The frame pointer (s0/fp) in call_on_irq_stack is set using
STACKFRAME_SIZE_ON_STACK, which equals ALIGN(sizeof(struct stackframe),
STACK_ALIGN). On RV64, sizeof(struct stackframe) is 16 and the aligned
size is also 16, so there is no difference. However, on RV32,
sizeof(struct stackframe) is 8 while STACKFRAME_SIZE_ON_STACK is 16 due
to 8 bytes of alignment padding.

The stack unwinder does 'frame = (struct stackframe *)fp - 1', which
reads from 'fp - sizeof(struct stackframe)'. On RV32, with fp set to
sp + STACKFRAME_SIZE_ON_STACK (sp + 16), the unwinder reads from
sp + 8, which falls in the alignment padding rather than where the
saved fp/ra are actually stored (sp + 0 and sp + 4).

Fix this by introducing STACKFRAME_SIZE (the unaligned sizeof) and using
it for frame pointer setup and restoration, while keeping
STACKFRAME_SIZE_ON_STACK for the stack pointer allocation/deallocation
which must remain 16-byte aligned.

Signed-off-by: Rui Qi <qirui.001@bytedance.com>
---
 arch/riscv/kernel/asm-offsets.c | 1 +
 arch/riscv/kernel/entry.S       | 4 ++--
 2 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/arch/riscv/kernel/asm-offsets.c b/arch/riscv/kernel/asm-offsets.c
index af827448a609..c1b5f7eb03fd 100644
--- a/arch/riscv/kernel/asm-offsets.c
+++ b/arch/riscv/kernel/asm-offsets.c
@@ -500,6 +500,7 @@ void asm_offsets(void)
 	OFFSET(SBI_HART_BOOT_TASK_PTR_OFFSET, sbi_hart_boot_data, task_ptr);
 	OFFSET(SBI_HART_BOOT_STACK_PTR_OFFSET, sbi_hart_boot_data, stack_ptr);
 
+	DEFINE(STACKFRAME_SIZE, sizeof(struct stackframe));
 	DEFINE(STACKFRAME_SIZE_ON_STACK, ALIGN(sizeof(struct stackframe), STACK_ALIGN));
 	OFFSET(STACKFRAME_FP, stackframe, fp);
 	OFFSET(STACKFRAME_RA, stackframe, ra);
diff --git a/arch/riscv/kernel/entry.S b/arch/riscv/kernel/entry.S
index d011fb51c59a..e8b654e2b7b5 100644
--- a/arch/riscv/kernel/entry.S
+++ b/arch/riscv/kernel/entry.S
@@ -383,7 +383,7 @@ SYM_FUNC_START(call_on_irq_stack)
 	addi	sp, sp, -STACKFRAME_SIZE_ON_STACK
 	REG_S	ra, STACKFRAME_RA(sp)
 	REG_S	s0, STACKFRAME_FP(sp)
-	addi	s0, sp, STACKFRAME_SIZE_ON_STACK
+	addi	s0, sp, STACKFRAME_SIZE
 
 	/* Switch to the per-CPU shadow call stack */
 	scs_save_current
@@ -399,7 +399,7 @@ SYM_FUNC_START(call_on_irq_stack)
 	scs_load_current
 
 	/* Switch back to the thread stack and restore ra and s0 */
-	addi	sp, s0, -STACKFRAME_SIZE_ON_STACK
+	addi	sp, s0, -STACKFRAME_SIZE
 	REG_L	ra, STACKFRAME_RA(sp)
 	REG_L	s0, STACKFRAME_FP(sp)
 	addi	sp, sp, STACKFRAME_SIZE_ON_STACK
-- 
2.20.1