This change makes later calculations about where the kernel is located
easier to reason about. To better understand this change, we must first
clarify what 'VO' and 'ZO' are. These values were introduced in commits
by hpa:
77d1a49995 ("x86, boot: make symbols from the main vmlinux available")
37ba7ab5e3 ("x86, boot: make kernel_alignment adjustable; new bzImage fields")
Specifically:
All names prefixed with 'VO_':
- relate to the uncompressed kernel image
- the size of the VO image is: VO__end-VO__text ("VO_INIT_SIZE" define)
All names prefixed with 'ZO_':
- relate to the bootable compressed kernel image (boot/compressed/vmlinux),
which is composed of the following memory areas:
- head text
- compressed kernel (VO image and relocs table)
- decompressor code
- the size of the ZO image is: ZO__end - ZO_startup_32 ("ZO_INIT_SIZE" define, though see below)
The 'INIT_SIZE' value is used to find the larger of the two image sizes:
#define ZO_INIT_SIZE (ZO__end - ZO_startup_32 + ZO_z_extract_offset)
#define VO_INIT_SIZE (VO__end - VO__text)
#if ZO_INIT_SIZE > VO_INIT_SIZE
# define INIT_SIZE ZO_INIT_SIZE
#else
# define INIT_SIZE VO_INIT_SIZE
#endif
The current code uses extract_offset to decide where to position the
copied ZO (i.e. ZO starts at extract_offset). (This is why ZO_INIT_SIZE
currently includes the extract_offset.)
Why does z_extract_offset exist? It's needed because we are trying to minimize
the amount of RAM used for the whole act of creating an uncompressed, executable,
properly relocation-linked kernel image in system memory. We do this so that
kernels can be booted on even very small systems.
To achieve the goal of minimal memory consumption we have implemented an in-place
decompression strategy: instead of cleanly separating the VO and ZO images and
also allocating some memory for the decompression code's runtime needs, we instead
create this elaborate layout of memory buffers where the output (decompressed)
stream, as it progresses, overlaps with and destroys the input (compressed)
stream. This can only be done safely if the ZO image is placed to the end of the
VO range, plus a certain amount of safety distance to make sure that when the last
bytes of the VO range are decompressed, the compressed stream pointer is safely
beyond the end of the VO range.
z_extract_offset is calculated in arch/x86/boot/compressed/mkpiggy.c during
the build process, at a point when we know the exact compressed and
uncompressed size of the kernel images and can calculate this safe minimum
offset value. (Note that the mkpiggy.c calculation is not perfect, because
we don't know the decompressor used at that stage, so the z_extract_offset
calculation is necessarily imprecise and is mostly based on gzip internals -
we'll improve that in the next patch.)
When INIT_SIZE is bigger than VO_INIT_SIZE (uncommon but possible),
the copied ZO occupies the memory from extract_offset to the end of
decompression buffer. It overlaps with the soon-to-be-uncompressed kernel
like this:
|-----compressed kernel image------|
V V
0 extract_offset +INIT_SIZE
|-----------|---------------|-------------------------|--------|
| | | |
VO__text startup_32 of ZO VO__end ZO__end
^ ^
|-------uncompressed kernel image---------|
When INIT_SIZE is equal to VO_INIT_SIZE (likely) there's still space
left from end of ZO to the end of decompressing buffer, like below.
|-compressed kernel image-|
V V
0 extract_offset +INIT_SIZE
|-----------|---------------|-------------------------|--------|
| | | |
VO__text startup_32 of ZO ZO__end VO__end
^ ^
|------------uncompressed kernel image-------------|
To simplify calculations and avoid special cases, it is cleaner to
always place the compressed kernel image in memory so that ZO__end
is at the end of the decompression buffer, instead of placing t at
the start of extract_offset as is currently done.
This patch adds BP_init_size (which is the INIT_SIZE as passed in from
the boot_params) into asm-offsets.c to make it visible to the assembly
code.
