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[romprefix] Avoid unaligned accesses within ROM headers

Ensure that all headers (PCI, UNDI, PnP, iPXE) are aligned to at least
four bytes, so that all accesses to header fields will be correctly
aligned even when reading directly from the expansion ROM BAR.

Reported-by: Peter von Konigsmark <peter@exablaze.com>
Signed-off-by: Michael Brown <mcb30@ipxe.org>
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mcb30 committed Aug 30, 2017
1 parent 8b104d8 commit 75acb3c775544b6ecc4bfb1bba633717c8ec9394
Showing with 4 additions and 0 deletions.
  1. +1 −0 src/arch/x86/prefix/mromprefix.S
  2. +3 −0 src/arch/x86/prefix/romprefix.S
@@ -492,6 +492,7 @@ mromheader:
.word 0
.size mromheader, . - mromheader

.align 4
mpciheader:
.ascii "PCIR" /* Signature */
.word pci_vendor_id /* Vendor identification */
@@ -88,6 +88,7 @@ checksum:
.previous

.ifeqs BUSTYPE, "PCIR"
.align 4
pciheader:
.ascii "PCIR" /* Signature */
.word pci_vendor_id /* Vendor identification */
@@ -183,6 +184,7 @@ prodstr_pci_id:

.globl undiheader
.weak undiloader
.align 4
undiheader:
.ascii "UNDI" /* Signature */
.byte undiheader_len /* Length of structure */
@@ -197,6 +199,7 @@ undiheader:
.equ undiheader_len, . - undiheader
.size undiheader, . - undiheader

.align 4
ipxeheader:
.ascii "iPXE" /* Signature */
.byte ipxeheader_len /* Length of structure */

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