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 17:22, schrieb Gleb Natapov:
> On Mon, Jan 23, 2012 at 05:20:22PM +0100, Kevin Wolf wrote:
>> 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?
>>
> Running one test to check all aspects of taskswitch emulation.

(We all know that top-posting is disliked, but middle-posting looks even
crazier!)

Does having one test provide any value in and of itself? It's just an
implementation detail of the test suite. When testing the KVM patches I
ran all three test cases with './run_tests.sh -g task', which is
hopefully easy enough.

Kevin

> 
>> 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.
> 
> --
> 			Gleb.