[PATCHv2] arm64: ftrace: fix !CONFIG_ARM64_MODULE_PLTS kernels
From: mark.rutland@arm.com (Mark Rutland)
Date: 2017-06-23 17:02:06
Subsystem:
arm64 port (aarch64 architecture), function hooks (ftrace), the rest · Maintainers:
Catalin Marinas, Will Deacon, Steven Rostedt, Masami Hiramatsu, Linus Torvalds
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 <mark.rutland@arm.com>
Reported-by: Marc Zyngier <redacted>
Reviewed-by: Ard Biesheuvel <redacted>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <redacted>
---
arch/arm64/kernel/ftrace.c | 14 ++++++++------
1 file changed, 8 insertions(+), 6 deletions(-)
Since v1:
* Kill redundant whitespace
* Add Ard's Reviewed-by
diff --git a/arch/arm64/kernel/ftrace.c b/arch/arm64/kernel/ftrace.c
index 401aa27..c13b1fc 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();
--
1.9.1