int __die(const char *str, struct pt_regs *regs, long err) { #ifdef CONFIG_X86_32 unsigned short ss; unsigned long sp; #endif printk(KERN_DEFAULT "%s: %04lx [#%d] ", str, err & 0xffff, ++die_counter); #ifdef CONFIG_PREEMPT printk("PREEMPT "); #endif #ifdef CONFIG_SMP printk("SMP "); #endif #ifdef CONFIG_DEBUG_PAGEALLOC printk("DEBUG_PAGEALLOC "); #endif #ifdef CONFIG_KASAN printk("KASAN"); #endif printk("\n"); if (notify_die(DIE_OOPS, str, regs, err, current->thread.trap_nr, SIGSEGV) == NOTIFY_STOP) return 1; /* FIXME this should probably also need to print into buffer */ print_modules(); show_regs(regs); #ifdef CONFIG_X86_32 if (user_mode(regs)) { sp = regs->sp; ss = regs->ss & 0xffff; } else { sp = kernel_stack_pointer(regs); savesegment(ss, ss); } printk(KERN_EMERG "EIP: [<%08lx>] ", regs->ip); print_symbol("%s", regs->ip); printk(" SS:ESP %04x:%08lx\n", ss, sp); #else /* Executive summary in case the oops scrolled away */ printk(KERN_ALERT "RIP "); /* FIXME */ printk_address(regs->ip); printk(" RSP <%016lx>\n", regs->sp); #endif return 0; }
int copy_thread(int nr, unsigned long clone_flags, unsigned long sp, unsigned long unused, struct task_struct * p, struct pt_regs * regs) { struct pt_regs * childregs; struct task_struct *tsk; int err; childregs = task_pt_regs(p); *childregs = *regs; childregs->ax = 0; childregs->sp = sp; p->thread.sp = (unsigned long) childregs; p->thread.sp0 = (unsigned long) (childregs+1); p->thread.ip = (unsigned long) ret_from_fork; savesegment(gs, p->thread.gs); tsk = current; if (unlikely(test_tsk_thread_flag(tsk, TIF_IO_BITMAP))) { p->thread.io_bitmap_ptr = kmemdup(tsk->thread.io_bitmap_ptr, IO_BITMAP_BYTES, GFP_KERNEL); if (!p->thread.io_bitmap_ptr) { p->thread.io_bitmap_max = 0; return -ENOMEM; } set_tsk_thread_flag(p, TIF_IO_BITMAP); } err = 0; /* * Set a new TLS for the child thread? */ if (clone_flags & CLONE_SETTLS) err = do_set_thread_area(p, -1, (struct user_desc __user *)childregs->si, 0); if (err && p->thread.io_bitmap_ptr) { kfree(p->thread.io_bitmap_ptr); p->thread.io_bitmap_max = 0; } return err; }
int __kprobes __die(const char *str, struct pt_regs *regs, long err) { #ifdef CONFIG_X86_32 unsigned short ss; unsigned long sp; #endif printk(KERN_EMERG "%s: %04lx [#%d] ", str, err & 0xffff, ++die_counter); #ifdef CONFIG_PREEMPT printk("PREEMPT "); #endif #ifdef CONFIG_SMP printk("SMP "); #endif #ifdef CONFIG_DEBUG_PAGEALLOC printk("DEBUG_PAGEALLOC"); #endif printk("\n"); sysfs_printk_last_file(); if (notify_die(DIE_OOPS, str, regs, err, current->thread.trap_no, SIGSEGV) == NOTIFY_STOP) return 1; show_registers(regs); #ifdef CONFIG_X86_32 if (user_mode_vm(regs)) { sp = regs->sp; ss = regs->ss & 0xffff; } else { sp = kernel_stack_pointer(regs); savesegment(ss, ss); } printk(KERN_EMERG "EIP: [<%08lx>] ", regs->ip); print_symbol("%s", regs->ip); printk(" SS:ESP %04x:%08lx\n", ss, sp); #else /* Executive summary in case the oops scrolled away */ printk(KERN_ALERT "RIP "); printk_address(regs->ip, 1); printk(" RSP <%016lx>\n", regs->sp); #endif return 0; }
