[PATCH 1/2] x86/math-emu: Add support for FCMOVcc and F[U]COMI[P] insns

[Denys Vlasenko]

Run-tested by booting with "no387 nofxsr" and running test programs:

# ./test_FCMOV
[RUN]	Testing fcmovCC instructions
[OK]	fcmovCC
# ./test_FCOMI
[RUN]	Testing f[u]comi[p] instructions
[OK]	f[u]comi[p]

Signed-off-by: Denys Vlasenko <dvlasenk@xxxxxxxxxx>
CC: Ingo Molnar <mingo@xxxxxxxxxx>
CC: Borislav Petkov <bp@xxxxxxxxx>
CC: "H. Peter Anvin" <hpa@xxxxxxxxx>
CC: Andy Lutomirski <luto@xxxxxxxxxxxxxx>
CC: Kees Cook <keescook@xxxxxxxxxxxx>
CC: x86@xxxxxxxxxx
CC: linux-kernel@xxxxxxxxxxxxxxx
---

The patches did not change since last submission.
The difference, now they are run-tested.

 arch/x86/math-emu/fpu_aux.c     |  70 ++++++++++++++++++++++
 arch/x86/math-emu/fpu_entry.c   |  49 +++++++++------
 arch/x86/math-emu/fpu_proto.h   |  12 ++++
 arch/x86/math-emu/reg_compare.c | 128 ++++++++++++++++++++++++++++++++++++++++
 4 files changed, 241 insertions(+), 18 deletions(-)

diff --git a/arch/x86/math-emu/fpu_aux.c b/arch/x86/math-emu/fpu_aux.c
index dd76a05..024f6e9 100644
--- a/arch/x86/math-emu/fpu_aux.c
+++ b/arch/x86/math-emu/fpu_aux.c
@@ -169,6 +169,76 @@ void fxch_i(void)
 	fpu_tag_word = tag_word;
 }
 
+static void fcmovCC(void)
+{
+	/* fcmovCC st(i) */
+	int i = FPU_rm;
+	FPU_REG *st0_ptr = &st(0);
+	FPU_REG *sti_ptr = &st(i);
+	long tag_word = fpu_tag_word;
+	int regnr = top & 7;
+	int regnri = (top + i) & 7;
+	u_char sti_tag = (tag_word >> (regnri * 2)) & 3;
+
+	if (sti_tag == TAG_Empty) {
+		FPU_stack_underflow();
+		clear_C1();
+		return;
+	}
+	reg_copy(sti_ptr, st0_ptr);
+	tag_word &= ~(3 << (regnr * 2));
+	tag_word |= (sti_tag << (regnr * 2));
+	fpu_tag_word = tag_word;
+}
+
+void fcmovb(void)
+{
+	if (FPU_EFLAGS & X86_EFLAGS_CF)
+		fcmovCC();
+}
+
+void fcmove(void)
+{
+	if (FPU_EFLAGS & X86_EFLAGS_ZF)
+		fcmovCC();
+}
+
+void fcmovbe(void)
+{
+	if (FPU_EFLAGS & (X86_EFLAGS_CF|X86_EFLAGS_ZF))
+		fcmovCC();
+}
+
+void fcmovu(void)
+{
+	if (FPU_EFLAGS & X86_EFLAGS_PF)
+		fcmovCC();
+}
+
+void fcmovnb(void)
+{
+	if (!(FPU_EFLAGS & X86_EFLAGS_CF))
+		fcmovCC();
+}
+
+void fcmovne(void)
+{
+	if (!(FPU_EFLAGS & X86_EFLAGS_ZF))
+		fcmovCC();
+}
+
+void fcmovnbe(void)
+{
+	if (!(FPU_EFLAGS & (X86_EFLAGS_CF|X86_EFLAGS_ZF)))
+		fcmovCC();
+}
+
+void fcmovnu(void)
+{
+	if (!(FPU_EFLAGS & X86_EFLAGS_PF))
+		fcmovCC();
+}
+
 void ffree_(void)
 {
 	/* ffree st(i) */
diff --git a/arch/x86/math-emu/fpu_entry.c b/arch/x86/math-emu/fpu_entry.c
index 929b1d5..77c6505 100644
--- a/arch/x86/math-emu/fpu_entry.c
+++ b/arch/x86/math-emu/fpu_entry.c
@@ -40,10 +40,10 @@
 