Then when moving the ZO, it calculates the starting position of
the copied ZO (via BP_init_size and the ZO run size) so that the VO__end
will be at the end of the decompression buffer. To make the position
calculation safe, the end of ZO is page aligned (and a comment is added
to the existing VO alignment for good measure).
Signed-off-by: Yinghai Lu <yinghai@kernel.org>
[ Rewrote changelog and comments. ]
Signed-off-by: Kees Cook <keescook@chromium.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Baoquan He <bhe@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Dave Young <dyoung@redhat.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vivek Goyal <vgoyal@redhat.com>
Cc: lasse.collin@tukaani.org
Link: http://lkml.kernel.org/r/1461888548-32439-3-git-send-email-keescook@chromium.org
[ Rewrote the changelog some more. ]
Signed-off-by: Ingo Molnar <mingo@kernel.org>
The comment that describes the analysis for the size of the decompressor
code only took gzip into account (there are currently 6 other decompressors
that could be used). The actual z_extract_offset calculation in code was
already handling the correct maximum size, but this documentation hadn't
been updated. This updates the documentation, fixes several typos, moves
the comment to header.S, updates references, and adds a note at the end
of the decompressor include list to remind us about updating the comment
in the future.
(Instead of moving the comment to mkpiggy.c, where the calculation
is currently happening, it is being moved to header.S because
the calculations in mkpiggy.c will be removed in favor of header.S
calculations in a following patch, and it seemed like overkill to move
the giant comment twice, especially when there's already reference to
z_extract_offset in header.S.)
Signed-off-by: Baoquan He <bhe@redhat.com>
[ Rewrote changelog, cleaned up comment style, moved comments around. ]
Signed-off-by: Kees Cook <keescook@chromium.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Borislav Petkov <bp@suse.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: H.J. Lu <hjl.tools@gmail.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Yinghai Lu <yinghai@kernel.org>
Link: http://lkml.kernel.org/r/1461185746-8017-2-git-send-email-keescook@chromium.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Pull device mapper fix from Mike Snitzer:
"Fix for earlier 4.6-rc4 stable@ commit that introduced improper use of
write lock in cmd_read_lock() -- due to cut-n-paste gone awry (and
sparse didn't catch it)"
* tag 'dm-4.6-fix-2' of git://git.kernel.org/pub/scm/linux/kernel/git/device-mapper/linux-dm:
dm cache metadata: fix cmd_read_lock() acquiring write lock
Commit 9567366fef ("dm cache metadata: fix READ_LOCK macros and
cleanup WRITE_LOCK macros") uses down_write() instead of down_read() in
cmd_read_lock(), yet up_read() is used to release the lock in
READ_UNLOCK(). Fix it.
Fixes: 9567366fef ("dm cache metadata: fix READ_LOCK macros and cleanup WRITE_LOCK macros")
Cc: stable@vger.kernel.org
Signed-off-by: Ahmed Samy <f.fallen45@gmail.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Pull char/misc fixes from Greg KH:
"Here are some small char/misc driver fixes for 4.6-rc4. Full details
are in the shortlog, nothing major here.
These have all been in linux-next for a while with no reported issues"
* tag 'char-misc-4.6-rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/char-misc:
lkdtm: do not leak free page on kmalloc failure
lkdtm: fix memory leak of base
lkdtm: fix memory leak of val
extcon: palmas: Drop stray IRQF_EARLY_RESUME flag
Pull misc fixes from Greg KH:
"Here are three small fixes for 4.6-rc4.
Two fix up some lz4 issues with big endian systems, and the remaining
one resolves a minor debugfs issue that was reported.
All have been in linux-next with no reported issues"
* tag 'driver-core-4.6-rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/driver-core:
lib: lz4: cleanup unaligned access efficiency detection
lib: lz4: fixed zram with lz4 on big endian machines
debugfs: Make automount point inodes permanently empty
Pull USB driver fixes from Greg KH:
"Here are some small USB fixes for 4.6-rc4.
Mostly xhci fixes for reported issues, a UAS bug that has hit a number
of people, including stable tree users, and a few other minor things.
