[RFC PATCH 11/15] powerpc/ftrace: Simplify ftrace_make_call()
Naveen N Rao
naveen at kernel.org
Thu Jun 8 02:55:26 AEST 2023
Now that we validate the ftrace location during initialization in
ftrace_init_nop(), we can simplify ftrace_make_call() to replace the nop
without worrying about the instructions surrounding the ftrace location.
Note that we continue to ensure that we have a nop at the ftrace
location before patching it.
Signed-off-by: Naveen N Rao <naveen at kernel.org>
---
arch/powerpc/kernel/trace/ftrace.c | 187 +++++------------------------
1 file changed, 31 insertions(+), 156 deletions(-)
diff --git a/arch/powerpc/kernel/trace/ftrace.c b/arch/powerpc/kernel/trace/ftrace.c
index 67773cd14da71a..8d5d91b8ae85a0 100644
--- a/arch/powerpc/kernel/trace/ftrace.c
+++ b/arch/powerpc/kernel/trace/ftrace.c
@@ -129,162 +129,6 @@ static unsigned long find_ftrace_tramp(unsigned long ip)
return 0;
}
-#ifdef CONFIG_MODULES
-/*
- * Examine the existing instructions for __ftrace_make_call.
- * They should effectively be a NOP, and follow formal constraints,
- * depending on the ABI. Return false if they don't.
- */
-static bool expected_nop_sequence(void *ip, ppc_inst_t op0, ppc_inst_t op1)
-{
- if (IS_ENABLED(CONFIG_DYNAMIC_FTRACE_WITH_REGS))
- return ppc_inst_equal(op0, ppc_inst(PPC_RAW_NOP()));
- else
- return ppc_inst_equal(op0, ppc_inst(PPC_RAW_BRANCH(8))) &&
- ppc_inst_equal(op1, ppc_inst(PPC_INST_LD_TOC));
-}
-
-static int
-__ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
-{
- ppc_inst_t op[2];
- void *ip = (void *)rec->ip;
- unsigned long entry, ptr, tramp;
- struct module *mod = rec->arch.mod;
-
- /* read where this goes */
- if (copy_inst_from_kernel_nofault(op, ip))
- return -EFAULT;
-
- if (!IS_ENABLED(CONFIG_DYNAMIC_FTRACE_WITH_REGS) &&
- copy_inst_from_kernel_nofault(op + 1, ip + 4))
- return -EFAULT;
-
- if (!expected_nop_sequence(ip, op[0], op[1])) {
- pr_err("Unexpected call sequence at %p: %08lx %08lx\n", ip,
- ppc_inst_as_ulong(op[0]), ppc_inst_as_ulong(op[1]));
- return -EINVAL;
- }
-
- /* If we never set up ftrace trampoline(s), then bail */
- if (!mod->arch.tramp ||
- (IS_ENABLED(CONFIG_DYNAMIC_FTRACE_WITH_REGS) && !mod->arch.tramp_regs)) {
- pr_err("No ftrace trampoline\n");
- return -EINVAL;
- }
-
- if (IS_ENABLED(CONFIG_DYNAMIC_FTRACE_WITH_REGS) && rec->flags & FTRACE_FL_REGS)
- tramp = mod->arch.tramp_regs;
- else
- tramp = mod->arch.tramp;
-
- if (module_trampoline_target(mod, tramp, &ptr)) {
- pr_err("Failed to get trampoline target\n");
- return -EFAULT;
- }
-
- pr_devel("trampoline target %lx", ptr);
-
- entry = ppc_global_function_entry((void *)addr);
- /* This should match what was called */
- if (ptr != entry) {
- pr_err("addr %lx does not match expected %lx\n", ptr, entry);
- return -EINVAL;
- }
-
- if (patch_branch(ip, tramp, BRANCH_SET_LINK)) {
- pr_err("REL24 out of range!\n");
- return -EINVAL;
- }
-
- return 0;
-}
-#else
-static int __ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
-{
- return 0;
-}
-#endif /* CONFIG_MODULES */
-
-static int __ftrace_make_call_kernel(struct dyn_ftrace *rec, unsigned long addr)
-{
- ppc_inst_t op;
- void *ip = (void *)rec->ip;
- unsigned long tramp, entry, ptr;
-
- /* Make sure we're being asked to patch branch to a known ftrace addr */
