unimore/kernel-hacking-2024-linux-steffo
unimore/kernel-hacking-2024-linux-steffo
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Linux kernel modifications for the Kernel Hacking exam
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Linus Torvalds 8b11ec1b5f mm: do not initialize TLB stack vma's with vma_init() 
Commit 2c4541e24c ("mm: use vma_init() to initialize VMAs on stack and
data segments") tried to initialize various left-over ad-hoc vma's
"properly", but actually made things worse for the temporary vma's used
for TLB flushing.

vma_init() doesn't actually initialize all of the vma, just a few
fields, so doing something like

   -       struct vm_area_struct vma = { .vm_mm = tlb->mm, };
   +       struct vm_area_struct vma;
   +
   +       vma_init(&vma, tlb->mm);

was actually very bad: instead of having a nicely initialized vma with
every field but "vm_mm" zeroed, you'd have an entirely uninitialized vma
with only a couple of fields initialized.  And they weren't even fields
that the code in question mostly cared about.

The flush_tlb_range() function takes a "struct vma" rather than a
"struct mm_struct", because a few architectures actually care about what
kind of range it is - being able to only do an ITLB flush if it's a
range that doesn't have data accesses enabled, for example.  And all the
normal users already have the vma for doing the range invalidation.

But a few people want to call flush_tlb_range() with a range they just
made up, so they also end up using a made-up vma.  x86 just has a
special "flush_tlb_mm_range()" function for this, but other
architectures (arm and ia64) do the "use fake vma" thing instead, and
thus got caught up in the vma_init() changes.

At the same time, the TLB flushing code really doesn't care about most
other fields in the vma, so vma_init() is just unnecessary and
pointless.

This fixes things by having an explicit "this is just an initializer for
the TLB flush" initializer macro, which is used by the arm/arm64/ia64
people who mis-use this interface with just a dummy vma.

Fixes: 2c4541e24c ("mm: use vma_init() to initialize VMAs on stack and data segments")
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Kirill Shutemov <kirill.shutemov@linux.intel.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: John Stultz <john.stultz@linaro.org>
Cc: Hugh Dickins <hughd@google.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2018-08-01 13:43:38 -07:00
arch mm: do not initialize TLB stack vma's with vma_init() 2018-08-01 13:43:38 -07:00
block for-linus-20180727 2018-07-27 12:51:00 -07:00
certs certs/blacklist: fix const confusion 2018-06-26 09:43:03 -07:00
crypto Merge branch 'linus' of git://git.kernel.org/pub/scm/linux/kernel/git/herbert/crypto-2.6 2018-07-19 07:32:44 -07:00
Documentation USB fixes for 4.18-rc7 2018-07-26 09:29:29 -07:00
drivers MMC host: 2018-08-01 11:43:13 -07:00
firmware
fs squashfs metadata 2: electric boogaloo 2018-08-01 10:38:43 -07:00
include mm: do not initialize TLB stack vma's with vma_init() 2018-08-01 13:43:38 -07:00
init Kbuild fixes for v4.18 2018-06-30 13:05:30 -07:00
ipc ipc/sem.c: prevent queue.status tearing in semop 2018-07-26 19:38:03 -07:00
kernel audit/stable-4.18 PR 20180731 2018-07-31 13:17:46 -07:00
lib kasan: only select SLUB_DEBUG with SYSFS=y 2018-07-26 19:38:03 -07:00
LICENSES LICENSES: Add Linux-OpenIB license text 2018-04-27 16:41:53 -06:00
mm mm: delete historical BUG from zap_pmd_range() 2018-08-01 12:23:45 -07:00
net netlink: Don't shift with UB on nlk->ngroups 2018-07-30 12:42:22 -07:00
samples Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2018-07-18 19:32:54 -07:00
scripts Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2018-07-18 19:32:54 -07:00
security selinux/stable-4.18 PR 20180629 2018-06-30 11:15:12 -07:00
sound ALSA: hda/realtek - Yet another Clevo P950 quirk entry 2018-07-18 12:17:46 +02:00
tools Urgent power management fixes for 4.18 2018-08-01 11:35:12 -07:00
usr kbuild: rename built-in.o to built-in.a 2018-03-26 02:01:19 +09:00
virt Miscellaneous bugfixes, plus a small patchlet related to Spectre v2. 2018-07-18 11:08:44 -07:00
.clang-format clang-format: add configuration file 2018-04-11 10:28:35 -07:00
.cocciconfig
.get_maintainer.ignore
.gitattributes
.gitignore Kbuild updates for v4.17 (2nd) 2018-04-15 17:21:30 -07:00
.mailmap Merge branch 'asoc-4.17' into asoc-4.18 for compress dependencies 2018-04-26 12:24:28 +01:00
COPYING COPYING: use the new text with points to the license files 2018-03-23 12:41:45 -06:00
CREDITS
Kbuild
Kconfig kconfig: add basic helper macros to scripts/Kconfig.include 2018-05-29 03:31:19 +09:00
MAINTAINERS Merge branch 'perf-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2018-07-30 11:45:30 -07:00
Makefile Linux 4.18-rc7 2018-07-29 14:44:52 -07:00
README Docs: Added a pointer to the formatted docs to README 2018-03-21 09:02:53 -06:00

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.
See Documentation/00-INDEX for a list of what is contained in each file.

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.