Fix the exception handlers.

cortex-a-rt/src/lib.rs

@@ -91,7 +91,7 @@
 //!
 //!   ```rust
 //!   #[unsafe(no_mangle)]
-//!   extern "C" fn _undefined_handler(faulting_instruction: u32);
+//!   extern "C" fn _undefined_handler(addr: usize);
 //!   ```
 //!
 //! * `_abort_handler` - an `extern "C"` function to call when a Data Abort Exception
@@ -103,7 +103,7 @@
 //!
 //!   ```rust
 //!   #[unsafe(no_mangle)]
-//!   extern "C" fn _abort_handler(faulting_instruction: u32);
+//!   extern "C" fn _abort_handler(addr: usize);
 //!   ```
 //!
 //! * `_prefetch_handler` - an `extern "C"` function to call when a Prefetch Abort Exception
@@ -115,7 +115,7 @@
 //!
 //!   ```rust
 //!   #[unsafe(no_mangle)]
-//!   extern "C" fn _prefetch_handler(faulting_instruction: u32);
+//!   extern "C" fn _prefetch_handler(addr: usize);
 //!   ```
 //!
 //! ### ASM functions
@@ -130,7 +130,7 @@
 //! * `_asm_undefined_handler` - a naked function to call when an Undefined
 //!   Exception occurs. Our linker script PROVIDEs a default function at
 //!   `_asm_default_undefined_handler` but you can override it.
-//! * `_asm_prefetch_handler` - a naked function to call when an Prefetch
+//! * `_asm_prefetch_handler` - a naked function to call when a Prefetch
 //!   Exception occurs. Our linker script PROVIDEs a default function at
 //!   `_asm_default_prefetch_handler` but you can override it. The provided default
 //!   handler will perform an exception return to the faulting address.
@@ -381,7 +381,7 @@ core::arch::global_asm!(
 
     // Called from the vector table when we have an software interrupt.
     // Saves state and calls a C-compatible handler like
-    // `extern "C" fn svc_handler(svc: u32, context: *const u32);`
+    // `extern "C" fn svc_handler(svc: u32);`
     .global _asm_svc_handler
     .type _asm_svc_handler, %function
     _asm_svc_handler:
@@ -426,44 +426,52 @@ core::arch::global_asm!(
 
     // Called from the vector table when we have an undefined exception.
     // Saves state and calls a C-compatible handler like
-    // `extern "C" fn _undefined_handler();`
+    // `extern "C" fn _undefined_handler(addr: usize);`
     .global _asm_default_undefined_handler
     .type _asm_default_undefined_handler, %function
     _asm_default_undefined_handler:
-        // First adjust LR for two purposes: Passing the faulting instruction to the C handler,
-        // and to return to the failing instruction after the C handler returns.
-        // Load processor status
-        mrs      r4, cpsr
-        // Occurred in Thumb state?
-        tst      r4, {t_bit}
-        // If not in Thumb mode, branch to not_thumb
-        beq     not_thumb
-        subs    lr, lr, #2
-        b       done
-not_thumb:
-        // Subtract 4 from LR (ARM mode)
-	      subs	lr, lr, #4
-done:
         // state save from compiled code
         srsfd   sp!, {und_mode}
+        // to work out what mode we're in, we need R0
+        push    {{r0}}
+        // First adjust LR for two purposes: Passing the faulting instruction to the C handler,
+        // and to return to the failing instruction after the C handler returns.
+        // Load processor status for the calling code
+        mrs     r0, spsr
+        // Was the code that triggered the exception in Thumb state?
+        tst     r0, {t_bit}
+        // Subtract 2 in Thumb Mode, 4 in Arm Mode - see p.1206 of the ARMv7-A architecture manual.
+        ite     eq
+        subeq   lr, lr, #4
+        subne   lr, lr, #2
+        // save the newly computed LR
+        push    {{lr}}
+        // now do our standard exception save
     "#,
     save_context!(),
     r#"
         // Pass the faulting instruction address to the handler.
-        mov r0, lr
+        mov     r0, lr
         // call C handler
         bl      _undefined_handler
+        // do our standard restore
     "#,
     restore_context!(),
     r#"
+        // get our saved LR
+        pop     {{lr}}
+        // get our real saved R0
+        pop     {{r0}}
+        // overwrite the saved LR with the adjusted one
+        str     lr, [sp]
         // Return to the failing instruction which is the recommended approach by ARM.
         rfefd   sp!
     .size _asm_default_undefined_handler, . - _asm_default_undefined_handler
 