All have been in linux-next for a while with no reported issues"
* tag 'usb-4.6-rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb:
usb: hcd: out of bounds access in for_each_companion
USB: uas: Add a new NO_REPORT_LUNS quirk
USB: uas: Limit qdepth at the scsi-host level
doc: usb: Fix typo in gadget_multi documentation
usb: host: xhci-plat: Make enum xhci_plat_type start at a non zero value
xhci: fix 10 second timeout on removal of PCI hotpluggable xhci controllers
usb: xhci: fix wild pointers in xhci_mem_cleanup
usb: host: xhci-plat: fix cannot work if R-Car Gen2/3 run on above 4GB phys
usb: host: xhci: add a new quirk XHCI_NO_64BIT_SUPPORT
xhci: resume USB 3 roothub first
usb: xhci: applying XHCI_PME_STUCK_QUIRK to Intel BXT B0 host
cdc-acm: fix crash if flushed with nothing buffered
Pull dmaengine fixes from Vinod Koul:
"This time we have some odd fixes in hsu, edma, omap and xilinx.
Usual fixes and nothing special"
* tag 'dmaengine-fix-4.6-rc4' of git://git.infradead.org/users/vkoul/slave-dma:
dmaengine: dw: fix master selection
dmaengine: edma: special case slot limit workaround
dmaengine: edma: Remove dynamic TPTC power management feature
dmaengine: vdma: don't crash when bad channel is requested
dmaengine: omap-dma: Do not suppress interrupts for memcpy
dmaengine: omap-dma: Fix polled channel completion detection and handling
dmaengine: hsu: correct use of channel status register
dmaengine: hsu: correct residue calculation of active descriptor
dmaengine: hsu: set HSU_CH_MTSR to memory width
Pull locking fixlet from Ingo Molnar:
"Fixes a build warning on certain Kconfig combinations"
* 'locking-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
locking/lockdep: Fix print_collision() unused warning
Pull block fixes from Jens Axboe:
"A few fixes for the current series. This contains:
- Two fixes for NVMe:
One fixes a reset race that can be triggered by repeated
insert/removal of the module.
The other fixes an issue on some platforms, where we get probe
timeouts since legacy interrupts isn't working. This used not to
be a problem since we had the worker thread poll for completions,
but since that was killed off, it means those poor souls can't
successfully probe their NVMe device. Use a proper IRQ check and
probe (msi-x -> msi ->legacy), like most other drivers to work
around this. Both from Keith.
- A loop corruption issue with offset in iters, from Ming Lei.
- A fix for not having the partition stat per cpu ref count
initialized before sending out the KOBJ_ADD, which could cause user
space to access the counter prior to initialization. Also from
Ming Lei.
- A fix for using the wrong congestion state, from Kaixu Xia"
* 'for-linus' of git://git.kernel.dk/linux-block:
block: loop: fix filesystem corruption in case of aio/dio
NVMe: Always use MSI/MSI-x interrupts
NVMe: Fix reset/remove race
writeback: fix the wrong congested state variable definition
block: partition: initialize percpuref before sending out KOBJ_ADD
Pull libnvdimm fixes from Ross Zwisler:
"Two fixes:
- Fix memcpy_from_pmem() to fallback to memcpy() for architectures
where CONFIG_ARCH_HAS_PMEM_API=n.
- Add a comment explaining why we write data twice when clearing
poison in pmem_do_bvec().
This has passed a boot test on an X86_32 config, which was the
architecture where issue #1 above was first noticed"
Dan Williams adds:
"We're giving this multi-maintainer setup a shot, so expect libnvdimm
pull requests from either Ross or I going forward"
* 'libnvdimm-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/nvdimm/nvdimm:
libnvdimm, pmem: clarify the write+clear_poison+write flow
pmem: fix BUG() error in pmem.h:48 on X86_32
Pull MTD fix from Brian Norris:
"One MTD fix for v4.6-rc4:
In the v4.4 cycle, we relaxed the requirement for assigning
mtd->owner, but we didn't remove this error case. It's hit only
by drivers that are both:
(a) using nand_scan() directly
and
(b) built as modules
We haven't seen explicit complaints about this (most use cases don't
fit one or both of the above), but we should definitely not be
BUG()'ing here"
* tag 'for-linus-20160415' of git://git.infradead.org/linux-mtd:
mtd: nand: Drop mtd.owner requirement in nand_scan
Pull MMC fixes from Ulf Hansson:
"Here are a couple of mmc fixes intended for v4.6 rc4.
