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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [PATCH v8 08/12] x86emul: support FLDENV and FRSTOR
While the Intel SDM claims that FRSTOR itself may raise #MF upon
completion, this was confirmed by Intel to be a doc error which will be
corrected in due course; behavior is like FLDENV, and like old hard copy
manuals describe it. Otherwise we'd have to emulate the insn by filling
st(N) in suitable order, followed by FLDENV.
Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
---
v7: New.
--- a/tools/tests/x86_emulator/test_x86_emulator.c
+++ b/tools/tests/x86_emulator/test_x86_emulator.c
@@ -2442,6 +2442,27 @@ int main(int argc, char **argv)
else
printf("skipped\n");
+ printf("%-40s", "Testing fldenv 8(%edx)...");
+ if ( stack_exec && cpu_has_fpu )
+ {
+ asm volatile ( "fnstenv %0\n\t"
+ "fninit"
+ : "=m" (res[2]) :: "memory" );
+ zap_fpsel(&res[2], true);
+ instr[0] = 0xd9; instr[1] = 0x62; instr[2] = 0x08;
+ regs.eip = (unsigned long)&instr[0];
+ regs.edx = (unsigned long)res;
+ rc = x86_emulate(&ctxt, &emulops);
+ asm volatile ( "fnstenv %0" : "=m" (res[9]) :: "memory" );
+ if ( (rc != X86EMUL_OKAY) ||
+ memcmp(res + 2, res + 9, 28) ||
+ (regs.eip != (unsigned long)&instr[3]) )
+ goto fail;
+ printf("okay\n");
+ }
+ else
+ printf("skipped\n");
+
printf("%-40s", "Testing 16-bit fnsave (%ecx)...");
if ( stack_exec && cpu_has_fpu )
{
@@ -2468,6 +2489,31 @@ int main(int argc, char **argv)
goto fail;
printf("okay\n");
}
+ else
+ printf("skipped\n");
+
+ printf("%-40s", "Testing frstor (%edx)...");
+ if ( stack_exec && cpu_has_fpu )
+ {
+ const uint16_t seven = 7;
+
+ asm volatile ( "fninit\n\t"
+ "fld1\n\t"
+ "fidivs %1\n\t"
+ "fnsave %0\n\t"
+ : "=&m" (res[0]) : "m" (seven) : "memory" );
+ zap_fpsel(&res[0], true);
+ instr[0] = 0xdd; instr[1] = 0x22;
+ regs.eip = (unsigned long)&instr[0];
+ regs.edx = (unsigned long)res;
+ rc = x86_emulate(&ctxt, &emulops);
+ asm volatile ( "fnsave %0" : "=m" (res[27]) :: "memory" );
+ if ( (rc != X86EMUL_OKAY) ||
+ memcmp(res, res + 27, 108) ||
+ (regs.eip != (unsigned long)&instr[2]) )
+ goto fail;
+ printf("okay\n");
+ }
else
printf("skipped\n");
--- a/xen/arch/x86/x86_emulate/x86_emulate.c
+++ b/xen/arch/x86/x86_emulate/x86_emulate.c
@@ -857,6 +857,7 @@ struct x86_emulate_state {
blk_NONE,
blk_enqcmd,
#ifndef X86EMUL_NO_FPU
+ blk_fld, /* FLDENV, FRSTOR */
blk_fst, /* FNSTENV, FNSAVE */
#endif
blk_movdir,
@@ -4948,21 +4949,14 @@ x86_emulate(
dst.bytes = 4;
emulate_fpu_insn_memdst(b, modrm_reg & 7, dst.val);
break;
- case 4: /* fldenv - TODO */
- state->fpu_ctrl = true;
- goto unimplemented_insn;
- case 5: /* fldcw m2byte */
- state->fpu_ctrl = true;
- fpu_memsrc16:
- if ( (rc = ops->read(ea.mem.seg, ea.mem.off, &src.val,
- 2, ctxt)) != X86EMUL_OKAY )
- goto done;
- emulate_fpu_insn_memsrc(b, modrm_reg & 7, src.val);
- break;
+ case 4: /* fldenv */
+ /* Raise #MF now if there are pending unmasked exceptions. */
+ emulate_fpu_insn_stub(0xd9, 0xd0 /* fnop */);
+ /* fall through */
case 6: /* fnstenv */
fail_if(!ops->blk);
- state->blk = blk_fst;
- /* REX is meaningless for this insn by this point. */
+ state->blk = modrm_reg & 2 ? blk_fst : blk_fld;
+ /* REX is meaningless for these insns by this point. */
rex_prefix = in_protmode(ctxt, ops);
if ( (rc = ops->blk(ea.mem.seg, ea.mem.off, NULL,