- entry = ppc_global_function_entry((void *)ftrace_caller);
- ptr = ppc_global_function_entry((void *)addr);
-
- if (ptr != entry && IS_ENABLED(CONFIG_DYNAMIC_FTRACE_WITH_REGS))
- entry = ppc_global_function_entry((void *)ftrace_regs_caller);
-
- if (ptr != entry) {
- pr_err("Unknown ftrace addr to patch: %ps\n", (void *)ptr);
- return -EINVAL;
- }
-
- /* Make sure we have a nop */
- if (copy_inst_from_kernel_nofault(&op, ip)) {
- pr_err("Unable to read ftrace location %p\n", ip);
- return -EFAULT;
- }
-
- if (!ppc_inst_equal(op, ppc_inst(PPC_RAW_NOP()))) {
- pr_err("Unexpected call sequence at %p: %08lx\n",
- ip, ppc_inst_as_ulong(op));
- return -EINVAL;
- }
-
- tramp = find_ftrace_tramp((unsigned long)ip);
- if (!tramp) {
- pr_err("No ftrace trampolines reachable from %ps\n", ip);
- return -EINVAL;
- }
-
- if (patch_branch(ip, tramp, BRANCH_SET_LINK)) {
- pr_err("Error patching branch to ftrace tramp!\n");
- return -EINVAL;
- }
-
- return 0;
-}
-
-int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
-{
- unsigned long ip = rec->ip;
- ppc_inst_t old, new;
-
- /*
- * If the calling address is more that 24 bits away,
- * then we had to use a trampoline to make the call.
- * Otherwise just update the call site.
- */
- if (test_24bit_addr(ip, addr)) {
- /* within range */
- old = ppc_inst(PPC_RAW_NOP());
- new = ftrace_call_replace(ip, addr, 1);
- return ftrace_modify_code(ip, old, new);
- } else if (core_kernel_text(ip)) {
- return __ftrace_make_call_kernel(rec, addr);
- } else if (!IS_ENABLED(CONFIG_MODULES)) {
- /* We should not get here without modules */
- return -EINVAL;
- }
-
- /*
- * Out of range jumps are called from modules.
- * Being that we are converting from nop, it had better
- * already have a module defined.
- */
- if (!rec->arch.mod) {
- pr_err("No module loaded\n");
- return -EINVAL;
- }
-
- return __ftrace_make_call(rec, addr);
-}
-
#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
#ifdef CONFIG_MODULES
static int
@@ -419,6 +263,37 @@ int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr,
}
#endif
+int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
+{
+ unsigned long tramp, ip = rec->ip;
+ ppc_inst_t old, new;
+ struct module *mod;
+
+ old = ppc_inst(PPC_RAW_NOP());
+ if (is_offset_in_branch_range(addr - ip)) {
+ /* Within range */
+ new = ftrace_create_branch_inst(ip, addr, 1);
+ return ftrace_modify_code(ip, old, new);
+ } else if (core_kernel_text(ip)) {
+ /* We would be branching to one of our ftrace tramps */
+ tramp = find_ftrace_tramp(ip);
+ if (!tramp) {
+ pr_err("0x%lx: No ftrace trampolines reachable\n", ip);
+ return -EINVAL;
+ }
+ new = ftrace_create_branch_inst(ip, tramp, 1);
+ return ftrace_modify_code(ip, old, new);
+ } else if (IS_ENABLED(CONFIG_MODULES)) {
+ /* Module code would be going to one of the module stubs */
+ mod = rec->arch.mod;
+ tramp = (addr == (unsigned long)ftrace_caller ? mod->arch.tramp : mod->arch.tramp_regs);
+ new = ftrace_create_branch_inst(ip, tramp, 1);
+ return ftrace_modify_code(ip, old, new);
+ }
+
+ return -EINVAL;
+}
+
int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec, unsigned long addr)
{
unsigned long tramp, ip = rec->ip;
--
2.40.1
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