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Linux kernel mirror (for testing) git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
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/* * Restartable sequences are a lightweight interface that allows * user-level code to be executed atomically relative to scheduler * preemption and signal delivery. Typically used for implementing * per-cpu operations. * * It allows user-space to perform update operations on per-cpu data * without requiring heavy-weight atomic operations. * * Detailed algorithm of rseq user-space assembly sequences: * * init(rseq_cs) * cpu = TLS->rseq::cpu_id_start * [1] TLS->rseq::rseq_cs = rseq_cs * [start_ip] ---------------------------- * [2] if (cpu != TLS->rseq::cpu_id) * goto abort_ip; * [3] <last_instruction_in_cs> * [post_commit_ip] ---------------------------- * * The address of jump target abort_ip must be outside the critical * region, i.e.: * * [abort_ip] < [start_ip] || [abort_ip] >= [post_commit_ip] * * Steps [2]-[3] (inclusive) need to be a sequence of instructions in * userspace that can handle being interrupted between any of those * instructions, and then resumed to the abort_ip. * * 1. Userspace stores the address of the struct rseq_cs assembly * block descriptor into the rseq_cs field of the registered * struct rseq TLS area. This update is performed through a single * store within the inline assembly instruction sequence. * [start_ip] * * 2. Userspace tests to check whether the current cpu_id field match * the cpu number loaded before start_ip, branching to abort_ip * in case of a mismatch. * * If the sequence is preempted or interrupted by a signal * at or after start_ip and before post_commit_ip, then the kernel * clears TLS->__rseq_abi::rseq_cs, and sets the user-space return * ip to abort_ip before returning to user-space, so the preempted * execution resumes at abort_ip. * * 3. Userspace critical section final instruction before * post_commit_ip is the commit. The critical section is * self-terminating. * [post_commit_ip] * * 4. <success> * * On failure at [2], or if interrupted by preempt or signal delivery * between [1] and [3]: * * [abort_ip] * F1. <failure> */
/* Required to select the proper per_cpu ops for rseq_stats_inc() */#define RSEQ_BUILD_SLOW_PATH
#include <linux/debugfs.h>#include <linux/hrtimer.h>#include <linux/percpu.h>#include <linux/prctl.h>#include <linux/ratelimit.h>#include <linux/rseq_entry.h>#include <linux/sched.h>#include <linux/syscalls.h>#include <linux/uaccess.h>#include <linux/types.h>#include <linux/rseq.h>#include <asm/ptrace.h>
#define CREATE_TRACE_POINTS#include <trace/events/rseq.h>
DEFINE_STATIC_KEY_MAYBE(CONFIG_RSEQ_DEBUG_DEFAULT_ENABLE, rseq_debug_enabled);
static inline void rseq_control_debug(bool on){ if (on) static_branch_enable(&rseq_debug_enabled); else static_branch_disable(&rseq_debug_enabled);}
static int __init rseq_setup_debug(char *str){ bool on;
if (kstrtobool(str, &on)) return -EINVAL; rseq_control_debug(on); return 1;}__setup("rseq_debug=", rseq_setup_debug);
#ifdef CONFIG_TRACEPOINTS/* * Out of line, so the actual update functions can be in a header to be * inlined into the exit to user code. */void __rseq_trace_update(struct task_struct *t){ trace_rseq_update(t);}
void __rseq_trace_ip_fixup(unsigned long ip, unsigned long start_ip, unsigned long offset, unsigned long abort_ip){ trace_rseq_ip_fixup(ip, start_ip, offset, abort_ip);}#endif /* CONFIG_TRACEPOINTS */