 #define __BAD__ FPU_illegal	/* Illegal on an 80486, causes SIGILL */
 
-/* WARNING: These codes are not documented by Intel in their 80486 manual
+/* WARNING: These codes are not all documented by Intel in their 80486 manual
    and may not work on FPU clones or later Intel FPUs. */
 
-/* Changes to support the un-doc codes provided by Linus Torvalds. */
+/* Changes to support the un-documented instructions provided by Linus Torvalds. */
 
 #define _d9_d8_ fstp_i		/* unofficial code (19) */
 #define _dc_d0_ fcom_st		/* unofficial code (14) */
@@ -55,15 +55,27 @@
 #define _df_d0_ fstp_i		/* unofficial code (17) */
 #define _df_d8_ fstp_i		/* unofficial code (1f) */
 
+/* fcmovCC and f(u)comi(p) are enabled if CPUID(1).EDX(15) "cmov" is set */
+
 static FUNC const st_instr_table[64] = {
-	fadd__, fld_i_, __BAD__, __BAD__, fadd_i, ffree_, faddp_, _df_c0_,
-	fmul__, fxch_i, __BAD__, __BAD__, fmul_i, _dd_c8_, fmulp_, _df_c8_,
-	fcom_st, fp_nop, __BAD__, __BAD__, _dc_d0_, fst_i_, _de_d0_, _df_d0_,
-	fcompst, _d9_d8_, __BAD__, __BAD__, _dc_d8_, fstp_i, fcompp, _df_d8_,
-	fsub__, FPU_etc, __BAD__, finit_, fsubri, fucom_, fsubrp, fstsw_,
-	fsubr_, fconst, fucompp, __BAD__, fsub_i, fucomp, fsubp_, __BAD__,
-	fdiv__, FPU_triga, __BAD__, __BAD__, fdivri, __BAD__, fdivrp, __BAD__,
-	fdivr_, FPU_trigb, __BAD__, __BAD__, fdiv_i, __BAD__, fdivp_, __BAD__,
+/* Opcode:	d8		d9		da		db */
+/*		dc		dd		de		df */
+/* c0..7 */	fadd__,		fld_i_,		fcmovb,		fcmovnb,
+/* c0..7 */	fadd_i,		ffree_,		faddp_,		_df_c0_,
+/* c8..f */	fmul__,		fxch_i,		fcmove,		fcmovne,
+/* c8..f */	fmul_i,		_dd_c8_,	fmulp_,		_df_c8_,
+/* d0..7 */	fcom_st,	fp_nop,		fcmovbe,	fcmovnbe,
+/* d0..7 */	_dc_d0_,	fst_i_,		_de_d0_,	_df_d0_,
+/* d8..f */	fcompst,	_d9_d8_,	fcmovu,		fcmovnu,
+/* d8..f */	_dc_d8_,	fstp_i,		fcompp,		_df_d8_,
+/* e0..7 */	fsub__,		FPU_etc,	__BAD__,	finit_,
+/* e0..7 */	fsubri,		fucom_,		fsubrp,		fstsw_,
+/* e8..f */	fsubr_,		fconst,		fucompp,	fucomi_,
+/* e8..f */	fsub_i,		fucomp,		fsubp_,		fucomip,
+/* f0..7 */	fdiv__,		FPU_triga,	__BAD__,	fcomi_,
+/* f0..7 */	fdivri,		__BAD__,	fdivrp,		fcomip,
+/* f8..f */	fdivr_,		FPU_trigb,	__BAD__,	__BAD__,
+/* f8..f */	fdiv_i,		__BAD__,	fdivp_,		__BAD__,
 };
 
