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Diffstat (limited to 'arch/arm64/kernel/ftrace.c')
-rw-r--r--arch/arm64/kernel/ftrace.c103
1 files changed, 100 insertions, 3 deletions
diff --git a/arch/arm64/kernel/ftrace.c b/arch/arm64/kernel/ftrace.c
index 40ad08ac569a..c13b1fca0e5b 100644
--- a/arch/arm64/kernel/ftrace.c
+++ b/arch/arm64/kernel/ftrace.c
@@ -10,10 +10,12 @@
*/
#include <linux/ftrace.h>
+#include <linux/module.h>
#include <linux/swab.h>
#include <linux/uaccess.h>
#include <asm/cacheflush.h>
+#include <asm/debug-monitors.h>
#include <asm/ftrace.h>
#include <asm/insn.h>
@@ -70,6 +72,58 @@ int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
{
unsigned long pc = rec->ip;
u32 old, new;
+ long offset = (long)pc - (long)addr;
+
+ if (offset < -SZ_128M || offset >= SZ_128M) {
+#ifdef CONFIG_ARM64_MODULE_PLTS
+ unsigned long *trampoline;
+ struct module *mod;
+
+ /*
+ * On kernels that support module PLTs, the offset between the
+ * branch instruction and its target may legally exceed the
+ * range of an ordinary relative 'bl' opcode. In this case, we
+ * need to branch via a trampoline in the module.
+ *
+ * NOTE: __module_text_address() must be called with preemption
+ * disabled, but we can rely on ftrace_lock to ensure that 'mod'
+ * retains its validity throughout the remainder of this code.
+ */
+ preempt_disable();
+ mod = __module_text_address(pc);
+ preempt_enable();
+
+ if (WARN_ON(!mod))
+ return -EINVAL;
+
+ /*
+ * There is only one ftrace trampoline per module. For now,
+ * this is not a problem since on arm64, all dynamic ftrace
+ * invocations are routed via ftrace_caller(). This will need
+ * to be revisited if support for multiple ftrace entry points
+ * is added in the future, but for now, the pr_err() below
+ * deals with a theoretical issue only.
+ */
+ trampoline = (unsigned long *)mod->arch.ftrace_trampoline;
+ if (trampoline[0] != addr) {
+ if (trampoline[0] != 0) {
+ 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);
+ trampoline[0] = addr;
+ module_enable_ro(mod, true);
+
+ /* update trampoline before patching in the branch */
+ 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);
@@ -84,12 +138,55 @@ int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec,
unsigned long addr)
{
unsigned long pc = rec->ip;
- u32 old, new;
+ bool validate = true;
+ u32 old = 0, new;
+ long offset = (long)pc - (long)addr;
+
+ if (offset < -SZ_128M || offset >= SZ_128M) {
+#ifdef CONFIG_ARM64_MODULE_PLTS
+ u32 replaced;
+
+ /*
+ * 'mod' is only set at module load time, but if we end up
+ * dealing with an out-of-range condition, we can assume it
+ * is due to a module being loaded far away from the kernel.
+ */
+ if (!mod) {
+ preempt_disable();
+ mod = __module_text_address(pc);
+ preempt_enable();
+
+ if (WARN_ON(!mod))
+ return -EINVAL;
+ }
+
+ /*
+ * The instruction we are about to patch may be a branch and
+ * link instruction that was redirected via a PLT entry. In
+ * this case, the normal validation will fail, but we can at
+ * least check that we are dealing with a branch and link
+ * instruction that points into the right module.
+ */
+ if (aarch64_insn_read((void *)pc, &replaced))
+ return -EFAULT;
+
+ if (!aarch64_insn_is_bl(replaced) ||
+ !within_module(pc + aarch64_get_branch_offset(replaced),
+ mod))
+ 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);
+ }
- old = aarch64_insn_gen_branch_imm(pc, addr, AARCH64_INSN_BRANCH_LINK);
new = aarch64_insn_gen_nop();
- return ftrace_modify_code(pc, old, new, true);
+ return ftrace_modify_code(pc, old, new, validate);
}
void arch_ftrace_update_code(int command)