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Filename Latest commit message Latest commit date
Paul Burton 7ed0402445 MIPS: BPF: Restore MIPS32 cBPF JIT 
commit 36366e367ee93ced84fddb8fae6675e12985f5a4 upstream.

Commit 716850ab10 ("MIPS: eBPF: Initial eBPF support for MIPS32
architecture.") enabled our eBPF JIT for MIPS32 kernels, whereas it has
previously only been availailable for MIPS64. It was my understanding at
the time that the BPF test suite was passing & JITing a comparable
number of tests to our cBPF JIT [1], but it turns out that was not the
case.

The eBPF JIT has a number of problems on MIPS32:

- Most notably various code paths still result in emission of MIPS64
  instructions which will cause reserved instruction exceptions & kernel
  panics when run on MIPS32 CPUs.

- The eBPF JIT doesn't account for differences between the O32 ABI used
  by MIPS32 kernels versus the N64 ABI used by MIPS64 kernels. Notably
  arguments beyond the first 4 are passed on the stack in O32, and this
  is entirely unhandled when JITing a BPF_CALL instruction. Stack space
  must be reserved for arguments even if they all fit in registers, and
  the callee is free to assume that stack space has been reserved for
  its use - with the eBPF JIT this is not the case, so calling any
  function can result in clobbering values on the stack & unpredictable
  behaviour. Function arguments in eBPF are always 64-bit values which
  is also entirely unhandled - the JIT still uses a single (32-bit)
  register per argument. As a result all function arguments are always
  passed incorrectly when JITing a BPF_CALL instruction, leading to
  kernel crashes or strange behavior.

- The JIT attempts to bail our on use of ALU64 instructions or 64-bit
  memory access instructions. The code doing this at the start of
  build_one_insn() incorrectly checks whether BPF_OP() equals BPF_DW,
  when it should really be checking BPF_SIZE() & only doing so when
  BPF_CLASS() is one of BPF_{LD,LDX,ST,STX}. This results in false
  positives that cause more bailouts than intended, and that in turns
  hides some of the problems described above.

- The kernel's cBPF->eBPF translation makes heavy use of 64-bit eBPF
  instructions that the MIPS32 eBPF JIT bails out on, leading to most
  cBPF programs not being JITed at all.

Until these problems are resolved, revert the removal of the cBPF JIT
performed by commit 716850ab10 ("MIPS: eBPF: Initial eBPF support for
MIPS32 architecture."). Together with commit f8fffebdea75 ("MIPS: BPF:
Disable MIPS32 eBPF JIT") this restores MIPS32 BPF JIT behavior back to
the same state it was prior to the introduction of the broken eBPF JIT
support.

[1] https://lore.kernel.org/linux-mips/MWHPR2201MB13583388481F01A422CE7D66D4410@MWHPR2201MB1358.namprd22.prod.outlook.com/

Signed-off-by: Paul Burton <paulburton@kernel.org>
Fixes: 716850ab10 ("MIPS: eBPF: Initial eBPF support for MIPS32 architecture.")
Cc: Daniel Borkmann <daniel@iogearbox.net>
Cc: Hassan Naveed <hnaveed@wavecomp.com>
Cc: Tony Ambardar <itugrok@yahoo.com>
Cc: bpf@vger.kernel.org
Cc: netdev@vger.kernel.org
Cc: linux-mips@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ovidiu Panait <ovidiu.panait@windriver.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2021-10-13 10:08:17 +02:00
arch MIPS: BPF: Restore MIPS32 cBPF JIT 2021-10-13 10:08:17 +02:00
block Revert "block, bfq: honor already-setup queue merges" 2021-10-06 15:42:34 +02:00
certs certs: Trigger creation of RSA module signing key if it's not an RSA key 2021-09-15 09:47:29 +02:00
crypto crypto: shash - avoid comparing pointers to exported functions under CFI 2021-07-14 16:53:13 +02:00
Documentation dt-bindings: mtd: gpmc: Fix the ECC bytes vs. OOB bytes equation 2021-09-22 12:26:43 +02:00
drivers xen/balloon: fix cancelled balloon action 2021-10-13 10:08:17 +02:00
fs nfsd4: Handle the NFSv4 READDIR 'dircount' hint being zero 2021-10-13 10:08:17 +02:00
include libata: Add ATA_HORKAGE_NO_NCQ_ON_ATI for Samsung 860 and 870 SSD. 2021-10-09 14:39:50 +02:00
init kbuild: add CONFIG_LD_IS_LLD 2021-06-30 08:47:44 -04:00
ipc
kernel cpufreq: schedutil: Use kobject release() method to free sugov_tunables 2021-10-06 15:42:29 +02:00
lib Kconfig.debug: drop selecting non-existing HARDLOCKUP_DETECTOR_ARCH 2021-09-26 14:07:10 +02:00
LICENSES
mm mm/memory_hotplug: use "unsigned long" for PFN in zone_for_pfn_range() 2021-09-22 12:26:43 +02:00
net netfilter: ipset: Fix oversized kvmalloc() calls 2021-10-06 15:42:39 +02:00
samples samples: bpf: Fix tracex7 error raised on the missing argument 2021-09-22 12:26:30 +02:00
scripts kbuild: Fix 'no symbols' warning when CONFIG_TRIM_UNUSD_KSYMS=y 2021-09-22 12:26:26 +02:00
security apparmor: remove duplicate macro list_entry_is_head() 2021-09-26 14:07:06 +02:00
sound ASoC: rockchip: i2s: Fixup config for DAIFMT_DSP_A/B 2021-09-22 12:26:35 +02:00
tools tools/vm/page-types: remove dependency on opt_file for idle page tracking 2021-10-09 14:39:50 +02:00
usr
virt KVM: do not shrink halt_poll_ns below grow_start 2021-10-09 14:39:50 +02:00
.clang-format
.cocciconfig
.get_maintainer.ignore
.gitattributes
.gitignore
.mailmap
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Makefile Linux 5.4.152 2021-10-09 14:39:50 +02:00
README

README 

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.