arm: vectors: use local symbol names for vector entry points

maillist inclusion
commit 11f8bbc5b0d4d76b3d7114bf9af1805607a20372
category: feature
feature: ARM kaslr support
bugzilla: 47952
CVE: NA

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/ardb/linux.git/commit/?h=arm-kaslr-latest&id=11f8bbc5b0d4d76b3d7114bf9af1805607a20372



-------------------------------------------------

The location of the ARM vector table in virtual memory is not
a compile time constant, and so the virtual addresses of the
various entry points are rather meaningless (although they are
most likely to reside at the offsets below)

  ffff1004 t vector_rst
  ffff1020 t vector_irq
  ffff10a0 t vector_dabt
  ffff1120 t vector_pabt
  ffff11a0 t vector_und
  ffff1220 t vector_addrexcptn
  ffff1240 T vector_fiq

However, when running with KASLR enabled, the virtual addresses are
subject to runtime relocation, which means we should avoid to take
absolute references to these symbols, not only directly (by taking
the address in C code), but also via /proc/kallsyms or other kernel
facilities that deal with ELF symbols. For instance, /proc/kallsyms
will list their addresses as

  0abf1004 t vector_rst
  0abf1020 t vector_irq
  0abf10a0 t vector_dabt
  0abf1120 t vector_pabt
  0abf11a0 t vector_und
  0abf1220 t vector_addrexcptn
  0abf1240 T vector_fiq

when running randomized, which may confuse tools like perf that may
use /proc/kallsyms to annotate stack traces.

So use .L prefixes for these symbols. This will prevent them from
being visible at all outside the assembler source.

Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Cui GaoSheng <cuigaosheng1@huawei.com>
Reviewed-by: Xiu Jianfeng <xiujianfeng@huawei.com>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>