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The underlying operating system for DifuseHQ's embedded routing devices
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Michał Kępień 626c84340d kernel: mtk_bmt: refactor to avoid deep recursion 
A Linksys E8450 (mt7622) device running current master has recently
started crashing:

    [    0.562900] mtk-ecc 1100e000.ecc: probed
    [    0.570254] spi-nand spi2.0: Fidelix SPI NAND was found.
    [    0.575576] spi-nand spi2.0: 128 MiB, block size: 128 KiB, page size: 2048, OOB size: 64
    [    0.583780] mtk-snand 1100d000.spi: ECC strength: 4 bits per 512 bytes
    [    0.682930] Insufficient stack space to handle exception!
    [    0.682939] ESR: 0x0000000096000047 -- DABT (current EL)
    [    0.682946] FAR: 0xffffffc008c47fe0
    [    0.682948] Task stack:     [0xffffffc008c48000..0xffffffc008c4c000]
    [    0.682951] IRQ stack:      [0xffffffc008008000..0xffffffc00800c000]
    [    0.682954] Overflow stack: [0xffffff801feb00a0..0xffffff801feb10a0]
    [    0.682959] CPU: 1 PID: 1 Comm: swapper/0 Tainted: G S                5.15.107 #0
    [    0.682966] Hardware name: Linksys E8450 (DT)
    [    0.682969] pstate: 800000c5 (Nzcv daIF -PAN -UAO -TCO -DIT -SSBS BTYPE=--)
    [    0.682975] pc : dequeue_entity+0x0/0x250
    [    0.682988] lr : dequeue_task_fair+0x98/0x290
    [    0.682992] sp : ffffffc008c48030
    [    0.682994] x29: ffffffc008c48030 x28: 0000000000000001 x27: ffffff801feb6380
    [    0.683004] x26: 0000000000000001 x25: ffffff801feb6300 x24: ffffff8000068000
    [    0.683011] x23: 0000000000000001 x22: 0000000000000009 x21: 0000000000000000
    [    0.683017] x20: ffffff801feb6380 x19: ffffff8000068080 x18: 0000000017a740a6
    [    0.683024] x17: ffffffc008bae748 x16: ffffffc008bae6d8 x15: ffffffffffffffff
    [    0.683031] x14: ffffffffffffffff x13: 0000000000000000 x12: 0000000f00000101
    [    0.683038] x11: 0000000000000449 x10: 0000000000000127 x9 : 0000000000000000
    [    0.683044] x8 : 0000000000000125 x7 : 0000000000116da1 x6 : 0000000000116da1
    [    0.683051] x5 : 00000000001165a1 x4 : ffffff801feb6e00 x3 : 0000000000000000
    [    0.683058] x2 : 0000000000000009 x1 : ffffff8000068080 x0 : ffffff801feb6380
    [    0.683066] Kernel panic - not syncing: kernel stack overflow
    [    0.683069] SMP: stopping secondary CPUs
    [    1.648361] SMP: failed to stop secondary CPUs 0-1
    [    1.648366] Kernel Offset: disabled
    [    1.648368] CPU features: 0x00003000,00000802
    [    1.648372] Memory Limit: none

Several factors contributed to this issue:

 1. The mtk_bmt driver recursively calls its scan_bmt() helper function
    during device initialization, while looking for a valid block
    mapping table (BMT).

 2. Commit fa4dc86e98 ("kernel: backport MEMREAD ioctl"):

      - increased the size of some stack-allocated structures (like
	struct mtd_oob_ops, used in bbt_nand_read(), which is indirectly
	called from scan_bmt()),

      - increased the stack size for some functions (for example,
	spinand_mtd_read(), which is indirectly called from scan_bmt(),
	now uses an extra stack-allocated struct mtd_ecc_stats).

 3. OpenWrt currently compiles the kernel with the
    -fno-optimize-sibling-calls flag, which prevents tail-call
    optimization.

Collectively, all of these factors caused stack usage in the mtk_bmt
driver to grow excessively large, triggering stack overflows.

Recursion is not really necessary in scan_bmt() as it simply iterates
over flash memory blocks in reverse order, looking for a valid BMT.
Refactor the logic contained in the scan_bmt() and read_bmt() functions
in target/linux/generic/files/drivers/mtd/nand/mtk_bmt_v2.c so that deep
recursion is prevented (and therefore also any potential stack overflows
it may cause).

