From: Alexander Sverdlin <alexander.sverdlin@nokia.com>
To: linux-arm-kernel@lists.infradead.org
Cc: Alexander Sverdlin <alexander.sverdlin@nokia.com>,
linux-kernel@vger.kernel.org,
Russell King <linux@armlinux.org.uk>,
Steven Rostedt <rostedt@goodmis.org>,
Ingo Molnar <mingo@redhat.com>
Subject: [PATCH v3 0/2] ARM: Implement MODULE_PLT support in FTRACE
Date: Fri, 9 Mar 2018 09:41:49 +0100 [thread overview]
Message-ID: <20180309084151.2379-1-alexander.sverdlin@nokia.com> (raw)
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:
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 | 58 ++++++++++++++++++++++++++--------------
4 files changed, 104 insertions(+), 29 deletions(-)
--
2.4.6
next reply other threads:[~2018-03-09 8:43 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-03-09 8:41 Alexander Sverdlin [this message]
2018-03-09 8:41 ` [PATCH v3 1/2] ARM: PLT: Move struct plt_entries definition to header Alexander Sverdlin
2018-03-09 8:41 ` [PATCH v3 2/2] ARM: ftrace: Add MODULE_PLTS support Alexander Sverdlin
2018-03-09 8:50 ` Ard Biesheuvel
2018-03-09 8:54 ` Alexander Sverdlin
2018-03-09 9:41 ` Ard Biesheuvel
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