[U-Boot] [PATCH 2/3] efi_loader: add checking for incorrect use of EFI_ENTRY/EXIT

[Rob Clark <robdclark@gmail.com>]

Missing an EFI_ENTRY() or doubling up EFI_EXIT() leads to non-obvious
crashes.  Let's add some error checking.

Signed-off-by: Rob Clark <robdclark@gmail.com>
---
 include/efi_loader.h          |  5 +++++
 lib/efi_loader/efi_boottime.c | 13 +++++++++++++
 2 files changed, 18 insertions(+)

diff --git a/include/efi_loader.h b/include/efi_loader.h
index 09bab7dbc6..4b49fac84b 100644
--- a/include/efi_loader.h
+++ b/include/efi_loader.h
@@ -15,11 +15,13 @@
 
 #include <linux/list.h>
 
+int __efi_check_nesting(int delta);
 /*
  * Enter the u-boot world from UEFI:
  */
 #define EFI_ENTRY(format, ...) do { \
 	efi_restore_gd(); \
+	assert(__efi_check_nesting(+1)); \
 	debug("EFI: Entry %s(" format ")\n", __func__, ##__VA_ARGS__); \
 	} while(0)
 
@@ -28,6 +30,7 @@
  */
 #define EFI_EXIT(ret) ({ \
 	debug("EFI: Exit: %s: %u\n", __func__, (u32)((ret) & ~EFI_ERROR_MASK)); \
+	assert(__efi_check_nesting(-1)); \
 	efi_exit_func(ret); \
 	})
 
@@ -36,10 +39,12 @@
  */
 #define EFI_CALL(exp) do { \
 	debug("EFI: Call: %s\n", #exp); \
+	assert(__efi_check_nesting(-1)); \
 	efi_exit_func(EFI_SUCCESS); \
 	exp; \
 	efi_restore_gd(); \
 	debug("EFI: Return From: %s\n", #exp); \
+	assert(__efi_check_nesting(+1)); \
 	} while(0)
 
 extern struct efi_runtime_services efi_runtime_services;
diff --git a/lib/efi_loader/efi_boottime.c b/lib/efi_loader/efi_boottime.c
index 76cafffc1d..b21df7bd5d 100644
--- a/lib/efi_loader/efi_boottime.c
+++ b/lib/efi_loader/efi_boottime.c
@@ -57,6 +57,17 @@ void efi_save_gd(void)
 #endif
 }
 
+/* Check for incorrect use of EFI_ENTRY() / EFI_EXIT() */
+int __efi_check_nesting(int delta)
+{
+	static int entry_count;
+	/* post-increment, pre-decrement: */
+	if (delta > 0)
+		return entry_count++ == 0;
+	else
+		return --entry_count == 0;
+}
+
 /* Called on every callback entry */
 void efi_restore_gd(void)
 {
@@ -716,7 +727,9 @@ static efi_status_t EFIAPI efi_start_image(efi_handle_t image_handle,
 		return EFI_EXIT(info->exit_status);
 	}
 
+	__efi_check_nesting(-1);
 	entry(image_handle, &systab);
+	__efi_check_nesting(+1);
 
 	/* Should usually never get here */
 	return EFI_EXIT(EFI_SUCCESS);
-- 
2.13.0