arch/risc-v: Fix stack alignment according to calling convention

The RISC-V Integer Calling Convention states that the stack pointer
shall always be aligned to a 128-bit boundary upon procedure entry, both
for RV32* and RV64* ISAs (exception to the RV32E ISA, which must follow a
specific convention)

arch/risc-v/src/bl602/bl602_head.S

@@ -150,16 +150,16 @@ exception_common:
  *  Name: g_intstackalloc and g_intstacktop
  ************************************************************************************/
 
-#if CONFIG_ARCH_INTERRUPTSTACK > 3
+#if CONFIG_ARCH_INTERRUPTSTACK > 15
   .bss
-  .align  4
+  .balign 16
   .global g_intstackalloc
   .global g_intstacktop
   .type   g_intstackalloc, object
   .type   g_intstacktop, object
 g_intstackalloc:
-  .skip  (CONFIG_ARCH_INTERRUPTSTACK & ~3)
+  .skip  ((CONFIG_ARCH_INTERRUPTSTACK + 8) & ~15)
 g_intstacktop:
   .size  g_intstacktop, 0
-  .size  g_intstackalloc, (CONFIG_ARCH_INTERRUPTSTACK & ~3)
+  .size  g_intstackalloc, (CONFIG_ARCH_INTERRUPTSTACK & ~15)
 #endif

arch/risc-v/src/c906/c906_head.S

@@ -264,16 +264,16 @@ exception_common:
  *  Name: g_intstackalloc and g_intstacktop
  ************************************************************************************/
 
-#if CONFIG_ARCH_INTERRUPTSTACK > 7
+#if CONFIG_ARCH_INTERRUPTSTACK > 15
   .bss
-  .align  8
+  .balign 16
   .global g_intstackalloc
   .global g_intstacktop
   .type   g_intstackalloc, object
   .type   g_intstacktop, object
 g_intstackalloc:
-  .skip  ((CONFIG_ARCH_INTERRUPTSTACK + 4) & ~7)
+  .skip  ((CONFIG_ARCH_INTERRUPTSTACK + 8) & ~15)
 g_intstacktop:
   .size  g_intstacktop, 0
-  .size  g_intstackalloc, (CONFIG_ARCH_INTERRUPTSTACK & ~7)
+  .size  g_intstackalloc, (CONFIG_ARCH_INTERRUPTSTACK & ~15)
 #endif

arch/risc-v/src/common/riscv_createstack.c

@@ -42,16 +42,9 @@
  * Pre-processor Macros
  ****************************************************************************/
 
-/* RISC-V requires at least a 4-byte stack alignment.
+/* RISC-V requires a 16-byte stack alignment. */
- * For floating point use, however, the stack must be aligned to 8-byte
- * addresses.
- */
 
-#if defined(CONFIG_LIBC_FLOATINGPOINT) || defined (CONFIG_ARCH_RV64GC)
+#define STACK_ALIGNMENT     16
-#  define STACK_ALIGNMENT   8
-#else
-#  define STACK_ALIGNMENT   4
-#endif
 
 /* Stack alignment macros */
 
@@ -193,18 +186,16 @@ int up_create_stack(FAR struct tcb_s *tcb, size_t stack_size, uint8_t ttype)
       uintptr_t top_of_stack;
       size_t size_of_stack;
 
-      /* RISCV uses a push-down stack:  the stack grows toward lower
+      /* RISC-V uses a push-down stack: the stack grows toward lower
        * addresses in memory. The stack pointer register points to the
        * lowest, valid working address (the "top" of the stack). Items on
-       * the stack are referenced as positive word offsets from sp.
+       * the stack are referenced as positive word offsets from SP.
        */
 
       top_of_stack = (uintptr_t)tcb->stack_alloc_ptr + stack_size;
 
