From 8486e54d30e170c969090f80bbdfa7142d33ed6a Mon Sep 17 00:00:00 2001 From: Mark Rutland Date: Fri, 23 Jun 2017 18:02:06 +0100 Subject: [PATCH] arm64: ftrace: fix !CONFIG_ARM64_MODULE_PLTS kernels 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: 687644209a6e9557 ("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: 687644209a6e9557 ("arm64: ftrace: fix building without CONFIG_MODULES") Signed-off-by: Mark Rutland Reported-by: Marc Zyngier Reviewed-by: Ard Biesheuvel Cc: Arnd Bergmann Cc: Catalin Marinas Cc: Will Deacon Signed-off-by: Will Deacon --- arch/arm64/kernel/ftrace.c | 14 ++++++++------ 1 file changed, 8 insertions(+), 6 deletions(-) diff --git a/arch/arm64/kernel/ftrace.c b/arch/arm64/kernel/ftrace.c index 401aa27808a4..c13b1fca0e5b 100644 --- a/arch/arm64/kernel/ftrace.c +++ b/arch/arm64/kernel/ftrace.c @@ -72,11 +72,10 @@ int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr) { unsigned long pc = rec->ip; u32 old, new; - -#ifdef CONFIG_ARM64_MODULE_PLTS long offset = (long)pc - (long)addr; if (offset < -SZ_128M || offset >= SZ_128M) { +#ifdef CONFIG_ARM64_MODULE_PLTS unsigned long *trampoline; struct module *mod; @@ -121,8 +120,10 @@ int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr) smp_wmb(); } addr = (unsigned long)&trampoline[1]; - } +#else /* CONFIG_ARM64_MODULE_PLTS */ + return -EINVAL; #endif /* CONFIG_ARM64_MODULE_PLTS */ + } old = aarch64_insn_gen_nop(); new = aarch64_insn_gen_branch_imm(pc, addr, AARCH64_INSN_BRANCH_LINK); @@ -139,11 +140,10 @@ int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec, unsigned long pc = rec->ip; bool validate = true; u32 old = 0, new; - -#ifdef CONFIG_ARM64_MODULE_PLTS long offset = (long)pc - (long)addr; if (offset < -SZ_128M || offset >= SZ_128M) { +#ifdef CONFIG_ARM64_MODULE_PLTS u32 replaced; /* @@ -176,11 +176,13 @@ int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec, return -EINVAL; validate = false; +#else /* CONFIG_ARM64_MODULE_PLTS */ + return -EINVAL; +#endif /* CONFIG_ARM64_MODULE_PLTS */ } else { old = aarch64_insn_gen_branch_imm(pc, addr, AARCH64_INSN_BRANCH_LINK); } -#endif /* CONFIG_ARM64_MODULE_PLTS */ new = aarch64_insn_gen_nop();