 #define _NONE_ 0		/* Take no special action */
@@ -78,14 +90,15 @@ static FUNC const st_instr_table[64] = {
 #define _REGIn 0		/* Uses st(0) and st(rm), but handle checks later */
 
 static u_char const type_table[64] = {
-	_REGI_, _NONE_, _null_, _null_, _REGIi, _REGi_, _REGIp, _REGi_,
-	_REGI_, _REGIn, _null_, _null_, _REGIi, _REGI_, _REGIp, _REGI_,
-	_REGIc, _NONE_, _null_, _null_, _REGIc, _REG0_, _REGIc, _REG0_,
-	_REGIc, _REG0_, _null_, _null_, _REGIc, _REG0_, _REGIc, _REG0_,
-	_REGI_, _NONE_, _null_, _NONE_, _REGIi, _REGIc, _REGIp, _NONE_,
-	_REGI_, _NONE_, _REGIc, _null_, _REGIi, _REGIc, _REGIp, _null_,
-	_REGI_, _NONE_, _null_, _null_, _REGIi, _null_, _REGIp, _null_,
-	_REGI_, _NONE_, _null_, _null_, _REGIi, _null_, _REGIp, _null_
+/* Opcode:	d8	d9	da	db	dc	dd	de	df */
+/* c0..7 */	_REGI_, _NONE_, _REGIn, _REGIn, _REGIi, _REGi_, _REGIp, _REGi_,
+/* c8..f */	_REGI_, _REGIn, _REGIn, _REGIn, _REGIi, _REGI_, _REGIp, _REGI_,
+/* d0..7 */	_REGIc, _NONE_, _REGIn, _REGIn, _REGIc, _REG0_, _REGIc, _REG0_,
+/* d8..f */	_REGIc, _REG0_, _REGIn, _REGIn, _REGIc, _REG0_, _REGIc, _REG0_,
+/* e0..7 */	_REGI_, _NONE_, _null_, _NONE_, _REGIi, _REGIc, _REGIp, _NONE_,
+/* e8..f */	_REGI_, _NONE_, _REGIc, _REGIc, _REGIi, _REGIc, _REGIp, _REGIc,
+/* f0..7 */	_REGI_, _NONE_, _null_, _REGIc, _REGIi, _null_, _REGIp, _REGIc,
+/* f8..f */	_REGI_, _NONE_, _null_, _null_, _REGIi, _null_, _REGIp, _null_,
 };
 
 #ifdef RE_ENTRANT_CHECKING
diff --git a/arch/x86/math-emu/fpu_proto.h b/arch/x86/math-emu/fpu_proto.h
index 9779df4..caff438 100644
--- a/arch/x86/math-emu/fpu_proto.h
+++ b/arch/x86/math-emu/fpu_proto.h
@@ -46,6 +46,14 @@ extern void fstsw_(void);
 extern void fp_nop(void);
 extern void fld_i_(void);
 extern void fxch_i(void);
+extern void fcmovb(void);
+extern void fcmove(void);
+extern void fcmovbe(void);
+extern void fcmovu(void);
+extern void fcmovnb(void);
+extern void fcmovne(void);
+extern void fcmovnbe(void);
+extern void fcmovnu(void);
 extern void ffree_(void);
 extern void ffreep(void);
 extern void fst_i_(void);
@@ -108,6 +116,10 @@ extern void fcompp(void);
 extern void fucom_(void);
 extern void fucomp(void);
 extern void fucompp(void);
+extern void fcomi_(void);
+extern void fcomip(void);
+extern void fucomi_(void);
+extern void fucomip(void);
 /* reg_constant.c */
 extern void fconst(void);
 /* reg_ld_str.c */
diff --git a/arch/x86/math-emu/reg_compare.c b/arch/x86/math-emu/reg_compare.c
index ecce55f..b77360f 100644
--- a/arch/x86/math-emu/reg_compare.c
+++ b/arch/x86/math-emu/reg_compare.c
@@ -249,6 +249,54 @@ static int compare_st_st(int nr)
 	return 0;
 }
 
