Clean up segment handling: switch user-space to using code and data

segments in the GDT instead of the LDT and eliminate the GDT slots
that we don't actually use.

tested on both amd and intel by several
not really the right person, but ok: kettenis@

4 files changed, 32 insertions, 47 deletions

diff --git a/sys/arch/amd64/amd64/cpu.c b/sys/arch/amd64/amd64/cpu.c
index a42691a6363..5661b800203 100644
--- a/sys/arch/amd64/amd64/cpu.c
+++ b/sys/arch/amd64/amd64/cpu.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: cpu.c,v 1.35 2010/07/25 21:43:38 deraadt Exp $	*/
+/*	$OpenBSD: cpu.c,v 1.36 2010/10/14 04:38:24 guenther Exp $	*/
 /* $NetBSD: cpu.c,v 1.1 2003/04/26 18:39:26 fvdl Exp $ */
 
 /*-
@@ -654,7 +654,7 @@ cpu_init_msrs(struct cpu_info *ci)
 {
 	wrmsr(MSR_STAR,
 	    ((uint64_t)GSEL(GCODE_SEL, SEL_KPL) << 32) |
-	    ((uint64_t)LSEL(LSYSRETBASE_SEL, SEL_UPL) << 48));
+	    ((uint64_t)GSEL(GUCODE32_SEL, SEL_UPL) << 48));
 	wrmsr(MSR_LSTAR, (uint64_t)Xsyscall);
 	wrmsr(MSR_CSTAR, (uint64_t)Xsyscall32);
 	wrmsr(MSR_SFMASK, PSL_NT|PSL_T|PSL_I|PSL_C);
diff --git a/sys/arch/amd64/amd64/locore.S b/sys/arch/amd64/amd64/locore.S
index 8d4459f86c9..2b47a252132 100644
--- a/sys/arch/amd64/amd64/locore.S
+++ b/sys/arch/amd64/amd64/locore.S
@@ -1,4 +1,4 @@
-/*	$OpenBSD: locore.S,v 1.40 2010/09/28 03:53:14 guenther Exp $	*/
+/*	$OpenBSD: locore.S,v 1.41 2010/10/14 04:38:24 guenther Exp $	*/
 /*	$NetBSD: locore.S,v 1.13 2004/03/25 18:33:17 drochner Exp $	*/
 
 /*
@@ -911,7 +911,7 @@ IDTVEC(syscall)
 	 * ss:rsp, etc, so that all GP registers can be
 	 * saved. Then, fill in the rest.
 	 */
-	pushq	$(LSEL(LUDATA_SEL, SEL_UPL))
+	pushq	$(GSEL(GUDATA_SEL, SEL_UPL))
 	pushq	%r15
 	subq	$(TF_RSP-TF_TRAPNO),%rsp
 	movq	CPUVAR(SCRATCH),%r15
@@ -920,9 +920,9 @@ IDTVEC(syscall)
 	movw	%fs,TF_FS(%rsp)
 	movw	%gs,TF_GS(%rsp)
 	movw	%es,TF_ES(%rsp)
-	movw	$(LSEL(LUDATA_SEL, SEL_UPL)),TF_DS(%rsp)
+	movw	$(GSEL(GUDATA_SEL, SEL_UPL)),TF_DS(%rsp)
 	movq	%r11, TF_RFLAGS(%rsp)	/* old rflags from syscall insn */
-	movq	$(LSEL(LUCODE_SEL, SEL_UPL)), TF_CS(%rsp)
+	movq	$(GSEL(GUCODE_SEL, SEL_UPL)), TF_CS(%rsp)
 	movq	%rcx,TF_RIP(%rsp)
 	movq	$2,TF_ERR(%rsp)
 	movq	$T_ASTFLT, TF_TRAPNO(%rsp)
@@ -961,7 +961,7 @@ syscall_return:
 	movw	TF_FS(%rsp),%fs
 	movw	TF_GS(%rsp),%gs
 	INTR_RESTORE_GPRS
-	movw	$(LSEL(LUDATA_SEL, SEL_UPL)),%r11
+	movw	$(GSEL(GUDATA_SEL, SEL_UPL)),%r11
 	movw	%r11,%ds
 	addq	$48,%rsp
 	popq	%rcx	/* return rip */
diff --git a/sys/arch/amd64/amd64/machdep.c b/sys/arch/amd64/amd64/machdep.c
index 46d8724262b..a666456e78d 100644
--- a/sys/arch/amd64/amd64/machdep.c
+++ b/sys/arch/amd64/amd64/machdep.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: machdep.c,v 1.124 2010/10/02 23:31:33 deraadt Exp $	*/
+/*	$OpenBSD: machdep.c,v 1.125 2010/10/14 04:38:24 guenther Exp $	*/
 /*	$NetBSD: machdep.c,v 1.3 2003/05/07 22:58:18 fvdl Exp $	*/
 
