Initial import

ape/relocations.h

@@ -0,0 +1,67 @@
+#ifndef COSMOPOLITAN_APE_RELOCATIONS_H_
+#define COSMOPOLITAN_APE_RELOCATIONS_H_
+/*─────────────────────────────────────────────────────────────────────────────╗
+│ αcτµαlly pδrταblε εxεcµταblε § relocations                                   │
+╚──────────────────────────────────────────────────────────────────────────────╝
+  One of the things αcτµαlly pδrταblε εxεcµταblε does a good job
+  abstracting, is how a program needs to exist at three addresses
+  simultaneously during the early stages of the loading process.
+
+  By default, the linker calculates all symbols using virtual addresses.
+  In some cases it's necessary to use addend macros that change virtual
+  addresses into the other two types: physical and real. */
+
+#ifndef IMAGE_BASE_VIRTUAL
+#define IMAGE_BASE_VIRTUAL 0x400000
+#endif
+
+#ifndef IMAGE_BASE_PHYSICAL
+#define IMAGE_BASE_PHYSICAL 0x100000
+#endif
+
+/**
+ * Location of anything goes memory for real mode.
+ *
+ * The MBR won't load program content beyond this address, so we have
+ * room for buffers, page tables, etc. before we reach the stack frame.
+ */
+#ifndef REAL_SCRATCH_AREA
+#define REAL_SCRATCH_AREA 0x40000
+#endif
+
+/**
+ * Location of real mode 64kb stack frame.
+ *
+ * This address was chosen because memory beyond 0x80000 can't be
+ * accessed safely without consulting e820.
+ */
+#ifndef REAL_STACK_FRAME
+#define REAL_STACK_FRAME 0x70000
+#endif
+
+/**
+ * Returns Relative Virtual Address.
+ */
+#define RVA(x) ((x) - (IMAGE_BASE_VIRTUAL))
+
+/**
+ * Adjusts virtual address so it's relative to load address.
+ */
+#define PHYSICAL(x) ((x) - (IMAGE_BASE_VIRTUAL - IMAGE_BASE_PHYSICAL))
+
+/**
+ * Makes high-entropy read-only addresses relocatable in real mode.
+ */
+#define REAL(x) ((x) - (IMAGE_BASE_VIRTUAL - IMAGE_BASE_REAL))
+
+#if IMAGE_BASE_VIRTUAL % 0x200000 != 0
+#error "IMAGE_BASE_VIRTUAL must be 2mb aligned"
+#endif
+#if IMAGE_BASE_PHYSICAL % 0x1000 != 0
+#error "IMAGE_BASE_PHYSICAL must be 4kb aligned"
+#endif
+#if IMAGE_BASE_REAL % 0x1000 != 0
+#error "IMAGE_BASE_REAL must be 4kb aligned"
+#endif
+
+#endif /* COSMOPOLITAN_APE_RELOCATIONS_H_ */