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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [PATCH v9 7/9] x86emul: support FNSTENV and FNSAVE
To avoid introducing another boolean into emulator state, the
rex_prefix field gets (ab)used to convey the real/VM86 vs protected mode
info (affecting structure layout, albeit not size) to x86_emul_blk().
Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
---
TBD: The full 16-bit padding fields in the 32-bit structures get filled
with all ones by modern CPUs (i.e. unlike what the comment says for
FIP and FDP). We may want to mirror this as well (for the real mode
variant), even if those fields' contents are unspecified.
---
v9: Fix !HVM build. Add /*state->*/ comments. Add memset(). Add/extend
comments.
v7: New.
--- a/tools/tests/x86_emulator/x86-emulate.h
+++ b/tools/tests/x86_emulator/x86-emulate.h
@@ -123,6 +123,7 @@ static inline bool xcr0_mask(uint64_t ma
}
#define cache_line_size() (cp.basic.clflush_size * 8)
+#define cpu_has_fpu cp.basic.fpu
#define cpu_has_mmx cp.basic.mmx
#define cpu_has_fxsr cp.basic.fxsr
#define cpu_has_sse cp.basic.sse
--- a/tools/tests/x86_emulator/test_x86_emulator.c
+++ b/tools/tests/x86_emulator/test_x86_emulator.c
@@ -748,6 +748,25 @@ static struct x86_emulate_ops emulops =
#define MMAP_ADDR 0x100000
+/*
+ * 64-bit OSes may not (be able to) properly restore the two selectors in
+ * the FPU environment. Zap them so that memcmp() on two saved images will
+ * work regardless of whether a context switch occurred in the middle.
+ */
+static void zap_fpsel(unsigned int *env, bool is_32bit)
+{
+ if ( is_32bit )
+ {
+ env[4] &= ~0xffff;
+ env[6] &= ~0xffff;
+ }
+ else
+ {
+ env[2] &= ~0xffff;
+ env[3] &= ~0xffff;
+ }
+}
+
#ifdef __x86_64__
# define STKVAL_DISP 64
static const struct {
@@ -2394,6 +2413,62 @@ int main(int argc, char **argv)
printf("okay\n");
}
else
+ printf("skipped\n");
+
+ printf("%-40s", "Testing fnstenv 4(%ecx)...");
+ if ( stack_exec && cpu_has_fpu )
+ {
+ const uint16_t three = 3;
+
+ asm volatile ( "fninit\n\t"
+ "fld1\n\t"
+ "fidivs %1\n\t"
+ "fstenv %0"
+ : "=m" (res[9]) : "m" (three) : "memory" );
+ zap_fpsel(&res[9], true);
+ instr[0] = 0xd9; instr[1] = 0x71; instr[2] = 0x04;
+ regs.eip = (unsigned long)&instr[0];
+ regs.ecx = (unsigned long)res;
+ res[8] = 0xaa55aa55;
+ rc = x86_emulate(&ctxt, &emulops);
+ zap_fpsel(&res[1], true);
+ if ( (rc != X86EMUL_OKAY) ||
+ memcmp(res + 1, res + 9, 28) ||
+ res[8] != 0xaa55aa55 ||
+ (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 )
+ {
+ const uint16_t five = 5;
+
+ asm volatile ( "fninit\n\t"
+ "fld1\n\t"
+ "fidivs %1\n\t"
+ "fsaves %0"
+ : "=m" (res[25]) : "m" (five) : "memory" );
+ zap_fpsel(&res[25], false);
+ asm volatile ( "frstors %0" :: "m" (res[25]) : "memory" );
+ instr[0] = 0x66; instr[1] = 0xdd; instr[2] = 0x31;
