[PATCH 6/6] efi: Show the location of the bounce buffer

[Simon Glass]

The EFI_LOADER_BOUNCE_BUFFER feature was added many years ago. It is not
clear whether it is still needed, but 24 boards (lx2160ardb_tfa_stmm,
lx2162aqds_tfa_SECURE_BOOT and the like) use it.

This feature uses EFI page allocation to create a 64MB buffer 'in space'
without any knowledge of where boards intend to load their images. This
may result in image corruption or other problems.

For example, if the feature is enabled on qemu_arm64 it puts the EFI
bounce buffer at 1045MB, with the kernel at 1028MB and the ramdisk at
1088MB. The kernel is probably smaller than 27MB but the buffer does
overlap the ramdisk.

The solution is probably to use BOUNCE_BUFFER instead, with the EFI
version being dropped. For now, show the address of the EFI bounce
buffer so people have a better chance to detect the problem.

Note: I avoided converting this #ifdef to use IS_ENABLED() since I hope
that the feature may be removed.

Signed-off-by: Simon Glass <sjg at chromium.org>
---

 lib/efi_loader/efi_bootbin.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/lib/efi_loader/efi_bootbin.c b/lib/efi_loader/efi_bootbin.c
index 07c8fca68cc..53e5e429d2e 100644
--- a/lib/efi_loader/efi_bootbin.c
+++ b/lib/efi_loader/efi_bootbin.c
@@ -211,6 +211,14 @@ efi_status_t efi_binary_run(void *image, size_t size, void *fdt)
 		return -1;
 	}
 
+#ifdef CONFIG_EFI_LOADER_BOUNCE_BUFFER
+	/*
+	 * Add a warning about this buffer, since it may conflict with other
+	 * things
+	 */
+	printf("EFI bounce buffer at %p\n", efi_bounce_buffer);
+#endif
+
 	ret = efi_install_fdt(fdt);
 	if (ret != EFI_SUCCESS)
 		return ret;
-- 
2.34.1