#ifdef CONFIG_RSEQ_STATSDEFINE_PER_CPU(struct rseq_stats, rseq_stats);
static int rseq_stats_show(struct seq_file *m, void *p){ struct rseq_stats stats = { }; unsigned int cpu;
for_each_possible_cpu(cpu) { stats.exit += data_race(per_cpu(rseq_stats.exit, cpu)); stats.signal += data_race(per_cpu(rseq_stats.signal, cpu)); stats.slowpath += data_race(per_cpu(rseq_stats.slowpath, cpu)); stats.fastpath += data_race(per_cpu(rseq_stats.fastpath, cpu)); stats.ids += data_race(per_cpu(rseq_stats.ids, cpu)); stats.cs += data_race(per_cpu(rseq_stats.cs, cpu)); stats.clear += data_race(per_cpu(rseq_stats.clear, cpu)); stats.fixup += data_race(per_cpu(rseq_stats.fixup, cpu)); if (IS_ENABLED(CONFIG_RSEQ_SLICE_EXTENSION)) { stats.s_granted += data_race(per_cpu(rseq_stats.s_granted, cpu)); stats.s_expired += data_race(per_cpu(rseq_stats.s_expired, cpu)); stats.s_revoked += data_race(per_cpu(rseq_stats.s_revoked, cpu)); stats.s_yielded += data_race(per_cpu(rseq_stats.s_yielded, cpu)); stats.s_aborted += data_race(per_cpu(rseq_stats.s_aborted, cpu)); } }
seq_printf(m, "exit: %16lu\n", stats.exit); seq_printf(m, "signal: %16lu\n", stats.signal); seq_printf(m, "slowp: %16lu\n", stats.slowpath); seq_printf(m, "fastp: %16lu\n", stats.fastpath); seq_printf(m, "ids: %16lu\n", stats.ids); seq_printf(m, "cs: %16lu\n", stats.cs); seq_printf(m, "clear: %16lu\n", stats.clear); seq_printf(m, "fixup: %16lu\n", stats.fixup); if (IS_ENABLED(CONFIG_RSEQ_SLICE_EXTENSION)) { seq_printf(m, "sgrant: %16lu\n", stats.s_granted); seq_printf(m, "sexpir: %16lu\n", stats.s_expired); seq_printf(m, "srevok: %16lu\n", stats.s_revoked); seq_printf(m, "syield: %16lu\n", stats.s_yielded); seq_printf(m, "sabort: %16lu\n", stats.s_aborted); } return 0;}
static int rseq_stats_open(struct inode *inode, struct file *file){ return single_open(file, rseq_stats_show, inode->i_private);}
static const struct file_operations stat_ops = { .open = rseq_stats_open, .read = seq_read, .llseek = seq_lseek, .release = single_release,};
static int __init rseq_stats_init(struct dentry *root_dir){ debugfs_create_file("stats", 0444, root_dir, NULL, &stat_ops); return 0;}#elsestatic inline void rseq_stats_init(struct dentry *root_dir) { }#endif /* CONFIG_RSEQ_STATS */
static int rseq_debug_show(struct seq_file *m, void *p){ bool on = static_branch_unlikely(&rseq_debug_enabled);
seq_printf(m, "%d\n", on); return 0;}
static ssize_t rseq_debug_write(struct file *file, const char __user *ubuf, size_t count, loff_t *ppos){ bool on;
if (kstrtobool_from_user(ubuf, count, &on)) return -EINVAL;
rseq_control_debug(on); return count;}
static int rseq_debug_open(struct inode *inode, struct file *file){ return single_open(file, rseq_debug_show, inode->i_private);}
static const struct file_operations debug_ops = { .open = rseq_debug_open, .read = seq_read, .write = rseq_debug_write, .llseek = seq_lseek, .release = single_release,};
static void rseq_slice_ext_init(struct dentry *root_dir);
static int __init rseq_debugfs_init(void){ struct dentry *root_dir = debugfs_create_dir("rseq", NULL);
debugfs_create_file("debug", 0644, root_dir, NULL, &debug_ops); rseq_stats_init(root_dir); if (IS_ENABLED(CONFIG_RSEQ_SLICE_EXTENSION)) rseq_slice_ext_init(root_dir); return 0;}__initcall(rseq_debugfs_init);
static bool rseq_handle_cs(struct task_struct *t, struct pt_regs *regs){ struct rseq __user *urseq = t->rseq.usrptr; u64 csaddr;
