From: ard.biesheuvel@linaro.org (Ard Biesheuvel)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH 0/2] arm64: ftrace: fix interop issues with module PLTs
Date: Mon, 10 Apr 2017 15:13:41 +0100 [thread overview]
Message-ID: <20170410141343.1045-1-ard.biesheuvel@linaro.org> (raw)
The arm64 ftrace code assumes that all core kernel symbols are withing the
range of an ordinary branch instruction from anywhere in the kernel, even
in modules. While this is usually the case, it may not be true when running
with KASLR enabled.
This series fixes two distinct but related issues involving ftrace under
KASLR:
- the initial sweep over all _mcount() calls in newly loaded modules
validates those calls by comparing each to a 'bl _mcount' opcode, which
will fail if _mcount() [which is in the core kernel] is out of range, and
which will result in false negatives, given that those call sites will
contain a correct branch to _mcount(), but via a PLT entry (patch #1)
- patching up those NOPs into calls to ftrace_caller() [which is the only
ftrace branch target that we ever use on arm64, IIUC] will fail in the
same way, and needs to be redirected via a trampoline as well (patch #2)
Ard Biesheuvel (2):
arm64: ftrace: don't validate branch via PLT in ftrace_make_nop()
arm64: ftrace: add support for far branches to dynamic ftrace
arch/arm64/Kconfig | 2 +-
arch/arm64/Makefile | 3 ++
arch/arm64/include/asm/module.h | 3 ++
arch/arm64/kernel/ftrace.c | 42 ++++++++++++++++++--
arch/arm64/kernel/module-plts.c | 10 +++++
arch/arm64/lib/Makefile | 2 +
arch/arm64/lib/ftrace-mod.S | 25 ++++++++++++
7 files changed, 82 insertions(+), 5 deletions(-)
create mode 100644 arch/arm64/lib/ftrace-mod.S
--
2.9.3
next reply other threads:[~2017-04-10 14:13 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-04-10 14:13 Ard Biesheuvel [this message]
2017-04-10 14:13 ` [PATCH 1/2] arm64: ftrace: don't validate branch via PLT in ftrace_make_nop() Ard Biesheuvel
2017-04-10 14:13 ` [PATCH 2/2] arm64: ftrace: add support for far branches to dynamic ftrace Ard Biesheuvel
2017-04-10 14:22 ` Ard Biesheuvel
2017-04-10 14:39 ` Steven Rostedt
2017-04-10 14:40 ` Ard Biesheuvel
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