diff options
Diffstat (limited to 'arch/x86/kernel/process.c')
| -rw-r--r-- | arch/x86/kernel/process.c | 854 |
1 files changed, 854 insertions, 0 deletions
diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c new file mode 100644 index 000000000..cd138bfd9 --- /dev/null +++ b/arch/x86/kernel/process.c @@ -0,0 +1,854 @@ +// SPDX-License-Identifier: GPL-2.0 +#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt + +#include <linux/errno.h> +#include <linux/kernel.h> +#include <linux/mm.h> +#include <linux/smp.h> +#include <linux/prctl.h> +#include <linux/slab.h> +#include <linux/sched.h> +#include <linux/sched/idle.h> +#include <linux/sched/debug.h> +#include <linux/sched/task.h> +#include <linux/sched/task_stack.h> +#include <linux/init.h> +#include <linux/export.h> +#include <linux/pm.h> +#include <linux/tick.h> +#include <linux/random.h> +#include <linux/user-return-notifier.h> +#include <linux/dmi.h> +#include <linux/utsname.h> +#include <linux/stackprotector.h> +#include <linux/cpuidle.h> +#include <trace/events/power.h> +#include <linux/hw_breakpoint.h> +#include <asm/cpu.h> +#include <asm/apic.h> +#include <asm/syscalls.h> +#include <linux/uaccess.h> +#include <asm/mwait.h> +#include <asm/fpu/internal.h> +#include <asm/debugreg.h> +#include <asm/nmi.h> +#include <asm/tlbflush.h> +#include <asm/mce.h> +#include <asm/vm86.h> +#include <asm/switch_to.h> +#include <asm/desc.h> +#include <asm/prctl.h> +#include <asm/spec-ctrl.h> + +#include "process.h" + +/* + * per-CPU TSS segments. Threads are completely 'soft' on Linux, + * no more per-task TSS's. The TSS size is kept cacheline-aligned + * so they are allowed to end up in the .data..cacheline_aligned + * section. Since TSS's are completely CPU-local, we want them + * on exact cacheline boundaries, to eliminate cacheline ping-pong. + */ +__visible DEFINE_PER_CPU_PAGE_ALIGNED(struct tss_struct, cpu_tss_rw) = { + .x86_tss = { + /* + * .sp0 is only used when entering ring 0 from a lower + * privilege level. Since the init task never runs anything + * but ring 0 code, there is no need for a valid value here. + * Poison it. + */ + .sp0 = (1UL << (BITS_PER_LONG-1)) + 1, + + /* + * .sp1 is cpu_current_top_of_stack. The init task never + * runs user code, but cpu_current_top_of_stack should still + * be well defined before the first context switch. + */ + .sp1 = TOP_OF_INIT_STACK, + +#ifdef CONFIG_X86_32 + .ss0 = __KERNEL_DS, + .ss1 = __KERNEL_CS, + .io_bitmap_base = INVALID_IO_BITMAP_OFFSET, +#endif + }, +#ifdef CONFIG_X86_32 + /* + * Note that the .io_bitmap member must be extra-big. This is because + * the CPU will access an additional byte beyond the end of the IO + * permission bitmap. The extra byte must be all 1 bits, and must + * be within the limit. + */ + .io_bitmap = { [0 ... IO_BITMAP_LONGS] = ~0 }, +#endif +}; +EXPORT_PER_CPU_SYMBOL(cpu_tss_rw); + +DEFINE_PER_CPU(bool, __tss_limit_invalid); +EXPORT_PER_CPU_SYMBOL_GPL(__tss_limit_invalid); + +/* + * this gets called so that we can store lazy state into memory and copy the + * current task into the new thread. + */ +int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src) +{ + memcpy(dst, src, arch_task_struct_size); +#ifdef CONFIG_VM86 + dst->thread.vm86 = NULL; +#endif + + return fpu__copy(&dst->thread.fpu, &src->thread.fpu); +} + +/* + * Free current thread data structures etc.. + */ +void exit_thread(struct task_struct *tsk) +{ + struct thread_struct *t = &tsk->thread; + unsigned long *bp = t->io_bitmap_ptr; + struct fpu *fpu = &t->fpu; + + if (bp) { + struct tss_struct *tss = &per_cpu(cpu_tss_rw, get_cpu()); + + t->io_bitmap_ptr = NULL; + clear_thread_flag(TIF_IO_BITMAP); + /* + * Careful, clear this in the TSS too: + */ + memset(tss->io_bitmap, 0xff, t->io_bitmap_max); + t->io_bitmap_max = 0; + put_cpu(); + kfree(bp); + } + + free_vm86(t); + + fpu__drop(fpu); +} + +void flush_thread(void) +{ + struct task_struct *tsk = current; + + flush_ptrace_hw_breakpoint(tsk); + memset(tsk->thread.tls_array, 0, sizeof(tsk->thread.tls_array)); + + fpu__clear(&tsk->thread.fpu); +} + +void disable_TSC(void) +{ + preempt_disable(); + if (!test_and_set_thread_flag(TIF_NOTSC)) + /* + * Must flip the CPU state synchronously with + * TIF_NOTSC in the current running context. + */ + cr4_set_bits(X86_CR4_TSD); + preempt_enable(); +} + +static void enable_TSC(void) +{ + preempt_disable(); + if (test_and_clear_thread_flag(TIF_NOTSC)) + /* + * Must flip the CPU state synchronously with + * TIF_NOTSC in the current running context. + */ + cr4_clear_bits(X86_CR4_TSD); + preempt_enable(); +} + +int get_tsc_mode(unsigned long adr) +{ + unsigned int val; + + if (test_thread_flag(TIF_NOTSC)) + val = PR_TSC_SIGSEGV; + else + val = PR_TSC_ENABLE; + + return put_user(val, (unsigned int __user *)adr); +} + +int set_tsc_mode(unsigned int val) +{ + if (val == PR_TSC_SIGSEGV) + disable_TSC(); + else if (val == PR_TSC_ENABLE) + enable_TSC(); + else + return -EINVAL; + + return 0; +} + +DEFINE_PER_CPU(u64, msr_misc_features_shadow); + +static void set_cpuid_faulting(bool on) +{ + u64 msrval; + + msrval = this_cpu_read(msr_misc_features_shadow); + msrval &= ~MSR_MISC_FEATURES_ENABLES_CPUID_FAULT; + msrval |= (on << MSR_MISC_FEATURES_ENABLES_CPUID_FAULT_BIT); + this_cpu_write(msr_misc_features_shadow, msrval); + wrmsrl(MSR_MISC_FEATURES_ENABLES, msrval); +} + +static void disable_cpuid(void) +{ + preempt_disable(); + if (!test_and_set_thread_flag(TIF_NOCPUID)) { + /* + * Must flip the CPU state synchronously with + * TIF_NOCPUID in the current running context. + */ + set_cpuid_faulting(true); + } + preempt_enable(); +} + +static void enable_cpuid(void) +{ + preempt_disable(); + if (test_and_clear_thread_flag(TIF_NOCPUID)) { + /* + * Must flip the CPU state synchronously with + * TIF_NOCPUID in the current running context. + */ + set_cpuid_faulting(false); + } + preempt_enable(); +} + +static int get_cpuid_mode(void) +{ + return !test_thread_flag(TIF_NOCPUID); +} + +static int set_cpuid_mode(struct task_struct *task, unsigned long cpuid_enabled) +{ + if (!static_cpu_has(X86_FEATURE_CPUID_FAULT)) + return -ENODEV; + + if (cpuid_enabled) + enable_cpuid(); + else + disable_cpuid(); + + return 0; +} + +/* + * Called immediately