static int setup_sigcontext(struct sigcontext __user *sc, struct _fpstate __user *fpstate, struct pt_regs *regs, unsigned long mask) { int tmp, err = 0; err |= __put_user(regs->xfs, (unsigned int __user *)&sc->fs); savesegment(gs, tmp); err |= __put_user(tmp, (unsigned int __user *)&sc->gs); err |= __put_user(regs->xes, (unsigned int __user *)&sc->es); err |= __put_user(regs->xds, (unsigned int __user *)&sc->ds); err |= __put_user(regs->edi, &sc->edi); err |= __put_user(regs->esi, &sc->esi); err |= __put_user(regs->ebp, &sc->ebp); err |= __put_user(regs->esp, &sc->esp); err |= __put_user(regs->ebx, &sc->ebx); err |= __put_user(regs->edx, &sc->edx); err |= __put_user(regs->ecx, &sc->ecx); err |= __put_user(regs->eax, &sc->eax); err |= __put_user(current->thread.trap_no, &sc->trapno); err |= __put_user(current->thread.error_code, &sc->err); err |= __put_user(regs->eip, &sc->eip); err |= __put_user(regs->xcs, (unsigned int __user *)&sc->cs); err |= __put_user(regs->eflags, &sc->eflags); err |= __put_user(regs->esp, &sc->esp_at_signal); err |= __put_user(regs->xss, (unsigned int __user *)&sc->ss); tmp = save_i387(fpstate); if (tmp < 0) err = 1; else err |= __put_user(tmp ? fpstate : NULL, &sc->fpstate); /* non-iBCS2 extensions.. */ err |= __put_user(mask, &sc->oldmask); err |= __put_user(current->thread.cr2, &sc->cr2); return err; }
int __die(const char *str, struct pt_regs *regs, long err) { #ifdef CONFIG_X86_32 unsigned short ss; unsigned long sp; #endif printk(KERN_DEFAULT "%s: %04lx [#%d]%s%s%s%s\n", str, err & 0xffff, ++die_counter, IS_ENABLED(CONFIG_PREEMPT) ? " PREEMPT" : "", IS_ENABLED(CONFIG_SMP) ? " SMP" : "", debug_pagealloc_enabled() ? " DEBUG_PAGEALLOC" : "", IS_ENABLED(CONFIG_KASAN) ? " KASAN" : ""); if (notify_die(DIE_OOPS, str, regs, err, current->thread.trap_nr, SIGSEGV) == NOTIFY_STOP) return 1; print_modules(); show_regs(regs); #ifdef CONFIG_X86_32 if (user_mode(regs)) { sp = regs->sp; ss = regs->ss & 0xffff; } else { sp = kernel_stack_pointer(regs); savesegment(ss, ss); } printk(KERN_EMERG "EIP: [<%08lx>] ", regs->ip); print_symbol("%s", regs->ip); printk(" SS:ESP %04x:%08lx\n", ss, sp); #else /* Executive summary in case the oops scrolled away */ printk(KERN_ALERT "RIP "); printk_address(regs->ip); printk(" RSP <%016lx>\n", regs->sp); #endif return 0; }
/* * fill in the user structure for a core dump.. */ void dump_thread(struct pt_regs * regs, struct user * dump) { int i; /* changed the size calculations - should hopefully work better. lbt */ dump->magic = CMAGIC; dump->start_code = 0; dump->start_stack = regs->esp & ~(PAGE_SIZE - 1); dump->u_tsize = ((unsigned long) current->mm->end_code) >> PAGE_SHIFT; dump->u_dsize = ((unsigned long) (current->mm->brk + (PAGE_SIZE-1))) >> PAGE_SHIFT; dump->u_dsize -= dump->u_tsize; dump->u_ssize = 0; for (i = 0; i < 8; i++) dump->u_debugreg[i] = current->thread.debugreg[i]; if (dump->start_stack < TASK_SIZE) dump->u_ssize = ((unsigned long) (TASK_SIZE - dump->start_stack)) >> PAGE_SHIFT; dump->regs.ebx = regs->ebx; dump->regs.ecx = regs->ecx; dump->regs.edx = regs->edx; dump->regs.esi = regs->esi; dump->regs.edi = regs->edi; dump->regs.ebp = regs->ebp; dump->regs.eax = regs->eax; dump->regs.ds = regs->xds; dump->regs.es = regs->xes; dump->regs.fs = regs->xfs; savesegment(gs,dump->regs.gs); dump->regs.orig_eax = regs->orig_eax; dump->regs.eip = regs->eip; dump->regs.cs = regs->xcs; dump->regs.eflags = regs->eflags; dump->regs.esp = regs->esp; dump->regs.ss = regs->xss; dump->u_fpvalid = dump_fpu (regs, &dump->i387); }