scoped_user_read_access(urseq, efault) unsafe_get_user(csaddr, &urseq->rseq_cs, efault); if (likely(!csaddr)) return true; return rseq_update_user_cs(t, regs, csaddr);efault: return false;}
static void rseq_slowpath_update_usr(struct pt_regs *regs){ /* * Preserve has_rseq and user_irq state. The generic entry code clears * user_irq on the way out, the non-generic entry architectures are not * setting user_irq. */ const struct rseq_event evt_mask = { .has_rseq = RSEQ_HAS_RSEQ_VERSION_MASK, .user_irq = true, }; struct task_struct *t = current; struct rseq_ids ids; bool event;
if (unlikely(t->flags & PF_EXITING)) return;
rseq_stat_inc(rseq_stats.slowpath);
/* * Read and clear the event pending bit first. If the task * was not preempted or migrated or a signal is on the way, * there is no point in doing any of the heavy lifting here * on production kernels. In that case TIF_NOTIFY_RESUME * was raised by some other functionality. * * This is correct because the read/clear operation is * guarded against scheduler preemption, which makes it CPU * local atomic. If the task is preempted right after * re-enabling preemption then TIF_NOTIFY_RESUME is set * again and this function is invoked another time _before_ * the task is able to return to user mode. * * On a debug kernel, invoke the fixup code unconditionally * with the result handed in to allow the detection of * inconsistencies. */ scoped_guard(irq) { event = t->rseq.event.sched_switch; t->rseq.event.all &= evt_mask.all; ids.cpu_id = task_cpu(t); ids.mm_cid = task_mm_cid(t); }
if (!event) return;
ids.node_id = cpu_to_node(ids.cpu_id);
if (unlikely(!rseq_update_usr(t, regs, &ids))) { /* * Clear the errors just in case this might survive magically, but * leave the rest intact. */ t->rseq.event.error = 0; force_sig(SIGSEGV); }}
void __rseq_handle_slowpath(struct pt_regs *regs){ /* * If invoked from hypervisors before entering the guest via * resume_user_mode_work(), then @regs is a NULL pointer. * * resume_user_mode_work() clears TIF_NOTIFY_RESUME and re-raises * it before returning from the ioctl() to user space when * rseq_event.sched_switch is set. * * So it's safe to ignore here instead of pointlessly updating it * in the vcpu_run() loop. */ if (!regs) return;
rseq_slowpath_update_usr(regs);}
void __rseq_signal_deliver(int sig, struct pt_regs *regs){ rseq_stat_inc(rseq_stats.signal);
/* * Don't update IDs yet, they are handled on exit to user if * necessary. The important thing is to abort a critical section of * the interrupted context as after this point the instruction * pointer in @regs points to the signal handler. */ if (unlikely(!rseq_handle_cs(current, regs))) { /* * Clear the errors just in case this might survive * magically, but leave the rest intact. */ current->rseq.event.error = 0; force_sigsegv(sig); }
/* * In legacy mode, force the update of IDs before returning to user * space to stay compatible. */ if (!rseq_v2(current)) rseq_force_update();}
/* * Terminate the process if a syscall is issued within a restartable * sequence. */void __rseq_debug_syscall_return(struct pt_regs *regs){ struct task_struct *t = current; u64 csaddr;
if (!t->rseq.event.has_rseq) return; if (get_user(csaddr, &t->rseq.usrptr->rseq_cs)) goto fail; if (likely(!csaddr)) return; if (unlikely(csaddr >= TASK_SIZE)) goto fail; if (rseq_debug_update_user_cs(t, regs, csaddr)) return;fail: force_sig(SIGSEGV);}
