@@ -185,6 +185,10 @@ config ARM64
select HAVE_DEBUG_KMEMLEAK
select HAVE_DMA_CONTIGUOUS
select HAVE_DYNAMIC_FTRACE
+ select HAVE_DYNAMIC_FTRACE_WITH_ARGS \
+ if $(cc-option,-fpatchable-function-entry=2)
+ select HAVE_DYNAMIC_FTRACE_WITH_DIRECT_CALLS \
+ if DYNAMIC_FTRACE_WITH_ARGS && DYNAMIC_FTRACE_WITH_CALL_OPS
select HAVE_DYNAMIC_FTRACE_WITH_CALL_OPS \
if (DYNAMIC_FTRACE_WITH_ARGS && !CFI_CLANG && \
!CC_OPTIMIZE_FOR_SIZE)
@@ -70,10 +70,19 @@ struct ftrace_ops;
#define arch_ftrace_get_regs(regs) NULL
+/*
+ * Note: sizeof(struct ftrace_regs) must be a multiple of 16 to ensure correct
+ * stack alignment
+ */
struct ftrace_regs {
/* x0 - x8 */
unsigned long regs[9];
+
+#ifdef CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS
+ unsigned long direct_tramp;
+#else
unsigned long __unused;
+#endif
unsigned long fp;
unsigned long lr;
@@ -136,6 +145,19 @@ int ftrace_init_nop(struct module *mod, struct dyn_ftrace *rec);
void ftrace_graph_func(unsigned long ip, unsigned long parent_ip,
struct ftrace_ops *op, struct ftrace_regs *fregs);
#define ftrace_graph_func ftrace_graph_func
+
+#ifdef CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS
+static inline void arch_ftrace_set_direct_caller(struct ftrace_regs *fregs,
+ unsigned long addr)
+{
+ /*
+ * The ftrace trampoline will return to this address instead of the
+ * instrumented function.
+ */
+ fregs->direct_tramp = addr;
+}
+#endif /* CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS */
+
#endif
#define ftrace_return_address(n) return_address(n)
@@ -93,6 +93,9 @@ int main(void)
DEFINE(FREGS_LR, offsetof(struct ftrace_regs, lr));
DEFINE(FREGS_SP, offsetof(struct ftrace_regs, sp));
DEFINE(FREGS_PC, offsetof(struct ftrace_regs, pc));
+#ifdef CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS
+ DEFINE(FREGS_DIRECT_TRAMP, offsetof(struct ftrace_regs, direct_tramp));
+#endif
DEFINE(FREGS_SIZE, sizeof(struct ftrace_regs));
BLANK();
#endif
@@ -197,6 +200,9 @@ int main(void)
#endif
#ifdef CONFIG_FUNCTION_TRACER
DEFINE(FTRACE_OPS_FUNC, offsetof(struct ftrace_ops, func));
+#ifdef CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS
+ DEFINE(FTRACE_OPS_DIRECT_CALL, offsetof(struct ftrace_ops, direct_call));
+#endif
#endif
return 0;
}
@@ -36,6 +36,31 @@
SYM_CODE_START(ftrace_caller)
bti c
+#ifdef CONFIG_DYNAMIC_FTRACE_WITH_CALL_OPS
+ /*
+ * The literal pointer to the ops is at an 8-byte aligned boundary
+ * which is either 12 or 16 bytes before the BL instruction in the call
+ * site. See ftrace_call_adjust() for details.
+ *
+ * Therefore here the LR points at `literal + 16` or `literal + 20`,
+ * and we can find the address of the literal in either case by
+ * aligning to an 8-byte boundary and subtracting 16. We do the
+ * alignment first as this allows us to fold the subtraction into the
+ * LDR.
+ */
+ bic x11, x30, 0x7
+ ldr x11, [x11, #-(4 * AARCH64_INSN_SIZE)] // op
+
+#ifdef CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS
+ /*
+ * If the op has a direct call, handle it immediately without
+ * saving/restoring registers.
+ */
+ ldr x17, [x11, #FTRACE_OPS_DIRECT_CALL] // op->direct_call
+ cbnz x17, ftrace_caller_direct
+#endif
+#endif
+
/* Save original SP */
mov x10, sp
@@ -49,6 +74,10 @@ SYM_CODE_START(ftrace_caller)
stp x6, x7, [sp, #FREGS_X6]
str x8, [sp, #FREGS_X8]
+#ifdef CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS
+ str xzr, [sp, #FREGS_DIRECT_TRAMP]
+#endif
+
/* Save the callsite's FP, LR, SP */
str x29, [sp, #FREGS_FP]
str x9, [sp, #FREGS_LR]
@@ -71,20 +100,7 @@ SYM_CODE_START(ftrace_caller)
mov x3, sp // regs
#ifdef CONFIG_DYNAMIC_FTRACE_WITH_CALL_OPS
- /*
- * The literal pointer to the ops is at an 8-byte aligned boundary
- * which is either 12 or 16 bytes before the BL instruction in the call
- * site. See ftrace_call_adjust() for details.
