On Fri, Apr 12, 2013 at 01:14:47PM +0200, Kevin Wolf wrote:
> This adds a test case that jumps into VM86 by iret-ing to a TSS and back
> to Protected Mode using a task gate in the IDT.
>
> Signed-off-by: Kevin Wolf <kwolf@xxxxxxxxxx>
Applied, thanks. Found a bug with it and emulate_invalid_guest_state=1
which is default. Are you running with emulate_invalid_guest_state=0?
> ---
> lib/x86/desc.c | 41 ++++------------------------------
> lib/x86/desc.h | 36 ++++++++++++++++++++++++++++++
> lib/x86/vm.c | 4 ++--
> lib/x86/vm.h | 1 +
> x86/taskswitch2.c | 67 ++++++++++++++++++++++++++++++++++++++++++++++++++-----
> 5 files changed, 104 insertions(+), 45 deletions(-)
>
> diff --git a/lib/x86/desc.c b/lib/x86/desc.c
> index 770c250..7c5c721 100644
> --- a/lib/x86/desc.c
> +++ b/lib/x86/desc.c
> @@ -27,41 +27,6 @@ typedef struct {
> u8 base_high;
> } gdt_entry_t;
>
> -typedef struct {
> - u16 prev;
> - u16 res1;
> - u32 esp0;
> - u16 ss0;
> - u16 res2;
> - u32 esp1;
> - u16 ss1;
> - u16 res3;
> - u32 esp2;
> - u16 ss2;
> - u16 res4;
> - u32 cr3;
> - u32 eip;
> - u32 eflags;
> - u32 eax, ecx, edx, ebx, esp, ebp, esi, edi;
> - u16 es;
> - u16 res5;
> - u16 cs;
> - u16 res6;
> - u16 ss;
> - u16 res7;
> - u16 ds;
> - u16 res8;
> - u16 fs;
> - u16 res9;
> - u16 gs;
> - u16 res10;
> - u16 ldt;
> - u16 res11;
> - u16 t:1;
> - u16 res12:15;
> - u16 iomap_base;
> -} tss32_t;
> -
> extern idt_entry_t boot_idt[256];
>
> void set_idt_entry(int vec, void *addr, int dpl)
> @@ -268,9 +233,11 @@ unsigned exception_error_code(void)
> * 0x18 - Not presend code segment
> * 0x20 - Primery task
> * 0x28 - Interrupt task
> + *
> + * 0x30 to 0x48 - Free to use for test cases
> */
>
> -static gdt_entry_t gdt[6];
> +static gdt_entry_t gdt[10];
> #define TSS_GDT_OFFSET 4
>
> void set_gdt_entry(int num, u32 base, u32 limit, u8 access, u8 gran)
> @@ -327,7 +294,7 @@ void setup_gdt(void)
> ".Lflush2: "::"r"(0x10));
> }
>
> -static void set_idt_task_gate(int vec, u16 sel)
> +void set_idt_task_gate(int vec, u16 sel)
> {
> idt_entry_t *e = &boot_idt[vec];
>
> diff --git a/lib/x86/desc.h b/lib/x86/desc.h
> index 0b4897c..f819452 100644
> --- a/lib/x86/desc.h
> +++ b/lib/x86/desc.h
> @@ -24,6 +24,41 @@ struct ex_regs {
> unsigned long rflags;
> };
>
> +typedef struct {
> + u16 prev;
> + u16 res1;
> + u32 esp0;
> + u16 ss0;
> + u16 res2;
> + u32 esp1;
> + u16 ss1;
> + u16 res3;
> + u32 esp2;
> + u16 ss2;
> + u16 res4;
> + u32 cr3;
> + u32 eip;
> + u32 eflags;
> + u32 eax, ecx, edx, ebx, esp, ebp, esi, edi;
> + u16 es;
> + u16 res5;
> + u16 cs;
> + u16 res6;
> + u16 ss;
> + u16 res7;
> + u16 ds;
> + u16 res8;
> + u16 fs;
> + u16 res9;
> + u16 gs;
> + u16 res10;
> + u16 ldt;
> + u16 res11;
> + u16 t:1;
> + u16 res12:15;
> + u16 iomap_base;
> +} tss32_t;
> +
> #define ASM_TRY(catch) \
> "movl $0, %%gs:4 \n\t" \
> ".pushsection .data.ex \n\t" \
> @@ -44,6 +79,7 @@ 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 num, u32 base, u32 limit, u8 access, u8 gran);
> +void set_idt_task_gate(int vec, u16 sel);
> void set_intr_task_gate(int e, void *fn);
> void print_current_tss_info(void);
> void handle_exception(u8 v, void (*func)(struct ex_regs *regs));
> diff --git a/lib/x86/vm.c b/lib/x86/vm.c