+ regs.eip = (unsigned long)&instr[0];
+ regs.ecx = (unsigned long)res;
+ res[23] = 0xaa55aa55;
+ res[24] = 0xaa55aa55;
+ rc = x86_emulate(&ctxt, &emulops);
+ if ( (rc != X86EMUL_OKAY) ||
+ memcmp(res, res + 25, 94) ||
+ (res[23] >> 16) != 0xaa55 ||
+ res[24] != 0xaa55aa55 ||
+ (regs.eip != (unsigned long)&instr[3]) )
+ goto fail;
+ printf("okay\n");
+ }
+ else
printf("skipped\n");
printf("%-40s", "Testing movq %mm3,(%ecx)...");
--- a/xen/arch/x86/x86_emulate/x86_emulate.c
+++ b/xen/arch/x86/x86_emulate/x86_emulate.c
@@ -856,6 +856,9 @@ struct x86_emulate_state {
enum {
blk_NONE,
blk_enqcmd,
+#ifndef X86EMUL_NO_FPU
+ blk_fst, /* FNSTENV, FNSAVE */
+#endif
blk_movdir,
} blk;
uint8_t modrm, modrm_mod, modrm_reg, modrm_rm;
@@ -897,6 +900,50 @@ struct x86_emulate_state {
#define PTR_POISON NULL /* 32-bit builds are for user-space, so NULL is OK. */
#endif
+#ifndef X86EMUL_NO_FPU
+struct x87_env16 {
+ uint16_t fcw;
+ uint16_t fsw;
+ uint16_t ftw;
+ union {
+ struct {
+ uint16_t fip_lo;
+ uint16_t fop:11, :1, fip_hi:4;
+ uint16_t fdp_lo;
+ uint16_t :12, fdp_hi:4;
+ } real;
+ struct {
+ uint16_t fip;
+ uint16_t fcs;
+ uint16_t fdp;
+ uint16_t fds;
+ } prot;
+ } mode;
+};
+
+struct x87_env32 {
+ uint32_t fcw:16, :16;
+ uint32_t fsw:16, :16;
+ uint32_t ftw:16, :16;
+ union {
+ struct {
+ /* some CPUs/FPUs also store the full FIP here */
+ uint32_t fip_lo:16, :16;
+ uint32_t fop:11, :1, fip_hi:16, :4;
+ /* some CPUs/FPUs also store the full FDP here */
+ uint32_t fdp_lo:16, :16;
+ uint32_t :12, fdp_hi:16, :4;
+ } real;
+ struct {
+ uint32_t fip;
+ uint32_t fcs:16, fop:11, :5;
+ uint32_t fdp;
+ uint32_t fds:16, :16;
+ } prot;
+ } mode;
+};
+#endif
+
typedef union {
uint64_t mmx;
uint64_t __attribute__ ((aligned(16))) xmm[2];
@@ -4912,9 +4959,22 @@ x86_emulate(
goto done;
emulate_fpu_insn_memsrc(b, modrm_reg & 7, src.val);
break;
- case 6: /* fnstenv - TODO */
+ case 6: /* fnstenv */
+ fail_if(!ops->blk);
+ state->blk = blk_fst;
+ /*
+ * REX is meaningless for this insn by this point - (ab)use
+ * the field to communicate real vs protected mode to ->blk().
+ */
+ /*state->*/rex_prefix = in_protmode(ctxt, ops);
+ if ( (rc = ops->blk(ea.mem.seg, ea.mem.off, NULL,
+ op_bytes > 2 ? sizeof(struct x87_env32)
+ : sizeof(struct x87_env16),
+ &_regs.eflags,
+ state, ctxt)) != X86EMUL_OKAY )
+ goto done;
state->fpu_ctrl = true;
- goto unimplemented_insn;
+ break;
case 7: /* fnstcw m2byte */
state->fpu_ctrl = true;
fpu_memdst16:
@@ -5068,9 +5128,24 @@ x86_emulate(
emulate_fpu_insn_memdst(b, modrm_reg & 7, dst.val);
break;
case 4: /* frstor - TODO */
- case 6: /* fnsave - TODO */
state->fpu_ctrl = true;
goto unimplemented_insn;
+ case 6: /* fnsave */
+ fail_if(!ops->blk);
+ state->blk = blk_fst;
+ /*
+ * REX is meaningless for this insn by this point - (ab)use
+ * the field to communicate real vs protected mode to ->blk().
