[PATCH v2 14/14] arm: efi: add PE/COFF debug table to EFI header

Ard Biesheuvel
2017-02-08T11:55:47Z

This updates the PE/COFF header to emit the absolute path to the
decompressor vmlinux ELF file into a so-called NB10 Codeview entry.
This is hugely helpful when debugging the firmware->stub handover.

Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
---
arch/arm/boot/compressed/Makefile | 4 ++
arch/arm/boot/compressed/efi-header.S | 45 ++++++++++++++++++++
2 files changed, 49 insertions(+)

diff --git a/arch/arm/boot/compressed/Makefile b/arch/arm/boot/compressed/Makefile
index d50430c40045..6b978bdbac3e 100644
--- a/arch/arm/boot/compressed/Makefile
+++ b/arch/arm/boot/compressed/Makefile
@@ -196,3 +196,7 @@ AFLAGS_hyp-stub.o := -Wa,-march=armv7-a

$(obj)/hyp-stub.S: $(srctree)/arch/$(SRCARCH)/kernel/hyp-stub.S
$(call cmd,shipped)
+
+ifeq ($(CONFIG_EFI)$(CONFIG_DEBUG_INFO),yy)
+AFLAGS_head.o += -DVMLINUX_PATH="\"$(realpath $(obj)/vmlinux)\""
+endif
diff --git a/arch/arm/boot/compressed/efi-header.S b/arch/arm/boot/compressed/efi-header.S
index 3cf09f7efced..dff3c72c7c5a 100644
--- a/arch/arm/boot/compressed/efi-header.S
+++ b/arch/arm/boot/compressed/efi-header.S
@@ -95,6 +95,11 @@ extra_header_fields:
.quad 0 @ CertificationTable
.quad 0 @ BaseRelocationTable

+#ifdef CONFIG_DEBUG_INFO
+ .long efi_debug_table - start @ DebugTable
+ .long efi_debug_table_size
+#endif
+
section_table:
.ascii ".text\0\0\0"
.long __pecoff_data_start - __efi_start @ VirtualSize
@@ -124,6 +129,46 @@ section_table:

.set section_count, (. - section_table) / 40

+#ifdef CONFIG_DEBUG_INFO
+ /*
+ * The debug table is referenced via its Relative Virtual Address (RVA),
+ * which is only defined for those parts of the image that are covered
+ * by a section declaration. Since this header is not covered by any
+ * section, the debug table must be emitted elsewhere. So stick it in
+ * the .init.rodata section instead.
+ *
+ * Note that the EFI debug entry itself may legally have a zero RVA,
+ * which means we can simply put it right after the section headers.
+ */
+ .section ".rodata", #alloc
+
+ .align 2
+efi_debug_table:
+ // EFI_IMAGE_DEBUG_DIRECTORY_ENTRY
+ .long 0 @ Characteristics
+ .long 0 @ TimeDateStamp
+ .short 0 @ MajorVersion
+ .short 0 @ MinorVersion
+ .long IMAGE_DEBUG_TYPE_CODEVIEW @ Type
+ .long efi_debug_entry_size @ SizeOfData
+ .long 0 @ RVA
+ .long efi_debug_entry - start @ FileOffset
+
+ .set efi_debug_table_size, . - efi_debug_table
+ .previous
+
+efi_debug_entry:
+ // EFI_IMAGE_DEBUG_CODEVIEW_NB10_ENTRY
+ .ascii "NB10" @ Signature
+ .long 0 @ Unknown
+ .long 0 @ Unknown2
+ .long 0 @ Unknown3
+
+ .asciz VMLINUX_PATH
+
+ .set efi_debug_entry_size, . - efi_debug_entry
+#endif
+
.align 12
__efi_start:
#endif
--
2.7.4