void __show_regs(struct pt_regs *regs, int all) { unsigned long cr0 = 0L, cr2 = 0L, cr3 = 0L, cr4 = 0L; unsigned long d0, d1, d2, d3, d6, d7; unsigned long sp; unsigned short ss, gs; const char *board; if (user_mode_vm(regs)) { sp = regs->sp; ss = regs->ss & 0xffff; gs = get_user_gs(regs); } else { sp = (unsigned long) (®s->sp); savesegment(ss, ss); savesegment(gs, gs); } printk("\n"); board = dmi_get_system_info(DMI_PRODUCT_NAME); if (!board) board = ""; printk("Pid: %d, comm: %s %s (%s %.*s) %s\n", task_pid_nr(current), current->comm, print_tainted(), init_utsname()->release, (int)strcspn(init_utsname()->version, " "), init_utsname()->version, board); printk("EIP: %04x:[<%08lx>] EFLAGS: %08lx CPU: %d\n", (u16)regs->cs, regs->ip, regs->flags, smp_processor_id()); print_symbol("EIP is at %s\n", regs->ip); printk("EAX: %08lx EBX: %08lx ECX: %08lx EDX: %08lx\n", regs->ax, regs->bx, regs->cx, regs->dx); printk("ESI: %08lx EDI: %08lx EBP: %08lx ESP: %08lx\n", regs->si, regs->di, regs->bp, sp); printk(" DS: %04x ES: %04x FS: %04x GS: %04x SS: %04x\n", (u16)regs->ds, (u16)regs->es, (u16)regs->fs, gs, ss); if (!all) return; cr0 = read_cr0(); cr2 = read_cr2(); cr3 = read_cr3(); cr4 = read_cr4_safe(); printk("CR0: %08lx CR2: %08lx CR3: %08lx CR4: %08lx\n", cr0, cr2, cr3, cr4); get_debugreg(d0, 0); get_debugreg(d1, 1); get_debugreg(d2, 2); get_debugreg(d3, 3); printk("DR0: %08lx DR1: %08lx DR2: %08lx DR3: %08lx\n", d0, d1, d2, d3); get_debugreg(d6, 6); get_debugreg(d7, 7); printk("DR6: %08lx DR7: %08lx\n", d6, d7); }
int copy_thread(int nr, unsigned long clone_flags, unsigned long esp, unsigned long unused, struct task_struct * p, struct pt_regs * regs) { struct pt_regs * childregs; struct task_struct *tsk; int err; childregs = task_pt_regs(p); *childregs = *regs; childregs->eax = 0; childregs->esp = esp; p->thread.esp = (unsigned long) childregs; p->thread.esp0 = (unsigned long) (childregs+1); p->thread.eip = (unsigned long) ret_from_fork; savesegment(fs,p->thread.fs); savesegment(gs,p->thread.gs); tsk = current; if (unlikely(test_tsk_thread_flag(tsk, TIF_IO_BITMAP))) { p->thread.io_bitmap_ptr = kmalloc(IO_BITMAP_BYTES, GFP_KERNEL); if (!p->thread.io_bitmap_ptr) { p->thread.io_bitmap_max = 0; return -ENOMEM; } memcpy(p->thread.io_bitmap_ptr, tsk->thread.io_bitmap_ptr, IO_BITMAP_BYTES); set_tsk_thread_flag(p, TIF_IO_BITMAP); } /* * Set a new TLS for the child thread? */ if (clone_flags & CLONE_SETTLS) { struct desc_struct *desc; struct user_desc info; int idx; err = -EFAULT; if (copy_from_user(&info, (void __user *)childregs->esi, sizeof(info))) goto out; err = -EINVAL; if (LDT_empty(&info)) goto out; idx = info.entry_number; if (idx < GDT_ENTRY_TLS_MIN || idx > GDT_ENTRY_TLS_MAX) goto out; desc = p->thread.tls_array + idx - GDT_ENTRY_TLS_MIN; desc->a = LDT_entry_a(&info); desc->b = LDT_entry_b(&info); } p->thread.iopl = current->thread.iopl; err = 0; out: if (err && p->thread.io_bitmap_ptr) { kfree(p->thread.io_bitmap_ptr); p->thread.io_bitmap_max = 0; } return err; }