after a successful exec. + */ +void arch_setup_new_exec(void) +{ + /* If cpuid was previously disabled for this task, re-enable it. */ + if (test_thread_flag(TIF_NOCPUID)) + enable_cpuid(); +} + +static inline void switch_to_bitmap(struct thread_struct *prev, + struct thread_struct *next, + unsigned long tifp, unsigned long tifn) +{ + struct tss_struct *tss = this_cpu_ptr(&cpu_tss_rw); + + if (tifn & _TIF_IO_BITMAP) { + /* + * Copy the relevant range of the IO bitmap. + * Normally this is 128 bytes or less: + */ + memcpy(tss->io_bitmap, next->io_bitmap_ptr, + max(prev->io_bitmap_max, next->io_bitmap_max)); + /* + * Make sure that the TSS limit is correct for the CPU + * to notice the IO bitmap. + */ + refresh_tss_limit(); + } else if (tifp & _TIF_IO_BITMAP) { + /* + * Clear any possible leftover bits: + */ + memset(tss->io_bitmap, 0xff, prev->io_bitmap_max); + } +} + +#ifdef CONFIG_SMP + +struct ssb_state { + struct ssb_state *shared_state; + raw_spinlock_t lock; + unsigned int disable_state; + unsigned long local_state; +}; + +#define LSTATE_SSB 0 + +static DEFINE_PER_CPU(struct ssb_state, ssb_state); + +void speculative_store_bypass_ht_init(void) +{ + struct ssb_state *st = this_cpu_ptr(&ssb_state); + unsigned int this_cpu = smp_processor_id(); + unsigned int cpu; + + st->local_state = 0; + + /* + * Shared state setup happens once on the first bringup + * of the CPU. It's not destroyed on CPU hotunplug. + */ + if (st->shared_state) + return; + + raw_spin_lock_init(&st->lock); + + /* + * Go over HT siblings and check whether one of them has set up the + * shared state pointer already. + */ + for_each_cpu(cpu, topology_sibling_cpumask(this_cpu)) { + if (cpu == this_cpu) + continue; + + if (!per_cpu(ssb_state, cpu).shared_state) + continue; + + /* Link it to the state of the sibling: */ + st->shared_state = per_cpu(ssb_state, cpu).shared_state; + return; + } + + /* + * First HT sibling to come up on the core. Link shared state of + * the first HT sibling to itself. The siblings on the same core + * which come up later will see the shared state pointer and link + * themself to the state of this CPU. + */ + st->shared_state = st; +} + +/* + * Logic is: First HT sibling enables SSBD for both siblings in the core + * and last sibling to disable it, disables it for the whole core. This how + * MSR_SPEC_CTRL works in "hardware": + * + * CORE_SPEC_CTRL = THREAD0_SPEC_CTRL | THREAD1_SPEC_CTRL + */ +static __always_inline void amd_set_core_ssb_state(unsigned long tifn) +{ + struct ssb_state *st = this_cpu_ptr(&ssb_state); + u64 msr = x86_amd_ls_cfg_base; + + if (!static_cpu_has(X86_FEATURE_ZEN)) { + msr |= ssbd_tif_to_amd_ls_cfg(tifn); + wrmsrl(MSR_AMD64_LS_CFG, msr); + return; + } + + if (tifn & _TIF_SSBD) { + /* + * Since this can race with prctl(), block reentry on the + * same CPU. + */ + if (__test_and_set_bit(LSTATE_SSB, &st->local_state)) + return; + + msr |= x86_amd_ls_cfg_ssbd_mask; + + raw_spin_lock(&st->shared_state->lock); + /* First sibling enables SSBD: */ + if (!st->shared_state->disable_state) + wrmsrl(MSR_AMD64_LS_CFG, msr); + st->shared_state->disable_state++; + raw_spin_unlock(&st->shared_state->lock); + } else { + if (!