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Diffstat (limited to 'arch/arm64/kernel/ftrace.c')
-rw-r--r--arch/arm64/kernel/ftrace.c137
1 files changed, 66 insertions, 71 deletions
diff --git a/arch/arm64/kernel/ftrace.c b/arch/arm64/kernel/ftrace.c
index f447c4a36f69..ea5dc7c90f46 100644
--- a/arch/arm64/kernel/ftrace.c
+++ b/arch/arm64/kernel/ftrace.c
@@ -78,47 +78,76 @@ static struct plt_entry *get_ftrace_plt(struct module *mod, unsigned long addr)
}
/*
- * Turn on the call to ftrace_caller() in instrumented function
+ * Find the address the callsite must branch to in order to reach '*addr'.
+ *
+ * Due to the limited range of 'BL' instructions, modules may be placed too far
+ * away to branch directly and must use a PLT.
+ *
+ * Returns true when '*addr' contains a reachable target address, or has been
+ * modified to contain a PLT address. Returns false otherwise.
*/
-int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
+static bool ftrace_find_callable_addr(struct dyn_ftrace *rec,
+ struct module *mod,
+ unsigned long *addr)
{
unsigned long pc = rec->ip;
- u32 old, new;
- long offset = (long)pc - (long)addr;
+ long offset = (long)*addr - (long)pc;
+ struct plt_entry *plt;
- if (offset < -SZ_128M || offset >= SZ_128M) {
- struct module *mod;
- struct plt_entry *plt;
+ /*
+ * When the target is within range of the 'BL' instruction, use 'addr'
+ * as-is and branch to that directly.
+ */
+ if (offset >= -SZ_128M && offset < SZ_128M)
+ return true;
- if (!IS_ENABLED(CONFIG_ARM64_MODULE_PLTS))
- return -EINVAL;
+ /*
+ * When the target is outside of the range of a 'BL' instruction, we
+ * must use a PLT to reach it. We can only place PLTs for modules, and
+ * only when module PLT support is built-in.
+ */
+ if (!IS_ENABLED(CONFIG_ARM64_MODULE_PLTS))
+ return false;
- /*
- * 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.
- */
+ /*
+ * '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.
+ *
+ * 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.
+ */
+ if (!mod) {
preempt_disable();
mod = __module_text_address(pc);
preempt_enable();
+ }
- if (WARN_ON(!mod))
- return -EINVAL;
+ if (WARN_ON(!mod))
+ return false;
- plt = get_ftrace_plt(mod, addr);
- if (!plt) {
- pr_err("ftrace: no module PLT for %ps\n", (void *)addr);
- return -EINVAL;
- }
-
- addr = (unsigned long)plt;
+ plt = get_ftrace_plt(mod, *addr);
+ if (!plt) {
+ pr_err("ftrace: no module PLT for %ps\n", (void *)*addr);
+ return false;
}
+ *addr = (unsigned long)plt;
+ return true;
+}
+
+/*
+ * Turn on the call to ftrace_caller() in instrumented function
+ */
+int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
+{
+ unsigned long pc = rec->ip;
+ u32 old, new;
+
+ if (!ftrace_find_callable_addr(rec, NULL, &addr))
+ return -EINVAL;
+
old = aarch64_insn_gen_nop();
new = aarch64_insn_gen_branch_imm(pc, addr, AARCH64_INSN_BRANCH_LINK);
@@ -132,6 +161,11 @@ int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr,
unsigned long pc = rec->ip;
u32 old, new;
+ if (!ftrace_find_callable_addr(rec, NULL, &old_addr))
+ return -EINVAL;
+ if (!ftrace_find_callable_addr(rec, NULL, &addr))
+ return -EINVAL;
+
old = aarch64_insn_gen_branch_imm(pc, old_addr,
AARCH64_INSN_BRANCH_LINK);
new = aarch64_insn_gen_branch_imm(pc, addr, AARCH64_INSN_BRANCH_LINK);
@@ -181,54 +215,15 @@ int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec,
unsigned long addr)
{
unsigned long pc = rec->ip;
- bool validate = true;
u32 old = 0, new;
- long offset = (long)pc - (long)addr;
- if (offset < -SZ_128M || offset >= SZ_128M) {
- u32 replaced;
-
- if (!IS_ENABLED(CONFIG_ARM64_MODULE_PLTS))
- return -EINVAL;
-
- /*
- * '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 {
- old = aarch64_insn_gen_branch_imm(pc, addr,
- AARCH64_INSN_BRANCH_LINK);
- }
+ if (!ftrace_find_callable_addr(rec, mod, &addr))
+ return -EINVAL;
+ old = aarch64_insn_gen_branch_imm(pc, addr, AARCH64_INSN_BRANCH_LINK);
new = aarch64_insn_gen_nop();
- return ftrace_modify_code(pc, old, new, validate);
+ return ftrace_modify_code(pc, old, new, true);
}
void arch_ftrace_update_code(int command)