[PATCH v2 10/10] efi: libstub: Simplify interfaces for primary_display

Thomas Zimmermann
2025-11-24T16:52:01Z

Rename alloc_primary_display() and __alloc_primary_display(), clarify
free semantics to make interfaces easier to understand.

Rename alloc_primary_display() to lookup_primary_display() as it
does not necessarily allocate. Then rename __alloc_primary_display()
to the new alloc_primary_display(). The helper belongs to
free_primary_display), so it should be named without underscores.

The lookup helper does not necessarily allocate, so the output
parameter needs_free to indicate when free should be called. Pass
an argument through the calls to track this state. Put the free
handling into release_primary_display() for simplificy.

Also move the comment fro primary_display.c to efi-stub-entry.c,
where it now describes lookup_primary_display().

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
---
drivers/firmware/efi/libstub/efi-stub-entry.c | 23 +++++++++++++++++--
drivers/firmware/efi/libstub/efi-stub.c | 22 ++++++++++++------
drivers/firmware/efi/libstub/efistub.h | 2 +-
.../firmware/efi/libstub/primary_display.c | 17 +-------------
drivers/firmware/efi/libstub/zboot.c | 6 +++--
5 files changed, 42 insertions(+), 28 deletions(-)

diff --git a/drivers/firmware/efi/libstub/efi-stub-entry.c b/drivers/firmware/efi/libstub/efi-stub-entry.c
index aa85e910fe59..3077b51fe0b2 100644
--- a/drivers/firmware/efi/libstub/efi-stub-entry.c
+++ b/drivers/firmware/efi/libstub/efi-stub-entry.c
@@ -14,10 +14,29 @@ static void *kernel_image_addr(void *addr)
return addr + kernel_image_offset;
}

-struct sysfb_display_info *alloc_primary_display(void)
+/*
+ * There are two ways of populating the core kernel's sysfb_primary_display
+ * via the stub:
+ *
+ * - using a configuration table, which relies on the EFI init code to
+ * locate the table and copy the contents; or
+ *
+ * - by linking directly to the core kernel's copy of the global symbol.
+ *
+ * The latter is preferred because it makes the EFIFB earlycon available very
+ * early, but it only works if the EFI stub is part of the core kernel image
+ * itself. The zboot decompressor can only use the configuration table
+ * approach.
+ */
+
+struct sysfb_display_info *lookup_primary_display(bool *needs_free)
{
+ *needs_free = true;
+
if (IS_ENABLED(CONFIG_ARM))
- return __alloc_primary_display();
+ return alloc_primary_display();
+
+ *needs_free = false;

if (IS_ENABLED(CONFIG_X86) ||
IS_ENABLED(CONFIG_EFI_EARLYCON) ||
diff --git a/drivers/firmware/efi/libstub/efi-stub.c b/drivers/firmware/efi/libstub/efi-stub.c
index 42d6073bcd06..dc545f62c62b 100644
--- a/drivers/firmware/efi/libstub/efi-stub.c
+++ b/drivers/firmware/efi/libstub/efi-stub.c
@@ -51,14 +51,14 @@ static bool flat_va_mapping = (EFI_RT_VIRTUAL_OFFSET != 0);
void __weak free_primary_display(struct sysfb_display_info *dpy)
{ }

-static struct sysfb_display_info *setup_primary_display(void)
+static struct sysfb_display_info *setup_primary_display(bool *dpy_needs_free)
{
struct sysfb_display_info *dpy;
struct screen_info *screen = NULL;
struct edid_info *edid = NULL;
efi_status_t status;

- dpy = alloc_primary_display();
+ dpy = lookup_primary_display(dpy_needs_free);
if (!dpy)
return NULL;
screen = &dpy->screen;
@@ -68,15 +68,22 @@ static struct sysfb_display_info *setup_primary_display(void)

status = efi_setup_graphics(screen, edid);
if (status != EFI_SUCCESS)
- goto err_free_primary_display;
+ goto err___free_primary_display;

return dpy;

