Linux 4.14 Release – Main Changes, ARM & MIPS Architecture

Linus Torvalds has announced the release of Linux 4.14:

No surprises this week, although it is probably worth pointing out how the 0day robot has been getting even better (it was very useful before, but Fengguang has been working on making it even better, and reporting the problems it has found).

Sure, some of the new reports turned out to be just 0day doing things that just don’t work (ie KASAN with old gcc versions, but also doing things like loading old ISA drivers in situations that just don’t make sense – remember when you couldn’t even ask if the hardware existed or not, and just had to know), but even then it’s been all good.

The appended shortlog is obviously only for the (small) haul since rc8, and it really is tiny. Not very many commits, and they are small. The biggest thing that stands out in the diffstat is the “leaking_addresses” perl script, which is actually under active development, but I put the first version in for 4.14 just so that people could see that initial state and start looking at the end result and perhaps ask themselves “should my code make these kernel addresses visible to user space”.

The actual changes will hopefully start percolating into 4.15, with one notable likely early change (which has been discussed extensively on the list) being to just hash any “%p” addresses by default. We used to have strict modes that just zeroed the address out, but that was actually counter-productive, in that often people use the address as a “kernel object identity” for debugging (or for cross-correlation -think network sockets), and so just clearing the pointer value makes those kinds of uses pointless. But using a secure hash allows for those kinds of identity uses, while not actually leaking the address itself.

(Other situations where the actual address is relevant then need other approaches – we’ll be restricting /proc/kallsyms only to entities that actually need them etc etc).

Anyway, apart from that one script, the rest of it really is one-liners or “few-liners”.

The most noticeable last-minute change is probably that we had to revert the code that showed a good MHz value in /proc/cpuinfo even for the modern “CPU picks frequency dynamically” case. It worked fine, but it was much too expensive on machines with tens or hundreds of CPU cores. There’s a cunning plan, but it didn’t make 4.14, so we’ll get it working and then back-port.

Anything else is pretty esoteric, you can just read the changelog..

And with this, the merge window for 4.15 is obviously open. As mentioned in the late rc announcements, the extra week for rc8 means that now Thanksgiving week ends up happening during the second half of the merge window, and I’ll be off on a family vacation.

We’ll see how that goes.

I might decide that I’ll extend the merge window if I feel that I can’t be responsive enough.

Or maybe you guys won’t even notice, because I _will_ have my laptop and Internet access.

Or maybe I will just decide that 4.14 was a painful release, and any late stragglers for 4.15 are not worth _another_ painful release, and I’ll just say “tough luck, you were late to the merge window, and I felt more like being out in the sun than taking your second-week pull request”.

Because it really would be lovely to have a smaller and calmer release for 4.15.

Anyway, go out and test the new 4.14 release, that is slated to be the next LTS kernel – and start sending me pull request for the 4.15 merge window.

Linux 4.13 brought us new features such as support for non-blocking buffered I/O operations at the block level, AppArmor security module’s “domain labeling” code, kernel-based TLS implementation for better performance, and CIFS/SAMBA default change to v3.0 for better security, among many other changes.

Some newsworthy changes in Linux 4.14 include:

• Bigger memory limits – x86-64 used to be limited by 4-level paging to 256 TiB of virtual address space and 64 TiB of physical address space. Some vendors already reached the limit with servers equipped with 64 TiB of memory, so support for 5-level paging has been introduced, increasing the limits to 128 PiB of virtual address space and 4 PiB of physical address space.
• Added AMD Secure Memory Encryption – Secure Memory Encryption can be used to protect the contents of DRAM from physical attacks on the system. Read LWN article or AMD whitepaper for details.
• Better kernel traces with the ORC unwinder – An “unwinder” is what prints the list of functions (aka. stack trace, callgraph, call stack…) that have been executed before reaching a determinate point of the code. The new unwinder is called ORC (Oops Rewind Capability), works more reliably than the current unwinder, and does not require adding code anywhere, hence having not effect on text size or runtime performance
• Compression in Btrfs and Squashfs – zstd compresses at speeds close to lz4 at compression ratio comparable to lzma. Support for zstd compression had been added to both Btrfs and Squash. See benchmarks in commit messages for Btrsfs and Squashfs.
• Zero-copy from user memory to sockets – The MSG_ZEROCOPY socket flag enables zero copy mechanism to common socket send calls. It is generally only effective at writes over around 10 KB. Checkout the documentation for more details.