+static int compare_i_st_st(int nr)
+{
+	int f, c;
+	FPU_REG *st_ptr;
+
+	if (!NOT_EMPTY(0) || !NOT_EMPTY(nr)) {
+		FPU_EFLAGS |= (X86_EFLAGS_ZF | X86_EFLAGS_PF | X86_EFLAGS_CF);
+		/* Stack fault */
+		EXCEPTION(EX_StackUnder);
+		return !(control_word & CW_Invalid);
+	}
+
+	partial_status &= ~SW_C0;
+	st_ptr = &st(nr);
+	c = compare(st_ptr, FPU_gettagi(nr));
+	if (c & COMP_NaN) {
+		FPU_EFLAGS |= (X86_EFLAGS_ZF | X86_EFLAGS_PF | X86_EFLAGS_CF);
+		EXCEPTION(EX_Invalid);
+		return !(control_word & CW_Invalid);
+	}
+
+	switch (c & 7) {
+	case COMP_A_lt_B:
+		f = X86_EFLAGS_CF;
+		break;
+	case COMP_A_eq_B:
+		f = X86_EFLAGS_ZF;
+		break;
+	case COMP_A_gt_B:
+		f = 0;
+		break;
+	case COMP_No_Comp:
+		f = X86_EFLAGS_ZF | X86_EFLAGS_PF | X86_EFLAGS_CF;
+		break;
+#ifdef PARANOID
+	default:
+		EXCEPTION(EX_INTERNAL | 0x122);
+		f = 0;
+		break;
+#endif /* PARANOID */
+	}
+	FPU_EFLAGS = (FPU_EFLAGS & ~(X86_EFLAGS_ZF | X86_EFLAGS_PF | X86_EFLAGS_CF)) | f;
+	if (c & COMP_Denormal) {
+		return denormal_operand() < 0;
+	}
+	return 0;
+}
+
 static int compare_u_st_st(int nr)
 {
 	int f = 0, c;
@@ -299,6 +347,58 @@ static int compare_u_st_st(int nr)
 	return 0;
 }
 
+static int compare_ui_st_st(int nr)
+{
+	int f = 0, c;
+	FPU_REG *st_ptr;
+
+	if (!NOT_EMPTY(0) || !NOT_EMPTY(nr)) {
+		FPU_EFLAGS |= (X86_EFLAGS_ZF | X86_EFLAGS_PF | X86_EFLAGS_CF);
+		/* Stack fault */
+		EXCEPTION(EX_StackUnder);
+		return !(control_word & CW_Invalid);
+	}
+
+	partial_status &= ~SW_C0;
+	st_ptr = &st(nr);
+	c = compare(st_ptr, FPU_gettagi(nr));
+	if (c & COMP_NaN) {
+		FPU_EFLAGS |= (X86_EFLAGS_ZF | X86_EFLAGS_PF | X86_EFLAGS_CF);
+		if (c & COMP_SNaN) {	/* This is the only difference between
+					   un-ordered and ordinary comparisons */
+			EXCEPTION(EX_Invalid);
+			return !(control_word & CW_Invalid);
+		}
+		return 0;
+	}
+
+	switch (c & 7) {
+	case COMP_A_lt_B:
+		f = X86_EFLAGS_CF;
+		break;
+	case COMP_A_eq_B:
+		f = X86_EFLAGS_ZF;
+		break;
+	case COMP_A_gt_B:
+		f = 0;
+		break;
+	case COMP_No_Comp:
+		f = X86_EFLAGS_ZF | X86_EFLAGS_PF | X86_EFLAGS_CF;
+		break;
+#ifdef PARANOID
+	default:
+		EXCEPTION(EX_INTERNAL | 0x123);
+		f = 0;
+		break;
+#endif /* PARANOID */
+	}
+	FPU_EFLAGS = (FPU_EFLAGS & ~(X86_EFLAGS_ZF | X86_EFLAGS_PF | X86_EFLAGS_CF)) | f;
+	if (c & COMP_Denormal) {
+		return denormal_operand() < 0;
+	}
+	return 0;
+}
+
 /*---------------------------------------------------------------------------*/
 
 void fcom_st(void)
@@ -348,3 +448,31 @@ void fucompp(void)
 	} else
 		FPU_illegal();
 }
+
+/* P6+ compare-to-EFLAGS ops */
+
+void fcomi_(void)
+{
+	/* fcomi st(i) */
+	compare_i_st_st(FPU_rm);
+}
+
+void fcomip(void)
+{
+	/* fcomip st(i) */
+	if (!compare_i_st_st(FPU_rm))
+		FPU_pop();
+}
+
+void fucomi_(void)
+{
+	/* fucomi st(i) */
+	compare_ui_st_st(FPU_rm);
+}
+
+void fucomip(void)
+{
+	/* fucomip st(i) */
+	if (!compare_ui_st_st(FPU_rm))
+		FPU_pop();
+}
-- 
1.8.1.4

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