Link: https://lists.openwrt.org/pipermail/openwrt-devel/2023-April/040872.html
Signed-off-by: Michał Kępień <openwrt@kempniu.pl>
2023-04-29 12:58:48 +02:00
.github ci: add Coverity Scan scheduled workflow 2023-04-26 17:24:50 +02:00
config build: add a config knob to enable LTO for all packages 2023-03-21 18:28:24 +01:00
include kernel: bump 5.10 to 5.10.178 2023-04-22 01:15:03 +02:00
LICENSES LICENSES: include all used licenses in LICENSES directory 2021-02-14 19:21:38 +01:00
package openssl: fix low-severity CVE-2023-1255 2023-04-29 12:33:44 +02:00
scripts scripts: sercomm-pid: add bmips support 2023-04-09 10:01:03 +02:00
target kernel: mtk_bmt: refactor to avoid deep recursion 2023-04-29 12:58:48 +02:00
toolchain toolchain/gcc: enable zstd support 2023-03-17 02:08:25 +01:00
tools tools/isl: update to 0.26 2023-04-22 01:33:16 +02:00
.gitattributes add .gitattributes to prevent the git autocrlf option from messing with CRLF/LF in files 2012-05-08 13:30:49 +00:00
.gitignore .gitgnore: add llvm-bpf 2021-11-21 18:18:01 +01:00
BSDmakefile build: use SPDX license tags 2021-02-05 14:54:47 +01:00
Config.in build: scripts/config - update to kconfig-v5.14 2022-02-19 13:10:01 +01:00
COPYING COPYING: add COPYING file to specify project licenses 2021-02-14 19:21:38 +01:00
feeds.conf.default feeds: use git-src-full to allow Git versioning 2022-02-15 00:24:24 +01:00
Makefile treewide: derive host and hostpkg path from STAGING_DIR 2023-01-09 21:33:20 +01:00
README.md README: add download section 2022-10-06 16:08:24 +02:00
rules.mk rules.mk: add FILECMD variable 2023-03-27 00:41:50 +02:00

README.md

OpenWrt logo

OpenWrt Project is a Linux operating system targeting embedded devices. Instead of trying to create a single, static firmware, OpenWrt provides a fully writable filesystem with package management. This frees you from the application selection and configuration provided by the vendor and allows you to customize the device through the use of packages to suit any application. For developers, OpenWrt is the framework to build an application without having to build a complete firmware around it; for users this means the ability for full customization, to use the device in ways never envisioned.

Sunshine!

Download

Built firmware images are available for many architectures and come with a package selection to be used as WiFi home router. To quickly find a factory image usable to migrate from a vendor stock firmware to OpenWrt, try the Firmware Selector.

If your device is supported, please follow the Info link to see install instructions or consult the support resources listed below.

An advanced user may require additional or specific package. (Toolchain, SDK, ...) For everything else than simple firmware download, try the wiki download page:

Development

To build your own firmware you need a GNU/Linux, BSD or MacOSX system (case sensitive filesystem required). Cygwin is unsupported because of the lack of a case sensitive file system.

Requirements

You need the following tools to compile OpenWrt, the package names vary between distributions. A complete list with distribution specific packages is found in the Build System Setup documentation.

binutils bzip2 diff find flex gawk gcc-6+ getopt grep install libc-dev libz-dev
make4.1+ perl python3.6+ rsync subversion unzip which

Quickstart

  1. Run ./scripts/feeds update -a to obtain all the latest package definitions defined in feeds.conf / feeds.conf.default

  2. Run ./scripts/feeds install -a to install symlinks for all obtained packages into package/feeds/

  3. Run make menuconfig to select your preferred configuration for the toolchain, target system & firmware packages.

  4. Run make to build your firmware. This will download all sources, build the cross-compile toolchain and then cross-compile the GNU/Linux kernel & all chosen applications for your target system.

Related Repositories

The main repository uses multiple sub-repositories to manage packages of different categories. All packages are installed via the OpenWrt package manager called opkg. If you're looking to develop the web interface or port packages to OpenWrt, please find the fitting repository below.

  • LuCI Web Interface: Modern and modular interface to control the device via a web browser.

  • OpenWrt Packages: Community repository of ported packages.

  • OpenWrt Routing: Packages specifically focused on (mesh) routing.

  • OpenWrt Video: Packages specifically focused on display servers and clients (Xorg and Wayland).

Support Information

For a list of supported devices see the OpenWrt Hardware Database

Documentation

Support Community

  • Forum: For usage, projects, discussions and hardware advise.
  • Support Chat: Channel #openwrt on oftc.net.

Developer Community

License

OpenWrt is licensed under GPL-2.0