start_stack); Thanks, Laurent
Le 25/01/2022 à 10:41, Laurent Vivier a écrit : > Le 25/01/2022 à 03:47, Cameron Esfahani a écrit : >> Instead of always returning 0, return actual starttime. >> >> Signed-off-by: Cameron Esfahani <dirty@apple.com> >> --- >> linux-user/syscall.c | 28 ++++++++++++++++++++++++++++ >> 1 file changed, 28 insertions(+) >> >> diff --git a/linux-user/syscall.c b/linux-user/syscall.c >> index 5950222a77..59265ab986 100644 >> --- a/linux-user/syscall.c >> +++ b/linux-user/syscall.c >> @@ -8107,6 +8107,34 @@ static int open_self_stat(void *cpu_env, int fd) >> } else if (i == 3) { >> /* ppid */ >> g_string_printf(buf, FMT_pid " ", getppid()); >> + } else if (i == 21) { > + /* starttime */ >> + FILE *fp = NULL; >> + char *line = NULL; >> + char *skipped_comm = NULL; >> + size_t n = 0; >> + unsigned long long starttime = 0; >> + >> + fp = fopen("/proc/self/stat", "r"); >> + if (fp) { >> + if (getdelim(&line, &n, '\0', fp) != -1) { >> + /* Find end of comm field */ >> + skipped_comm = strrchr(line, ')'); >> + if (skipped_comm != NULL) { >> + /* Skip over parenthesis and space */ >> + skipped_comm += 2; >> + /* Scan starttime (field 20 after pid and comm) */ >> + (void) sscanf(skipped_comm, "%*c %*d %*d %*d %*d %*d " >> + "%*u %*u %*u %*u %*u %*u %*u %*d " >> + "%*d %*d %*d %*d %*d %llu", >> + &starttime); >> + } >> + free(line); >> + } >> + fclose(fp); >> + } >> + >> + g_string_printf(buf, "%llu ", starttime); > > According to the kernel code: > > start_time = nsec_to_clock_t(timens_add_boottime_ns(task->start_boottime)); > > (timens_add_boottime_ns() is to adjust time offset according to the namespace) > (nsec_to_clock_t() is "div_u64(x, NSEC_PER_SEC / USER_HZ);") > > and > > p->start_boottime = ktime_get_boottime_ns(); > ... > static inline u64 ktime_get_boottime_ns(void) > { > return ktime_to_ns(ktime_get_boottime()); > } > ... > /** > * ktime_get_boottime - Returns monotonic time since boot in ktime_t format > * > * This is similar to CLOCK_MONTONIC/ktime_get, but also includes the > * time spent in suspend. > */ > static inline ktime_t ktime_get_boottime(void) > { > return ktime_get_with_offset(TK_OFFS_BOOT); > } > > So I think rather than scanning /proc/self/stat you could use clock_gettime(CLOCK_BOOTTIME, ...) to > get the value. > > https://linux.die.net/man/2/clock_gettime > > CLOCK_BOOTTIME (since Linux 2.6.39; Linux-specific) > > Identical to CLOCK_MONOTONIC, except it also includes any time that the system is suspended. > This allows applications to get a suspend-aware monotonic clock without having to deal with > the complications of CLOCK_REALTIME, which may have discontinuities if the time is changed > using settimeofday(2). > > https://man7.org/linux/man-pages/man5/proc.5.html > > /proc/[pid]/stat > ... > (22) starttime %llu > > The time the process started after system boot. In > kernels before Linux 2.6, this value was expressed > in jiffies. Since Linux 2.6, the value is > expressed in clock ticks (divide by > sysconf(_SC_CLK_TCK)). > > The format for this field was %lu before Linux 2.6. > >> } else if (i == 27) { >> /* stack bottom */ >> g_string_printf(buf, TARGET_ABI_FMT_ld " ", ts->info->start_stack); > and we could add a field in TaskState (start_boottime) to set the bootime value in init_task_state() when the task is started and to read it in open_self_stat(). Thanks, Laurent
diff --git a/linux-user/syscall.c b/linux-user/syscall.c index 5950222a77..59265ab986 100644 --- a/linux-user/syscall.c +++ b/linux-user/syscall.c @@ -8107,6 +8107,34 @@ static int open_self_stat(void *cpu_env, int fd) } else if (i == 3) { /* ppid */ g_string_printf(buf, FMT_pid " ", getppid()); + } else if (i == 21) { + /* starttime */ + FILE *fp = NULL; + char *line = NULL; + char *skipped_comm = NULL; + size_t n = 0; + unsigned long long starttime = 0; + + fp = fopen("/proc/self/stat", "r"); + if (fp) { + if (getdelim(&line, &n, '\0', fp) != -1) { + /* Find end of comm field */ + skipped_comm = strrchr(line, ')'); + if (skipped_comm != NULL) { + /* Skip over parenthesis and space */ + skipped_comm += 2; + /* Scan starttime (field 20 after pid and comm) */ + (void) sscanf(skipped_comm, "%*c %*d %*d %*d %*d %*d " + "%*u %*u %*u %*u %*u %*u %*u %*d " + "%*d %*d %*d %*d %*d %llu", + &starttime); + } + free(line); + } + fclose(fp); + } + + g_string_printf(buf, "%llu ", starttime); } else if (i == 27) { /* stack bottom */ g_string_printf(buf, TARGET_ABI_FMT_ld " ", ts->info->start_stack);
Instead of always returning 0, return actual starttime. Signed-off-by: Cameron Esfahani <dirty@apple.com> --- linux-user/syscall.c | 28 ++++++++++++++++++++++++++++ 1 file changed, 28 insertions(+)