Burn more LDT deadwood: stop allocating one for each idle thread,

load the ldt register with the null selector (disabling use of it),
stop reloading it on every context switch, and blow away the table
itself, as well as the pcb and pmap bits that were used to track
it (making sure to keep pcb_savefpu correctly aligned).

testing naddy@
ok kettenis@ mpi@ mlarkin@

10 files changed, 29 insertions, 92 deletions

diff --git a/sys/arch/i386/i386/autoconf.c b/sys/arch/i386/i386/autoconf.c
index 6660ebb992d..6660701dc9f 100644
--- a/sys/arch/i386/i386/autoconf.c
+++ b/sys/arch/i386/i386/autoconf.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: autoconf.c,v 1.95 2015/12/27 04:31:34 jsg Exp $	*/
+/*	$OpenBSD: autoconf.c,v 1.96 2016/03/15 03:17:50 guenther Exp $	*/
 /*	$NetBSD: autoconf.c,v 1.20 1996/05/03 19:41:56 christos Exp $	*/
 
 /*-
@@ -122,8 +122,8 @@ cpu_configure(void)
 
 	gdt_init();		/* XXX - pcibios uses gdt stuff */
 
-	/* Set up proc0's TSS and LDT */
-	i386_proc0_tss_ldt_init();
+	/* Set up proc0's TSS */
+	i386_proc0_tss_init();
 
 #ifdef KVM86
 	kvm86_init();
@@ -158,7 +158,7 @@ cpu_configure(void)
 	proc0.p_addr->u_pcb.pcb_cr0 = rcr0();
 
 #ifdef MULTIPROCESSOR
-	/* propagate TSS and LDT configuration to the idle pcb's. */
+	/* propagate TSS configuration to the idle pcb's. */
 	cpu_init_idle_pcbs();
 #endif
 	spl0();
diff --git a/sys/arch/i386/i386/cpu.c b/sys/arch/i386/i386/cpu.c
index a5de783722f..e88373c3898 100644
--- a/sys/arch/i386/i386/cpu.c
+++ b/sys/arch/i386/i386/cpu.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: cpu.c,v 1.72 2016/03/07 05:32:46 naddy Exp $	*/
+/*	$OpenBSD: cpu.c,v 1.73 2016/03/15 03:17:50 guenther Exp $	*/
 /* $NetBSD: cpu.c,v 1.1.2.7 2000/06/26 02:04:05 sommerfeld Exp $ */
 
 /*-
@@ -272,8 +272,6 @@ cpu_attach(struct device *parent, struct device *self, void *aux)
 	    sizeof (struct trapframe);
 	pcb->pcb_pmap = pmap_kernel();
 	pcb->pcb_cr3 = pcb->pcb_pmap->pm_pdirpa;
-
-	cpu_default_ldt(ci);	/* Use the `global' ldt until one alloc'd */
 #endif
 	ci->ci_curpmap = pmap_kernel();
 
@@ -323,7 +321,6 @@ cpu_attach(struct device *parent, struct device *self, void *aux)
 
 #ifdef MULTIPROCESSOR
 		gdt_alloc_cpu(ci);
-		cpu_alloc_ldt(ci);
 		ci->ci_flags |= CPUF_PRESENT | CPUF_AP;
 		identifycpu(ci);
 		sched_init_cpu(ci);
@@ -522,7 +519,7 @@ cpu_init_idle_pcbs(void)
 			continue;
 		if ((ci->ci_flags & CPUF_PRESENT) == 0)
 			continue;
-		i386_init_pcb_tss_ldt(ci);
+		i386_init_pcb_tss(ci);
 	}
 }
 
@@ -579,9 +576,8 @@ cpu_hatch(void *v)
 	lapic_startclock();
 	lapic_set_lvt();
 	gdt_init_cpu(ci);
-	cpu_init_ldt(ci);
 
-	lldt(GSEL(GLDT_SEL, SEL_KPL));
+	lldt(0);
 
 	npxinit(ci);
 
