arm64: ftrace: Ensure module ftrace trampoline is coherent with I-side (b6143d10) · Commits · 戴 / test

The initial support for dynamic ftrace trampolines in modules made use of an indirect branch which loaded its target from the beginning of a special section ( ("arm64: ftrace: add support for far branches to dynamic ftrace")). Since no instructions were being patched, no cache maintenance was needed. However, later in ("arm64: ftrace: emit ftrace-mod.o contents through code") this code was reworked to output the trampoline instructions directly into the PLT entry but, unfortunately, the necessary cache maintenance was overlooked. Add a call to __flush_icache_range() after writing the new trampoline instructions but before patching in the branch to the trampoline. Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org> Cc: James Morse <james.morse@arm.com> Cc: <stable@vger.kernel.org> Fixes: ("arm64: ftrace: emit ftrace-mod.o contents through code") Signed-off-by:

Will Deacon <will@kernel.org> Signed-off-by:

Catalin Marinas <catalin.marinas@arm.com>

arch/arm64/kernel/ftrace.c

+13 −9

Original line number	Diff line number	Diff line
		@@ -73,7 +73,7 @@ int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)

		if (offset < -SZ_128M \|\| offset >= SZ_128M) {
		#ifdef CONFIG_ARM64_MODULE_PLTS
		struct plt_entry trampoline;
		struct plt_entry trampoline, *dst;
		struct module *mod;

		/*
		@@ -106,23 +106,27 @@ int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
		* to check if the actual opcodes are in fact identical,
		* regardless of the offset in memory so use memcmp() instead.
		*/
		trampoline = get_plt_entry(addr, mod->arch.ftrace_trampoline);
		if (memcmp(mod->arch.ftrace_trampoline, &trampoline,
		sizeof(trampoline))) {
		if (plt_entry_is_initialized(mod->arch.ftrace_trampoline)) {
		dst = mod->arch.ftrace_trampoline;
		trampoline = get_plt_entry(addr, dst);
		if (memcmp(dst, &trampoline, sizeof(trampoline))) {
		if (plt_entry_is_initialized(dst)) {
		pr_err("ftrace: far branches to multiple entry points unsupported inside a single module\n");
		return -EINVAL;
		}

		/* point the trampoline to our ftrace entry point */
		module_disable_ro(mod);
		*mod->arch.ftrace_trampoline = trampoline;
		*dst = trampoline;
		module_enable_ro(mod, true);

		/* update trampoline before patching in the branch */
		smp_wmb();
		/*
		* Ensure updated trampoline is visible to instruction
		* fetch before we patch in the branch.
		*/
		__flush_icache_range((unsigned long)&dst[0],
		(unsigned long)&dst[1]);
		}
		addr = (unsigned long)(void *)mod->arch.ftrace_trampoline;
		addr = (unsigned long)dst;
		#else /* CONFIG_ARM64_MODULE_PLTS */
		return -EINVAL;
		#endif /* CONFIG_ARM64_MODULE_PLTS */

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