[gentoo-hardened] Disappearing root on 2.6.36-hardened-r6 upgrade

[Michael Orlitzky <michael@orlitzky.com>]

I've got (at least) two servers that lose their root partition after
this upgrade. One of them has an HP cciss SCSI RAID controller; the
other has a single IDE hard drive. Assuming the problem is something
common, I'll stick to describing the one with the array for now.

First of all, I didn't touch /etc/fstab:

  /dev/cciss/c0d0p2	/boot	ext3	noauto,noatime	1 2
  /dev/cciss/c0d0p3	/	ext4	acl,noatime	0 1
  /dev/cciss/c0d0p1	none	swap	sw		0 0

I built the kernel after a make oldconfig, and updated grub.conf:

  title Gentoo Linux 2.6.36-hardened-r6
  root (hd0,1)
  kernel /kernel-2.6.36-hardened-r6

It's actually there:

  # /bin/ls /boot/kernel-2.6.36-hardened-r6
  /boot/kernel-2.6.36-hardened-r6

But upon reboot, this happens:

  http://michael.orlitzky.com/images/untouched.jpg

So, I tried it with root=/dev/cciss/c0d0p3:

  http://michael.orlitzky.com/images/with_root_param.jpg

It clearly sees my partitions, since it lists them all. The root is
ext4, which is compiled into the kernel:

  # grep EXT4 .config
  CONFIG_EXT4_FS=y
  CONFIG_EXT4_FS_XATTR=y
  CONFIG_EXT4_FS_POSIX_ACL=y
  # CONFIG_EXT4_FS_SECURITY is not set
  # CONFIG_EXT4_DEBUG is not set

Now I'm at a loss. There must have been something else that I did during
the make oldconfig that broke it. I keep my kernel configs in git, so
here's the diff (with context stripped) from my previous kernel,
2.6.32-hardened-r22. If anyone has any ideas, I'd appreciate it:

   +CONFIG_INSTRUCTION_DECODER=y
   -CONFIG_GENERIC_TIME=y
   +CONFIG_NEED_SG_DMA_LENGTH=y
   +CONFIG_HAVE_EARLY_RES=y
   +CONFIG_ARCH_HWEIGHT_CFLAGS="-fcall-saved-ecx -fcall-saved-edx"
   +CONFIG_CROSS_COMPILE=""
   +CONFIG_HAVE_KERNEL_LZO=y
   +CONFIG_PERF_EVENTS=y
   +CONFIG_HAVE_OPTPROBES=y
   +CONFIG_HAVE_REGS_AND_STACK_ACCESS_API=y
   +CONFIG_HAVE_HW_BREAKPOINT=y
   +CONFIG_HAVE_MIXED_BREAKPOINTS_REGS=y
   +CONFIG_HAVE_USER_RETURN_NOTIFIER=y
   +CONFIG_HAVE_PERF_EVENTS_NMI=y
   +CONFIG_INLINE_SPIN_UNLOCK=y
   +CONFIG_INLINE_SPIN_UNLOCK_IRQ=y
   +CONFIG_INLINE_READ_UNLOCK=y
   +CONFIG_INLINE_READ_UNLOCK_IRQ=y
   +CONFIG_INLINE_WRITE_UNLOCK=y
   +CONFIG_INLINE_WRITE_UNLOCK_IRQ=y
   +CONFIG_MUTEX_SPIN_ON_OWNER=y
   +CONFIG_NO_BOOTMEM=y
   -CONFIG_X86_L1_CACHE_BYTES=64
   -CONFIG_X86_INTERNODE_CACHE_BYTES=64
   +CONFIG_X86_INTERNODE_CACHE_SHIFT=7
   -CONFIG_HAVE_MLOCK=y
   -CONFIG_HAVE_MLOCKED_PAGE_BIT=y
   -CONFIG_ACPI_DOCK=y
   +CONFIG_ACPI_HED=m
   +CONFIG_ACPI_APEI=y
   +CONFIG_ACPI_APEI_GHES=m
   +CONFIG_INTEL_IDLE=y
   +CONFIG_PCIEASPM=y
   +CONFIG_PCI_IOAPIC=y
   -CONFIG_PACKET_MMAP=y
   +
   +
   +
   +CONFIG_NETFILTER_XT_MATCH_OSF=m
   -CONFIG_NETFILTER_XT_MATCH_OSF=m
   +CONFIG_RPS=y
   +
   +CONFIG_SCSI_MOD=y
   +
   +
   -
   +CONFIG_VGA_ARB_MAX_GPUS=2
   +CONFIG_USB_EHCI_TT_NEWSCHED=y
   -
   -CONFIG_INOTIFY=y
   +CONFIG_PAX_ELFRELOCS=y
   +CONFIG_DEFAULT_SECURITY_DAC=y
   +CONFIG_DEFAULT_SECURITY=""
   -CONFIG_CRYPTO_FIPS=y
   -CONFIG_CRYPTO_AEAD2=y
   -CONFIG_CRYPTO_BLKCIPHER=m
   -CONFIG_CRYPTO_BLKCIPHER2=y
   -CONFIG_CRYPTO_RNG=m
   -CONFIG_CRYPTO_RNG2=y
   -CONFIG_CRYPTO_PCOMP=y
   -CONFIG_CRYPTO_MANAGER=y
   -CONFIG_CRYPTO_MANAGER2=y
   -CONFIG_CRYPTO_WORKQUEUE=y
   -CONFIG_CRYPTO_ECB=m
   -CONFIG_CRYPTO_CRC32C_INTEL=m
   -CONFIG_CRYPTO_MD5=m
   -CONFIG_CRYPTO_SHA512=m
   +CONFIG_CRYPTO_AES_586=m
   -CONFIG_CRYPTO_DES=m
   -CONFIG_CRYPTO_ZLIB=y
   -CONFIG_CRYPTO_ANSI_CPRNG=m
   -CONFIG_ZLIB_INFLATE=y
   -CONFIG_ZLIB_DEFLATE=y