linux.git/arch/arm64/kernel/module-plts.c, branch v6.0

arm64: fix typos in comments

2022-04-04T09:32:50+00:00

Various spelling mistakes in comments.
Detected with the help of Coccinelle.

Signed-off-by: Julia Lawall 
Link: https://lore.kernel.org/r/20220318103729.157574-10-Julia.Lawall@inria.fr
[will: Squashed in 20220318103729.157574-28-Julia.Lawall@inria.fr]
Signed-off-by: Will Deacon

arm64: improve whitespace

2021-02-04T13:59:49+00:00

In a few places we don't have whitespace between macro parameters,
which makes them hard to read. This patch adds whitespace to clearly
separate the parameters.

In a few places we have unnecessary whitespace around unary operators,
which is confusing, This patch removes the unnecessary whitespace.

Signed-off-by: Zhiyuan Dai 
Link: https://lore.kernel.org/r/1612403029-5011-1-git-send-email-daizhiyuan@phytium.com.cn
Signed-off-by: Will Deacon

arm64/module: set trampoline section flags regardless of CONFIG_DYNAMIC_FTRACE

2020-09-02T07:35:33+00:00

In the arm64 module linker script, the section .text.ftrace_trampoline
is specified unconditionally regardless of whether CONFIG_DYNAMIC_FTRACE
is enabled (this is simply due to the limitation that module linker
scripts are not preprocessed like the vmlinux one).

Normally, for .plt and .text.ftrace_trampoline, the section flags
present in the module binary wouldn't matter since module_frob_arch_sections()
would assign them manually anyway. However, the arm64 module loader only
sets the section flags for .text.ftrace_trampoline when CONFIG_DYNAMIC_FTRACE=y.
That's only become problematic recently due to a recent change in
binutils-2.35, where the .text.ftrace_trampoline section (along with the
.plt section) is now marked writable and executable (WAX).

We no longer allow writable and executable sections to be loaded due to
commit 5c3a7db0c7ec ("module: Harden STRICT_MODULE_RWX"), so this is
causing all modules linked with binutils-2.35 to be rejected under arm64.
Drop the IS_ENABLED(CONFIG_DYNAMIC_FTRACE) check in module_frob_arch_sections()
so that the section flags for .text.ftrace_trampoline get properly set to
SHF_EXECINSTR|SHF_ALLOC, without SHF_WRITE.

Signed-off-by: Jessica Yu 
Acked-by: Will Deacon 
Acked-by: Ard Biesheuvel 
Link: http://lore.kernel.org/r/20200831094651.GA16385@linux-8ccs
Link: https://lore.kernel.org/r/20200901160016.3646-1-jeyu@kernel.org
Signed-off-by: Catalin Marinas

arm64/module: Optimize module load time by optimizing PLT counting

2020-07-02T11:17:13+00:00

When loading a module, module_frob_arch_sections() tries to figure out
the number of PLTs that'll be needed to handle all the RELAs. While
doing this, it tries to dedupe PLT allocations for multiple
R_AARCH64_CALL26 relocations to the same symbol. It does the same for
R_AARCH64_JUMP26 relocations.

To make checks for duplicates easier/faster, it sorts the relocation
list by type, symbol and addend. That way, to check for a duplicate
relocation, it just needs to compare with the previous entry.

However, sorting the entire relocation array is unnecessary and
expensive (O(n log n)) because there are a lot of other relocation types
that don't need deduping or can't be deduped.

So this commit partitions the array into entries that need deduping and
those that don't. And then sorts just the part that needs deduping. And
when CONFIG_RANDOMIZE_BASE is disabled, the sorting is skipped entirely
because PLTs are not allocated for R_AARCH64_CALL26 and R_AARCH64_JUMP26
if it's disabled.

This gives significant reduction in module load time for modules with
large number of relocations with no measurable impact on modules with a
small number of relocations. In my test setup with CONFIG_RANDOMIZE_BASE
enabled, these were the results for a few downstream modules:

Module		Size (MB)
wlan		14
video codec	3.8
drm		1.8
IPA		2.5
audio		1.2
gpu		1.8

Without this patch:
Module		Number of entries sorted	Module load time (ms)
wlan		243739				283
video codec	74029				138
drm		53837				67
IPA		42800				90
audio		21326				27
gpu		20967				32

Total time to load all these module: 637 ms

With this patch:
Module		Number of entries sorted	Module load time (ms)
wlan		22454				61
video codec	10150				47
drm		13014				40
IPA		8097				63
audio		4606				16
gpu		6527				20

Total time to load all these modules: 247

Time saved during boot for just these 6 modules: 390 ms

Signed-off-by: Saravana Kannan 
Acked-by: Will Deacon 
Cc: Ard Biesheuvel 
Link: https://lore.kernel.org/r/20200623011803.91232-1-saravanak@google.com
Signed-off-by: Catalin Marinas

arm64: implement ftrace with regs

2019-11-06T14:17:35+00:00

This patch implements FTRACE_WITH_REGS for arm64, which allows a traced
function's arguments (and some other registers) to be captured into a
struct pt_regs, allowing these to be inspected and/or modified. This is
a building block for live-patching, where a function's arguments may be
forwarded to another function. This is also necessary to enable ftrace
and in-kernel pointer authentication at the same time, as it allows the
LR value to be captured and adjusted prior to signing.

Using GCC's -fpatchable-function-entry=N option, we can have the
compiler insert a configurable number of NOPs between the function entry
point and the usual prologue. This also ensures functions are AAPCS
compliant (e.g. disabling inter-procedural register allocation).