#ifdef CONFIG_DEBUG_RSEQ/* Kept around to keep GENERIC_ENTRY=n architectures supported. */void rseq_syscall(struct pt_regs *regs){ __rseq_debug_syscall_return(regs);}#endif
static bool rseq_reset_ids(void){ struct rseq __user *rseq = current->rseq.usrptr;
/* * If this fails, terminate it because this leaves the kernel in * stupid state as exit to user space will try to fixup the ids * again. */ scoped_user_rw_access(rseq, efault) { unsafe_put_user(0, &rseq->cpu_id_start, efault); unsafe_put_user(RSEQ_CPU_ID_UNINITIALIZED, &rseq->cpu_id, efault); unsafe_put_user(0, &rseq->node_id, efault); unsafe_put_user(0, &rseq->mm_cid, efault); } return true;
efault: force_sig(SIGSEGV); return false;}
/* The original rseq structure size (including padding) is 32 bytes. */#define ORIG_RSEQ_SIZE 32
static long rseq_register(struct rseq __user * rseq, u32 rseq_len, int flags, u32 sig){ u32 rseqfl = 0; u8 version = 1;
if (!access_ok(rseq, rseq_len)) return -EFAULT;
/* * Architectures, which use the generic IRQ entry code (at least) enable * registrations with a size greater than the original v1 fixed sized * @rseq_len, which has been validated already to utilize the optimized * v2 ABI mode which also enables extended RSEQ features beyond MMCID. */ if (IS_ENABLED(CONFIG_GENERIC_IRQ_ENTRY) && rseq_len > ORIG_RSEQ_SIZE) version = 2;
if (IS_ENABLED(CONFIG_RSEQ_SLICE_EXTENSION) && version > 1) { if (rseq_slice_extension_enabled()) { rseqfl |= RSEQ_CS_FLAG_SLICE_EXT_AVAILABLE; if (flags & RSEQ_FLAG_SLICE_EXT_DEFAULT_ON) rseqfl |= RSEQ_CS_FLAG_SLICE_EXT_ENABLED; } }
scoped_user_write_access(rseq, efault) { /* * If the rseq_cs pointer is non-NULL on registration, clear it to * avoid a potential segfault on return to user-space. The proper thing * to do would have been to fail the registration but this would break * older libcs that reuse the rseq area for new threads without * clearing the fields. Don't bother reading it, just reset it. */ unsafe_put_user(0UL, &rseq->rseq_cs, efault); unsafe_put_user(rseqfl, &rseq->flags, efault); /* Initialize IDs in user space */ unsafe_put_user(RSEQ_CPU_ID_UNINITIALIZED, &rseq->cpu_id_start, efault); unsafe_put_user(RSEQ_CPU_ID_UNINITIALIZED, &rseq->cpu_id, efault); unsafe_put_user(0U, &rseq->node_id, efault); unsafe_put_user(0U, &rseq->mm_cid, efault);
/* * All fields past mm_cid are only valid for non-legacy v2 * registrations. */ if (version > 1) { if (IS_ENABLED(CONFIG_RSEQ_SLICE_EXTENSION)) unsafe_put_user(0U, &rseq->slice_ctrl.all, efault); } }
/* * Activate the registration by setting the rseq area address, length * and signature in the task struct. */ current->rseq.usrptr = rseq; current->rseq.len = rseq_len; current->rseq.sig = sig;
#ifdef CONFIG_RSEQ_SLICE_EXTENSION current->rseq.slice.state.enabled = !!(rseqfl & RSEQ_CS_FLAG_SLICE_EXT_ENABLED);#endif
/* * Ensure the cpu_id_start and cpu_id fields are updated before * returning to user-space. */ current->rseq.event.has_rseq = version; rseq_force_update(); return 0;
efault: return -EFAULT;}
static long rseq_unregister(struct rseq __user * rseq, u32 rseq_len, int flags, u32 sig){ if (flags & ~RSEQ_FLAG_UNREGISTER) return -EINVAL; if (current->rseq.usrptr != rseq || !current->rseq.usrptr) return -EINVAL; if (rseq_len != current->rseq.len) return -EINVAL; if (current->rseq.sig != sig) return -EPERM; if (!rseq_reset_ids()) return -EFAULT; rseq_reset(current); return 0;}