+ */
+ /*state->*/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
+ : sizeof(struct x87_env16) +
80,
+ &_regs.eflags,
+ state, ctxt)) != X86EMUL_OKAY )
+ goto done;
+ state->fpu_ctrl = true;
+ break;
case 7: /* fnstsw m2byte */
state->fpu_ctrl = true;
goto fpu_memdst16;
@@ -11550,6 +11625,14 @@ int x86_emul_blk(
switch ( state->blk )
{
bool zf;
+#ifndef X86EMUL_NO_FPU
+ struct {
+ struct x87_env32 env;
+ struct {
+ uint8_t bytes[10];
+ } freg[8];
+ } fpstate;
+#endif
/*
* Throughout this switch(), memory clobbers are used to compensate
@@ -11579,6 +11662,98 @@ int x86_emul_blk(
*eflags |= X86_EFLAGS_ZF;
break;
+#ifndef X86EMUL_NO_FPU
+
+ case blk_fst:
+ ASSERT(!data);
+
+ /* Don't chance consuming uninitialized data. */
+ memset(&fpstate, 0, sizeof(fpstate));
+ if ( bytes > sizeof(fpstate.env) )
+ asm ( "fnsave %0" : "+m" (fpstate) );
+ else
+ asm ( "fnstenv %0" : "+m" (fpstate.env) );
+
+ /* state->rex_prefix carries CR0.PE && !EFLAGS.VM setting */
+ switch ( bytes )
+ {
+ case sizeof(fpstate.env): /* 32-bit FNSTENV */
+ case sizeof(fpstate): /* 32-bit FNSAVE */
+ if ( !state->rex_prefix )
+ {
+ /* Convert 32-bit prot to 32-bit real/vm86 format. */
+ unsigned int fip = fpstate.env.mode.prot.fip +
+ (fpstate.env.mode.prot.fcs << 4);
+ unsigned int fdp = fpstate.env.mode.prot.fdp +
+ (fpstate.env.mode.prot.fds << 4);
+ unsigned int fop = fpstate.env.mode.prot.fop;
+
+ memset(&fpstate.env.mode, 0, sizeof(fpstate.env.mode));
+ fpstate.env.mode.real.fip_lo = fip;
+ fpstate.env.mode.real.fip_hi = fip >> 16;
+ fpstate.env.mode.real.fop = fop;
+ fpstate.env.mode.real.fdp_lo = fdp;
+ fpstate.env.mode.real.fdp_hi = fdp >> 16;
+ }
+ memcpy(ptr, &fpstate.env, sizeof(fpstate.env));
+ if ( bytes == sizeof(fpstate.env) )
+ ptr = NULL;
+ else
+ ptr += sizeof(fpstate.env);
+ break;
+
+ case sizeof(struct x87_env16): /* 16-bit
FNSTENV */
+ case sizeof(struct x87_env16) + sizeof(fpstate.freg): /* 16-bit FNSAVE
*/
+ if ( state->rex_prefix )
+ {
+ /* Convert 32-bit prot to 16-bit prot format. */
+ struct x87_env16 *env = ptr;
+
+ env->fcw = fpstate.env.fcw;
+ env->fsw = fpstate.env.fsw;
+ env->ftw = fpstate.env.ftw;
+ env->mode.prot.fip = fpstate.env.mode.prot.fip;
+ env->mode.prot.fcs = fpstate.env.mode.prot.fcs;
+ env->mode.prot.fdp = fpstate.env.mode.prot.fdp;
+ env->mode.prot.fds = fpstate.env.mode.prot.fds;
+ }
+ else
+ {
+ /* Convert 32-bit prot to 16-bit real/vm86 format. */
+ unsigned int fip = fpstate.env.mode.prot.fip +
+ (fpstate.env.mode.prot.fcs << 4);
+ unsigned int fdp = fpstate.env.mode.prot.fdp +
+ (fpstate.env.mode.prot.fds << 4);
+ struct x87_env16 env = {
+ .fcw = fpstate.env.fcw,
+ .fsw = fpstate.env.fsw,
+ .ftw = fpstate.env.ftw,
+ .mode.real.fip_lo = fip,
+ .mode.real.fip_hi = fip >> 16,
+ .mode.real.fop = fpstate.env.mode.prot.fop,
+ .mode.real.fdp_lo = fdp,
+ .mode.real.fdp_hi = fdp >> 16
+ };
+
+ memcpy(ptr, &env, sizeof(env));
+ }
+ if ( bytes == sizeof(struct x87_env16) )
+ ptr = NULL;
+ else
+ ptr += sizeof(struct x87_env16);
+ break;
+
+ default:
+ ASSERT_UNREACHABLE();
+ return X86EMUL_UNHANDLEABLE;
+ }
+
+ if ( ptr )
+ memcpy(ptr, fpstate.freg, sizeof(fpstate.freg));
+ break;
+
+#endif /* X86EMUL_NO_FPU */
+
case blk_movdir:
switch ( bytes )
{
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