[kvm-unit-tests,06/18] x86: taskswitch: use desc library

Commit Message

Paolo Bonzini April 28, 2014, 3:22 p.m. UTC

The APIs in desc.c make it much simpler to understand what the test
is doing.

Signed-off-by: Paolo Bonzini <[e-mail]>
---
 lib/x86/desc.c   |   7 ++-
 lib/x86/desc.h   |   2 +
 x86/taskswitch.c | 134 +++++--------------------------------------------------
 3 files changed, 18 insertions(+), 125 deletions(-)

Patch

diff --git a/lib/x86/desc.c b/lib/x86/desc.c
index 812295c..442c9a1 100644
--- a/lib/x86/desc.c
+++ b/lib/x86/desc.c
@@ -217,6 +217,11 @@  void set_gdt_entry(int sel, u32 base,  u32 limit, u8 access, u8 gran)
 	gdt32[num].access = access;
 }
 
+void set_gdt_task_gate(u16 sel, u16 tss_sel)
+{
+    set_gdt_entry(sel, tss_sel, 0, 0x85, 0); // task, present
+}
+
 void set_idt_task_gate(int vec, u16 sel)
 {
     idt_entry_t *e = &boot_idt[vec];
@@ -235,7 +240,7 @@  void set_idt_task_gate(int vec, u16 sel)
  * 1 - interrupt task
  */
 
-static tss32_t tss_intr;
+tss32_t tss_intr;
 static char tss_stack[4096];
 
 void setup_tss32(void)
diff --git a/lib/x86/desc.h b/lib/x86/desc.h
index e0af335..4689474 100644
--- a/lib/x86/desc.h
+++ b/lib/x86/desc.h
@@ -106,6 +106,7 @@  extern idt_entry_t boot_idt[256];
 #ifndef __x86_64__
 extern gdt_entry_t gdt32[];
 extern tss32_t tss;
+extern tss32_t tss_intr;
 #endif
 
 unsigned exception_vector(void);
@@ -113,6 +114,7 @@  unsigned exception_error_code(void);
 void set_idt_entry(int vec, void *addr, int dpl);
 void set_idt_sel(int vec, u16 sel);
 void set_gdt_entry(int sel, u32 base,  u32 limit, u8 access, u8 gran);
+void set_gdt_task_gate(u16 tss_sel, u16 sel);
 void set_idt_task_gate(int vec, u16 sel);
 void set_intr_task_gate(int e, void *fn);
 void print_current_tss_info(void);
diff --git a/x86/taskswitch.c b/x86/taskswitch.c
index 8ed8a93..423f51e 100644
--- a/x86/taskswitch.c
+++ b/x86/taskswitch.c
@@ -6,152 +6,38 @@ 
  */
 
 #include "libcflat.h"
+#include "lib/x86/desc.h"
 
-#define FIRST_SPARE_SEL		0x18
-
-struct exception_frame {
-	unsigned long error_code;
-	unsigned long ip;
-	unsigned long cs;
-	unsigned long flags;
-};
-
-struct tss32 {
-	unsigned short prev;
-	unsigned short res1;
-	unsigned long esp0;
-	unsigned short ss0;
-	unsigned short res2;
-	unsigned long esp1;
-	unsigned short ss1;
-	unsigned short res3;
-	unsigned long esp2;
-	unsigned short ss2;
-	unsigned short res4;
-	unsigned long cr3;
-	unsigned long eip;
-	unsigned long eflags;
-	unsigned long eax, ecx, edx, ebx, esp, ebp, esi, edi;
-	unsigned short es;
-	unsigned short res5;
-	unsigned short cs;
-	unsigned short res6;
-	unsigned short ss;
-	unsigned short res7;
-	unsigned short ds;
-	unsigned short res8;
-	unsigned short fs;
-	unsigned short res9;
-	unsigned short gs;
-	unsigned short res10;
-	unsigned short ldt;
-	unsigned short res11;
-	unsigned short t:1;
-	unsigned short res12:15;
-	unsigned short iomap_base;
-};
-
-static char main_stack[4096];
-static char fault_stack[4096];
-static struct tss32 main_tss;
-static struct tss32 fault_tss;
-
-static unsigned long long gdt[] __attribute__((aligned(16))) = {
-	0,
-	0x00cf9b000000ffffull,
-	0x00cf93000000ffffull,
-	0, 0,	/* TSS segments */
-	0,	/* task return gate */
-};
-
-static unsigned long long gdtr;
+#define TSS_RETURN		(FIRST_SPARE_SEL)
 