/* * Set a given TLS descriptor: */ int do_set_thread_area(struct task_struct *p, int idx, struct user_desc __user *u_info, int can_allocate) { struct user_desc info; unsigned short __maybe_unused sel, modified_sel; if (copy_from_user(&info, u_info, sizeof(info))) return -EFAULT; if (!tls_desc_okay(&info)) return -EINVAL; if (idx == -1) idx = info.entry_number; /* * index -1 means the kernel should try to find and * allocate an empty descriptor: */ if (idx == -1 && can_allocate) { idx = get_free_idx(); if (idx < 0) return idx; if (put_user(idx, &u_info->entry_number)) return -EFAULT; } if (idx < GDT_ENTRY_TLS_MIN || idx > GDT_ENTRY_TLS_MAX) return -EINVAL; set_tls_desc(p, idx, &info, 1); /* * If DS, ES, FS, or GS points to the modified segment, forcibly * refresh it. Only needed on x86_64 because x86_32 reloads them * on return to user mode. */ modified_sel = (idx << 3) | 3; if (p == current) { #ifdef CONFIG_X86_64 savesegment(ds, sel); if (sel == modified_sel) loadsegment(ds, sel); savesegment(es, sel); if (sel == modified_sel) loadsegment(es, sel); savesegment(fs, sel); if (sel == modified_sel) loadsegment(fs, sel); savesegment(gs, sel); if (sel == modified_sel) load_gs_index(sel); #endif #ifdef CONFIG_X86_32_LAZY_GS savesegment(gs, sel); if (sel == modified_sel) loadsegment(gs, sel); #endif } else { #ifdef CONFIG_X86_64 if (p->thread.fsindex == modified_sel) p->thread.fsbase = info.base_addr; if (p->thread.gsindex == modified_sel) p->thread.gsbase = info.base_addr; #endif } return 0; }
long vmadump_store_cpu(cr_chkpt_proc_req_t *ctx, struct file *file, struct pt_regs *regs) { long bytes = 0, r; /* Store struct pt_regs */ #ifdef CONFIG_XEN /* Ensure CS and SS are not Xen-modified, others restore based on CS */ { struct pt_regs regtmp = *regs; if (test_thread_flag(TIF_IA32)) { regtmp.cs = __USER32_CS; regtmp.ss = __USER32_DS; } else { regtmp.cs = __USER_CS; regtmp.ss = __USER_DS; } r = write_kern(ctx, file, ®tmp, sizeof(regtmp)); } #else r = write_kern(ctx, file, regs, sizeof(*regs)); #endif if (r != sizeof(*regs)) goto err; bytes += r; /* Store FPU info (and later general "extended state") */ r = vmadump_store_i387(ctx, file); if (r <= 0) goto err; bytes += r; /* Store debugging state */ r = vmadump_store_debugreg(ctx, file); if (r < 0) goto err; bytes += r; /* user(r)sp, since we don't use the ptrace entry path in BLCR */ #if HAVE_THREAD_USERSP current->thread.usersp = vmad_read_oldrsp(); r = write_kern(ctx, file, ¤t->thread.usersp, sizeof(current->thread.usersp)); if (r != sizeof(current->thread.usersp)) goto err; #elif HAVE_THREAD_USERRSP current->thread.userrsp = vmad_read_oldrsp(); r = write_kern(ctx, file, ¤t->thread.userrsp, sizeof(current->thread.userrsp)); if (r != sizeof(current->thread.userrsp)) goto err; #else #error #endif bytes += r; /* Store all weird segmenty crap */ /* 64-bit offsets for FS and GS */ r = write_kern(ctx, file, ¤t->thread.fs, sizeof(current->thread.fs)); if (r != sizeof(current->thread.fs)) goto err; bytes += r; r = write_kern(ctx, file, ¤t->thread.gs, sizeof(current->thread.gs)); if (r != sizeof(current->thread.gs)) goto err; bytes += r; savesegment(fs,current->thread.fsindex); savesegment(gs,current->thread.gsindex); /* 32-bit segment descriptors for FS and