[v3,0/6] Allocate module text and data separately

Message

Christophe Leroy Jan. 29, 2022, 5:02 p.m. UTC

This series allow architectures to request having modules data in
vmalloc area instead of module area.

This is required on powerpc book3s/32 in order to set data non
executable, because it is not possible to set executability on page
basis, this is done per 256 Mbytes segments. The module area has exec
right, vmalloc area has noexec. Without this change module data
remains executable regardless of CONFIG_STRICT_MODULES_RWX.

This can also be useful on other powerpc/32 in order to maximize the
chance of code being close enough to kernel core to avoid branch
trampolines.

Changes in v3:
- Fixed the tree for data_layout at one place (Thanks Miroslav)
- Moved removal of module_addr_min/module_addr_max macro out of patch 1 in a new patch at the end of the series to reduce churn.

Changes in v2:
- Dropped first two patches which are not necessary. They may be added back later as a follow-up series.
- Fixed the printks in GDB

Christophe Leroy (6):
  modules: Always have struct mod_tree_root
  modules: Prepare for handling several RB trees
  modules: Introduce data_layout
  modules: Add CONFIG_ARCH_WANTS_MODULES_DATA_IN_VMALLOC
  modules: Remove module_addr_min and module_addr_max
  powerpc: Select ARCH_WANTS_MODULES_DATA_IN_VMALLOC on book3s/32 and
    8xx

 arch/Kconfig                |   6 ++
 arch/powerpc/Kconfig        |   1 +
 include/linux/module.h      |   8 ++
 kernel/debug/kdb/kdb_main.c |  10 +-
 kernel/module.c             | 193 +++++++++++++++++++++++++-----------
 5 files changed, 156 insertions(+), 62 deletions(-)

Comments

Luis Chamberlain Feb. 3, 2022, 12:05 a.m. UTC | #1

On Sat, Jan 29, 2022 at 05:02:03PM +0000, Christophe Leroy wrote:
> This series allow architectures to request having modules data in
> vmalloc area instead of module area.
> 
> This is required on powerpc book3s/32 in order to set data non
> executable, because it is not possible to set executability on page
> basis, this is done per 256 Mbytes segments. The module area has exec
> right, vmalloc area has noexec. Without this change module data
> remains executable regardless of CONFIG_STRICT_MODULES_RWX.
> 
> This can also be useful on other powerpc/32 in order to maximize the
> chance of code being close enough to kernel core to avoid branch
> trampolines.
> 

This looks good, however I'd like to see Aaron's changes go in first,
and then yours. Aaron's changes still need to be tested by 0-day and I
need to finish review, but that's the order of how I'd prefer to see
changes merged / tested. I'll try to review his changes, dump them to
modules-next and then I'd like to trouble you to rebase ontop of that.

We should get all this tested early for the next release.

  Luis