@@ -632,7 +628,7 @@ cpu_init_tss(struct i386tss *tss, void *stack, void *func)
 	    tss->__tss_ss = GSEL(GDATA_SEL, SEL_KPL);
 	tss->tss_cr3 = pmap_kernel()->pm_pdirpa;
 	tss->tss_esp = (int)((char *)stack + USPACE - 16);
-	tss->tss_ldt = GSEL(GLDT_SEL, SEL_KPL);
+	tss->tss_ldt = 0;
 	tss->__tss_eflags = PSL_MBO | PSL_NT;	/* XXX not needed? */
 	tss->__tss_eip = (int)func;
 }
diff --git a/sys/arch/i386/i386/genassym.cf b/sys/arch/i386/i386/genassym.cf
index 37c302bf06a..56857faa88e 100644
--- a/sys/arch/i386/i386/genassym.cf
+++ b/sys/arch/i386/i386/genassym.cf
@@ -1,4 +1,4 @@
-#	$OpenBSD: genassym.cf,v 1.38 2016/02/28 15:46:18 naddy Exp $
+#	$OpenBSD: genassym.cf,v 1.39 2016/03/15 03:17:51 guenther Exp $
 #
 # Copyright (c) 1982, 1990 The Regents of the University of California.
 # All rights reserved.
@@ -93,8 +93,6 @@ member	pcb_cr3
 member	pcb_ebp
 member	pcb_esp
 member	pcb_cr0
-member	pcb_ldt
-member	pcb_ldt_sel
 member	pcb_onfault
 member	pcb_fpcpu
 member	pcb_flags
diff --git a/sys/arch/i386/i386/locore.s b/sys/arch/i386/i386/locore.s
index e533b6d3684..9581f32d310 100644
--- a/sys/arch/i386/i386/locore.s
+++ b/sys/arch/i386/i386/locore.s
@@ -1,4 +1,4 @@
-/*	$OpenBSD: locore.s,v 1.166 2016/03/09 13:46:14 mpi Exp $	*/
+/*	$OpenBSD: locore.s,v 1.167 2016/03/15 03:17:51 guenther Exp $	*/
 /*	$NetBSD: locore.s,v 1.145 1996/05/03 19:41:19 christos Exp $	*/
 
 /*-
@@ -1187,8 +1187,8 @@ switch_exited:
 	movl	%ebx, CPUVAR(CURPCB)
 
 	/*
-	 * Activate the address space.  The pcb copy of %cr3 and the
-	 * LDT will be refreshed from the pmap, and because we're
+	 * Activate the address space.  The pcb copy of %cr3 will
+	 * be refreshed from the pmap, and because we're
 	 * curproc they'll both be reloaded into the CPU.
 	 */
 	pushl	%edi
diff --git a/sys/arch/i386/i386/machdep.c b/sys/arch/i386/i386/machdep.c
index 372f439a0ac..cb66e9d4a66 100644
--- a/sys/arch/i386/i386/machdep.c
+++ b/sys/arch/i386/i386/machdep.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: machdep.c,v 1.581 2016/03/07 05:32:46 naddy Exp $	*/
+/*	$OpenBSD: machdep.c,v 1.582 2016/03/15 03:17:51 guenther Exp $	*/
 /*	$NetBSD: machdep.c,v 1.214 1996/11/10 03:16:17 thorpej Exp $	*/
 
 /*-
@@ -454,10 +454,10 @@ cpu_startup(void)
 }
 
 /*
- * Set up proc0's TSS and LDT.
+ * Set up proc0's TSS
  */
 void
-i386_proc0_tss_ldt_init(void)
+i386_proc0_tss_init(void)
 {
 	int x;
 	struct pcb *pcb;
@@ -470,8 +470,6 @@ i386_proc0_tss_ldt_init(void)
 		pcb->pcb_iomap[x] = 0xffffffff;
 	pcb->pcb_iomap_pad = 0xff;
 
