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When a kernel is built without CONFIG_ARM64_MODULE_PLTS, we don't generate the expected branch instruction in ftrace_make_nop(). This means we pass zero (rather than a valid branch) to ftrace_modify_code() as the expected instruction to validate. This causes us to return -EINVAL to the core ftrace code for a valid case, resulting in a splat at boot time. This was an unintended effect of commit:687644209a("arm64: ftrace: fix building without CONFIG_MODULES") ... which incorrectly moved the generation of the branch instruction into the ifdef for CONFIG_ARM64_MODULE_PLTS. This patch fixes the issue by moving the ifdef inside of the relevant if-else case, and always checking that the branch is in range, regardless of CONFIG_ARM64_MODULE_PLTS. This ensures that we generate the expected branch instruction, and also improves our sanity checks. For consistency, both ftrace_make_nop() and ftrace_make_call() are updated with this pattern. Fixes:687644209a("arm64: ftrace: fix building without CONFIG_MODULES") Signed-off-by: Mark Rutland <mark.rutland@arm.com> Reported-by: Marc Zyngier <marc.zyngier@arm.com> Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> Cc: Arnd Bergmann <arnd@arndb.de> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Will Deacon <will.deacon@arm.com> Signed-off-by: Will Deacon <will.deacon@arm.com>
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. Please read the Documentation/process/changes.rst file, as it contains the requirements for building and running the kernel, and information about the problems which may result by upgrading your kernel.