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Message-Id: <20180313135314.18780-1-alexander.sverdlin@nokia.com>
Date: Tue, 13 Mar 2018 14:53:12 +0100
From: Alexander Sverdlin <alexander.sverdlin@...ia.com>
To: linux-arm-kernel@...ts.infradead.org
Cc: Alexander Sverdlin <alexander.sverdlin@...ia.com>,
linux-kernel@...r.kernel.org, Russell King <linux@...linux.org.uk>,
Steven Rostedt <rostedt@...dmis.org>,
Ingo Molnar <mingo@...hat.com>,
Ard Biesheuvel <ard.biesheuvel@...aro.org>
Subject: [PATCH v4 0/2] ARM: Implement MODULE_PLT support in FTRACE
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.
Changelog:
v4:
* Fixed build without CONFIG_FUNCTION_TRACER
* Reorganized pre-allocated PLTs handling in get_module_plt(),
now compiler eliminates the whole FTRACE-related handling code
if ARRAY_SIZE(fixed_plts) == 0
v3:
* Only extend struct dyn_arch_ftrace when ARM_MODULE_PLTS is enabled
v2:
* As suggested by Steven Rostedt, refrain from tree-wide API modification,
save module pointer in struct dyn_arch_ftrace instead (PowerPC way)
Alexander Sverdlin (2):
ARM: PLT: Move struct plt_entries definition to header
ARM: ftrace: Add MODULE_PLTS support
arch/arm/include/asm/ftrace.h | 3 +++
arch/arm/include/asm/module.h | 10 +++++++
arch/arm/kernel/ftrace.c | 62 ++++++++++++++++++++++++++++++++++++-------
arch/arm/kernel/module-plts.c | 52 ++++++++++++++++++++++++++++--------
4 files changed, 107 insertions(+), 20 deletions(-)
--
2.4.6
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