[PATCH v4 5/9] efi: Show the location of the bounce buffer when debugging

[Simon Glass]

The EFI_LOADER_BOUNCE_BUFFER feature was added many years ago. It is
still needed and 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 debug any problem.

Signed-off-by: Simon Glass <sjg at chromium.org>
---
In response to questions on how to show this problem:

First, add CONFIG_EFI_LOADER_BOUNCE_BUFFER=y to
configs/qemu_arm64_defconfig and build

Then, to run:
qemu-system-aarch64 -machine virt -nographic -cpu cortex-a57 \
   -bios u-boot.bin

U-Boot 2024.10-00809-gae29e5f76e4a-dirty (Oct 11 2024 - 11:48:46 -0600)

DRAM:  128 MiB
Core:  51 devices, 14 uclasses, devicetree: board
Flash: 64 MiB
Loading Environment from Flash... *** Warning - bad CRC, using default environment

In:    serial,usbkbd
Out:   serial,vidconsole
Err:   serial,vidconsole
No USB controllers found
Net:   eth0: virtio-net#32

starting USB...
No USB controllers found
Hit any key to stop autoboot:  0
=> bootefi hello
Enabling coop memory
No EFI system partition
No EFI system partition
Failed to persist EFI variables
Missing TPMv2 device for EFI_TCG_PROTOCOL
Missing RNG device for EFI_RNG_PROTOCOL
Warning: EFI bounce buffer 000000004157f000-000000004557f000
Not loaded from disk
Booting /MemoryMapped(0x0,0x47763730,0x31b0)
EFI: Call: efi_load_image(false, efi_root, file_path, source_buffer, source_size, &handle)
EFI: 0 returned by efi_load_image(false, efi_root, file_path, source_buffer, source_size, &handle)
Hello, world!
Running on UEFI 2.10
Firmware vendor: Das U-Boot
Firmware revision: 20241000
Have device tree
Load options: <none>
File path: <none>
Boot device: /MemoryMapped(0x0,0x47763730,0x31b0)
=> print kernel_addr_r
kernel_addr_r=0x40400000
=> print ramdisk_addr_r
ramdisk_addr_r=0x44000000
=>

The EFI bounce buffer overlaps with the ramdisk.

Changes in v5:
- Drop the word 'warning'

Changes in v4:
- Reword the commit message since this feature is needed

 lib/efi_loader/efi_bootbin.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/lib/efi_loader/efi_bootbin.c b/lib/efi_loader/efi_bootbin.c
index a87006b3c0e..6f02c5ed5dd 100644
--- a/lib/efi_loader/efi_bootbin.c
+++ b/lib/efi_loader/efi_bootbin.c
@@ -209,6 +209,15 @@ 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
+	 */
+	log_debug("EFI bounce buffer %p-%p\n", efi_bounce_buffer,
+		  efi_bounce_buffer + EFI_LOADER_BOUNCE_BUFFER_SIZE);
+#endif
+
 	ret = efi_install_fdt(fdt);
 	if (ret != EFI_SUCCESS)
 		return ret;
-- 
2.43.0