powerpc/ftrace: Simplify ftrace_make_call()
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@kernel.org> Reviewed-by: Christophe Leroy <christophe.leroy@csgroup.eu> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://msgid.link/2d28866d2f556488a663981abe5621511efb207b.1687166935.git.naveen@kernel.org
This commit is contained in:
Naveen N Rao
Michael Ellerman
parent
562bde0bfc
commit
9365e23b15
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@ -129,162 +129,6 @@ static unsigned long find_ftrace_tramp(unsigned long ip)
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return 0;
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}
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#ifdef CONFIG_MODULES
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/*
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* Examine the existing instructions for __ftrace_make_call.
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* They should effectively be a NOP, and follow formal constraints,
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* depending on the ABI. Return false if they don't.
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*/
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static bool expected_nop_sequence(void *ip, ppc_inst_t op0, ppc_inst_t op1)
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{
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if (IS_ENABLED(CONFIG_DYNAMIC_FTRACE_WITH_REGS))
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return ppc_inst_equal(op0, ppc_inst(PPC_RAW_NOP()));
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else
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return ppc_inst_equal(op0, ppc_inst(PPC_RAW_BRANCH(8))) &&
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ppc_inst_equal(op1, ppc_inst(PPC_INST_LD_TOC));
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}
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static int
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__ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
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{
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ppc_inst_t op[2];
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void *ip = (void *)rec->ip;
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unsigned long entry, ptr, tramp;
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struct module *mod = rec->arch.mod;
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/* read where this goes */
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if (copy_inst_from_kernel_nofault(op, ip))
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return -EFAULT;
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if (!IS_ENABLED(CONFIG_DYNAMIC_FTRACE_WITH_REGS) &&
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copy_inst_from_kernel_nofault(op + 1, ip + 4))
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return -EFAULT;
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if (!expected_nop_sequence(ip, op[0], op[1])) {
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pr_err("Unexpected call sequence at %p: %08lx %08lx\n", ip,
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ppc_inst_as_ulong(op[0]), ppc_inst_as_ulong(op[1]));
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return -EINVAL;
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}
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/* If we never set up ftrace trampoline(s), then bail */
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if (!mod->arch.tramp ||
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(IS_ENABLED(CONFIG_DYNAMIC_FTRACE_WITH_REGS) && !mod->arch.tramp_regs)) {
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pr_err("No ftrace trampoline\n");
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return -EINVAL;
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}
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if (IS_ENABLED(CONFIG_DYNAMIC_FTRACE_WITH_REGS) && rec->flags & FTRACE_FL_REGS)
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tramp = mod->arch.tramp_regs;
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else
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tramp = mod->arch.tramp;
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if (module_trampoline_target(mod, tramp, &ptr)) {
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pr_err("Failed to get trampoline target\n");
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return -EFAULT;
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}
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pr_devel("trampoline target %lx", ptr);
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entry = ppc_global_function_entry((void *)addr);
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/* This should match what was called */
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if (ptr != entry) {
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pr_err("addr %lx does not match expected %lx\n", ptr, entry);
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return -EINVAL;
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}
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if (patch_branch(ip, tramp, BRANCH_SET_LINK)) {
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pr_err("REL24 out of range!\n");
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return -EINVAL;
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}
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return 0;
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}
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#else
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static int __ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
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{
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return 0;
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}
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#endif /* CONFIG_MODULES */
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static int __ftrace_make_call_kernel(struct dyn_ftrace *rec, unsigned long addr)
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{
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ppc_inst_t op;
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void *ip = (void *)rec->ip;
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unsigned long tramp, entry, ptr;
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/* Make sure we're being asked to patch branch to a known ftrace addr */
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entry = ppc_global_function_entry((void *)ftrace_caller);
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ptr = ppc_global_function_entry((void *)addr);
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if (ptr != entry && IS_ENABLED(CONFIG_DYNAMIC_FTRACE_WITH_REGS))
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entry = ppc_global_function_entry((void *)ftrace_regs_caller);
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if (ptr != entry) {
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pr_err("Unknown ftrace addr to patch: %ps\n", (void *)ptr);
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return -EINVAL;
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}
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/* Make sure we have a nop */
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if (copy_inst_from_kernel_nofault(&op, ip)) {
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pr_err("Unable to read ftrace location %p\n", ip);
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return -EFAULT;
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}
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if (!ppc_inst_equal(op, ppc_inst(PPC_RAW_NOP()))) {
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pr_err("Unexpected call sequence at %p: %08lx\n",
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ip, ppc_inst_as_ulong(op));
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return -EINVAL;
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}
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tramp = find_ftrace_tramp((unsigned long)ip);
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if (!tramp) {
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pr_err("No ftrace trampolines reachable from %ps\n", ip);
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return -EINVAL;
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}
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if (patch_branch(ip, tramp, BRANCH_SET_LINK)) {
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pr_err("Error patching branch to ftrace tramp!\n");
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return -EINVAL;
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}
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return 0;
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}
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int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
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{
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unsigned long ip = rec->ip;
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ppc_inst_t old, new;
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/*
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* If the calling address is more that 24 bits away,
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* then we had to use a trampoline to make the call.
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* Otherwise just update the call site.
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*/
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if (test_24bit_addr(ip, addr)) {
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/* within range */
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old = ppc_inst(PPC_RAW_NOP());
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new = ftrace_call_replace(ip, addr, 1);
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return ftrace_modify_code(ip, old, new);
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} else if (core_kernel_text(ip)) {
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return __ftrace_make_call_kernel(rec, addr);
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} else if (!IS_ENABLED(CONFIG_MODULES)) {
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/* We should not get here without modules */
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return -EINVAL;
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}
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/*
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* Out of range jumps are called from modules.
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* Being that we are converting from nop, it had better
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* already have a module defined.
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*/
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if (!rec->arch.mod) {
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pr_err("No module loaded\n");
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return -EINVAL;
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}
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return __ftrace_make_call(rec, addr);
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}
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#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
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#ifdef CONFIG_MODULES
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static int
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@ -419,6 +263,37 @@ int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr,
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}
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#endif
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int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
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{
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unsigned long tramp, ip = rec->ip;
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ppc_inst_t old, new;
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struct module *mod;
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old = ppc_inst(PPC_RAW_NOP());
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if (is_offset_in_branch_range(addr - ip)) {
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/* Within range */
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new = ftrace_create_branch_inst(ip, addr, 1);
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return ftrace_modify_code(ip, old, new);
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} else if (core_kernel_text(ip)) {
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/* We would be branching to one of our ftrace tramps */
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tramp = find_ftrace_tramp(ip);
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if (!tramp) {
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pr_err("0x%lx: No ftrace trampolines reachable\n", ip);
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return -EINVAL;
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}
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new = ftrace_create_branch_inst(ip, tramp, 1);
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return ftrace_modify_code(ip, old, new);
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} else if (IS_ENABLED(CONFIG_MODULES)) {
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/* Module code would be going to one of the module stubs */
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mod = rec->arch.mod;
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tramp = (addr == (unsigned long)ftrace_caller ? mod->arch.tramp : mod->arch.tramp_regs);
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new = ftrace_create_branch_inst(ip, tramp, 1);
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return ftrace_modify_code(ip, old, new);
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}
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return -EINVAL;
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}
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int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec, unsigned long addr)
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{
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unsigned long tramp, ip = rec->ip;
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