static long rseq_reregister(struct rseq __user * rseq, u32 rseq_len, u32 sig){ /* * If rseq is already registered, check whether the provided address * differs from the prior one. */ if (current->rseq.usrptr != rseq || rseq_len != current->rseq.len) return -EINVAL; if (current->rseq.sig != sig) return -EPERM; /* Already registered. */ return -EBUSY;}
static bool rseq_length_valid(struct rseq __user *rseq, unsigned int rseq_len){ /* * Ensure the provided rseq is properly aligned, as communicated to * user-space through the ELF auxiliary vector AT_RSEQ_ALIGN. If * rseq_len is the original rseq size, the required alignment is the * original struct rseq alignment. * * In order to be valid, rseq_len is either the original rseq size, or * large enough to contain all supported fields, as communicated to * user-space through the ELF auxiliary vector AT_RSEQ_FEATURE_SIZE. */ if (rseq_len < ORIG_RSEQ_SIZE) return false;
if (rseq_len == ORIG_RSEQ_SIZE) return IS_ALIGNED((unsigned long)rseq, ORIG_RSEQ_SIZE);
return IS_ALIGNED((unsigned long)rseq, rseq_alloc_align()) && rseq_len >= offsetof(struct rseq, end);}
#define RSEQ_FLAGS_SUPPORTED (RSEQ_FLAG_SLICE_EXT_DEFAULT_ON)
/* * sys_rseq - Register or unregister restartable sequences for the caller thread. */SYSCALL_DEFINE4(rseq, struct rseq __user *, rseq, u32, rseq_len, int, flags, u32, sig){ if (flags & RSEQ_FLAG_UNREGISTER) return rseq_unregister(rseq, rseq_len, flags, sig);
if (unlikely(flags & ~RSEQ_FLAGS_SUPPORTED)) return -EINVAL;
if (current->rseq.usrptr) return rseq_reregister(rseq, rseq_len, sig);
if (!rseq_length_valid(rseq, rseq_len)) return -EINVAL;
return rseq_register(rseq, rseq_len, flags, sig);}
#ifdef CONFIG_RSEQ_SLICE_EXTENSIONstruct slice_timer { struct hrtimer timer; void *cookie;};
static const unsigned int rseq_slice_ext_nsecs_min = 5 * NSEC_PER_USEC;static const unsigned int rseq_slice_ext_nsecs_max = 50 * NSEC_PER_USEC;unsigned int rseq_slice_ext_nsecs __read_mostly = rseq_slice_ext_nsecs_min;static DEFINE_PER_CPU(struct slice_timer, slice_timer);DEFINE_STATIC_KEY_TRUE(rseq_slice_extension_key);
/* * When the timer expires and the task is still in user space, the return * from interrupt will revoke the grant and schedule. If the task already * entered the kernel via a syscall and the timer fires before the syscall * work was able to cancel it, then depending on the preemption model this * will either reschedule on return from interrupt or in the syscall work * below. */static enum hrtimer_restart rseq_slice_expired(struct hrtimer *tmr){ struct slice_timer *st = container_of(tmr, struct slice_timer, timer);
/* * Validate that the task which armed the timer is still on the * CPU. It could have been scheduled out without canceling the * timer. */ if (st->cookie == current && current->rseq.slice.state.granted) { rseq_stat_inc(rseq_stats.s_expired); set_need_resched_current(); } return HRTIMER_NORESTART;}
bool __rseq_arm_slice_extension_timer(void){ struct slice_timer *st = this_cpu_ptr(&slice_timer); struct task_struct *curr = current;
lockdep_assert_irqs_disabled();
/* * This check prevents a task, which got a time slice extension * granted, from exceeding the maximum scheduling latency when the * grant expired before going out to user space. Don't bother to * clear the grant here, it will be cleaned up automatically before * going out to user space after being scheduled back in. */ if ((unlikely(curr->rseq.slice.expires < ktime_get_mono_fast_ns()))) { set_need_resched_current(); return true; }
