[PATCH] lib: sbi: Add runtime stack overrun detection

[Xiang W]

Implement lightweight stack overrun detection using toolchain's
-finstrument-functions instrumentation

Reviewed-by: Xiang W <wangxiang at iscas.ac.cn>
---
 Makefile                      |  4 +++
 firmware/fw_base.S            |  3 +++
 firmware/payloads/test_head.S | 16 ++++++++++++
 lib/sbi/Kconfig               |  4 +++
 lib/sbi/objects.mk            |  2 ++
 lib/sbi/sbi_sochk.c           | 47 +++++++++++++++++++++++++++++++++++
 6 files changed, 76 insertions(+)
 create mode 100644 lib/sbi/sbi_sochk.c

diff --git a/Makefile b/Makefile
index 398eabe8..cd7d1ad5 100644
--- a/Makefile
+++ b/Makefile
@@ -449,6 +449,10 @@ else
 CFLAGS		+=	-O2
 endif
 
+ifneq ($(CONFIG_SBI_SOCHK),)
+CFLAGS		+=	-finstrument-functions
+endif
+
 # Setup functions for compilation
 define dynamic_flags
 -I$(shell dirname $(2)) -D__OBJNAME__=$(subst -,_,$(shell basename $(1) .o))
diff --git a/firmware/fw_base.S b/firmware/fw_base.S
index 5300ecf2..6cd5725f 100644
--- a/firmware/fw_base.S
+++ b/firmware/fw_base.S
@@ -366,6 +366,9 @@ _start_warm:
 	/* Setup stack */
 	add	sp, tp, zero
 
+#ifdef CONFIG_SBI_SOCHK
+	call	sbi_sochk_init
+#endif
 	/* Setup trap handler */
 	lla	a4, _trap_handler
 	csrr	a5, CSR_MISA
diff --git a/firmware/payloads/test_head.S b/firmware/payloads/test_head.S
index 070ce8aa..de4e334f 100644
--- a/firmware/payloads/test_head.S
+++ b/firmware/payloads/test_head.S
@@ -112,3 +112,19 @@ _boot_a1:
 	.type __stack_chk_guard, %object
 __stack_chk_guard:
 	RISCV_PTR	0x95B5FF5A
+
+#ifdef CONFIG_SBI_SOCHK
+	.section .text
+	.align 3
+	.weak __cyg_profile_func_enter
+	.type __cyg_profile_func_enter, %function
+__cyg_profile_func_enter:
+	ret
+
+.section .text
+	.align 3
+	.weak __cyg_profile_func_exit
+	.type __cyg_profile_func_exit, %function
+__cyg_profile_func_exit:
+	ret
+#endif
diff --git a/lib/sbi/Kconfig b/lib/sbi/Kconfig
index c6cc04bc..77077991 100644
--- a/lib/sbi/Kconfig
+++ b/lib/sbi/Kconfig
@@ -6,6 +6,10 @@ config CONSOLE_EARLY_BUFFER_SIZE
 	int "Early console buffer size (bytes)"
 	default 256
 
+config SBI_SOCHK
+	bool "Enable Stack Overflow runtime checking"
+	default n
+
 config SBI_ECALL_TIME
 	bool "Timer extension"
 	default y
diff --git a/lib/sbi/objects.mk b/lib/sbi/objects.mk
index 8abe1e8e..ed6107ad 100644
--- a/lib/sbi/objects.mk
+++ b/lib/sbi/objects.mk
@@ -64,6 +64,8 @@ libsbi-objs-$(CONFIG_SBI_ECALL_SSE) += sbi_ecall_sse.o
 carray-sbi_ecall_exts-$(CONFIG_SBI_ECALL_MPXY) += ecall_mpxy
 libsbi-objs-$(CONFIG_SBI_ECALL_MPXY) += sbi_ecall_mpxy.o
 
+libsbi-objs-$(CONFIG_SBI_SOCHK) += sbi_sochk.o
+
 libsbi-objs-y += sbi_bitmap.o
 libsbi-objs-y += sbi_bitops.o
 libsbi-objs-y += sbi_console.o
diff --git a/lib/sbi/sbi_sochk.c b/lib/sbi/sbi_sochk.c
new file mode 100644
index 00000000..950275d1
--- /dev/null
+++ b/lib/sbi/sbi_sochk.c
@@ -0,0 +1,47 @@
+
+#include <sbi/sbi_scratch.h>
+#include <sbi/sbi_platform.h>
+#include <sbi/sbi_console.h>
+#include <sbi/sbi_hart.h>
+
+extern struct sbi_platform platform;
+
+static bool __scratch_init_done = false;
+
+__attribute__((no_instrument_function, weak))
+void sbi_sochk_init(void)
+{
+	__scratch_init_done = true;
+}
+
+
+__attribute__((no_instrument_function, weak))
+void __cyg_profile_func_enter(void *this_func, void *call_site)
+{
+	struct sbi_scratch * scratch;
+	unsigned long sp, stack_start, stack_end;
+
+	if (!__scratch_init_done)
+		return;
+
+	scratch = sbi_scratch_thishart_ptr();
+
+	asm volatile("mv %0, sp" : "=r"(sp));
+	stack_start = (unsigned long)scratch + SBI_SCRATCH_SIZE - platform.hart_stack_size;
+	stack_end = (unsigned long)scratch;
+
+	if (sp < stack_start || sp > stack_end) {
+		/* Reset SP to output error messages */
+		asm volatile("mv sp, %0"::"r"(stack_end));
+		sbi_printf("Stack overflow detected in function %p (caller %p), "
+			   "sp=%p (%p - %p)\n",
+			   this_func, call_site, (void*)sp,
+			   (void*)stack_start, (void*)stack_end);
+		sbi_hart_hang();
+	}
+}
+
+__attribute__((no_instrument_function, weak))
+void __cyg_profile_func_exit(void *this_func, void *call_site)
+{
+}
-- 
2.47.3