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kvm: Setup stack for the kernel

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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>
This commit is contained in:
Pekka Enberg
2015-06-01 16:39:38 +01:00
committed by Will Deacon
parent b08e9ec449
commit dbdb74c21e
2 changed files with 34 additions and 13 deletions
Download Patch File Download Diff File Expand all files Collapse all files
include/kvm/kvm.h
+2 -1
View File
@@ -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;
kvm.c
+32 -12
View File
@@ -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)