-	pcb->pcb_ldt_sel = pmap_kernel()->pm_ldt_sel = GSEL(GLDT_SEL, SEL_KPL);
-	pcb->pcb_ldt = ldt;
 	pcb->pcb_cr0 = rcr0();
 	pcb->pcb_tss.tss_ss0 = GSEL(GDATA_SEL, SEL_KPL);
 	pcb->pcb_tss.tss_esp0 = (int)proc0.p_addr + USPACE - 16;
@@ -479,12 +477,12 @@ i386_proc0_tss_ldt_init(void)
 	proc0.p_md.md_tss_sel = tss_alloc(pcb);
 
 	ltr(proc0.p_md.md_tss_sel);
-	lldt(pcb->pcb_ldt_sel);
+	lldt(0);
 }
 
 #ifdef MULTIPROCESSOR
 void
-i386_init_pcb_tss_ldt(struct cpu_info *ci)
+i386_init_pcb_tss(struct cpu_info *ci)
 {
 	int x;
 	struct pcb *pcb = ci->ci_idle_pcb;
@@ -495,8 +493,6 @@ i386_init_pcb_tss_ldt(struct cpu_info *ci)
 		pcb->pcb_iomap[x] = 0xffffffff;
 	pcb->pcb_iomap_pad = 0xff;
 
-	pcb->pcb_ldt_sel = pmap_kernel()->pm_ldt_sel = GSEL(GLDT_SEL, SEL_KPL);
-	pcb->pcb_ldt = ci->ci_ldt;
 	pcb->pcb_cr0 = rcr0();
 	ci->ci_idle_tss_sel = tss_alloc(pcb);
 }
@@ -2954,7 +2950,6 @@ setregs(struct proc *p, struct exec_package *pack, u_long stack,
  * Initialize segments and descriptor tables
  */
 
-union descriptor ldt[NLDT];
 struct gate_descriptor idt_region[NIDT];
 struct gate_descriptor *idt = idt_region;
 
@@ -3062,33 +3057,7 @@ cpu_init_idt(void)
 	setregion(&region, idt, NIDT * sizeof(idt[0]) - 1);
 	lidt(&region);
 }
-
-void
-cpu_default_ldt(struct cpu_info *ci)
-{
-	ci->ci_ldt = ldt;
-	ci->ci_ldt_len = sizeof(ldt);
-}
-
-void
-cpu_alloc_ldt(struct cpu_info *ci)
-{
-	union descriptor *cpu_ldt;
-	size_t len = sizeof(ldt);
-
-	cpu_ldt = (union descriptor *)uvm_km_alloc(kernel_map, len);
-	bcopy(ldt, cpu_ldt, len);
-	ci->ci_ldt = cpu_ldt;
-	ci->ci_ldt_len = len;
-}
-
-void
-cpu_init_ldt(struct cpu_info *ci)
-{
-	setsegment(&ci->ci_gdt[GLDT_SEL].sd, ci->ci_ldt, ci->ci_ldt_len - 1,
-	    SDT_SYSLDT, SEL_KPL, 0, 0);
-}
-#endif	/* MULTIPROCESSOR */
+#endif /* MULTIPROCESSOR */
 
 void
 init386(paddr_t first_avail)
@@ -3105,8 +3074,6 @@ init386(paddr_t first_avail)
 	setsegment(&gdt[GCODE_SEL].sd, 0, 0xfffff, SDT_MEMERA, SEL_KPL, 1, 1);
 	setsegment(&gdt[GICODE_SEL].sd, 0, 0xfffff, SDT_MEMERA, SEL_KPL, 1, 1);
 	setsegment(&gdt[GDATA_SEL].sd, 0, 0xfffff, SDT_MEMRWA, SEL_KPL, 1, 1);
-	setsegment(&gdt[GLDT_SEL].sd, ldt, sizeof(ldt) - 1, SDT_SYSLDT,
-	    SEL_KPL, 0, 0);
 	setsegment(&gdt[GUCODE_SEL].sd, 0, atop(I386_MAX_EXE_ADDR) - 1,
 	    SDT_MEMERA, SEL_UPL, 1, 1);
 	setsegment(&gdt[GUDATA_SEL].sd, 0, atop(VM_MAXUSER_ADDRESS) - 1,
diff --git a/sys/arch/i386/i386/pmap.c b/sys/arch/i386/i386/pmap.c
index ba5d469be92..7e81b2ad43f 100644
--- a/sys/arch/i386/i386/pmap.c
+++ b/sys/arch/i386/i386/pmap.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: pmap.c,v 1.188 2016/03/07 05:32:47 naddy Exp $	*/
+/*	$OpenBSD: pmap.c,v 1.189 2016/03/15 03:17:51 guenther Exp $	*/
 /*	$NetBSD: pmap.c,v 1.91 2000/06/02 17:46:37 thorpej Exp $	*/
 