Linux 4.14 will be a long term support kernel with 6-years of support, so it will be found in devices for the years to come. [Update: While Linux 4.4 will be supported for 6 years until February 2022, the plan is to support Linux 4.14 until January 2020, right from the horse’s mouth]

The ARM architecture has gone through many changes as per usual. Here’s a non-exhaustive list of changes:

• Allwinner:
  • Allwinner A10s – HDMI DDC I2C Adapter,HDMI CEC support
  • Allwinner A10/A20 – CCU Clock-ng support
  • Allwinner A64 – SRAM controller driver
  • Allwinner A83T –  SD/MMC support, AXP813 PMIC,USB support
  • Allwinner H3 – I2S support
  • Allwinner R40 –  CCU sunxi-ng style clock driver support,pinctrl support
  • AXP PMICs – PEK time fix for AXP22x
  • sun4i-ss SecuritySystem PRNG driver added to most SoCs
  • MUSB fixes for A10/A20/A31/A33/H3
  • New boards – Banana Pi M2 Magic,  Olimex A64-OLinuXino, NanoPi A64, Banana Pi M3

• Rockchip
  • Clock driver – Fixes for RK3128, added RK3126 support within RK3128 driver
  • Pinctrl – Rockchip RK3128 subdriver
  • Power domains for Rockchip RK3366
  • New power key driver for Rockchip RK805 PMIC
  • PCI driver – Added Rockchip per-lane PHY support for better power management
  • SPI driver – Explicit support for Rockchip RV1108
  • DRM driver – Added dw_hdmi support for RK3399
  • Added ROCK64 board, RK3399 Sapphire module on Excavator carrier-board, and Theobroma Systems RK3399-Q7 SoM
  • Device tree changes:
    • pinctrl typos
    • keep-power-in-suspend in non-sdio nodes
    • removal of the deprecated num-slots property from dwmmc nodes.
    • RK3328 – support for spdif, io-domains and usb (including enablement of usb on the evaluation board)
    • RK3368 – support for spdif.
    • RK3399 – pcie changes, support for the mali gpu, a new power-domain, sdmmc support on the firefly board and dynamic-power-coefficients.
    • Removal of the deprectated num-slots property from all Rockchip dw-mmc nodes
    • RV1108 – support for sd-cards on the evaluation board
    • RK3288 – EVB gains support saradc and the adc-key, mali gpu enabled in some boards (fennec, evb, tinker).
    • RK3228/RK3229 – Support for efuse, sdmmc, sdio, io-domans and spdif; separate rk3229.dtsi;  The evaluation board also gets regulators, io-domains, emmc, tsadc keys

• Amlogic
  • Clock driver – Added gxbb CEC32 and sd_emmc clocks, meson8b reset controller
  • SoC info driver – “Amlogic SoCs have a SoC information register for SoC type, package type and revision information. This patchs adds support for this register decoding and exposing with the SoC bus infrastructure”
  • Added Amlogic Meson AO CEC Controller driver
  • Device tree changes:
    • Updates for new MMC driver features/fixes, support for high-speed modes
    • Clock updates
    • Add GPIO line names to a few boards
    • Update clock controler for use as reset controller
• Samsung
  • Clock driver – suspend fix for Samsung Exynos SoCs where we need to keep clks on across suspend
  • Samsung Exynos5420/5422/5800 audio fixes
  • S3C24xx platform – Cleanup from non-existent CONFIG entries, fix unmet NET dependency when H1940 bluetooth chip is selected
  • Pinctrl driver – Fix NULL pointer dereference on S3C24XX, fix invalid register offset used for external interrupts on Exynos5433, consolidate between drivers and bindings the defines for pin mux functions, minor code improvements
  • Samsung DTS ARM64 changes
    • Remove deprecated and unneeded properties from Exynos boards.
    • Implement proper (working) support for USB On-The-Go on Exynos5433 TM2/TM2E boards.
  • Samsung defconfig changes
    • Enable some drivers useful on our boards (communication: Bluetooth, WiFi, NFC, USB; codepages and crypto algorithms).
    • Enable debugging and lock testing options.
• Qualcomm
  • IPQ8074 – Added SoC & HK01 board support, PCI driver
  • APQ8016 – Force USB host mode; jack detection support in ASoC
  • MSM8916 – Updated coresight nodes, added GPU, IOMMU, Venus video codec, and CEC clock nodes
  • MSM8996 – Add  support for USB, PCIE phy, RPM/GLink, and modem SMP2P; SMMU clks
  • Pinctrl driver – Qualcomm APQ8064 can handle general purpose clock muxing
  • NAND driver – Various fixes
  • Qualcomm GLINK SMEM driver – Fix memory leak, and unlock  on error
  • V4l – Update the Qualcomm Camera Subsystem driver document with a media controller pipeline graph diagram, VFE scale and crop modules support, and PIX interface and format conversion support.
  • Added DB820c PM8994 regulator node
  • Add PMI8994 gpios
  • Device tree changes:
    • Fixup XO, timer nodes, and pinctrl on IPQ4019
    • Add IPQ4019 RNG and wifi blocks
    • Update MSM8974 coresight node
    • Add IPQ8074 bindings
• Mediatek
  • Pinctrl driver – Mediatek MT7623 PCIe mux data fixed up.
  • PCI Driver – Added MediaTek MT2712 and MT7622 support
  • Thermal driver – Added Mediatek thermal driver for mt2712
  • Added support for MediaTek MT2712 SoC and avaluation board
  • New board – Mediatek mt7623-based Banana Pi R2
• Other new ARM hardware platforms and SoCs:
  • Broadcom – Stingray communication processor, Raspberry Pi Zero W
  • Marvell – ARMADA 8080 SoC
  • Microchip/Atmel – SAMA5D28 SoM1 EK
  • NXP – Toradex Apalis module + Apalis and Ixora carrier boards, Engicam GEAM6UL Starter Kit, Beckhoff CX9020 Embedded PC (i.MX53)
  • Renesas – R-Car D3 board (R8A77995)
  • Storlink/Cortina –
  • Texas Instruments – TI DT76x, TI AM335x Moxa UC-8100-ME-T open platform, TI AM57xx Beaglebone X15 Rev C
  • Uniphier – PXs3 STB SoC and development board
  • ZTE – ZX296718 PCBOX Board

