1 files changed, 88 insertions, 0 deletions
diff --git a/src/boot/psr.h b/src/boot/psr.h
new file mode 100644
index 0000000..f300a7a
--- /dev/null
+++ b/src/boot/psr.h
@@ -0,0 +1,88 @@
+#ifndef PSR_H
+#define PSR_H
+
+#include <stdint.h>
+
+enum execution_mode {
+  MODE_USER       = 0b10000,
+  MODE_FIQ        = 0b10001,
+  MODE_IRQ        = 0b10010,
+  MODE_SUPERVISOR = 0b10011,
+  MODE_MONITOR    = 0b10110,
+  MODE_ABORT      = 0b10111,
+  MODE_HYPERVISOR = 0b11010,
+  MODE_UNDEFINED  = 0b11011,
+  MODE_SYSTEM     = 0b11111,
+};
+
+typedef union
+{
+  uint32_t raw;
+  struct
+  {
+    uint32_t M_4_0      : 5; // bits 4:0
+    uint32_t T          : 1; // bit  5
+    uint32_t F          : 1; // bit  6
+    uint32_t I          : 1; // bit  7
+    uint32_t A          : 1; // bit  8
+    uint32_t E          : 1; // bit  9
+    uint32_t IT_7_2     : 6; // bits 15:10
+    uint32_t GE_3_0     : 4; // bits 19:16
+    uint32_t Bits_23_20 : 4; // bits 23:20
+    uint32_t J          : 1; // bit  24
+    uint32_t IT_1_0     : 2; // bits 26:25
+    uint32_t Q          : 1; // bit  27
+    uint32_t V          : 1; // bit  28
+    uint32_t C          : 1; // bit  29
+    uint32_t Z          : 1; // bit  30
+    uint32_t N          : 1; // bit  31
+#define PSR_MODE_4_0                    M_4_0
+#define PSR_THUMB_BIT                   T
+#define PSR_FIQ_MASKK_BIT               F
+#define PSR_IRQ_MASK_BIT                I
+#define PSR_ASYNC_ABORT_MASK_BIT        A
+#define PSR_ENDIANNESS_BIT              E
+#define PSR_IF_THEN_STATE_7_2           IT_7_2
+#define PSR_GREATER_THAN_OR_EQUAL_FLAGS GE_3_0
+    // bits 23:20 are reserved
+#define PSR_JAZELLE_BIT                 J
+#define PSR_IF_THEN_STATE_1_0           IT_1_0
+#define PSR_CUMULATIVE_SATURATION_BIT   Q
+#define PSR_OVERFLOW_CONDITION_BIT      V
+#define PSR_CARRY_CONDITION_BIT         C
+#define PSR_ZERO_CONDITION_BIT          Z
+#define PSR_NEGATIVE_CONDITION_BIT      N
+  } fields;
+} PSR_t;
+
+inline static PSR_t read_CPSR(void)
+{
+  PSR_t CPSR;
+  // get content of current program status register
+  asm("mrs %0, cpsr" : "=r" (CPSR.raw) :: "memory");
+
+  return CPSR;
+}
+
+inline static void write_CPSR(PSR_t CPSR)
+{
+  // set content of current program status register
+  asm("msr cpsr, %0" :: "r" (CPSR.raw) : "memory");
+}
+
+inline static PSR_t read_SPSR(void)
+{
+  PSR_t SPSR;
+  // get content of saved program status register
+  asm("mrs %0, spsr" : "=r" (SPSR.raw) :: "memory");
+  
+  return SPSR;
+}
+
+inline static void write_SPSR(PSR_t SPSR)
+{
+  // set content of saved program status register
+  asm("msr spsr, %0" :: "r" (SPSR.raw));
+}
+
+#endif // PSR_H