op_bytes > 2 ? sizeof(struct x87_env32)
@@ -4972,6 +4966,14 @@ x86_emulate(
goto done;
state->fpu_ctrl = true;
break;
+ case 5: /* fldcw m2byte */
+ state->fpu_ctrl = true;
+ fpu_memsrc16:
+ if ( (rc = ops->read(ea.mem.seg, ea.mem.off, &src.val,
+ 2, ctxt)) != X86EMUL_OKAY )
+ goto done;
+ emulate_fpu_insn_memsrc(b, modrm_reg & 7, src.val);
+ break;
case 7: /* fnstcw m2byte */
state->fpu_ctrl = true;
fpu_memdst16:
@@ -5124,13 +5126,14 @@ x86_emulate(
dst.bytes = 8;
emulate_fpu_insn_memdst(b, modrm_reg & 7, dst.val);
break;
- case 4: /* frstor - TODO */
- state->fpu_ctrl = true;
- goto unimplemented_insn;
+ case 4: /* frstor */
+ /* Raise #MF now if there are pending unmasked exceptions. */
+ emulate_fpu_insn_stub(0xd9, 0xd0 /* fnop */);
+ /* fall through */
case 6: /* fnsave */
fail_if(!ops->blk);
- state->blk = blk_fst;
- /* REX is meaningless for this insn by this point. */
+ state->blk = modrm_reg & 2 ? blk_fst : blk_fld;
+ /* REX is meaningless for these insns by this point. */
rex_prefix = in_protmode(ctxt, ops);
if ( (rc = ops->blk(ea.mem.seg, ea.mem.off, NULL,
op_bytes > 2 ? sizeof(struct x87_env32) +
80
@@ -11648,6 +11651,89 @@ int x86_emul_blk(
#ifndef X86EMUL_NO_FPU
+ case blk_fld:
+ ASSERT(!data);
+
+ /* state->rex_prefix carries CR0.PE && !EFLAGS.VM setting */
+ switch ( bytes )
+ {
+ case sizeof(fpstate.env):
+ case sizeof(fpstate):
+ memcpy(&fpstate.env, ptr, sizeof(fpstate.env));
+ if ( !state->rex_prefix )
+ {
+ unsigned int fip = fpstate.env.mode.real.fip_lo +
+ (fpstate.env.mode.real.fip_hi << 16);
+ unsigned int fdp = fpstate.env.mode.real.fdp_lo +
+ (fpstate.env.mode.real.fdp_hi << 16);
+ unsigned int fop = fpstate.env.mode.real.fop;
+
+ fpstate.env.mode.prot.fip = fip & 0xf;
+ fpstate.env.mode.prot.fcs = fip >> 4;
+ fpstate.env.mode.prot.fop = fop;
+ fpstate.env.mode.prot.fdp = fdp & 0xf;
+ fpstate.env.mode.prot.fds = fdp >> 4;
+ }
+
+ if ( bytes == sizeof(fpstate.env) )
+ ptr = NULL;
+ else
+ ptr += sizeof(fpstate.env);
+ break;
+
+ case sizeof(struct x87_env16):
+ case sizeof(struct x87_env16) + sizeof(fpstate.freg):
+ {
+ const struct x87_env16 *env = ptr;
+
+ fpstate.env.fcw = env->fcw;
+ fpstate.env.fsw = env->fsw;
+ fpstate.env.ftw = env->ftw;
+
+ if ( state->rex_prefix )
+ {
+ fpstate.env.mode.prot.fip = env->mode.prot.fip;
+ fpstate.env.mode.prot.fcs = env->mode.prot.fcs;
+ fpstate.env.mode.prot.fdp = env->mode.prot.fdp;
+ fpstate.env.mode.prot.fds = env->mode.prot.fds;
+ fpstate.env.mode.prot.fop = 0; /* unknown */
+ }
+ else
+ {
+ unsigned int fip = env->mode.real.fip_lo +
+ (env->mode.real.fip_hi << 16);
+ unsigned int fdp = env->mode.real.fdp_lo +
+ (env->mode.real.fdp_hi << 16);
+ unsigned int fop = env->mode.real.fop;
+
+ fpstate.env.mode.prot.fip = fip & 0xf;
+ fpstate.env.mode.prot.fcs = fip >> 4;
+ fpstate.env.mode.prot.fop = fop;
+ fpstate.env.mode.prot.fdp = fdp & 0xf;
+ fpstate.env.mode.prot.fds = fdp >> 4;
+ }
+
+ if ( bytes == sizeof(*env) )
+ ptr = NULL;
+ else
+ ptr += sizeof(*env);
+ break;
+ }
+
+ default:
+ ASSERT_UNREACHABLE();
+ return X86EMUL_UNHANDLEABLE;
+ }
+
+ if ( ptr )
+ {
+ memcpy(fpstate.freg, ptr, sizeof(fpstate.freg));
+ asm volatile ( "frstor %0" :: "m" (fpstate) );
+ }
+ else
+ asm volatile ( "fldenv %0" :: "m" (fpstate.env) );
+ break;
+
case blk_fst:
ASSERT(!data);
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