Regarding the fix for the regression about mmcblk device indexes. The
approach taken to solve the problem seems to be good enough. There
were some discussions around the solution, but it seems like people
were happy about it in the end.
MMC core:
- Restore similar old behaviour when assigning mmcblk device indexes
MMC host:
- tegra: Disable UHS-I modes for Tegra124 to fix regression"
* tag 'mmc-v4.6-rc3' of git://git.linaro.org/people/ulf.hansson/mmc:
mmc: tegra: Disable UHS-I modes for Tegra124
mmc: block: Use the mmc host device index as the mmcblk device index
Pull drm fixes from Dave Airlie:
"This contains fixes for exynos, amdgpu, radeon, i915 and qxl.
It also contains some fixes to the core drm edid parser.
qxl:
- fix for a cursor hotspot issue
radeon:
- some MST fixes that I've been running locally and make my monitor a
bit happier
exynos:
- fix some regressions and build fixes
amdgpu:
- a couple of small fixes
i915:
- two DP MST fixes and a couple of other regression fixes
Nothing too out of the ordinary or surprising at this point"
* 'drm-fixes' of git://people.freedesktop.org/~airlied/linux:
drm/exynos: Use VIDEO_SAMSUNG_S5P_G2D=n as G2D Kconfig dependency
drm/exynos: fix a warning message
drm/exynos: mic: fix an error code
drm/exynos: fimd: fix broken dp_clock control
drm/exynos: build fbdev code conditionally
drm/exynos: fix adjusted_mode pointer in exynos_plane_mode_set
drm/exynos: fix error handling in exynos_drm_subdrv_open
drm/amd/amdgpu: fix irq domain remove for tonga ih
drm/i915: fix deadlock on lid open
drm/radeon: use helper for mst connector dpms.
drm/radeon/mst: port some MST setup code from DAL.
drm/amdgpu: add invisible pin size statistic
drm/edid: Fix DMT 1024x768@43Hz (interlaced) timings
drm/i915: Exit cherryview_irq_handler() after one pass
drm/i915: Call intel_dp_mst_resume() before resuming displays
drm/i915: Fix race condition in intel_dp_destroy_mst_connector()
drm/edid: Fix parsing of EDID 1.4 Established Timings III descriptor
drm/edid: Fix EDID Established Timings I and II
drm/qxl: fix cursor position with non-zero hotspot
Pull parisc ftrace fixes from Helge Deller:
"This is (most likely) the last pull request for v4.6 for the parisc
architecture.
It fixes the FTRACE feature for parisc, which is horribly broken since
quite some time and doesn't even compile. This patch just fixes the
bare minimum (it actually removes more lines than it adds), so that
the function tracer works again on 32- and 64bit kernels.
I've queued up additional patches on top of this patch which e.g. add
the syscall tracer, but those have to wait for the merge window for
v4.7."
* 'parisc-4.6-4' of git://git.kernel.org/pub/scm/linux/kernel/git/deller/parisc-linux:
parisc: Fix ftrace function tracer
The ACPI specification does not specify the state of data after a clear
poison operation. Potential future libnvdimm bus implementations for
other architectures also might not specify or disagree on the state of
data after clear poison. Clarify why we write twice.
Reported-by: Jeff Moyer <jmoyer@redhat.com>
Reported-by: Vishal Verma <vishal.l.verma@intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
Reviewed-by: Jeff Moyer <jmoyer@redhat.com>
Reviewed-by: Vishal Verma <vishal.l.verma@intel.com>