GS */ r = write_kern(ctx, file, ¤t->thread.fsindex, sizeof(current->thread.fsindex)); if (r != sizeof(current->thread.fsindex)) goto err; bytes += r; r = write_kern(ctx, file, ¤t->thread.gsindex, sizeof(current->thread.gsindex)); if (r != sizeof(current->thread.gsindex)) goto err; bytes += r; /* TLS segment descriptors */ r = write_kern(ctx, file, ¤t->thread.tls_array, sizeof(current->thread.tls_array)); if (r != sizeof(current->thread.tls_array)) goto err; bytes += r; #if HAVE_THREAD_INFO_SYSENTER_RETURN { void *sysenter_return = current_thread_info()->sysenter_return; r = write_kern(ctx, file, &sysenter_return, sizeof(sysenter_return)); if (r != sizeof(sysenter_return)) goto err; } #endif return bytes; err: if (r >= 0) r = -EIO; return r; }
int copy_thread(int nr, unsigned long clone_flags, unsigned long esp, unsigned long unused, struct task_struct * p, struct pt_regs * regs) { struct pt_regs * childregs; struct task_struct *tsk; int err, i; childregs = ((struct pt_regs *) (THREAD_SIZE + (unsigned long) p->thread_info)) - 1; *childregs = *regs; childregs->eax = 0; childregs->esp = esp; p->set_child_tid = p->clear_child_tid = NULL; p->thread.esp = (unsigned long) childregs; p->thread.esp0 = (unsigned long) (childregs+1); /* * get the two stack pages, for the virtual stack. * * IMPORTANT: this code relies on the fact that the task * structure is an THREAD_SIZE aligned piece of physical memory. */ for (i = 0; i < ARRAY_SIZE(p->thread.stack_page); i++) p->thread.stack_page[i] = virt_to_page((unsigned long)p->thread_info + (i*PAGE_SIZE)); p->thread.eip = (unsigned long) ret_from_fork; p->thread_info->real_stack = p->thread_info; savesegment(fs,p->thread.fs); savesegment(gs,p->thread.gs); tsk = current; if (unlikely(NULL != tsk->thread.io_bitmap_ptr)) { p->thread.io_bitmap_ptr = kmalloc(IO_BITMAP_BYTES, GFP_KERNEL); if (!p->thread.io_bitmap_ptr) { p->thread.io_bitmap_max = 0; return -ENOMEM; } memcpy(p->thread.io_bitmap_ptr, tsk->thread.io_bitmap_ptr, IO_BITMAP_BYTES); } /* * Set a new TLS for the child thread? */ if (clone_flags & CLONE_SETTLS) { struct desc_struct *desc; struct user_desc info; int idx; err = -EFAULT; if (copy_from_user(&info, (void __user *)childregs->esi, sizeof(info))) goto out; err = -EINVAL; if (LDT_empty(&info)) goto out; idx = info.entry_number; if (idx < GDT_ENTRY_TLS_MIN || idx > GDT_ENTRY_TLS_MAX) goto out; desc = p->thread.tls_array + idx - GDT_ENTRY_TLS_MIN; desc->a = LDT_entry_a(&info); desc->b = LDT_entry_b(&info); } p->thread.io_pl = current->thread.io_pl; err = 0; out: if (err && p->thread.io_bitmap_ptr) { kfree(p->thread.io_bitmap_ptr); p->thread.io_bitmap_max = 0; } return err; }
int copy_thread(unsigned long clone_flags, unsigned long sp, unsigned long arg, struct task_struct *p) { struct pt_regs *childregs = task_stack_page(p) + THREAD_SIZE - sizeof(struct pt_regs) - 8; struct task_struct *tsk; int err; p->thread.sp = (unsigned long) childregs; p->thread.sp0 = (unsigned long) (childregs+1); p->tinfo.lowest_stack = (unsigned long)task_stack_page(p); if (unlikely(p->flags & PF_KTHREAD)) { /* kernel thread */ memset(childregs, 0, sizeof(struct pt_regs)); p->thread.ip = (unsigned long) ret_from_kernel_thread; savesegment(gs, childregs->gs); childregs->ds = __KERNEL_DS; childregs->es = __KERNEL_DS; childregs->fs = __KERNEL_PERCPU; childregs->bx = sp; /* function */ childregs->bp = arg; childregs->orig_ax = -1; childregs->cs = __KERNEL_CS | get_kernel_rpl(); childregs->flags = X86_EFLAGS_IF | X86_EFLAGS_BIT1; p->fpu_counter = 0; p->thread.io_bitmap_ptr = NULL; memset(p->thread.ptrace_bps, 0, sizeof(p->thread.ptrace_bps)); return 0; } *childregs = *current_pt_regs(); childregs->ax = 0; if (sp) childregs->sp = sp; p->thread.ip = (unsigned long) ret_from_fork; task_user_gs(p) = get_user_gs(current_pt_regs()); p->fpu_counter = 0; p->thread.io_bitmap_ptr = NULL; tsk = current; err = -ENOMEM; memset(p->thread.ptrace_bps, 0, sizeof(p->thread.ptrace_bps)); if (unlikely(test_tsk_thread_flag(tsk, TIF_IO_BITMAP))) { p->thread.io_bitmap_ptr = kmemdup(tsk->thread.io_bitmap_ptr, IO_BITMAP_BYTES, GFP_KERNEL); if (!p->thread.io_bitmap_ptr) { p->thread.io_bitmap_max = 0; return -ENOMEM; } set_tsk_thread_flag(p, TIF_IO_BITMAP); } err = 0; /* * Set a new TLS for the child thread? */ if (clone_flags & CLONE_SETTLS) err = do_set_thread_area(p, -1, (struct user_desc __user *)childregs->si, 0); if (err && p->thread.io_bitmap_ptr) { kfree(p->thread.io_bitmap_ptr); p->thread.io_bitmap_max = 0; } return err; }
static int __cpuinit cpu_initialize_context(unsigned int cpu, struct task_struct *idle) { struct vcpu_guest_context *ctxt; struct desc_struct *gdt; unsigned long gdt_mfn; if (cpumask_test_and_set_cpu(cpu, xen_cpu_initialized_map)) return 0; ctxt = kzalloc(sizeof(*ctxt), GFP_KERNEL); if (ctxt == NULL) return -ENOMEM; gdt = get_cpu_gdt_table(cpu); ctxt->flags = VGCF_IN_KERNEL; ctxt->user_regs.ss = __KERNEL_DS; #ifdef CONFIG_X86_32 ctxt->user_regs.fs = __KERNEL_PERCPU; savesegment(gs, ctxt->user_regs.gs); #else ctxt->gs_base_kernel = per_cpu_offset(cpu); #endif ctxt->user_regs.eip = (unsigned long)cpu_bringup_and_idle; memset(&ctxt->fpu_ctxt, 0, sizeof(ctxt->fpu_ctxt)); { ctxt->user_regs.eflags = 0x1000; /* IOPL_RING1 */ ctxt->user_regs.ds = __KERNEL_DS; ctxt->user_regs.es = __KERNEL_DS; xen_copy_trap_info(ctxt->trap_ctxt); ctxt->ldt_ents = 0; BUG_ON((unsigned long)gdt & ~PAGE_MASK); gdt_mfn = arbitrary_virt_to_mfn(gdt); make_lowmem_page_readonly(gdt); make_lowmem_page_readonly(mfn_to_virt(gdt_mfn)); ctxt->gdt_frames[0] = gdt_mfn; ctxt->gdt_ents = GDT_ENTRIES; ctxt->kernel_ss = __KERNEL_DS; ctxt->kernel_sp = idle->thread.sp0; #ifdef CONFIG_X86_32 ctxt->event_callback_cs = __KERNEL_CS; ctxt->failsafe_callback_cs = __KERNEL_CS; #endif ctxt->event_callback_eip = (unsigned long)xen_hypervisor_callback; ctxt->failsafe_callback_eip = (unsigned long)xen_failsafe_callback; } ctxt->user_regs.cs = __KERNEL_CS; ctxt->user_regs.esp = idle->thread.sp0 - sizeof(struct pt_regs); per_cpu(xen_cr3, cpu) = __pa(swapper_pg_dir); ctxt->ctrlreg[3] = xen_pfn_to_cr3(virt_to_mfn(swapper_pg_dir)); if (HYPERVISOR_vcpu_op(VCPUOP_initialise, cpu, ctxt)) BUG(); kfree(ctxt); return 0; }
