Changeset 3194d83 in mainline

Timestamp:

2012-11-29T12:05:08Z (11 years ago)

Author:

Jan Vesely <jano.vesely@…>

Branches:

lfn, master, serial, ticket/834-toolchain-update, topic/msim-upgrade, topic/simplify-dev-export

Children:

69c1995

Parents:

e1c6d5df

Message:

Deobfuscate and document x86 and amd64 fpu initialization.

Location:

kernel/arch

Files:

• amd64/src/fpu_context.c (modified) (1 diff)
• ia32/src/fpu_context.c (modified) (3 diffs)

kernel/arch/amd64/src/fpu_context.c

@@ -57 +57 @@
 {
         /* TODO: Zero all SSE, MMX etc. registers */
+        /* Default value of SCR register is 0x1f80,
+         * it masks all FPU exceptions*/
         asm volatile (
                 "fninit\n"

kernel/arch/ia32/src/fpu_context.c

@@ -37 +37 @@
 #include <arch.h>
 #include <cpu.h>
+
+
+/** x87 FPU scr values (P3+ MMX2) */
+enum {
+        X87_FLUSH_ZERO_FLAG = (1 << 15),
+        X87_ROUND_CONTROL_MASK = (0x3 << 13),
+        x87_ROUND_TO_NEAREST_EVEN = (0x0 << 13),
+        X87_ROUND_DOWN_TO_NEG_INF = (0x1 << 13),
+        X87_ROUND_UP_TO_POS_INF = (0x2 << 13),
+        X87_ROUND_TO_ZERO = (0x3 << 13),
+        X87_PRECISION_MASK = (1 << 12),
+        X87_UNDERFLOW_MASK = (1 << 11),
+        X87_OVERFLOW_MASK = (1 << 10),
+        X87_ZERO_DIV_MASK = (1 << 9),
+        X87_DENORMAL_OP_MASK = (1 << 8),
+        X87_INVALID_OP_MASK = (1 << 7),
+        X87_DENOM_ZERO_FLAG = (1 << 6),
+        X87_PRECISION_EXC_FLAG = (1 << 5),
+        X87_UNDERFLOW_EXC_FLAG = (1 << 4),
+        X87_OVERFLOW_EXC_FLAG = (1 << 3),
+        X87_ZERO_DIV_EXC_FLAG = (1 << 2),
+        X87_DENORMAL_EXC_FLAG = (1 << 1),
+        X87_INVALID_OP_EXC_FLAG = (1 << 0),
+
+        X87_ALL_MASK = X87_PRECISION_MASK | X87_UNDERFLOW_MASK | X87_OVERFLOW_MASK | X87_ZERO_DIV_MASK | X87_DENORMAL_OP_MASK | X87_INVALID_OP_MASK,
+};
+
 
 typedef void (*fpu_context_function)(fpu_context_t *fctx);
@@ -98 +125 @@
 }
 
+/** Initialize x87 FPU. Mask all exceptions. */
 void fpu_init()
 {
@@ -111 +139 @@
                 "ldmxcsr %[help0]\n"
                 : [help0] "+m" (help0), [help1] "+r" (help1)
-                : [magic] "i" (0x1f80)
+                : [magic] "i" (X87_ALL_MASK)
         );
 }