__test_and_clear_bit(LSTATE_SSB, &st->local_state)) + return; + + raw_spin_lock(&st->shared_state->lock); + st->shared_state->disable_state--; + if (!st->shared_state->disable_state) + wrmsrl(MSR_AMD64_LS_CFG, msr); + raw_spin_unlock(&st->shared_state->lock); + } +} +#else +static __always_inline void amd_set_core_ssb_state(unsigned long tifn) +{ + u64 msr = x86_amd_ls_cfg_base | ssbd_tif_to_amd_ls_cfg(tifn); + + wrmsrl(MSR_AMD64_LS_CFG, msr); +} +#endif + +static __always_inline void amd_set_ssb_virt_state(unsigned long tifn) +{ + /* + * SSBD has the same definition in SPEC_CTRL and VIRT_SPEC_CTRL, + * so ssbd_tif_to_spec_ctrl() just works. + */ + wrmsrl(MSR_AMD64_VIRT_SPEC_CTRL, ssbd_tif_to_spec_ctrl(tifn)); +} + +/* + * Update the MSRs managing speculation control, during context switch. + * + * tifp: Previous task's thread flags + * tifn: Next task's thread flags + */ +static __always_inline void __speculation_ctrl_update(unsigned long tifp, + unsigned long tifn) +{ + unsigned long tif_diff = tifp ^ tifn; + u64 msr = x86_spec_ctrl_base; + bool updmsr = false; + + lockdep_assert_irqs_disabled(); + + /* Handle change of TIF_SSBD depending on the mitigation method. */ + if (static_cpu_has(X86_FEATURE_VIRT_SSBD)) { + if (tif_diff & _TIF_SSBD) + amd_set_ssb_virt_state(tifn); + } else if (static_cpu_has(X86_FEATURE_LS_CFG_SSBD)) { + if (tif_diff & _TIF_SSBD) + amd_set_core_ssb_state(tifn); + } else if (static_cpu_has(X86_FEATURE_SPEC_CTRL_SSBD) || + static_cpu_has(X86_FEATURE_AMD_SSBD)) { + updmsr |= !!(tif_diff & _TIF_SSBD); + msr |= ssbd_tif_to_spec_ctrl(tifn); + } + + /* Only evaluate TIF_SPEC_IB if conditional STIBP is enabled. */ + if (IS_ENABLED(CONFIG_SMP) && + static_branch_unlikely(&switch_to_cond_stibp)) { + updmsr |= !!(tif_diff & _TIF_SPEC_IB); + msr |= stibp_tif_to_spec_ctrl(tifn); + } + + if (updmsr) + wrmsrl(MSR_IA32_SPEC_CTRL, msr); +} + +static unsigned long speculation_ctrl_update_tif(struct task_struct *tsk) +{ + if (test_and_clear_tsk_thread_flag(tsk, TIF_SPEC_FORCE_UPDATE)) { + if (task_spec_ssb_disable(tsk)) + set_tsk_thread_flag(tsk, TIF_SSBD); + else + clear_tsk_thread_flag(tsk, TIF_SSBD); + + if (task_spec_ib_disable(tsk)) + set_tsk_thread_flag(tsk, TIF_SPEC_IB); + else + clear_tsk_thread_flag(tsk, TIF_SPEC_IB); + } + /* Return the updated threadinfo flags*/ + return task_thread_info(tsk)->flags; +} + +void speculation_ctrl_update(unsigned long tif) +{ + unsigned long flags; + + /* Forced update. Make sure all relevant TIF flags are different */ + local_irq_save(flags); + __speculation_ctrl_update(~tif, tif); + local_irq_restore(flags); +} + +/* Called from seccomp/prctl update */ +void speculation_ctrl_update_current(void) +{ + preempt_disable(); + speculation_ctrl_update(speculation_ctrl_update_tif(current)); + preempt_enable(); +} + +void __switch_to_xtra(struct task_struct *prev_p, struct task_struct *next_p) +{ + struct thread_struct *prev, *next; + unsigned long tifp, tifn; + + prev = &prev_p->thread; + next = &next_p->thread; + + tifn = READ_ONCE(task_thread_info(next_p)->flags); + tifp = READ_ONCE(task_thread_info(prev_p)->flags); + switch_to_bitmap(prev, next, tifp, tifn); + + propagate_user_return_notify(prev_p, next_p); + + if ((tifp & _TIF_BLOCKSTEP || tifn & _TIF_BLOCKSTEP) && + arch_has_block_step()) { + unsigned long debugctl, msk; + + rdmsrl(MSR_IA32_DEBUGCTLMSR, debugctl); + debugctl &= ~DEBUGCTLMSR_BTF; + msk = tifn & _TIF_BLOCKSTEP; + debugctl |= (msk >> TIF_BLOCKSTEP) << DEBUGCTLMSR_BTF_SHIFT; + wrmsrl(MSR_IA32_DEBUGCTLMSR, debugctl); + } + + if ((tifp ^ tifn) & _TIF_NOTSC) + cr4_toggle_bits_irqsoff(X86_CR4_TSD); + + if ((tifp ^ tifn) & _TIF_NOCPUID) + set_cpuid_faulting(!!(tifn & _TIF_NOCPUID)); + + if (likely(!((tifp | tifn) & _TIF_SPEC_FORCE_UPDATE))) { + __speculation_ctrl_update(tifp, tifn); + } else { + speculation_ctrl_update_tif(prev_p); + tifn = speculation_ctrl_update_tif(next_p); + + /* Enforce MSR update to ensure consistent state */ + __speculation_ctrl_update(~tifn, tifn); + } +} + +/* + * Idle related variables and functions + */ +unsigned long boot_option_idle_override = IDLE_NO_OVERRIDE; +EXPORT_SYMBOL(boot_option_idle_override); + +static void (*x86_idle)(void); + +#ifndef CONFIG_SMP +static inline void play_dead(void) +{ + BUG(); +} +#endif + +void arch_cpu_idle_enter(void) +{ + tsc_verify_tsc_adjust(false); + local_touch_nmi(); +} + +void arch_cpu_idle_dead(void) +{ + play_dead(); +} + +/* + * Called from the generic idle code. + */ +void arch_cpu_idle(void) +{ + x86_idle(); +} + +/* + * We use this if we don't have any better idle routine.. + */ +void __cpuidle default_idle(void) +{ + trace_cpu_idle_rcuidle(1, smp_processor_id()); + safe_halt(); + trace_cpu_idle_rcuidle(PWR_EVENT_EXIT, smp_processor_id()); +} +#ifdef CONFIG_APM_MODULE +EXPORT_SYMBOL(default_idle); +#endif + +#ifdef CONFIG_XEN +bool xen_set_default_idle(void) +{ + bool ret = !!x86_idle; + + x86_idle = default_idle; + + return ret; +} +#endif + +void stop_this_cpu(void *dummy) +{ + local_irq_disable(); + /* + * Remove this CPU: + */ + set_cpu_online(smp_processor_id(), false); + disable_local_APIC(); + mcheck_cpu_clear(this_cpu_ptr(&cpu_info)); + + /* + * Use wbinvd on processors that support SME. This provides support + * for performing a successful kexec when going from SME inactive + * to SME active (or vice-versa). The cache must be cleared so that + * if there are entries with the same physical address, both with and + * without the encryption bit, they don't race each other when flushed + * and potentially end up with the wrong entry being committed to + * memory. + */ + if (boot_cpu_has(X86_FEATURE_SME)) + native_wbinvd(); + for (;;) { + /* + * Use native_halt() so that memory contents don't change + * (stack usage and variables) after possibly issuing the + * native_wbinvd() above. + */ + native_halt(); + } +} + +/* + * AMD Erratum 400 aware idle routine. We handle it the same way as C3 power + * states (local apic timer and TSC stop). + */ +static void amd_e400_idle(void) +{ + /* + * We cannot use static_cpu_has_bug() here because X86_BUG_AMD_APIC_C1E + * gets set after static_cpu_has() places