- *
- * Therefore here the LR points at `literal + 16` or `literal + 20`,
- * and we can find the address of the literal in either case by
- * aligning to an 8-byte boundary and subtracting 16. We do the
- * alignment first as this allows us to fold the subtraction into the
- * LDR.
- */
- bic x2, x30, 0x7
- ldr x2, [x2, #-16] // op
-
+ mov x2, x11 // op
ldr x4, [x2, #FTRACE_OPS_FUNC] // op->func
blr x4 // op->func(ip, parent_ip, op, regs)
@@ -107,8 +123,15 @@ SYM_INNER_LABEL(ftrace_call, SYM_L_GLOBAL)
ldp x6, x7, [sp, #FREGS_X6]
ldr x8, [sp, #FREGS_X8]
- /* Restore the callsite's FP, LR, PC */
+ /* Restore the callsite's FP */
ldr x29, [sp, #FREGS_FP]
+
+#ifdef CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS
+ ldr x17, [sp, #FREGS_DIRECT_TRAMP]
+ cbnz x17, ftrace_caller_direct_late
+#endif
+
+ /* Restore the callsite's LR and PC */
ldr x30, [sp, #FREGS_LR]
ldr x9, [sp, #FREGS_PC]
@@ -116,8 +139,45 @@ SYM_INNER_LABEL(ftrace_call, SYM_L_GLOBAL)
add sp, sp, #FREGS_SIZE + 32
ret x9
+
+#ifdef CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS
+SYM_INNER_LABEL(ftrace_caller_direct_late, SYM_L_LOCAL)
+ /*
+ * Head to a direct trampoline in x17 after having run other tracers.
+ * The ftrace_regs are live, and x0-x8 and FP have been restored. The
+ * LR, PC, and SP have not been restored.
+ */
+
+ /*
+ * Restore the callsite's LR and PC matching the trampoline calling
+ * convention.
+ */
+ ldr x9, [sp, #FREGS_LR]
+ ldr x30, [sp, #FREGS_PC]
+
+ /* Restore the callsite's SP */
+ add sp, sp, #FREGS_SIZE + 32
+
+SYM_INNER_LABEL(ftrace_caller_direct, SYM_L_LOCAL)
+ /*
+ * Head to a direct trampoline in x17.
+ *
+ * We use `BR X17` as this can safely land on a `BTI C` or `PACIASP` in
+ * the trampoline, and will not unbalance any return stack.
+ */
+ br x17
+#endif /* CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS */
SYM_CODE_END(ftrace_caller)
+#ifdef CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS
+SYM_CODE_START(ftrace_stub_direct_tramp)
+ bti c
+ mov x10, x30
+ mov x30, x9
+ ret x10
+SYM_CODE_END(ftrace_stub_direct_tramp)
+#endif /* CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS */
+
#else /* CONFIG_DYNAMIC_FTRACE_WITH_ARGS */
/*
@@ -206,6 +206,13 @@ static struct plt_entry *get_ftrace_plt(struct module *mod, unsigned long addr)
return NULL;
}
+static bool reachable_by_bl(unsigned long addr, unsigned long pc)
+{
+ long offset = (long)addr - (long)pc;
+
+ return offset >= -SZ_128M && offset < SZ_128M;
+}
+
/*
* Find the address the callsite must branch to in order to reach '*addr'.
*
@@ -220,14 +227,21 @@ static bool ftrace_find_callable_addr(struct dyn_ftrace *rec,
unsigned long *addr)
{
unsigned long pc = rec->ip;
- long offset = (long)*addr - (long)pc;
struct plt_entry *plt;
+ /*
+ * If a custom trampoline is unreachable, rely on the ftrace_caller
+ * trampoline which knows how to indirectly reach that trampoline
+ * through ops->direct_call.
+ */
+ if (*addr != FTRACE_ADDR && !reachable_by_bl(*addr, pc))
+ *addr = FTRACE_ADDR;
+
/*
* 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)
+ if (reachable_by_bl(*addr, pc))
return true;
/*
@@ -330,12 +344,24 @@ int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr,
unsigned long addr)
{
- if (WARN_ON_ONCE(old_addr != (unsigned long)ftrace_caller))
+ unsigned long pc = rec->ip;
+ u32 old, new;
+ int ret;
+
+ ret = ftrace_rec_set_ops(rec, arm64_rec_get_ops(rec));
+ if (ret)
+ return ret;
+
+ if (!ftrace_find_callable_addr(rec, NULL, &old_addr))
return -EINVAL;
- if (WARN_ON_ONCE(addr != (unsigned long)ftrace_caller))
+ if (!ftrace_find_callable_addr(rec, NULL, &addr))
return -EINVAL;
- return ftrace_rec_update_ops(rec);
+ 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);
+
+ return ftrace_modify_code(pc, old, new, true);
}
#endif