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[ Upstream commit 6e803e2e6e367db9a0d6ecae1bd24bb5752011bd ] The core ftrace code requires that when it is handed the PC of an instrumented function, this PC is the address of the instrumented instruction. This is necessary so that the core ftrace code can identify the specific instrumentation site. Since the instrumented function will be a BL, the address of the instrumented function is LR - 4 at entry to the ftrace code. This fixup is applied in the mcount_get_pc and mcount_get_pc0 helpers, which acquire the PC of the instrumented function. The mcount_get_lr helper is used to acquire the LR of the instrumented function, whose value does not require this adjustment, and cannot be adjusted to anything meaningful. No adjustment of this value is made on other architectures, including arm. However, arm64 adjusts this value by 4. This patch brings arm64 in line with other architectures and removes the adjustment of the LR value. Signed-off-by: Mark Rutland <mark.rutland@arm.com> Cc: AKASHI Takahiro <takahiro.akashi@linaro.org> Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Torsten Duwe <duwe@suse.de> Cc: Will Deacon <will.deacon@arm.com> Signed-off-by: Will Deacon <will.deacon@arm.com> Signed-off-by: Sasha Levin <sashal@kernel.org>
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.