> index 2852c6c..260ec45 100644
> --- a/lib/x86/vm.c
> +++ b/lib/x86/vm.c
> @@ -109,14 +109,14 @@ void install_large_page(unsigned long *cr3,
> unsigned long phys,
> void *virt)
> {
> - install_pte(cr3, 2, virt, phys | PTE_PRESENT | PTE_WRITE | PTE_PSE, 0);
> + install_pte(cr3, 2, virt, phys | PTE_PRESENT | PTE_WRITE | PTE_USER | PTE_PSE, 0);
> }
>
> void install_page(unsigned long *cr3,
> unsigned long phys,
> void *virt)
> {
> - install_pte(cr3, 1, virt, phys | PTE_PRESENT | PTE_WRITE, 0);
> + install_pte(cr3, 1, virt, phys | PTE_PRESENT | PTE_WRITE | PTE_USER, 0);
> }
>
>
> diff --git a/lib/x86/vm.h b/lib/x86/vm.h
> index 3473f8d..0b5b5c7 100644
> --- a/lib/x86/vm.h
> +++ b/lib/x86/vm.h
> @@ -13,6 +13,7 @@
> #define PTE_PRESENT (1ull << 0)
> #define PTE_PSE (1ull << 7)
> #define PTE_WRITE (1ull << 1)
> +#define PTE_USER (1ull << 2)
> #define PTE_ADDR (0xffffffffff000ull)
>
> void setup_vm();
> diff --git a/x86/taskswitch2.c b/x86/taskswitch2.c
> index 683834e..6573696 100644
> --- a/x86/taskswitch2.c
> +++ b/x86/taskswitch2.c
> @@ -5,6 +5,10 @@
> #include "processor.h"
> #include "vm.h"
>
> +#define FREE_GDT_INDEX 6
> +#define MAIN_TSS_INDEX (FREE_GDT_INDEX + 0)
> +#define VM86_TSS_INDEX (FREE_GDT_INDEX + 1)
> +
> #define xstr(s) str(s)
> #define str(s) #s
>
> @@ -113,15 +117,10 @@ start:
> goto start;
> }
>
> -int main()
> +void test_kernel_mode_int()
> {
> unsigned int res;
>
> - setup_vm();
> - setup_idt();
> - setup_gdt();
> - setup_tss32();
> -
> /* test that int $2 triggers task gate */
> test_count = 0;
> set_intr_task_gate(2, nmi_tss);
> @@ -217,6 +216,62 @@ int main()
> asm volatile ("ljmp $" xstr(TSS_INTR) ", $0xf4f4f4f4");
> printf("Jump back succeeded\n");
> report("ljmp", test_count == 1);
> +}
> +
> +void test_vm86_switch(void)
> +{
> + static tss32_t main_tss;
> + static tss32_t vm86_tss;
> +
> + u8 *vm86_start;
> +
> + /* Write a 'ud2' instruction somewhere below 1 MB */
> + vm86_start = (void*) 0x42000;
> + vm86_start[0] = 0x0f;
> + vm86_start[1] = 0x0b;
> +
> + /* Main TSS */
> + set_gdt_entry(MAIN_TSS_INDEX, (u32)&main_tss, sizeof(tss32_t) - 1, 0x89, 0);
> + ltr(MAIN_TSS_INDEX << 3);
> + main_tss = (tss32_t) {
> + .prev = VM86_TSS_INDEX << 3,
> + .cr3 = read_cr3(),
> + };
> +
> + /* VM86 TSS (marked as busy, so we can iret to it) */
> + set_gdt_entry(VM86_TSS_INDEX, (u32)&vm86_tss, sizeof(tss32_t) - 1, 0x8b, 0);
> + vm86_tss = (tss32_t) {
> + .eflags = 0x20002,
> + .cr3 = read_cr3(),
> + .eip = (u32) vm86_start & 0x0f,
> + .cs = (u32) vm86_start >> 4,
> + .ds = 0x1234,
> + .es = 0x2345,
> + };
> +
> + /* Setup task gate to main TSS for #UD */
> + set_idt_task_gate(6, MAIN_TSS_INDEX << 3);
> +
> + /* Jump into VM86 task with iret, #UD lets it come back immediately */
> + printf("Switch to VM86 task and back\n");
> + asm volatile(
> + "pushf\n"
> + "orw $0x4000, (%esp)\n"
> + "popf\n"
> + "iret\n"
> + );
> + report("VM86", 1);
> +}
> +
> +int main()
> +{
> + setup_vm();
> + setup_idt();
> + setup_gdt();
> + setup_tss32();
> +
> + test_kernel_mode_int();
> + test_vm86_switch();
>
> printf("\nsummary: %d tests, %d failures\n", g_tests, g_fail);
>
> --
> 1.8.1.4
--
Gleb.
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