// SPDX-License-Identifier: GPL-2.0 /* * linux/kernel/acct.c * * BSD Process Accounting for Linux * * Author: Marco van Wieringen <[email protected]> * * Some code based on ideas and code from: * Thomas K. Dyas <[email protected]> * * This file implements BSD-style process accounting. Whenever any * process exits, an accounting record of type "struct acct" is * written to the file specified with the acct() system call. It is * up to user-level programs to do useful things with the accounting * log. The kernel just provides the raw accounting information. * * (C) Copyright 1995 - 1997 Marco van Wieringen - ELM Consultancy B.V. * * Plugged two leaks. 1) It didn't return acct_file into the free_filps if * the file happened to be read-only. 2) If the accounting was suspended * due to the lack of space it happily allowed to reopen it and completely * lost the old acct_file. 3/10/98, Al Viro. * * Now we silently close acct_file on attempt to reopen. Cleaned sys_acct(). * XTerms and EMACS are manifestations of pure evil. 21/10/98, AV. * * Fixed a nasty interaction with sys_umount(). If the accounting * was suspeneded we failed to stop it on umount(). Messy. * Another one: remount to readonly didn't stop accounting. * Question: what should we do if we have CAP_SYS_ADMIN but not * CAP_SYS_PACCT? Current code does the following: umount returns -EBUSY * unless we are messing with the root. In that case we are getting a * real mess with do_remount_sb(). 9/11/98, AV. * * Fixed a bunch of races (and pair of leaks). Probably not the best way, * but this one obviously doesn't introduce deadlocks. Later. BTW, found * one race (and leak) in BSD implementation. * OK, that's better. ANOTHER race and leak in BSD variant. There always * is one more bug... 10/11/98, AV. * * Oh, fsck... Oopsable SMP race in do_process_acct() - we must hold * ->mmap_lock to walk the vma list of current->mm. Nasty, since it leaks * a struct file opened for write. Fixed. 2/6/2000, AV. */ #include <linux/mm.h> #include <linux/slab.h> #include <linux/acct.h> #include <linux/capability.h> #include <linux/file.h> #include <linux/tty.h> #include <linux/security.h> #include <linux/vfs.h> #include <linux/jiffies.h> #include <linux/times.h> #include <linux/syscalls.h> #include <linux/mount.h> #include <linux/uaccess.h> #include <linux/sched/cputime.h> #include <asm/div64.h> #include <linux/pid_namespace.h> #include <linux/fs_pin.h> /* * These constants control the amount of freespace that suspend and * resume the process accounting system, and the time delay between * each check. * Turned into sysctl-controllable parameters. AV, 12/11/98 */ static int acct_parm[3] = …; #define RESUME … #define SUSPEND … #define ACCT_TIMEOUT … #ifdef CONFIG_SYSCTL static struct ctl_table kern_acct_table[] = …; static __init int kernel_acct_sysctls_init(void) { … } late_initcall(kernel_acct_sysctls_init); #endif /* CONFIG_SYSCTL */ /* * External references and all of the globals. */ struct bsd_acct_struct { … }; static void do_acct_process(struct bsd_acct_struct *acct); /* * Check the amount of free space and suspend/resume accordingly. */ static int check_free_space(struct bsd_acct_struct *acct) { … } static void acct_put(struct bsd_acct_struct *p) { … } static inline struct bsd_acct_struct *to_acct(struct fs_pin *p) { … } static struct bsd_acct_struct *acct_get(struct pid_namespace *ns) { … } static void acct_pin_kill(struct fs_pin *pin) { … } static void close_work(struct work_struct *work) { … } static int acct_on(struct filename *pathname) { … } static DEFINE_MUTEX(acct_on_mutex); /** * sys_acct - enable/disable process accounting * @name: file name for accounting records or NULL to shutdown accounting * * sys_acct() is the only system call needed to implement process * accounting. It takes the name of the file where accounting records * should be written. If the filename is NULL, accounting will be * shutdown. * * Returns: 0 for success or negative errno values for failure. */ SYSCALL_DEFINE1(acct, const char __user *, name) { … } void acct_exit_ns(struct pid_namespace *ns) { … } /* * encode an u64 into a comp_t * * This routine has been adopted from the encode_comp_t() function in * the kern_acct.c file of the FreeBSD operating system. The encoding * is a 13-bit fraction with a 3-bit (base 8) exponent. */ #define MANTSIZE … #define EXPSIZE … #define MAXFRACT … static comp_t encode_comp_t(u64 value) { … } #if ACCT_VERSION == 1 || ACCT_VERSION == 2 /* * encode an u64 into a comp2_t (24 bits) * * Format: 5 bit base 2 exponent, 20 bits mantissa. * The leading bit of the mantissa is not stored, but implied for * non-zero exponents. * Largest encodable value is 50 bits. */ #define MANTSIZE2 … #define EXPSIZE2 … #define MAXFRACT2 … #define MAXEXP2 … static comp2_t encode_comp2_t(u64 value) { int exp, rnd; exp = (value > (MAXFRACT2>>1)); rnd = 0; while (value > MAXFRACT2) { rnd = value & 1; value >>= 1; exp++; } /* * If we need to round up, do it (and handle overflow correctly). */ if (rnd && (++value > MAXFRACT2)) { value >>= 1; exp++; } if (exp > MAXEXP2) { /* Overflow. Return largest representable number instead. */ return (1ul << (MANTSIZE2+EXPSIZE2-1)) - 1; } else { return (value & (MAXFRACT2>>1)) | (exp << (MANTSIZE2-1)); } } #elif ACCT_VERSION == 3 /* * encode an u64 into a 32 bit IEEE float */ static u32 encode_float(u64 value) { … } #endif /* * Write an accounting entry for an exiting process * * The acct_process() call is the workhorse of the process * accounting system. The struct acct is built here and then written * into the accounting file. This function should only be called from * do_exit() or when switching to a different output file. */ static void fill_ac(acct_t *ac) { … } /* * do_acct_process does all actual work. Caller holds the reference to file. */ static void do_acct_process(struct bsd_acct_struct *acct) { … } /** * acct_collect - collect accounting information into pacct_struct * @exitcode: task exit code * @group_dead: not 0, if this thread is the last one in the process. */ void acct_collect(long exitcode, int group_dead) { … } static void slow_acct_process(struct pid_namespace *ns) { … } /** * acct_process - handles process accounting for an exiting task */ void acct_process(void) { … }
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