arm64: Fix vdso-offsets.h dependency
arch/arm64/kernel/{vdso,signal}.c include generated/vdso-offsets.h, and therefore the symbol offsets must be generated before these files are compiled. The current rules in arm64/kernel/Makefile do not actually enforce this, because even though $(obj)/vdso is listed as a prerequisite for vdso-offsets.h, this does not result in the intended effect of building the vdso subdirectory (before all the other objects). As a consequence, depending on the order in which the rules are followed, vdso-offsets.h is updated or not before arm64/kernel/{vdso,signal}.o are built. The current rules also impose an unnecessary dependency on vdso-offsets.h for all arm64/kernel/*.o, resulting in unnecessary rebuilds. This patch removes the arch/arm64/kernel/vdso/vdso-offsets.h file generation, leaving only the include/generated/vdso-offsets.h one. It adds a forced dependency check of the vdso-offsets.h file in arch/arm64/kernel/Makefile which, if not up to date according to the arch/arm64/kernel/vdso/Makefile rules (depending on vdso.so.dbg), will trigger the vdso/ subdirectory build and vdso-offsets.h re-generation. Automatic kbuild dependency rules between kernel/{vdso,signal}.c rules and vdso-offsets.h will guarantee that the vDSO object is built first, followed by the generated symbol offsets header file. Reported-by: Kevin Brodsky <kevin.brodsky@arm.com> Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
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