On 25.07.17 01:47, Rob Clark wrote:
To implement efi_load_image() for the case of loading an image from a
device path rather than image already loaded into source_buffer, it is
convenient to be able to re-use simple-file-system and efi-file
interfaces. But these are already using EFI_ENTER()/EFI_EXIT(). Allow
entry into EFI interfaces to be recursive, since this greatly simplifies
things.
(And hypothetically this would be needed anyways to allow grub to call
into interfaces installed by something outside of grub.)
Signed-off-by: Rob Clark <robdcl...@gmail.com>
So there are 2 ways to do this:
1) Keep a refcount, only transition when passing the 0 level
2) Explicitly split functions with ENTRY/EXIT from their core functions
So far we used approach 2, splitting functions that are used by both
internal and external code into _ext (for externally called) and normal
functions. You can see this pattern quite a few times throughout efi_loader.
I definitely did try the refcount approach back when I decided for
approach 2 and it failed on me in some case, but I can't remember where.
Either way, we should definitely be consistent. Either we always use
refcounting or we shouldn't bother with it. So if you can make a version
work where all _ext variants disappear and we're magically reentrant,
I'll be happy to take that. I'm fairly sure it'll break somewhere though :).
Alex
---
lib/efi_loader/efi_boottime.c | 5 +++++
1 file changed, 5 insertions(+)
diff --git a/lib/efi_loader/efi_boottime.c b/lib/efi_loader/efi_boottime.c
index 8735b1f418..a113124708 100644
--- a/lib/efi_loader/efi_boottime.c
+++ b/lib/efi_loader/efi_boottime.c
@@ -47,6 +47,7 @@ static struct efi_configuration_table __efi_runtime_data
efi_conf_table[2];
* EFI callback entry/exit.
*/
static volatile void *efi_gd, *app_gd;
+static int entry_level = 0;
#endif
/* Called from do_bootefi_exec() */
@@ -61,6 +62,8 @@ void efi_save_gd(void)
void efi_restore_gd(void)
{
#ifdef CONFIG_ARM
+ if (entry_level++)
+ return;
/* Only restore if we're already in EFI context */
if (!efi_gd)
return;
@@ -75,6 +78,8 @@ void efi_restore_gd(void)
efi_status_t efi_exit_func(efi_status_t ret)
{
#ifdef CONFIG_ARM
+ if (--entry_level)
+ return ret;
gd = app_gd;
#endif
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