For example, with -fpatchable-function-entry=2, GCC 8.1.0 compiles the
following:

| unsigned long bar(void);
|
| unsigned long foo(void)
| {
|         return bar() + 1;
| }

... to:

| :
|         nop
|         nop
|         stp     x29, x30, [sp, #-16]!
|         mov     x29, sp
|         bl      0 
|         add     x0, x0, #0x1
|         ldp     x29, x30, [sp], #16
|         ret

This patch builds the kernel with -fpatchable-function-entry=2,
prefixing each function with two NOPs. To trace a function, we replace
these NOPs with a sequence that saves the LR into a GPR, then calls an
ftrace entry assembly function which saves this and other relevant
registers:

| mov	x9, x30
| bl	

Since patchable functions are AAPCS compliant (and the kernel does not
use x18 as a platform register), x9-x18 can be safely clobbered in the
patched sequence and the ftrace entry code.

There are now two ftrace entry functions, ftrace_regs_entry (which saves
all GPRs), and ftrace_entry (which saves the bare minimum). A PLT is
allocated for each within modules.

Signed-off-by: Torsten Duwe 
[Mark: rework asm, comments, PLTs, initialization, commit message]
Signed-off-by: Mark Rutland 
Reviewed-by: Amit Daniel Kachhap 
Reviewed-by: Ard Biesheuvel 
Reviewed-by: Torsten Duwe 
Tested-by: Amit Daniel Kachhap 
Tested-by: Torsten Duwe 
Cc: AKASHI Takahiro 
Cc: Catalin Marinas 
Cc: Josh Poimboeuf 
Cc: Julien Thierry 
Cc: Will Deacon

arm64: Replace strncmp with str_has_prefix

2019-08-05T10:06:34+00:00

In commit b6b2735514bc
("tracing: Use str_has_prefix() instead of using fixed sizes")
the newly introduced str_has_prefix() was used
to replace error-prone strncmp(str, const, len).
Here fix codes with the same pattern.

Signed-off-by: Chuhong Yuan 
Signed-off-by: Will Deacon

treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 500

2019-06-19T15:09:55+00:00

Based on 2 normalized pattern(s):

  this program is free software you can redistribute it and or modify
  it under the terms of the gnu general public license version 2 as
  published by the free software foundation

  this program is free software you can redistribute it and or modify
  it under the terms of the gnu general public license version 2 as
  published by the free software foundation #

extracted by the scancode license scanner the SPDX license identifier

  GPL-2.0-only

has been chosen to replace the boilerplate/reference in 4122 file(s).

Signed-off-by: Thomas Gleixner 
Reviewed-by: Enrico Weigelt 
Reviewed-by: Kate Stewart 
Reviewed-by: Allison Randal 
Cc: linux-spdx@vger.kernel.org
Link: https://lkml.kernel.org/r/20190604081206.933168790@linutronix.de
Signed-off-by: Greg Kroah-Hartman

arm64/module: switch to ADRP/ADD sequences for PLT entries

2018-11-27T19:00:45+00:00

Now that we have switched to the small code model entirely, and
reduced the extended KASLR range to 4 GB, we can be sure that the
targets of relative branches that are out of range are in range
for a ADRP/ADD pair, which is one instruction shorter than our
current MOVN/MOVK/MOVK sequence, and is more idiomatic and so it
is more likely to be implemented efficiently by micro-architectures.

So switch over the ordinary PLT code and the special handling of
the Cortex-A53 ADRP errata, as well as the ftrace trampline
handling.

Reviewed-by: Torsten Duwe 
Signed-off-by: Ard Biesheuvel 
[will: Added a couple of comments in the plt equality check]
Signed-off-by: Will Deacon

arm64/module: use plt section indices for relocations

2018-11-20T11:38:26+00:00

Instead of saving a pointer to the .plt and .init.plt sections to apply
plt-based relocations, save and use their section indices instead.

The mod->arch.{core,init}.plt pointers were problematic for livepatch
because they pointed within temporary section headers (provided by the
module loader via info->sechdrs) that would be freed after module load.
Since livepatch modules may need to apply relocations post-module-load
(for example, to patch a module that is loaded later), using section
indices to offset into the section headers (instead of accessing them
through a saved pointer) allows livepatch modules on arm64 to pass in
their own copy of the section headers to apply_relocate_add() to apply
delayed relocations.

Reviewed-by: Ard Biesheuvel 
Reviewed-by: Miroslav Benes 
Signed-off-by: Jessica Yu 
Signed-off-by: Will Deacon

arm64/kernel: rename module_emit_adrp_veneer->module_emit_veneer_for_adrp

2018-04-24T18:07:35+00:00

Commit a257e02579e ("arm64/kernel: don't ban ADRP to work around
Cortex-A53 erratum #843419") introduced a function whose name ends with
"_veneer".

This clashes with commit bd8b22d2888e ("Kbuild: kallsyms: ignore veneers
emitted by the ARM linker"), which removes symbols ending in "_veneer"
from kallsyms.

The problem was manifested as 'perf test -vvvvv vmlinux' failed,
correctly claiming the symbol 'module_emit_adrp_veneer' was present in
vmlinux, but not in kallsyms.

...
    ERR : 0xffff00000809aa58: module_emit_adrp_veneer not on kallsyms
...
    test child finished with -1
    ---- end ----
    vmlinux symtab matches kallsyms: FAILED!

Fix the problem by renaming module_emit_adrp_veneer to
module_emit_veneer_for_adrp.  Now the test passes.

Fixes: a257e02579e ("arm64/kernel: don't ban ADRP to work around Cortex-A53 erratum #843419")
Acked-by: Ard Biesheuvel 
Cc: Will Deacon 
Cc: Catalin Marinas 
Cc: Michal Marek 
Signed-off-by: Kim Phillips 
Signed-off-by: Will Deacon