-err_free_primary_display:
- free_primary_display(dpy);
+err___free_primary_display:
+ if (*dpy_needs_free)
+ free_primary_display(dpy);
return NULL;
}

+static void release_primary_display(struct sysfb_display_info *dpy, bool dpy_needs_free)
+{
+ if (dpy && dpy_needs_free)
+ free_primary_display(dpy);
+}
+
static void install_memreserve_table(void)
{
struct linux_efi_memreserve *rsv;
@@ -156,13 +163,14 @@ efi_status_t efi_stub_common(efi_handle_t handle,
char *cmdline_ptr)
{
struct sysfb_display_info *dpy;
+ bool dpy_needs_free;
efi_status_t status;

status = check_platform_features();
if (status != EFI_SUCCESS)
return status;

- dpy = setup_primary_display();
+ dpy = setup_primary_display(&dpy_needs_free);

efi_retrieve_eventlog();

@@ -182,7 +190,7 @@ efi_status_t efi_stub_common(efi_handle_t handle,

status = efi_boot_kernel(handle, image, image_addr, cmdline_ptr);

- free_primary_display(dpy);
+ release_primary_display(dpy, dpy_needs_free);

return status;
}
diff --git a/drivers/firmware/efi/libstub/efistub.h b/drivers/firmware/efi/libstub/efistub.h
index 979a21818cc1..1503ffb82903 100644
--- a/drivers/firmware/efi/libstub/efistub.h
+++ b/drivers/firmware/efi/libstub/efistub.h
@@ -1176,8 +1176,8 @@ efi_enable_reset_attack_mitigation(void) { }

void efi_retrieve_eventlog(void);

+struct sysfb_display_info *lookup_primary_display(bool *needs_free);
struct sysfb_display_info *alloc_primary_display(void);
-struct sysfb_display_info *__alloc_primary_display(void);
void free_primary_display(struct sysfb_display_info *dpy);

void efi_cache_sync_image(unsigned long image_base,
diff --git a/drivers/firmware/efi/libstub/primary_display.c b/drivers/firmware/efi/libstub/primary_display.c
index cdaebab26514..34c54ac1e02a 100644
--- a/drivers/firmware/efi/libstub/primary_display.c
+++ b/drivers/firmware/efi/libstub/primary_display.c
@@ -7,24 +7,9 @@

#include "efistub.h"

-/*
- * There are two ways of populating the core kernel's sysfb_primary_display
- * via the stub:
- *
- * - using a configuration table, which relies on the EFI init code to
- * locate the table and copy the contents; or
- *
- * - by linking directly to the core kernel's copy of the global symbol.
- *
- * The latter is preferred because it makes the EFIFB earlycon available very
- * early, but it only works if the EFI stub is part of the core kernel image
- * itself. The zboot decompressor can only use the configuration table
- * approach.
- */
-
static efi_guid_t primary_display_guid = LINUX_EFI_PRIMARY_DISPLAY_TABLE_GUID;

-struct sysfb_display_info *__alloc_primary_display(void)
+struct sysfb_display_info *alloc_primary_display(void)
{
struct sysfb_display_info *dpy;
efi_status_t status;
diff --git a/drivers/firmware/efi/libstub/zboot.c b/drivers/firmware/efi/libstub/zboot.c
index 4b76f74c56da..c1fd1fdbcb08 100644
--- a/drivers/firmware/efi/libstub/zboot.c
+++ b/drivers/firmware/efi/libstub/zboot.c
@@ -26,9 +26,11 @@ void __weak efi_cache_sync_image(unsigned long image_base,
// executable code loaded into memory to be safe for execution.
}

-struct sysfb_display_info *alloc_primary_display(void)
+struct sysfb_display_info *lookup_primary_display(bool *needs_free)
{
- return __alloc_primary_display();
+ *needs_free = true;
+
+ return alloc_primary_display();
}

asmlinkage efi_status_t __efiapi
--
2.51.1