 /*
@@ -1287,11 +1287,6 @@ pmap_create(void)
 	pmap->pm_hiexec = 0;
 	pmap->pm_flags = 0;
 
-	/* init the LDT */
-	pmap->pm_ldt = NULL;
-	pmap->pm_ldt_len = 0;
-	pmap->pm_ldt_sel = GSEL(GLDT_SEL, SEL_KPL);
-
 	setsegment(&pmap->pm_codeseg, 0, atop(I386_MAX_EXE_ADDR) - 1,
 	    SDT_MEMERA, SEL_UPL, 1, 1);
 
@@ -1398,13 +1393,6 @@ pmap_switch(struct proc *o, struct proc *p)
 	opmap = self->ci_curpmap;
 
 	pcb->pcb_pmap = pmap;
-	/* Get the LDT that this process will actually use */
-#ifdef MULTIPROCESSOR
-	pcb->pcb_ldt = pmap->pm_ldt == NULL ? self->ci_ldt : pmap->pm_ldt;
-#else
-	pcb->pcb_ldt = pmap->pm_ldt == NULL ? ldt : pmap->pm_ldt;
-#endif
-	pcb->pcb_ldt_sel = pmap->pm_ldt_sel;
 	pcb->pcb_cr3 = pmap->pm_pdirpa;
 
 	if (opmap == pmap) {
@@ -1424,8 +1412,6 @@ pmap_switch(struct proc *o, struct proc *p)
 	self->ci_gdt[GUCODE_SEL].sd = pmap->pm_codeseg;
 	self->ci_gdt[GUFS_SEL].sd = pcb->pcb_threadsegs[TSEG_FS];
 	self->ci_gdt[GUGS_SEL].sd = pcb->pcb_threadsegs[TSEG_GS];
-
-	lldt(pcb->pcb_ldt_sel);
 }
 
 void
diff --git a/sys/arch/i386/include/cpu.h b/sys/arch/i386/include/cpu.h
index 3d9bc1bef7a..18166923abd 100644
--- a/sys/arch/i386/include/cpu.h
+++ b/sys/arch/i386/include/cpu.h
@@ -1,4 +1,4 @@
-/*	$OpenBSD: cpu.h,v 1.146 2016/03/03 12:41:30 naddy Exp $	*/
+/*	$OpenBSD: cpu.h,v 1.147 2016/03/15 03:17:51 guenther Exp $	*/
 /*	$NetBSD: cpu.h,v 1.35 1996/05/05 19:29:26 christos Exp $	*/
 
 /*-
@@ -142,8 +142,6 @@ struct cpu_info {
 	int		ci_want_resched;
 
 	union descriptor *ci_gdt;
-	union descriptor *ci_ldt;	/* per-cpu default LDT */
-	int		ci_ldt_len;	/* in bytes */
 
 	volatile int ci_ddb_paused;	/* paused due to other proc in ddb */
 #define CI_DDB_RUNNING		0
@@ -387,8 +385,8 @@ extern void (*update_cpuspeed)(void);
 /* machdep.c */
 void	dumpconf(void);
 void	cpu_reset(void);
-void	i386_proc0_tss_ldt_init(void);
-void	i386_init_pcb_tss_ldt(struct cpu_info *);
+void	i386_proc0_tss_init(void);
+void	i386_init_pcb_tss(struct cpu_info *);
 void	cpuid(u_int32_t, u_int32_t *);
 
 /* locore.s */
diff --git a/sys/arch/i386/include/pcb.h b/sys/arch/i386/include/pcb.h
index 8fd23c94a81..62fafde53f4 100644
--- a/sys/arch/i386/include/pcb.h
+++ b/sys/arch/i386/include/pcb.h
@@ -1,4 +1,4 @@
-/*	$OpenBSD: pcb.h,v 1.18 2015/05/05 02:13:46 guenther Exp $	*/
+/*	$OpenBSD: pcb.h,v 1.19 2016/03/15 03:17:51 guenther Exp $	*/
 /*	$NetBSD: pcb.h,v 1.21 1996/01/08 13:51:42 mycroft Exp $	*/
 