 void fault_entry(void);
 
 static __attribute__((used, regparm(1))) void
 fault_handler(unsigned long error_code)
 {
-	unsigned short *desc;
-
-	printf("fault at %x:%x, prev task %x, error code %x\n",
-	       main_tss.cs, main_tss.eip, fault_tss.prev, error_code);
+	print_current_tss_info();
+	printf("error code %x\n", error_code);
 
-	main_tss.eip += 2;
+	tss.eip += 2;
 
-	desc = (unsigned short *)&gdt[3];
-	desc[2] &= ~0x0200;
+	gdt32[TSS_MAIN / 8].access &= ~2;
 
-	desc = (unsigned short *)&gdt[5];
-	desc[0] = 0;
-	desc[1] = fault_tss.prev;
-	desc[2] = 0x8500;
-	desc[3] = 0;
+	set_gdt_task_gate(TSS_RETURN, tss_intr.prev);
 }
 
 asm (
 	"fault_entry:\n"
 	"	mov (%esp),%eax\n"
 	"	call fault_handler\n"
-	"	jmp $0x28, $0\n"
+	"	jmp $" xstr(TSS_RETURN) ", $0\n"
 );
 
-static void setup_tss(struct tss32 *tss, void *entry,
-		      void *stack_base, unsigned long stack_size)
-{
-	unsigned long cr3;
-	unsigned short cs, ds;
-
-	asm ("mov %%cr3,%0" : "=r" (cr3));
-	asm ("mov %%cs,%0" : "=r" (cs));
-	asm ("mov %%ds,%0" : "=r" (ds));
-
-	tss->ss0 = tss->ss1 = tss->ss2 = tss->ss = ds;
-	tss->esp0 = tss->esp1 = tss->esp2 = tss->esp =
-		(unsigned long)stack_base + stack_size;
-	tss->ds = tss->es = tss->fs = tss->gs = ds;
-	tss->cs = cs;
-	tss->eip = (unsigned long)entry;
-	tss->cr3 = cr3;
-}
-
-static void setup_tss_desc(unsigned short tss_sel, struct tss32 *tss)
-{
-	unsigned long addr = (unsigned long)tss;
-	unsigned short *desc;
-
-	desc = (unsigned short *)&gdt[tss_sel/8];
-	desc[0] = sizeof(*tss) - 1;
-	desc[1] = addr;
-	desc[2] = 0x8900 | ((addr & 0x00ff0000) >> 16);
-	desc[3] = (addr & 0xff000000) >> 16;
-}
-
-static void set_intr_task(unsigned short tss_sel, int intr, struct tss32 *tss)
-{
-	unsigned short *desc = (void *)(intr* sizeof(long) * 2);
-
-	setup_tss_desc(tss_sel, tss);
-
-	desc[0] = 0;
-	desc[1] = tss_sel;
-	desc[2] = 0x8500;
-	desc[3] = 0;
-}
-
 int main(int ac, char **av)
 {
 	const long invalid_segment = 0x1234;
 
-	gdtr = ((unsigned long long)(unsigned long)&gdt << 16) |
-		(sizeof(gdt) - 1);
-	asm ("lgdt %0" : : "m" (gdtr));
-
-	setup_tss(&main_tss, 0, main_stack, sizeof(main_stack));
-	setup_tss_desc(FIRST_SPARE_SEL, &main_tss);
-	asm ("ltr %0" : : "r" ((unsigned short)FIRST_SPARE_SEL));
-
-	setup_tss(&fault_tss, fault_entry, fault_stack, sizeof(fault_stack));
-	set_intr_task(FIRST_SPARE_SEL+8, 13, &fault_tss);
+	setup_tss32();
+	set_intr_task_gate(13, fault_entry);
 
 	asm (
 		"mov %0,%%es\n"