have been converted via + * alternatives. + */ + if (!boot_cpu_has_bug(X86_BUG_AMD_APIC_C1E)) { + default_idle(); + return; + } + + tick_broadcast_enter(); + + default_idle(); + + /* + * The switch back from broadcast mode needs to be called with + * interrupts disabled. + */ + local_irq_disable(); + tick_broadcast_exit(); + local_irq_enable(); +} + +/* + * Intel Core2 and older machines prefer MWAIT over HALT for C1. + * We can't rely on cpuidle installing MWAIT, because it will not load + * on systems that support only C1 -- so the boot default must be MWAIT. + * + * Some AMD machines are the opposite, they depend on using HALT. + * + * So for default C1, which is used during boot until cpuidle loads, + * use MWAIT-C1 on Intel HW that has it, else use HALT. + */ +static int prefer_mwait_c1_over_halt(const struct cpuinfo_x86 *c) +{ + if (c->x86_vendor != X86_VENDOR_INTEL) + return 0; + + if (!cpu_has(c, X86_FEATURE_MWAIT) || static_cpu_has_bug(X86_BUG_MONITOR)) + return 0; + + return 1; +} + +/* + * MONITOR/MWAIT with no hints, used for default C1 state. This invokes MWAIT + * with interrupts enabled and no flags, which is backwards compatible with the + * original MWAIT implementation. + */ +static __cpuidle void mwait_idle(void) +{ + if (!current_set_polling_and_test()) { + trace_cpu_idle_rcuidle(1, smp_processor_id()); + if (this_cpu_has(X86_BUG_CLFLUSH_MONITOR)) { + mb(); /* quirk */ + clflush((void *)¤t_thread_info()->flags); + mb(); /* quirk */ + } + + __monitor((void *)¤t_thread_info()->flags, 0, 0); + if (!need_resched()) + __sti_mwait(0, 0); + else + local_irq_enable(); + trace_cpu_idle_rcuidle(PWR_EVENT_EXIT, smp_processor_id()); + } else { + local_irq_enable(); + } + __current_clr_polling(); +} + +void select_idle_routine(const struct cpuinfo_x86 *c) +{ +#ifdef CONFIG_SMP + if (boot_option_idle_override == IDLE_POLL && smp_num_siblings > 1) + pr_warn_once("WARNING: polling idle and HT enabled, performance may degrade\n"); +#endif + if (x86_idle || boot_option_idle_override == IDLE_POLL) + return; + + if (boot_cpu_has_bug(X86_BUG_AMD_E400)) { + pr_info("using AMD E400 aware idle routine\n"); + x86_idle = amd_e400_idle; + } else if (prefer_mwait_c1_over_halt(c)) { + pr_info("using mwait in idle threads\n"); + x86_idle = mwait_idle; + } else + x86_idle = default_idle; +} + +void amd_e400_c1e_apic_setup(void) +{ + if (boot_cpu_has_bug(X86_BUG_AMD_APIC_C1E)) { + pr_info("Switch to broadcast mode on CPU%d\n", smp_processor_id()); + local_irq_disable(); + tick_broadcast_force(); + local_irq_enable(); + } +} + +void __init arch_post_acpi_subsys_init(void) +{ + u32 lo, hi; + + if (!boot_cpu_has_bug(X86_BUG_AMD_E400)) + return; + + /* + * AMD E400 detection needs to happen after ACPI has been enabled. If + * the machine is affected K8_INTP_C1E_ACTIVE_MASK bits are set in + * MSR_K8_INT_PENDING_MSG. + */ + rdmsr(MSR_K8_INT_PENDING_MSG, lo, hi); + if (!