 
-    // Called from the vector table when we have an undefined exception.
+    // Called from the vector table when we have a prefetch exception.
     // Saves state and calls a C-compatible handler like
-    // `extern "C" fn _prefetch_handler();`
+    // `extern "C" fn _prefetch_handler(addr: usize);`
     .global _asm_default_prefetch_handler
     .type _asm_default_prefetch_handler, %function
     _asm_default_prefetch_handler:
@@ -488,7 +496,7 @@ done:
 
     // Called from the vector table when we have an undefined exception.
     // Saves state and calls a C-compatible handler like
-    // `extern "C" fn _abort_handler();`
+    // `extern "C" fn _abort_handler(addr: usize);`
     .global _asm_default_abort_handler
     .type _asm_default_abort_handler, %function
     _asm_default_abort_handler:
@@ -500,7 +508,7 @@ done:
     save_context!(),
     r#"
         // Pass the faulting instruction address to the handler.
-        mov r0, lr
+        mov     r0, lr
         // call C handler
         bl      _abort_handler
     "#,

cortex-r-rt/link.x

@@ -92,11 +92,13 @@ ASSERT(_abt_stack_size % 8 == 0, "ERROR(cortex-r-rt): size of ABT stack is not 8
 ASSERT(_und_stack_size % 8 == 0, "ERROR(cortex-r-rt): size of UND stack is not 8-byte aligned");
 ASSERT(_svc_stack_size % 8 == 0, "ERROR(cortex-r-rt): size of SVC stack is not 8-byte aligned");
 
-PROVIDE(_asm_undefined_handler =_asm_default_handler);
-PROVIDE(_asm_prefetch_handler  =_asm_default_handler);
-PROVIDE(_asm_abort_handler     =_asm_default_handler);
+/* Weak aliases for ASM default handlers */
+PROVIDE(_asm_undefined_handler =_asm_default_undefined_handler);
+PROVIDE(_asm_prefetch_handler  =_asm_default_prefetch_handler);
+PROVIDE(_asm_abort_handler     =_asm_default_abort_handler);
 PROVIDE(_asm_fiq_handler       =_asm_default_fiq_handler);
 
+/* Weak aliases for C default handlers */
 PROVIDE(_undefined_handler     =_default_handler);
 PROVIDE(_abort_handler         =_default_handler);
 PROVIDE(_prefetch_handler      =_default_handler);

cortex-r-rt/src/lib.rs

@@ -74,7 +74,7 @@
 //!
 //!   ```rust
 //!   #[unsafe(no_mangle)]
-//!   extern "C" fn _undefined_handler(faulting_instruction: u32);
+//!   extern "C" fn _undefined_handler(addr: usize);
 //!   ```
 //!
 //! * `_abort_handler` - an `extern "C"` function to call when a Data Abort Exception
@@ -86,7 +86,7 @@
 //!
 //!   ```rust
 //!   #[unsafe(no_mangle)]
-//!   extern "C" fn _abort_handler(faulting_instruction: u32);
+//!   extern "C" fn _abort_handler(addr: usize);
 //!   ```
 //!
 //! * `_prefetch_handler` - an `extern "C"` function to call when a Prefetch Abort Exception
@@ -98,7 +98,7 @@
 //!
 //!   ```rust
 //!   #[unsafe(no_mangle)]
-//!   extern "C" fn _prefetch_handler(faulting_instruction: u32);
+//!   extern "C" fn _prefetch_handler(addr: usize);
 //!   ```
 //!
 //! ### ASM functions
@@ -113,7 +113,7 @@
 //! * `_asm_undefined_handler` - a naked function to call when an Undefined
 //!   Exception occurs. Our linker script PROVIDEs a default function at
 //!   `_asm_default_undefined_handler` but you can override it.
-//! * `_asm_prefetch_handler` - a naked function to call when an Prefetch
+//! * `_asm_prefetch_handler` - a naked function to call when a Prefetch
 //!   Exception occurs. Our linker script PROVIDEs a default function at
 //!   `_asm_default_prefetch_handler` but you can override it. The provided default
 //!   handler will perform an exception return to the faulting address.
@@ -313,7 +313,7 @@ core::arch::global_asm!(
 
