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The displacement field in the decoded instruction should be treated as a 8-bit

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or 32-bit signed integer.

Simplify the handling of indirect addressing with displacement by
unconditionally adding the 'instruction->disp' to the target address.
This is alright since 'instruction->disp' is non-zero only for the
addressing modes that specify a displacement.

Obtained from: NetApp
This commit is contained in:
Neel Natu 2012-08-04 23:51:21 +00:00
parent 96b1c4db60
commit da91bbd7a7
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/projects/bhyve/; revision=239044
1 changed files with 14 additions and 20 deletions
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34
usr.sbin/bhyve/instruction_emul.c
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@ -135,7 +135,7 @@ struct decoded_instruction
uint8_t *opcode;
uint8_t *modrm;
uint8_t *sib;
uint8_t *displacement;
uint8_t *displacement;
uint8_t *immediate;
uint8_t opcode_flags;
@ -337,9 +337,9 @@ decode_extension_operands(struct decoded_instruction *decoded)
if (decoded->displacement) {
if (decoded->addressing_mode == MOD_INDIRECT_DISP8) {
decoded->disp = (int32_t)*decoded->displacement;
decoded->disp = *((int8_t *)decoded->displacement);
} else if (decoded->addressing_mode == MOD_INDIRECT_DISP32) {
decoded->disp = *((int32_t*)decoded->displacement);
decoded->disp = *((int32_t *)decoded->displacement);
}
}
@ -432,14 +432,6 @@ get_operand(struct vmctx *vm, int vcpu, uint64_t guest_cr3,
*operand = reg;
return (0);
case MOD_INDIRECT:
target = gla2gpa(reg, guest_cr3);
emulated_memory = find_region(target);
if (emulated_memory) {
return emulated_memory->memread(vm, vcpu, target,
4, operand,
emulated_memory->arg);
}
return (-1);
case MOD_INDIRECT_DISP8:
case MOD_INDIRECT_DISP32:
target = gla2gpa(reg, guest_cr3);
@ -450,7 +442,7 @@ get_operand(struct vmctx *vm, int vcpu, uint64_t guest_cr3,
4, operand,
emulated_memory->arg);
}
return (-1);
return (-1);
default:
return (-1);
}
@ -473,19 +465,22 @@ perform_write(struct vmctx *vm, int vcpu, uint64_t guest_cr3,
} else if (instruction->opcode_flags & TO_REG) {
reg = instruction->reg;
addressing_mode = MOD_DIRECT;
} else
} else
return (-1);
regname = get_vm_reg_name(reg);
error = vm_get_register(vm, vcpu, regname, &reg);
if (error)
if (error)
return (error);
switch(addressing_mode) {
case MOD_DIRECT:
return vm_set_register(vm, vcpu, regname, operand);
case MOD_INDIRECT:
case MOD_INDIRECT_DISP8:
case MOD_INDIRECT_DISP32:
target = gla2gpa(reg, guest_cr3);
target += instruction->disp;
emulated_memory = find_region(target);
if (emulated_memory) {
return emulated_memory->memwrite(vm, vcpu, target,
@ -506,7 +501,7 @@ emulate_decoded_instruction(struct vmctx *vm, int vcpu, uint64_t cr3,
int error;
error = get_operand(vm, vcpu, cr3, instruction, &operand);
if (error)
if (error)
return (error);
return perform_write(vm, vcpu, cr3, instruction, operand);
@ -519,17 +514,17 @@ emulate_instruction(struct vmctx *vm, int vcpu, uint64_t rip, uint64_t cr3)
int error;
void *instruction = gla2hla(rip, cr3);
if ((error = decode_instruction(instruction, &instr)) != 0)
if ((error = decode_instruction(instruction, &instr)) != 0)
return (error);
return emulate_decoded_instruction(vm, vcpu, cr3, &instr);
}
struct memory_region *
register_emulated_memory(uintptr_t start, size_t len, emulated_read_func_t memread,
register_emulated_memory(uintptr_t start, size_t len, emulated_read_func_t memread,
emulated_write_func_t memwrite, void *arg)
{
if (registered_regions > MAX_EMULATED_REGIONS)
if (registered_regions >= MAX_EMULATED_REGIONS)
return (NULL);
struct memory_region *region = &emulated_regions[registered_regions];
@ -552,4 +547,3 @@ move_memory_region(struct memory_region *region, uintptr_t start)
region->start = start;
region->end = start + len;
}