Re: [PATCH kvm-unit-tests 4/4] x86/taskswitch_vm86: Task switches into/out of VM86

[Kevin Wolf <kwolf@redhat.com>]

Am 23.01.2012 17:10, schrieb Gleb Natapov:
> On Mon, Jan 23, 2012 at 05:07:13PM +0100, 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.
>>
> Can you add the test case to taskswitch2.c?

That's actually what I intended to do at first, but there's nothing to
share and having a clean environment that can't interfere with other
tests feels nicer.

What would we gain from merging the files?

Kevin


> 
>> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
>> ---
>>  config-i386.mak       |    3 +-
>>  lib/x86/desc.c        |   37 +-----------------------------
>>  lib/x86/desc.h        |   36 +++++++++++++++++++++++++++++
>>  lib/x86/vm.c          |    4 +-
>>  lib/x86/vm.h          |    1 +
>>  x86/taskswitch_vm86.c |   59 +++++++++++++++++++++++++++++++++++++++++++++++++
>>  x86/unittests.cfg     |    6 +++++
>>  7 files changed, 107 insertions(+), 39 deletions(-)
>>  create mode 100644 x86/taskswitch_vm86.c
>>
>> diff --git a/config-i386.mak b/config-i386.mak
>> index de52f3d..b5c3b9c 100644
>> --- a/config-i386.mak
>> +++ b/config-i386.mak
>> @@ -5,9 +5,10 @@ ldarch = elf32-i386
>>  CFLAGS += -D__i386__
>>  CFLAGS += -I $(KERNELDIR)/include
>>  
>> -tests = $(TEST_DIR)/taskswitch.flat $(TEST_DIR)/taskswitch2.flat
>> +tests = $(TEST_DIR)/taskswitch.flat $(TEST_DIR)/taskswitch2.flat $(TEST_DIR)/taskswitch_vm86.flat
>>  
>>  include config-x86-common.mak
>>  
>>  $(TEST_DIR)/taskswitch.elf: $(cstart.o) $(TEST_DIR)/taskswitch.o
>>  $(TEST_DIR)/taskswitch2.elf: $(cstart.o) $(TEST_DIR)/taskswitch2.o
>> +$(TEST_DIR)/taskswitch_vm86.elf: $(cstart.o) $(TEST_DIR)/taskswitch_vm86.o
>> diff --git a/lib/x86/desc.c b/lib/x86/desc.c
>> index 770c250..c4a3607 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)
>> @@ -327,7 +292,7 @@ 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 abbb0c9..aae044a 100644
>> --- a/lib/x86/vm.c
>> +++ b/lib/x86/vm.c
>> @@ -108,14 +108,14 @@ 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 bf8fd52..aebc5c3 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/taskswitch_vm86.c b/x86/taskswitch_vm86.c
>> new file mode 100644
>> index 0000000..363cb00
>> --- /dev/null
>> +++ b/x86/taskswitch_vm86.c
>> @@ -0,0 +1,59 @@
>> +#include "libcflat.h"
>> +#include "desc.h"
>> +#include "processor.h"
>> +#include "vm.h"
>> +
>> +static tss32_t main_tss;
>> +static tss32_t vm86_tss;
>> +
>> +#define FREE_GDT_INDEX 4
>> +#define MAIN_TSS_INDEX (FREE_GDT_INDEX + 0)
>> +#define VM86_TSS_INDEX (FREE_GDT_INDEX + 1)
>> +
>> +extern void vm86_start(void);
>> +
>> +int main(void)
>> +{
>> +    u8 *vm86_start;
>> +
>> +    setup_vm();
>> +    setup_idt();
>> +    setup_gdt();
>> +
>> +    /* 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 */
>> +    asm volatile(
>> +        "pushf\n"
>> +        "orw $0x4000, (%esp)\n"
>> +        "popf\n"
>> +        "iret\n"
>> +    );
>> +
>> +    return 0;
>> +}
>> diff --git a/x86/unittests.cfg b/x86/unittests.cfg
>> index dac7d44..194850b 100644
>> --- a/x86/unittests.cfg
>> +++ b/x86/unittests.cfg
>> @@ -76,6 +76,12 @@ smp = 2
>>  extra_params = -cpu qemu64,-svm
>>  groups = task
>>  
>> +[taskswitch_vm86]
>> +file = taskswitch_vm86.flat
>> +smp = 2
>> +extra_params = -cpu qemu64,-svm
>> +groups = task
>> +
>>  [kvmclock_test]
>>  file = kvmclock_test.flat
>>  smp = 2
>> -- 
>> 1.7.6.5
>>
>> --
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> 
> --
> 			Gleb.