     // Called from the vector table when we have an software interrupt.
     // Saves state and calls a C-compatible handler like
-    // `extern "C" fn svc_handler(svc: u32, context: *const u32);`
+    // `extern "C" fn svc_handler(svc: u32);`
     .global _asm_svc_handler
     .type _asm_svc_handler, %function
     _asm_svc_handler:
@@ -335,6 +335,7 @@ core::arch::global_asm!(
         rfefd   sp!
     .size _asm_svc_handler, . - _asm_svc_handler
 
+
     // Called from the vector table when we have an interrupt.
     // Saves state and calls a C-compatible handler like
     // `extern "C" fn irq_handler();`
@@ -357,56 +358,64 @@ core::arch::global_asm!(
 
     // Called from the vector table when we have an undefined exception.
     // Saves state and calls a C-compatible handler like
-    // `extern "C" fn _undefined_handler();`
+    // `extern "C" fn _undefined_handler(addr: usize);`
     .global _asm_default_undefined_handler
     .type _asm_default_undefined_handler, %function
     _asm_default_undefined_handler:
-        // First adjust LR for two purposes: Passing the faulting instruction to the C handler,
-        // and to return to the failing instruction after the C handler returns.
-        // Load processor status
-        mrs      r4, cpsr
-        // Occurred in Thumb state?
-        tst      r4, {t_bit}
-        // If not in Thumb mode, branch to not_thumb
-        beq     not_thumb
-        subs	lr, lr, #2
-        b       done
-not_thumb:
-        // Subtract 4 from LR (ARM mode)
-        subs    lr, lr, #4
-done:
         // state save from compiled code
         srsfd   sp!, {und_mode}
+        // to work out what mode we're in, we need R0
+        push    {{r0}}
+        // First adjust LR for two purposes: Passing the faulting instruction to the C handler,
+        // and to return to the failing instruction after the C handler returns.
+        // Load processor status for the calling code
+        mrs     r0, spsr
+        // Was the code that triggered the exception in Thumb state?
+        tst     r0, {t_bit}
+        // Subtract 2 in Thumb Mode, 4 in Arm Mode - see p.1206 of the ARMv7-A architecture manual.
+        ite     eq
+        subeq   lr, lr, #4
+        subne   lr, lr, #2
+        // save the newly computed LR
+        push    {{lr}}
+        // now do our standard exception save
     "#,
     save_context!(),
     r#"
         // Pass the faulting instruction address to the handler.
         mov     r0, lr
         // call C handler
         bl      _undefined_handler
+        // do our standard restore
     "#,
     restore_context!(),
     r#"
+        // get our saved LR
+        pop     {{lr}}
+        // get our real saved R0
+        pop     {{r0}}
+        // overwrite the saved LR with the adjusted one
+        str     lr, [sp]
         // Return to the failing instruction which is the recommended approach by ARM.
         rfefd   sp!
     .size _asm_default_undefined_handler, . - _asm_default_undefined_handler
 