/* * Store the task pointer as a cookie for comparison in the timer * function. This is safe as the timer is CPU local and cannot be * in the expiry function at this point. */ st->cookie = curr; hrtimer_start(&st->timer, curr->rseq.slice.expires, HRTIMER_MODE_ABS_PINNED_HARD); /* Arm the syscall entry work */ set_task_syscall_work(curr, SYSCALL_RSEQ_SLICE); return false;}
static void rseq_cancel_slice_extension_timer(void){ struct slice_timer *st = this_cpu_ptr(&slice_timer);
/* * st->cookie can be safely read as preemption is disabled and the * timer is CPU local. * * As this is most probably the first expiring timer, the cancel is * expensive as it has to reprogram the hardware, but that's less * expensive than going through a full hrtimer_interrupt() cycle * for nothing. * * hrtimer_try_to_cancel() is sufficient here as the timer is CPU * local and once the hrtimer code disabled interrupts the timer * callback cannot be running. */ if (st->cookie == current) hrtimer_try_to_cancel(&st->timer);}
static inline void rseq_slice_set_need_resched(struct task_struct *curr){ /* * The interrupt guard is required to prevent inconsistent state in * this case: * * set_tsk_need_resched() * --> Interrupt * wakeup() * set_tsk_need_resched() * set_preempt_need_resched() * schedule_on_return() * clear_tsk_need_resched() * clear_preempt_need_resched() * set_preempt_need_resched() <- Inconsistent state * * This is safe vs. a remote set of TIF_NEED_RESCHED because that * only sets the already set bit and does not create inconsistent * state. */ scoped_guard(irq) set_need_resched_current();}
static void rseq_slice_validate_ctrl(u32 expected){ u32 __user *sctrl = ¤t->rseq.usrptr->slice_ctrl.all; u32 uval;
if (get_user(uval, sctrl) || uval != expected) force_sig(SIGSEGV);}
/* * Invoked from syscall entry if a time slice extension was granted and the * kernel did not clear it before user space left the critical section. * * While the recommended way to relinquish the CPU side effect free is * rseq_slice_yield(2), any syscall within a granted slice terminates the * grant and immediately reschedules if required. This supports onion layer * applications, where the code requesting the grant cannot control the * code within the critical section. */void rseq_syscall_enter_work(long syscall){ struct task_struct *curr = current; struct rseq_slice_ctrl ctrl = { .granted = curr->rseq.slice.state.granted };
clear_task_syscall_work(curr, SYSCALL_RSEQ_SLICE);
if (static_branch_unlikely(&rseq_debug_enabled)) rseq_slice_validate_ctrl(ctrl.all);
/* * The kernel might have raced, revoked the grant and updated * userspace, but kept the SLICE work set. */ if (!ctrl.granted) return;
/* * Required to stabilize the per CPU timer pointer and to make * set_tsk_need_resched() correct on PREEMPT[RT] kernels. * * Leaving the scope will reschedule on preemption models FULL, * LAZY and RT if necessary. */ scoped_guard(preempt) { rseq_cancel_slice_extension_timer(); /* * Now that preemption is disabled, quickly check whether * the task was already rescheduled before arriving here. */ if (!curr->rseq.event.sched_switch) { rseq_slice_set_need_resched(curr);
if (syscall == __NR_rseq_slice_yield) { rseq_stat_inc(rseq_stats.s_yielded); /* Update the yielded state for syscall return */ curr->rseq.slice.yielded = 1; } else { rseq_stat_inc(rseq_stats.s_aborted); } } } /* Reschedule on NONE/VOLUNTARY preemption models */ cond_resched();