MIPS had a huge changelog this time, summarized below:

• CM – Rename mips_cm_base to mips_gcr_base; Specify register size when generating accessors; Use BIT/GENMASK for register fields, order & drop shifts; Add cluster & block args to mips_cm_lock_other()
• CPC – Use common CPS accessor generation macros; Use BIT/GENMASK for register fields, order & drop shifts; Introduce register modify (set/clear/change) ; Use change_*, set_* & clear_* where appropriate, etc…
• CPS – Read GIC_VL_IDENT directly, not via irqchip driver
• DMA – Consolidate coherent and non-coherent dma_alloc code, Don’t use dma_cache_sync to implement fd_cacheflush
• FPU emulation / FP assist code – Corner cases fixes such as NaN propagation and other special input values; Zero bits 32-63 of the result for a CLASS.D instruction; enhanced statics via debugfs; do not use bools for arithmetic. GCC 7.1 moans about this; correct user fault_addr type
• Generic MIPS
  • Enhancement of stack backtraces
  • Cleanup from non-existing options
  • Handle non word sized instructions when examining frame
  • Fix detection and decoding of ADDIUSP instruction
  • Fix decoding of SWSP16 instruction
  • Refactor handling of stack pointer in get_frame_info
  • Remove unreachable code from force_fcr31_sig()
  • Many more fixes and cleanups
• GIC – Introduce asm/mips-gic.h with accessor functions; Use new GIC accessor functions in mips-gic-timer; Remove counter access functions from irq-mips-gic.c; Remove gic_read_local_vp_id() from irq-mips-gic.c, etc…
• microMIPS – Fix microMIPS stack unwinding on big endian systems
• MIPS-GIC – SYNC after enabling GIC region
• NUMA – Remove the unused parent_node() macro
• R6 – Constify r2_decoder_tables; add accessor & bit definitions for GlobalNumber
• SMP – Constify smp ops, allow boot_secondary SMP op to return errors
• VDSO – Drop gic_get_usm_range() usage, avoid use of linux/irqchip/mips-gic.h
• Platform changes
  • Alchemy – Add devboard machine type to cpuinfo, update cpu feature overrides,threaded carddetect irqs for devboards
  • AR7 – allow NULL clock for clk_get_rate
  • BCM63xx – Fix ENETDMA_6345_MAXBURST_REG offset, allow NULL clock for clk_get_rate
  • CI20 – Enable GPIO and RTC drivers in defconfig; add ethernet and fixed-regulator nodes to DTS
  • Generic platform
    • Move Boston and NI 169445 FIT image source to their own files
    • Include asm/bootinfo.h for plat_fdt_relocated()
    • Include asm/time.h for get_c0_*_int()
    • Include asm/bootinfo.h for plat_fdt_relocated()
    • Include asm/time.h for get_c0_*_int()
    • Allow filtering enabled boards by requirements
    • Don’t explicitly disable CONFIG_USB_SUPPORT
    • Bump default NR_CPUS to 16
  • JZ4700 – Probe the jz4740-rtc driver from devicetree
  • Lantiq – Drop check of boot select from the spi-falcon and lantiq-flash MTD drivers, access boot cause register in the watchdog driver through regmap, add device tree binding documentation for the watchdog driver, add docs for the RCU DT bindings, etc…
  • Loongson 2F – Allow NULL clock for clk_get_rate
  • Malta – Use new GIC accessor functions
  • NI 169445 – Add support for NI 169445 board; only include in 32r2el kernels
  • Octeon – Add support for watchdog of 78XX SOCs, add support for watchdog of CN68XX SOCs, expose support for mips32r1, mips32r2 and mips64r1, enable more drivers in config file, etc…
  • Omega2+ – New board, add support and defconfig
  • Pistachio – Enable Root FS on NFS in defconfig
  • Mediatek/Ralink – Add Mediatek MT7628A SoC, allow NULL clock for clk_get_rate, explicitly request exclusive reset control in the pci-mt7620 PCI driver.
  • SEAD3 – Only include in 32 bit kernels by default
  • VoCore board – Add VoCore as a vendor t0 dt-bindings, add defconfig file

For the complete details, you could check out the full Linux 4.14 changelog – with comments only – generated using git log v4.13..v4.14 --stat, or – kinder to your eyes – read kernelnewsbies’s Linux 4.14 changelog.

Jean-Luc Aufranc (CNXSoft)

Jean-Luc started CNX Software in 2010 as a part-time endeavor, before quitting his job as a software engineering manager, and starting to write daily news, and reviews full time later in 2011.

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