kvm: Setup stack for the kernel

The Linux kernel expects stack to be set up for it.  Fixes a bug in the program
where we start to run an instruction stream filled with zeros.

Signed-off-by: Pekka Enberg <penberg@cs.helsinki.fi>

diff --git a/tools/kvm/include/kvm/kvm.h b/tools/kvm/include/kvm/kvm.h
index edec88b8bee566fc2df57dc87cd72a3ef8bbe5e4..dd5cb1f9164d884343797ae5d355627e5d3341a7 100644 (file)
--- a/tools/kvm/include/kvm/kvm.h
+++ b/tools/kvm/include/kvm/kvm.h
@@ -15,8 +15,9 @@ struct kvm {
        uint64_t                ram_size;
        void                    *ram_start;
 
-       uint16_t                boot_cs;
+       uint16_t                boot_selector;
        uint16_t                boot_ip;
+       uint16_t                boot_sp;
 
        struct kvm_regs         regs;
        struct kvm_sregs        sregs;

diff --git a/tools/kvm/kvm.c b/tools/kvm/kvm.c
index 6f7112900fcd7b8cafca562b0fdb78c338c70c42..859d7567396bf951ee98eba76af1109a6dd791d3 100644 (file)
--- a/tools/kvm/kvm.c
+++ b/tools/kvm/kvm.c
@@ -153,8 +153,9 @@ static inline uint32_t segment_to_flat(uint16_t selector, uint16_t offset)
        return ((uint32_t)selector << 4) + (uint32_t) offset;
 }
 
-#define BOOT_LOADER_CS         0x0100
+#define BOOT_LOADER_SELECTOR   0x0100
 #define BOOT_LOADER_IP         0x0000
+#define BOOT_LOADER_SP         0x8000
 
 static int load_flat_binary(struct kvm *self, int fd)
 {
@@ -164,13 +165,14 @@ static int load_flat_binary(struct kvm *self, int fd)
        if (lseek(fd, 0, SEEK_SET) < 0)
                die_perror("lseek");
 
-       p = guest_addr_to_host(self, segment_to_flat(BOOT_LOADER_CS, BOOT_LOADER_IP));
+       p = guest_addr_to_host(self, segment_to_flat(BOOT_LOADER_SELECTOR, BOOT_LOADER_IP));
 
        while ((nr = read(fd, p, 65536)) > 0)
                p += nr;
 
-       self->boot_cs           = BOOT_LOADER_CS;
+       self->boot_selector     = BOOT_LOADER_SELECTOR;
        self->boot_ip           = BOOT_LOADER_IP;
+       self->boot_sp           = BOOT_LOADER_SP;
 
        return true;
 }
@@ -214,7 +216,7 @@ static bool load_bzimage(struct kvm *self, int fd)
                setup_sects      = BZ_DEFAULT_SETUP_SECTS;
 
        setup_size = setup_sects << 9;
-       p = guest_addr_to_host(self, segment_to_flat(BOOT_LOADER_CS, BOOT_LOADER_IP));
+       p = guest_addr_to_host(self, segment_to_flat(BOOT_LOADER_SELECTOR, BOOT_LOADER_IP));
 
        if (read(fd, p, setup_size) != setup_size)
                die_perror("read");
@@ -224,12 +226,13 @@ static bool load_bzimage(struct kvm *self, int fd)
        while ((nr = read(fd, p, 65536)) > 0)
                p += nr;
 
-       self->boot_cs           = BOOT_LOADER_CS;
+       self->boot_selector     = BOOT_LOADER_SELECTOR;
        /*
         * The real-mode setup code starts at offset 0x200 of a bzImage. See
         * Documentation/x86/boot.txt for details.
         */
        self->boot_ip           = BOOT_LOADER_IP + 0x200;
+       self->boot_sp           = BOOT_LOADER_SP;
 
        return true;
 }
@@ -271,17 +274,21 @@ static inline uint64_t ip_real_to_flat(struct kvm *self, uint64_t ip)
        return ip + (cs << 4);
 }
 
+static inline uint32_t selector_to_base(uint16_t selector)
+{
+       /*
+        * KVM on Intel requires 'base' to be 'selector * 16' in real mode.
+        */
+       return (uint32_t)selector * 16;
+}
+
 void kvm__reset_vcpu(struct kvm *self)
 {
        self->sregs = (struct kvm_sregs) {
                .cr0            = 0x60000010ULL,
                .cs             = (struct kvm_segment) {
-                       /*
-                        * KVM on Intel requires 'base' to be 'selector * 16' in
-                        * real mode.
-                        */
-                       .selector       = self->boot_cs,
-                       .base           = self->boot_cs * 16,
+                       .selector       = self->boot_selector,
+                       .base           = selector_to_base(self->boot_selector),
                        .limit          = 0xffffU,
                        .type           = 0x0bU,
                        .present        = 1,
@@ -289,6 +296,8 @@ void kvm__reset_vcpu(struct kvm *self)
                        .s              = 1,
                },
                .ss             = (struct kvm_segment) {
+                       .selector       = self->boot_selector,
+                       .base           = selector_to_base(self->boot_selector),
                        .limit          = 0xffffU,
                        .type           = 0x03U,
                        .present        = 1,
@@ -296,6 +305,8 @@ void kvm__reset_vcpu(struct kvm *self)
                        .s              = 1,
                },
                .ds             = (struct kvm_segment) {
+                       .selector       = self->boot_selector,
+                       .base           = selector_to_base(self->boot_selector),
                        .limit          = 0xffffU,
                        .type           = 0x03U,
                        .present        = 1,
@@ -303,6 +314,8 @@ void kvm__reset_vcpu(struct kvm *self)
                        .s              = 1,
                },
                .es             = (struct kvm_segment) {
+                       .selector       = self->boot_selector,
+                       .base           = selector_to_base(self->boot_selector),
                        .limit          = 0xffffU,
                        .type           = 0x03U,
                        .present        = 1,
@@ -310,6 +323,8 @@ void kvm__reset_vcpu(struct kvm *self)
                        .s              = 1,
                },
                .fs             = (struct kvm_segment) {
+                       .selector       = self->boot_selector,
+                       .base           = selector_to_base(self->boot_selector),
                        .limit          = 0xffffU,
                        .type           = 0x03U,
                        .present        = 1,
@@ -317,6 +332,8 @@ void kvm__reset_vcpu(struct kvm *self)
                        .s              = 1,
                },
                .gs             = (struct kvm_segment) {
+                       .selector       = self->boot_selector,
+                       .base           = selector_to_base(self->boot_selector),
                        .limit          = 0xffffU,
                        .type           = 0x03U,
                        .present        = 1,
@@ -345,9 +362,12 @@ void kvm__reset_vcpu(struct kvm *self)
                die_perror("KVM_SET_SREGS failed");
 
        self->regs = (struct kvm_regs) {
-               .rip            = self->boot_ip,
                /* We start the guest in 16-bit real mode  */
                .rflags         = 0x0000000000000002ULL,
+
+               .rip            = self->boot_ip,
+               .rsp            = self->boot_sp,
+               .rbp            = self->boot_sp,
        };
 
        if (self->regs.rip > USHRT_MAX)