efi/arm/libstub: Pack FDT after populating it

Ard Biesheuvel · Ingo Molnar · commit 72a58a63a164 · 2018-11-15T10:04:46.000+01:00
Commit: 24d7c49 ("efi/arm-stub: Round up FDT allocation to mapping size") increased the allocation size for the FDT image created by the stub to a fixed value of 2 MB, to simplify the former code that made several attempts with increasing values for the size. This is reasonable given that the allocation is of type EFI_LOADER_DATA, which is released to the kernel unless it is explicitly memblock_reserve()d by the early boot code. However, this allocation size leaked into the 'size' field of the FDT header metadata, and so the entire allocation remains occupied by the device tree binary, even if most of it is not used to store device tree information. So call fdt_pack() to shrink the FDT data structure to its minimum size after populating all the fields, so that the remaining memory is no longer wasted. Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> Cc: <stable@vger.kernel.org> # v4.12+ Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: linux-efi@vger.kernel.org Fixes: 24d7c49 ("efi/arm-stub: Round up FDT allocation to mapping size") Link: http://lkml.kernel.org/r/20181114175544.12860-4-ard.biesheuvel@linaro.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
diff --git a/drivers/firmware/efi/libstub/fdt.c b/drivers/firmware/efi/libstub/fdt.c
@@ -158,6 +158,10 @@ static efi_status_t update_fdt(efi_system_table_t *sys_table, void *orig_fdt,
 			return efi_status;
 		}
 	}
+
+	/* shrink the FDT back to its minimum size */
+	fdt_pack(fdt);
+
 	return EFI_SUCCESS;
 
 fdt_set_fail:

Original file line number	Diff line number	Diff line change
`@@ -158,6 +158,10 @@ static efi_status_t update_fdt(efi_system_table_t sys_table, void orig_fdt,`
`158`	`158`	`return efi_status;`
`159`	`159`	`}`
`160`	`160`	`}`
	`161`	`+`
	`162`	`+ /* shrink the FDT back to its minimum size */`
	`163`	`+ fdt_pack(fdt);`
	`164`	`+`
`161`	`165`	`return EFI_SUCCESS;`
`162`	`166`
`163`	`167`	`fdt_set_fail:`