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

On 26.07.17 15:55, Rob Clark wrote:

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;

I'd prefer if we marked globals as such (read: somewhere at the top of a .c file).

Also I think this function would be better off as a static inline in a header, as it should get compressed quite well.

• /* post-increment, pre-decrement: */
• if (delta > 0)

• return entry_count++ == 0;
  

• else

• return --entry_count == 0;
  

I have a hard time to wrap my head around the logic. At least, couldn't you split this into 2 functions? :)

Alex

+}

• /* 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);