/* Clear the grant in kernel state and user space */ curr->rseq.slice.state.granted = false; if (put_user(0U, &curr->rseq.usrptr->slice_ctrl.all)) force_sig(SIGSEGV);}
int rseq_slice_extension_prctl(unsigned long arg2, unsigned long arg3){ switch (arg2) { case PR_RSEQ_SLICE_EXTENSION_GET: if (arg3) return -EINVAL; return current->rseq.slice.state.enabled ? PR_RSEQ_SLICE_EXT_ENABLE : 0;
case PR_RSEQ_SLICE_EXTENSION_SET: { u32 rflags, valid = RSEQ_CS_FLAG_SLICE_EXT_AVAILABLE; bool enable = !!(arg3 & PR_RSEQ_SLICE_EXT_ENABLE);
if (arg3 & ~PR_RSEQ_SLICE_EXT_ENABLE) return -EINVAL; if (!rseq_slice_extension_enabled()) return -ENOTSUPP; if (!current->rseq.usrptr) return -ENXIO; if (!rseq_v2(current)) return -ENOTSUPP;
/* No change? */ if (enable == !!current->rseq.slice.state.enabled) return 0;
if (get_user(rflags, ¤t->rseq.usrptr->flags)) goto die;
if (current->rseq.slice.state.enabled) valid |= RSEQ_CS_FLAG_SLICE_EXT_ENABLED;
if ((rflags & valid) != valid) goto die;
rflags &= ~RSEQ_CS_FLAG_SLICE_EXT_ENABLED; rflags |= RSEQ_CS_FLAG_SLICE_EXT_AVAILABLE; if (enable) rflags |= RSEQ_CS_FLAG_SLICE_EXT_ENABLED;
if (put_user(rflags, ¤t->rseq.usrptr->flags)) goto die;
current->rseq.slice.state.enabled = enable; return 0; } default: return -EINVAL; }die: force_sig(SIGSEGV); return -EFAULT;}
/** * sys_rseq_slice_yield - yield the current processor side effect free if a * task granted with a time slice extension is done with * the critical work before being forced out. * * Return: 1 if the task successfully yielded the CPU within the granted slice. * 0 if the slice extension was either never granted or was revoked by * going over the granted extension, using a syscall other than this one * or being scheduled out earlier due to a subsequent interrupt. * * The syscall does not schedule because the syscall entry work immediately * relinquishes the CPU and schedules if required. */SYSCALL_DEFINE0(rseq_slice_yield){ int yielded = !!current->rseq.slice.yielded;
current->rseq.slice.yielded = 0; return yielded;}
static int rseq_slice_ext_show(struct seq_file *m, void *p){ seq_printf(m, "%d\n", rseq_slice_ext_nsecs); return 0;}
static ssize_t rseq_slice_ext_write(struct file *file, const char __user *ubuf, size_t count, loff_t *ppos){ unsigned int nsecs;
if (kstrtouint_from_user(ubuf, count, 10, &nsecs)) return -EINVAL;
if (nsecs < rseq_slice_ext_nsecs_min) return -ERANGE;
if (nsecs > rseq_slice_ext_nsecs_max) return -ERANGE;
rseq_slice_ext_nsecs = nsecs;
return count;}
static int rseq_slice_ext_open(struct inode *inode, struct file *file){ return single_open(file, rseq_slice_ext_show, inode->i_private);}
static const struct file_operations slice_ext_ops = { .open = rseq_slice_ext_open, .read = seq_read, .write = rseq_slice_ext_write, .llseek = seq_lseek, .release = single_release,};
static void rseq_slice_ext_init(struct dentry *root_dir){ debugfs_create_file("slice_ext_nsec", 0644, root_dir, NULL, &slice_ext_ops);}
static int __init rseq_slice_cmdline(char *str){ bool on;
if (kstrtobool(str, &on)) return 0;
if (!on) static_branch_disable(&rseq_slice_extension_key); return 1;}__setup("rseq_slice_ext=", rseq_slice_cmdline);
static int __init rseq_slice_init(void){ unsigned int cpu;
for_each_possible_cpu(cpu) { hrtimer_setup(per_cpu_ptr(&slice_timer.timer, cpu), rseq_slice_expired, CLOCK_MONOTONIC, HRTIMER_MODE_REL_PINNED_HARD); } return 0;}device_initcall(rseq_slice_init);#elsestatic void rseq_slice_ext_init(struct dentry *root_dir) { }#endif /* CONFIG_RSEQ_SLICE_EXTENSION */