[PATCH 0/3] ARM: Implement MODULE_PLT support in FTRACE

From: Alexander Sverdlin
Date: Fri Feb 23 2018 - 12:00:18 EST


FTRACE's function tracer currently doesn't always work on ARM with
MODULE_PLT option enabled. If the module is loaded too far, FTRACE's
code modifier cannot cope with introduced veneers and turns the
function tracer off globally.

ARM64 already has a solution for the problem, refer to the following
patches:

arm64: ftrace: emit ftrace-mod.o contents through code
arm64: module-plts: factor out PLT generation code for ftrace
arm64: ftrace: fix !CONFIG_ARM64_MODULE_PLTS kernels
arm64: ftrace: fix building without CONFIG_MODULES
arm64: ftrace: add support for far branches to dynamic ftrace
arm64: ftrace: don't validate branch via PLT in ftrace_make_nop()

But the presented ARM variant has just a half of the footprint in terms of
the changed LoCs. It also retains the code validation-before-modification
instead of switching it off.

Alexander Sverdlin (3):
ftrace: Add module to ftrace_make_call() parameters
ARM: PLT: Move struct plt_entries definition to header
ftrace: Add MODULE_PLTS support

arch/arm/include/asm/module.h | 10 ++++++
arch/arm/kernel/ftrace.c | 73 ++++++++++++++++++++++++++++++++------
arch/arm/kernel/module-plts.c | 58 +++++++++++++++++++-----------
arch/arm64/kernel/ftrace.c | 3 +-
arch/blackfin/kernel/ftrace.c | 3 +-
arch/ia64/kernel/ftrace.c | 3 +-
arch/metag/kernel/ftrace.c | 3 +-
arch/microblaze/kernel/ftrace.c | 3 +-
arch/mips/kernel/ftrace.c | 3 +-
arch/powerpc/kernel/trace/ftrace.c | 3 +-
arch/s390/kernel/ftrace.c | 3 +-
arch/sh/kernel/ftrace.c | 3 +-
arch/sparc/kernel/ftrace.c | 3 +-
arch/tile/kernel/ftrace.c | 3 +-
arch/x86/kernel/ftrace.c | 3 +-
include/linux/ftrace.h | 4 ++-
kernel/trace/ftrace.c | 6 ++--
17 files changed, 140 insertions(+), 47 deletions(-)

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2.4.6