(lo & K8_INTP_C1E_ACTIVE_MASK)) + return; + + boot_cpu_set_bug(X86_BUG_AMD_APIC_C1E); + + if (!boot_cpu_has(X86_FEATURE_NONSTOP_TSC)) + mark_tsc_unstable("TSC halt in AMD C1E"); + pr_info("System has AMD C1E enabled\n"); +} + +static int __init idle_setup(char *str) +{ + if (!str) + return -EINVAL; + + if (!strcmp(str, "poll")) { + pr_info("using polling idle threads\n"); + boot_option_idle_override = IDLE_POLL; + cpu_idle_poll_ctrl(true); + } else if (!strcmp(str, "halt")) { + /* + * When the boot option of idle=halt is added, halt is + * forced to be used for CPU idle. In such case CPU C2/C3 + * won't be used again. + * To continue to load the CPU idle driver, don't touch + * the boot_option_idle_override. + */ + x86_idle = default_idle; + boot_option_idle_override = IDLE_HALT; + } else if (!strcmp(str, "nomwait")) { + /* + * If the boot option of "idle=nomwait" is added, + * it means that mwait will be disabled for CPU C2/C3 + * states. In such case it won't touch the variable + * of boot_option_idle_override. + */ + boot_option_idle_override = IDLE_NOMWAIT; + } else + return -1; + + return 0; +} +early_param("idle", idle_setup); + +unsigned long arch_align_stack(unsigned long sp) +{ + if (!(current->personality & ADDR_NO_RANDOMIZE) && randomize_va_space) + sp -= get_random_int() % 8192; + return sp & ~0xf; +} + +unsigned long arch_randomize_brk(struct mm_struct *mm) +{ + return randomize_page(mm->brk, 0x02000000); +} + +/* + * Called from fs/proc with a reference on @p to find the function + * which called into schedule(). This needs to be done carefully + * because the task might wake up and we might look at a stack + * changing under us. + */ +unsigned long get_wchan(struct task_struct *p) +{ + unsigned long start, bottom, top, sp, fp, ip, ret = 0; + int count = 0; + + if (!p || p == current || p->state == TASK_RUNNING) + return 0; + + if (!try_get_task_stack(p)) + return 0; + + start = (unsigned long)task_stack_page(p); + if (!start) + goto out; + + /* + * Layout of the stack page: + * + * ----------- topmax = start + THREAD_SIZE - sizeof(unsigned long) + * PADDING + * ----------- top = topmax - TOP_OF_KERNEL_STACK_PADDING + * stack + * ----------- bottom = start + * + * The tasks stack pointer points at the location where the + * framepointer is stored. The data on the stack is: + * ... IP FP ... IP FP + * + * We need to read FP and IP, so we need to adjust the upper + * bound by another unsigned long. + */ + top = start + THREAD_SIZE - TOP_OF_KERNEL_STACK_PADDING; + top -= 2 * sizeof(unsigned long); + bottom = start; + + sp = READ_ONCE(p->thread.sp); + if (sp < bottom || sp > top) + goto out; + + fp = READ_ONCE_NOCHECK(((struct inactive_task_frame *)sp)->bp); + do { + if (fp < bottom || fp > top) + goto out; + ip = READ_ONCE_NOCHECK(*(unsigned long *)(fp + sizeof(unsigned long))); + if (!in_sched_functions(ip)) { + ret = ip; + goto out; + } + fp = READ_ONCE_NOCHECK(*(unsigned long *)fp); + } while (count++ < 16 && p->state != TASK_RUNNING); + +out: + put_task_stack(p); + return ret; +} + +long do_arch_prctl_common(struct task_struct *task, int option, + unsigned long cpuid_enabled) +{ + switch (option) { + case ARCH_GET_CPUID: + return get_cpuid_mode(); + case ARCH_SET_CPUID: + return set_cpuid_mode(task, cpuid_enabled); + } + + return -EINVAL; +} |