 /*-
@@ -58,11 +58,9 @@ struct pcb {
 #define	pcb_esp	pcb_tss.tss_esp
 #define	pcb_ebp	pcb_tss.tss_ebp
 #define	pcb_cs	pcb_tss.tss_cs
-#define	pcb_ldt_sel	pcb_tss.tss_ldt
-	union	descriptor *pcb_ldt;	/* per process (user) LDT */
-	int	pcb_ldt_len;		/*      number of LDT entries */
-	union	savefpu pcb_savefpu;	/* floating point state for FPU */
 	int	pcb_cr0;		/* saved image of CR0 */
+	int	__pcb_padding;		/* for 16-byte align of pcb_savefpu */
+	union	savefpu pcb_savefpu;	/* floating point state for FPU */
 	struct	segment_descriptor pcb_threadsegs[2];
 					/* per-thread descriptors */
 /*
diff --git a/sys/arch/i386/include/pmap.h b/sys/arch/i386/include/pmap.h
index 656ad424e9c..1614b117cab 100644
--- a/sys/arch/i386/include/pmap.h
+++ b/sys/arch/i386/include/pmap.h
@@ -1,4 +1,4 @@
-/*	$OpenBSD: pmap.h,v 1.81 2016/03/07 05:32:47 naddy Exp $	*/
+/*	$OpenBSD: pmap.h,v 1.82 2016/03/15 03:17:51 guenther Exp $	*/
 /*	$NetBSD: pmap.h,v 1.44 2000/04/24 17:18:18 thorpej Exp $	*/
 
 /*
@@ -106,9 +106,6 @@ struct pmap {
 	int pm_flags;			/* see below */
 
 	struct segment_descriptor pm_codeseg;	/* cs descriptor for process */
-	union descriptor *pm_ldt;	/* user-set LDT */
-	int pm_ldt_len;			/* number of LDT entries */
-	int pm_ldt_sel;			/* LDT selector */
 };
 
 /*
diff --git a/sys/arch/i386/include/segments.h b/sys/arch/i386/include/segments.h
index f19433322a0..8fe19ab2299 100644
--- a/sys/arch/i386/include/segments.h
+++ b/sys/arch/i386/include/segments.h
@@ -1,4 +1,4 @@
-/*	$OpenBSD: segments.h,v 1.20 2011/03/23 16:54:35 pirofti Exp $	*/
+/*	$OpenBSD: segments.h,v 1.21 2016/03/15 03:17:51 guenther Exp $	*/
 /*	$NetBSD: segments.h,v 1.23 1996/02/01 22:31:03 mycroft Exp $	*/
 
 /*-
@@ -116,7 +116,7 @@ struct region_descriptor {
 } __packed;
 
 #ifdef _KERNEL
-extern union descriptor *gdt, ldt[];
+extern union descriptor *gdt;
 extern struct gate_descriptor idt_region[];
 extern struct gate_descriptor *idt;
 
@@ -126,9 +126,6 @@ void setsegment(struct segment_descriptor *, void *, size_t, int, int,
     int, int);
 void unsetgate(struct gate_descriptor *);
 void cpu_init_idt(void);
-void cpu_default_ldt(struct cpu_info *);
-void cpu_alloc_ldt(struct cpu_info *);
-void cpu_init_ldt(struct cpu_info *);
 
 int idt_vec_alloc(int, int);
 void idt_vec_set(int, void (*)(void));
@@ -214,7 +211,7 @@ void idt_vec_free(int);
 #define	GNULL_SEL	0	/* Null descriptor */
 #define	GCODE_SEL	1	/* Kernel code descriptor */
 #define	GDATA_SEL	2	/* Kernel data descriptor */
-#define	GLDT_SEL	3	/* Default LDT descriptor */
+#define	GLDT_SEL	3	/* Default LDT descriptor (UNUSED) */
 #define	GCPU_SEL	4	/* per-CPU segment */
 #define	GUCODE_SEL	5	/* User code descriptor (a stack short) */
 #define	GUDATA_SEL	6	/* User data descriptor */