/* * switch_to(x,yn) should switch tasks from x to y. * * We fsave/fwait so that an exception goes off at the right time * (as a call from the fsave or fwait in effect) rather than to * the wrong process. Lazy FP saving no longer makes any sense * with modern CPU's, and this simplifies a lot of things (SMP * and UP become the same). * * NOTE! We used to use the x86 hardware context switching. The * reason for not using it any more becomes apparent when you * try to recover gracefully from saved state that is no longer * valid (stale segment register values in particular). With the * hardware task-switch, there is no way to fix up bad state in * a reasonable manner. * * The fact that Intel documents the hardware task-switching to * be slow is a fairly red herring - this code is not noticeably * faster. However, there _is_ some room for improvement here, * so the performance issues may eventually be a valid point. * More important, however, is the fact that this allows us much * more flexibility. * * The return value (in %eax) will be the "prev" task after * the task-switch, and shows up in ret_from_fork in entry.S, * for example. */ struct task_struct fastcall * __switch_to(struct task_struct *prev_p, struct task_struct *next_p) { struct thread_struct *prev = &prev_p->thread, *next = &next_p->thread; int cpu = smp_processor_id(); struct tss_struct *tss = &per_cpu(init_tss, cpu); /* never put a printk in __switch_to... printk() calls wake_up*() indirectly */ __unlazy_fpu(prev_p); /* we're going to use this soon, after a few expensive things */ if (next_p->fpu_counter > 5) prefetch(&next->i387.fxsave); /* * Reload esp0. */ load_esp0(tss, next); /* * Save away %gs. No need to save %fs, as it was saved on the * stack on entry. No need to save %es and %ds, as those are * always kernel segments while inside the kernel. Doing this * before setting the new TLS descriptors avoids the situation * where we temporarily have non-reloadable segments in %fs * and %gs. This could be an issue if the NMI handler ever * used %fs or %gs (it does not today), or if the kernel is * running inside of a hypervisor layer. */ savesegment(gs, prev->gs); /* * Load the per-thread Thread-Local Storage descriptor. */ load_TLS(next, cpu); /* * Restore IOPL if needed. In normal use, the flags restore * in the switch assembly will handle this. But if the kernel * is running virtualized at a non-zero CPL, the popf will * not restore flags, so it must be done in a separate step. */ if (get_kernel_rpl() && unlikely(prev->iopl != next->iopl)) set_iopl_mask(next->iopl); /* * Now maybe handle debug registers and/or IO bitmaps */ if (unlikely((task_thread_info(next_p)->flags & _TIF_WORK_CTXSW) || test_tsk_thread_flag(prev_p, TIF_IO_BITMAP))) __switch_to_xtra(next_p, tss); disable_tsc(prev_p, next_p); /* * Leave lazy mode, flushing any hypercalls made here. * This must be done before restoring TLS segments so * the GDT and LDT are properly updated, and must be * done before math_state_restore, so the TS bit is up * to date. */ arch_leave_lazy_cpu_mode(); /* If the task has used fpu the last 5 timeslices, just do a full * restore of the math state immediately to avoid the trap; the * chances of needing FPU soon are obviously high now */ if (next_p->fpu_counter > 5) math_state_restore(); /* * Restore %gs if needed (which is common) */ if (prev->gs | next->gs) loadsegment(gs, next->gs); x86_write_percpu(current_task, next_p); return prev_p; }