linux-toradex.git/arch/arm/lib/memcpy.S, branch v5.18

ARM: memcpy: use frame pointer as unwind anchor

2021-12-03T14:11:32+00:00

The memcpy template is a bit unusual in the way it manages the stack
pointer: depending on the execution path through the function, the SP
assumes different values as different subsets of the register file are
preserved and restored again. This is problematic when it comes to EHABI
unwind info, as it is not instruction accurate, and does not allow
tracking the SP value as it changes.

Commit 279f487e0b471 ("ARM: 8225/1: Add unwinding support for memory
copy functions") addressed this by carving up the function in different
chunks as far as the unwinder is concerned, and keeping a set of unwind
directives for each of them, each corresponding with the state of the
stack pointer during execution of the chunk in question. This not only
duplicates unwind info unnecessarily, but it also complicates unwinding
the stack upon overflow.

Instead, let's do what the compiler does when the SP is updated halfway
through a function, which is to use a frame pointer and emit the
appropriate unwind directives to communicate this to the unwinder.

Note that Thumb-2 uses R7 for this, while ARM uses R11 aka FP. So let's
avoid touching R7 in the body of the template, so that Thumb-2 can use
it as the frame pointer. R11 was not modified in the first place.

Signed-off-by: Ard Biesheuvel 
Tested-by: Keith Packard 
Tested-by: Marc Zyngier 
Tested-by: Vladimir Murzin  # ARMv7M

ARM: 9022/1: Change arch/arm/lib/mem*.S to use WEAK instead of .weak

2020-11-12T14:53:19+00:00

Commit d6d51a96c7d6 ("ARM: 9014/2: Replace string mem* functions for
KASan") add .weak directives to memcpy/memmove/memset to avoid collision
with KASAN interceptors.

This does not work with LLVM's integrated assembler (the assembly snippet
`.weak memcpy ... .globl memcpy` produces a STB_GLOBAL memcpy while GNU as
produces a STB_WEAK memcpy). LLVM 12 (since https://reviews.llvm.org/D90108)
will error on such an overridden symbol binding.

Use the appropriate WEAK macro instead.

Link: https://github.com/ClangBuiltLinux/linux/issues/1190
--

Fixes: d6d51a96c7d6 ("ARM: 9014/2: Replace string mem* functions for KASan")
Reported-by: Nick Desaulniers 
Signed-off-by: Fangrui Song 
Reviewed-by: Nick Desaulniers 
Tested-by: Nick Desaulniers 
Signed-off-by: Russell King

ARM: 9014/2: Replace string mem* functions for KASan

2020-10-27T12:11:06+00:00

Functions like memset()/memmove()/memcpy() do a lot of memory
accesses.

If a bad pointer is passed to one of these functions it is important
to catch this. Compiler instrumentation cannot do this since these
functions are written in assembly.

KASan replaces these memory functions with instrumented variants.

The original functions are declared as weak symbols so that
the strong definitions in mm/kasan/kasan.c can replace them.

The original functions have aliases with a '__' prefix in their
name, so we can call the non-instrumented variant if needed.

We must use __memcpy()/__memset() in place of memcpy()/memset()
when we copy .data to RAM and when we clear .bss, because
kasan_early_init cannot be called before the initialization of
.data and .bss.

For the kernel compression and EFI libstub's custom string
libraries we need a special quirk: even if these are built
without KASan enabled, they rely on the global headers for their
custom string libraries, which means that e.g. memcpy()
will be defined to __memcpy() and we get link failures.
Since these implementations are written i C rather than
assembly we use e.g. __alias(memcpy) to redirected any
users back to the local implementation.

Cc: Andrey Ryabinin 
Cc: Alexander Potapenko 
Cc: Dmitry Vyukov 
Cc: kasan-dev@googlegroups.com
Reviewed-by: Ard Biesheuvel 
Tested-by: Ard Biesheuvel  # QEMU/KVM/mach-virt/LPAE/8G
Tested-by: Florian Fainelli  # Brahma SoCs
Tested-by: Ahmad Fatoum  # i.MX6Q
Reported-by: Russell King - ARM Linux 
Signed-off-by: Ahmad Fatoum 
Signed-off-by: Abbott Liu 
Signed-off-by: Florian Fainelli 
Signed-off-by: Linus Walleij 
Signed-off-by: Russell King

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

ARM: 8841/1: use unified assembler in macros

2019-02-26T11:25:43+00:00

Use unified assembler syntax (UAL) in macros. Divided syntax is
considered deprecated. This will also allow to build the kernel
using LLVM's integrated assembler.

Signed-off-by: Stefan Agner 
Acked-by: Nicolas Pitre 
Signed-off-by: Russell King

Revert "arm: move exports to definitions"

2016-11-23T10:00:03+00:00

This reverts commit 4dd1837d7589f468ed109556513f476e7a7f9121.

Moving the exports for assembly code into the assembly files breaks
KSYM trimming, but also breaks modversions.

While fixing the KSYM trimming is trivial, fixing modversions brings
us to a technically worse position that we had prior to the above
change:

- We end up with the prototype definitions divorsed from everything
  else, which means that adding or removing assembly level ksyms
  become more fragile:
  * if adding a new assembly ksyms export, a missed prototype in
    asm-prototypes.h results in a successful build if no module in
    the selected configuration makes use of the symbol.
  * when removing a ksyms export, asm-prototypes.h will get forgotten,
    with armksyms.c, you'll get a build error if you forget to touch
    the file.

- We end up with the same amount of include files and prototypes,
  they're just in a header file instead of a .c file with their
  exports.

As for lines of code, we don't get much of a size reduction:
 (original commit)
 47 files changed, 131 insertions(+), 208 deletions(-)
 (fix for ksyms trimming)
 7 files changed, 18 insertions(+), 5 deletions(-)
 (two fixes for modversions)
 1 file changed, 34 insertions(+)
 3 files changed, 7 insertions(+), 2 deletions(-)
which results in a net total of only 25 lines deleted.

As there does not seem to be much benefit from this change of approach,
revert the change.

Signed-off-by: Russell King

arm: move exports to definitions

2016-08-08T03:47:21+00:00

Signed-off-by: Al Viro

ARM: avoid unwanted GCC memset()/memcpy() optimisations for IO variants

2015-07-03T19:46:15+00:00

We don't want GCC optimising our memset_io(), memcpy_fromio() or
memcpy_toio() variants, so we must not call one of the standard
functions.  Provide a separate name for our assembly memcpy() and
memset() functions, and use that instead, thereby bypassing GCC's
ability to optimise these operations.

GCCs optimisation may introduce unaligned accesses which are invalid
for device mappings.

Signed-off-by: Russell King

ARM: 8225/1: Add unwinding support for memory copy functions

2014-11-27T16:00:25+00:00

The memory copy functions(memcpy, __copy_from_user, __copy_to_user)
never had unwinding annotations added. Currently, when accessing
invalid pointer by these functions occurs the backtrace shown will
stop at these functions or some completely unrelated function.
Add unwinding annotations in hopes of getting a more useful backtrace
in following cases:
1. die on accessing invalid pointer by these functions
2. kprobe trapped at any instruction within these functions
3. interrupted at any instruction within these functions

Signed-off-by: Lin Yongting 
Signed-off-by: Russell King

Thumb-2: Implement the unified arch/arm/lib functions

2009-07-24T11:32:57+00:00

This patch adds the ARM/Thumb-2 unified support for the arch/arm/lib/*
files.

Signed-off-by: Catalin Marinas