From mboxrd@z Thu Jan 1 00:00:00 1970 From: mark.rutland@arm.com (Mark Rutland) Date: Fri, 23 Jun 2017 14:57:41 +0100 Subject: [PATCH] arm64: ftrace: fix !CONFIG_ARM64_MODULE_PLTS kernels Message-ID: <1498226261-21204-1-git-send-email-mark.rutland@arm.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org 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 Cc: Ard Biesheuvel Cc: Arnd Bergmann Cc: Catalin Marinas Cc: Will Deacon --- arch/arm64/kernel/ftrace.c | 12 ++++++++---- 1 file changed, 8 insertions(+), 4 deletions(-) Marc spotted this breakage atop of the arm64 for-next/core branch when ftrace was enabled. I've given this fix a go with all combinations of MODULES and RANDOMIZE_BASE, with the ftrace boot time self test, and everything seems happy in all combinations. Mark. diff --git a/arch/arm64/kernel/ftrace.c b/arch/arm64/kernel/ftrace.c index 401aa27..945f506 100644 --- a/arch/arm64/kernel/ftrace.c +++ b/arch/arm64/kernel/ftrace.c @@ -73,10 +73,10 @@ 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 +121,10 @@ 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); @@ -140,10 +142,10 @@ int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec, 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 +178,13 @@ 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(); -- 1.9.1