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authorArd Biesheuvel <ard.biesheuvel@linaro.org>2017-06-06 17:00:22 +0000
committerWill Deacon <will.deacon@arm.com>2017-06-07 11:52:02 +0100
commite71a4e1bebaf7fd990efbdc04b38e5526914f0f1 (patch)
tree0f8906d0ba3979cd8020dd896aa6d764afb360df /arch/arm64/Kconfig
parentarm64: ftrace: don't validate branch via PLT in ftrace_make_nop() (diff)
downloadlinux-dev-e71a4e1bebaf7fd990efbdc04b38e5526914f0f1.tar.xz
linux-dev-e71a4e1bebaf7fd990efbdc04b38e5526914f0f1.zip
arm64: ftrace: add support for far branches to dynamic ftrace
Currently, dynamic ftrace support in the arm64 kernel assumes that all core kernel code is within range of ordinary branch instructions that occur in module code, which is usually the case, but is no longer guaranteed now that we have support for module PLTs and address space randomization. Since on arm64, all patching of branch instructions involves function calls to the same entry point [ftrace_caller()], we can emit the modules with a trampoline that has unlimited range, and patch both the trampoline itself and the branch instruction to redirect the call via the trampoline. Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> [will: minor clarification to smp_wmb() comment] Signed-off-by: Will Deacon <will.deacon@arm.com>
Diffstat (limited to 'arch/arm64/Kconfig')
-rw-r--r--arch/arm64/Kconfig2
1 files changed, 1 insertions, 1 deletions
diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 3dcd7ec69bca..22f769b254b4 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -982,7 +982,7 @@ config RANDOMIZE_BASE
config RANDOMIZE_MODULE_REGION_FULL
bool "Randomize the module region independently from the core kernel"
- depends on RANDOMIZE_BASE && !DYNAMIC_FTRACE
+ depends on RANDOMIZE_BASE
default y
help
Randomizes the location of the module region without considering the