 /*-
@@ -612,10 +612,10 @@ sendsig(sig_t catcher, int sig, int mask, u_long code, int type,
 	/*
 	 * Build context to run handler in.
 	 */
-	tf->tf_ds = LSEL(LUDATA_SEL, SEL_UPL);
-	tf->tf_es = LSEL(LUDATA_SEL, SEL_UPL);
-	tf->tf_fs = LSEL(LUDATA_SEL, SEL_UPL);
-	tf->tf_gs = LSEL(LUDATA_SEL, SEL_UPL);
+	tf->tf_ds = GSEL(GUDATA_SEL, SEL_UPL);
+	tf->tf_es = GSEL(GUDATA_SEL, SEL_UPL);
+	tf->tf_fs = GSEL(GUDATA_SEL, SEL_UPL);
+	tf->tf_gs = GSEL(GUDATA_SEL, SEL_UPL);
 
 	tf->tf_rax = (u_int64_t)catcher;
 	tf->tf_rdi = sig;
@@ -623,10 +623,10 @@ sendsig(sig_t catcher, int sig, int mask, u_long code, int type,
 	tf->tf_rdx = scp;
 
 	tf->tf_rip = (u_int64_t)p->p_sigcode;
-	tf->tf_cs = LSEL(LUCODE_SEL, SEL_UPL);
+	tf->tf_cs = GSEL(GUCODE_SEL, SEL_UPL);
 	tf->tf_rflags &= ~(PSL_T|PSL_D|PSL_VM|PSL_AC);
 	tf->tf_rsp = scp;
-	tf->tf_ss = LSEL(LUDATA_SEL, SEL_UPL);
+	tf->tf_ss = GSEL(GUDATA_SEL, SEL_UPL);
 
 #ifdef DEBUG
 	if ((sigdebug & SDB_FOLLOW) && (!sigpid || p->p_pid == sigpid))
@@ -1018,10 +1018,10 @@ setregs(struct proc *p, struct exec_package *pack, u_long stack,
 	pcb->pcb_flags = 0;
 
 	tf = p->p_md.md_regs;
-	tf->tf_ds = LSEL(LUDATA_SEL, SEL_UPL);
-	tf->tf_es = LSEL(LUDATA_SEL, SEL_UPL);
-	tf->tf_fs = LSEL(LUDATA_SEL, SEL_UPL);
-	tf->tf_gs = LSEL(LUDATA_SEL, SEL_UPL);
+	tf->tf_ds = GSEL(GUDATA_SEL, SEL_UPL);
+	tf->tf_es = GSEL(GUDATA_SEL, SEL_UPL);
+	tf->tf_fs = GSEL(GUDATA_SEL, SEL_UPL);
+	tf->tf_gs = GSEL(GUDATA_SEL, SEL_UPL);
 	tf->tf_rdi = 0;
 	tf->tf_rsi = 0;
 	tf->tf_rbp = 0;
@@ -1038,10 +1038,10 @@ setregs(struct proc *p, struct exec_package *pack, u_long stack,
 	tf->tf_r14 = 0;
 	tf->tf_r15 = 0;
 	tf->tf_rip = pack->ep_entry;
-	tf->tf_cs = LSEL(LUCODE_SEL, SEL_UPL);
+	tf->tf_cs = GSEL(GUCODE_SEL, SEL_UPL);
 	tf->tf_rflags = PSL_USERSET;
 	tf->tf_rsp = stack;
-	tf->tf_ss = LSEL(LUDATA_SEL, SEL_UPL);
+	tf->tf_ss = GSEL(GUDATA_SEL, SEL_UPL);
 
 	retval[1] = 0;
 }
@@ -1498,12 +1498,15 @@ init_x86_64(paddr_t first_avail)
 	set_sys_segment(GDT_ADDR_SYS(gdtstore, GLDT_SEL), ldtstore, LDT_SIZE - 1,
 	    SDT_SYSLDT, SEL_KPL, 0);
 