-      /* The RISC-V stack must be aligned at word (4 byte) boundaries; for
+      /* The RISC-V stack must be aligned at 128-bit (16-byte) boundaries.
-       * floating point use, the stack must be aligned to 8-byte addresses.
+       * If necessary top_of_stack must be rounded down to the next boundary.
-       * If necessary top_of_stack must be rounded down to the next
-       * boundary to meet these alignment requirements.
        */
 
       top_of_stack = STACK_ALIGN_DOWN(top_of_stack);

arch/risc-v/src/common/riscv_stackframe.c

@@ -37,16 +37,9 @@
  * Pre-processor Macros
  ****************************************************************************/
 
-/* RISC-V requires at least a 4-byte stack alignment.
+/* RISC-V requires a 16-byte stack alignment. */
- * For floating point use, however, the stack must be aligned to 8-byte
- * addresses.
- */
 
-#if defined(CONFIG_LIBC_FLOATINGPOINT) || defined (CONFIG_ARCH_RV64GC)
+#define STACK_ALIGNMENT     16
-#  define STACK_ALIGNMENT   8
-#else
-#  define STACK_ALIGNMENT   4
-#endif
 
 /* Stack alignment macros */
 

arch/risc-v/src/common/riscv_usestack.c

@@ -39,16 +39,9 @@
  * Pre-processor Definitions
  ****************************************************************************/
 
-/* RISC-V requires at least a 4-byte stack alignment.
+/* RISC-V requires a 16-byte stack alignment. */
- * For floating point use, however, the stack must be aligned to 8-byte
- * addresses.
- */
 
-#if defined(CONFIG_LIBC_FLOATINGPOINT) || defined (CONFIG_ARCH_RV64GC)
+#define STACK_ALIGNMENT     16
-#  define STACK_ALIGNMENT   8
-#else
-#  define STACK_ALIGNMENT   4
-#endif
 
 /* Stack alignment macros */
 
@@ -115,14 +108,13 @@ int up_use_stack(FAR struct tcb_s *tcb, FAR void *stack, size_t stack_size)
   /* RISC-V uses a push-down stack: the stack grows toward lower addresses in
    * memory. The stack pointer register, points to the lowest, valid work
    * address (the "top" of the stack). Items on the stack are referenced
-   * as positive word offsets from sp.
+   * as positive word offsets from SP.
    */
 
   top_of_stack = (uintptr_t)tcb->stack_alloc_ptr + stack_size;
 
-  /* The RISC-V stack must be aligned at word (4 byte) or double word
+  /* The RISC-V stack must be aligned at 128-bit (16-byte) boundaries.
-   * (8 byte) boundaries.  If necessary top_of_stack must be rounded down to
+   * If necessary top_of_stack must be rounded down to the next boundary.
-   * the next boundary.
    */
 
   top_of_stack = STACK_ALIGN_DOWN(top_of_stack);

arch/risc-v/src/esp32c3/esp32c3_interrupt.S

@@ -42,14 +42,14 @@
 
   .section  .noinit
 
-#if CONFIG_ARCH_INTERRUPTSTACK > 3
+#if CONFIG_ARCH_INTERRUPTSTACK > 15
-  .align    4
+  .balign   16
   .type     g_intstackalloc, @object
   .type     g_intstacktop,  @object
 g_intstackalloc:
-  .skip     (CONFIG_ARCH_INTERRUPTSTACK & ~3)
+  .skip     ((CONFIG_ARCH_INTERRUPTSTACK + 8) & ~15)
 g_intstacktop:
-  .size     g_intstackalloc, (CONFIG_ARCH_INTERRUPTSTACK & ~3)
+  .size     g_intstackalloc, (CONFIG_ARCH_INTERRUPTSTACK & ~15)
 #endif
 
 /****************************************************************************

arch/risc-v/src/fe310/fe310_head.S

@@ -201,16 +201,16 @@ exception_common:
  *  Name: g_intstackalloc and g_intstacktop
  ************************************************************************************/
 