 
-    // Called from the vector table when we have an undefined exception.
+    // Called from the vector table when we have a prefetch exception.
     // Saves state and calls a C-compatible handler like
-    // `extern "C" fn _prefetch_handler();`
+    // `extern "C" fn _prefetch_handler(addr: usize);`
     .global _asm_default_prefetch_handler
     .type _asm_default_prefetch_handler, %function
     _asm_default_prefetch_handler:
         // Subtract 4 from the stored LR, see p.1212 of the ARMv7-A architecture manual.
-        subs	lr, lr, #4
+        subs    lr, lr, #4
         // state save from compiled code
         srsfd   sp!, {abt_mode}
     "#,
     save_context!(),
     r#"
         // Pass the faulting instruction address to the handler.
-        mov r0, lr
+        mov     r0, lr
         // call C handler
         bl      _prefetch_handler
     "#,
@@ -419,12 +428,12 @@ done:
 
     // Called from the vector table when we have an undefined exception.
     // Saves state and calls a C-compatible handler like
-    // `extern "C" fn _abort_handler();`
+    // `extern "C" fn _abort_handler(addr: usize);`
     .global _asm_default_abort_handler
     .type _asm_default_abort_handler, %function
     _asm_default_abort_handler:
         // Subtract 8 from the stored LR, see p.1214 of the ARMv7-A architecture manual.
-        subs	lr, lr, #8
+        subs    lr, lr, #8
         // state save from compiled code
         srsfd   sp!, {abt_mode}
     "#,

examples/mps3-an536/reference/abt-exception-armv8r-none-eabihf.out

@@ -0,0 +1,9 @@
+Hello, this is an data abort exception example
+data abort occurred
+DFSR (Fault Status Register): DFSR { ext=false wnr=false Domain=0b0010 Status=0b00001 }
+DFSR Status: Ok(AlignmentFault)
+DFAR (Faulting Address Register): Dfar(4097)
+data abort occurred
+DFSR (Fault Status Register): DFSR { ext=false wnr=false Domain=0b0010 Status=0b00001 }
+DFSR Status: Ok(AlignmentFault)
+DFAR (Faulting Address Register): Dfar(4097)

examples/mps3-an536/reference/prefetch-exception-a32-armv8r-none-eabihf.out

@@ -0,0 +1,11 @@
+Hello, this is a prefetch exception example
+prefetch abort occurred
+IFSR (Fault Status Register): IFSR { ext=false Domain=0b0010 Status=0b00010 }
+IFSR Status: Ok(DebugEvent)
+IFAR (Faulting Address Register): Ifar(0)
+caught bkpt_from_a32
+prefetch abort occurred
+IFSR (Fault Status Register): IFSR { ext=false Domain=0b0010 Status=0b00010 }
+IFSR Status: Ok(DebugEvent)
+IFAR (Faulting Address Register): Ifar(0)
+caught bkpt_from_a32

examples/mps3-an536/reference/prefetch-exception-t32-armv8r-none-eabihf.out

@@ -0,0 +1,11 @@
+Hello, this is a prefetch exception example
+prefetch abort occurred
+IFSR (Fault Status Register): IFSR { ext=false Domain=0b0010 Status=0b00010 }
+IFSR Status: Ok(DebugEvent)
+IFAR (Faulting Address Register): Ifar(0)
+caught bkpt_from_t32
+prefetch abort occurred
+IFSR (Fault Status Register): IFSR { ext=false Domain=0b0010 Status=0b00010 }
+IFSR Status: Ok(DebugEvent)
+IFAR (Faulting Address Register): Ifar(0)
+caught bkpt_from_t32

examples/mps3-an536/reference/undef-exception-a32-armv8r-none-eabihf.out

@@ -0,0 +1,5 @@
+Hello, this is a undef exception example
+undefined abort occurred
+caught udf_from_a32
+undefined abort occurred
+caught udf_from_a32

examples/mps3-an536/reference/undef-exception-t32-armv8r-none-eabihf.out

@@ -0,0 +1,5 @@
+Hello, this is a undef exception example
+undefined abort occurred
+caught udf_from_t32
+undefined abort occurred
+caught udf_from_t32