-	set_mem_segment(GDT_ADDR_MEM(gdtstore, GUCODE_SEL), 0,
-	    atop(VM_MAXUSER_ADDRESS) - 1, SDT_MEMERA, SEL_UPL, 1, 0, 1);
+	set_mem_segment(GDT_ADDR_MEM(gdtstore, GUCODE32_SEL), 0,
+	    atop(VM_MAXUSER_ADDRESS) - 1, SDT_MEMERA, SEL_UPL, 1, 1, 0);
 
 	set_mem_segment(GDT_ADDR_MEM(gdtstore, GUDATA_SEL), 0,
 	    atop(VM_MAXUSER_ADDRESS) - 1, SDT_MEMRWA, SEL_UPL, 1, 0, 1);
 
+	set_mem_segment(GDT_ADDR_MEM(gdtstore, GUCODE_SEL), 0,
+	    atop(VM_MAXUSER_ADDRESS) - 1, SDT_MEMERA, SEL_UPL, 1, 0, 1);
+
 	/* make ldt gates and memory segments */
 	setgate((struct gate_descriptor *)(ldtstore + LSYS5CALLS_SEL),
 	    &IDTVEC(oosyscall), 0, SDT_SYS386CGT, SEL_UPL,
@@ -1515,16 +1518,6 @@ init_x86_64(paddr_t first_avail)
 	    *GDT_ADDR_MEM(gdtstore, GUDATA_SEL);
 
 	/*
-	 * 32 bit GDT entries.
-	 */
-
-	set_mem_segment(GDT_ADDR_MEM(gdtstore, GUCODE32_SEL), 0,
-	    atop(VM_MAXUSER_ADDRESS) - 1, SDT_MEMERA, SEL_UPL, 1, 1, 0);
-
-	set_mem_segment(GDT_ADDR_MEM(gdtstore, GUDATA32_SEL), 0,
-	    atop(VM_MAXUSER_ADDRESS) - 1, SDT_MEMRWA, SEL_UPL, 1, 1, 0);
-
-	/*
 	 * 32 bit LDT entries.
 	 */
 	ldt_segp = (struct mem_segment_descriptor *)(ldtstore + LUCODE32_SEL);
diff --git a/sys/arch/amd64/include/segments.h b/sys/arch/amd64/include/segments.h
index 5e9fbd6b2bc..87acb9c7c4b 100644
--- a/sys/arch/amd64/include/segments.h
+++ b/sys/arch/amd64/include/segments.h
@@ -1,4 +1,4 @@
-/*	$OpenBSD: segments.h,v 1.5 2008/05/23 15:39:43 jasper Exp $	*/
+/*	$OpenBSD: segments.h,v 1.6 2010/10/14 04:38:24 guenther Exp $	*/
 /*	$NetBSD: segments.h,v 1.1 2003/04/26 18:39:47 fvdl Exp $	*/
 
 /*-
@@ -253,24 +253,17 @@ void cpu_init_idt(void);
  *
  * Then come the predefined LDT (and possibly TSS) descriptors.
  * There are NGDT_SYS of them.
+ *
+ * The particular order of the UCODE32, UDATA, and UCODE descriptors is 
+ * required by the syscall/sysret instructions.
  */
 #define	GNULL_SEL	0	/* Null descriptor */
 #define	GCODE_SEL	1	/* Kernel code descriptor */
 #define	GDATA_SEL	2	/* Kernel data descriptor */
-#define	GUCODE_SEL	3	/* User code descriptor */
+#define	GUCODE32_SEL	3	/* User 32bit code descriptor (unused) */
 #define	GUDATA_SEL	4	/* User data descriptor */
-#define	GAPM32CODE_SEL	5
-#define	GAPM16CODE_SEL	6
-#define	GAPMDATA_SEL	7
-#define	GBIOSCODE_SEL	8
-#define	GBIOSDATA_SEL	9
-#define GPNPBIOSCODE_SEL 10
-#define GPNPBIOSDATA_SEL 11
-#define GPNPBIOSSCRATCH_SEL 12
-#define GPNPBIOSTRAMP_SEL 13
-#define GUCODE32_SEL	14
-#define GUDATA32_SEL	15
-#define NGDT_MEM 16
+#define	GUCODE_SEL	5	/* User code descriptor */
+#define NGDT_MEM 6
 
 #define	GLDT_SEL	0	/* Default LDT descriptor */
 #define NGDT_SYS	1
@@ -296,7 +289,6 @@ void cpu_init_idt(void);
 
 #define LDT_SIZE	144
 
-#define LSYSRETBASE_SEL	LUCODE32_SEL
 
 /*
  * Checks for valid user selectors.