-#if CONFIG_ARCH_INTERRUPTSTACK > 3
+#if CONFIG_ARCH_INTERRUPTSTACK > 15
   .bss
-  .align  4
+  .balign 16
   .global g_intstackalloc
   .global g_intstacktop
   .type   g_intstackalloc, object
   .type   g_intstacktop, object
 g_intstackalloc:
-  .skip  (CONFIG_ARCH_INTERRUPTSTACK & ~3)
+  .skip  ((CONFIG_ARCH_INTERRUPTSTACK + 8) & ~15)
 g_intstacktop:
   .size  g_intstacktop, 0
-  .size  g_intstackalloc, (CONFIG_ARCH_INTERRUPTSTACK & ~3)
+  .size  g_intstackalloc, (CONFIG_ARCH_INTERRUPTSTACK & ~15)
 #endif

arch/risc-v/src/k210/k210_head.S

@@ -242,24 +242,24 @@ normal_irq:
  *  Name: g_intstackalloc and g_intstacktop
  ************************************************************************************/
 
-#if CONFIG_ARCH_INTERRUPTSTACK > 7
+#if CONFIG_ARCH_INTERRUPTSTACK > 15
   .bss
-  .align  8
+  .balign 16
   .global g_intstackalloc
   .global g_intstacktop
   .type   g_intstackalloc, object
   .type   g_intstacktop, object
 g_intstackalloc:
 #ifndef CONFIG_SMP
-  .skip  ((CONFIG_ARCH_INTERRUPTSTACK + 4) & ~7)
+  .skip  ((CONFIG_ARCH_INTERRUPTSTACK + 8) & ~15)
 #else
-  .skip  (((CONFIG_ARCH_INTERRUPTSTACK * CONFIG_SMP_NCPUS) + 4) & ~7)
+  .skip  (((CONFIG_ARCH_INTERRUPTSTACK * CONFIG_SMP_NCPUS) + 8) & ~15)
 #endif
 g_intstacktop:
   .size  g_intstacktop, 0
 #ifndef CONFIG_SMP
-  .size  g_intstackalloc, (CONFIG_ARCH_INTERRUPTSTACK & ~7)
+  .size  g_intstackalloc, (CONFIG_ARCH_INTERRUPTSTACK & ~15)
 #else
-  .size  g_intstackalloc, ((CONFIG_ARCH_INTERRUPTSTACK * CONFIG_SMP_NCPUS) & ~7)
+  .size  g_intstackalloc, ((CONFIG_ARCH_INTERRUPTSTACK * CONFIG_SMP_NCPUS) & ~15)
 #endif
 #endif

arch/risc-v/src/litex/litex_head.S

@@ -188,16 +188,16 @@ exception_common:
  *  Name: g_intstackalloc and g_intstacktop
  ************************************************************************************/
 
-#if CONFIG_ARCH_INTERRUPTSTACK > 3
+#if CONFIG_ARCH_INTERRUPTSTACK > 15
   .bss
-  .align  4
+  .balign 16
   .global g_intstackalloc
   .global g_intstacktop
   .type   g_intstackalloc, object
   .type   g_intstacktop, object
 g_intstackalloc:
-  .skip  (CONFIG_ARCH_INTERRUPTSTACK & ~3)
+  .skip  ((CONFIG_ARCH_INTERRUPTSTACK + 8) & ~15)
 g_intstacktop:
   .size  g_intstacktop, 0
-  .size  g_intstackalloc, (CONFIG_ARCH_INTERRUPTSTACK & ~3)
+  .size  g_intstackalloc, (CONFIG_ARCH_INTERRUPTSTACK & ~15)
 #endif

arch/risc-v/src/rv32im/riscv_vfork.c

@@ -41,10 +41,6 @@
  * Pre-processor Definitions
  ****************************************************************************/
 
-#ifndef CONFIG_STACK_ALIGNMENT
-#  define CONFIG_STACK_ALIGNMENT 4
-#endif
-
 /****************************************************************************
  * Private Functions
  ****************************************************************************/