From 562bde0bfc968d212d10ba6bf921a0774feebbac Mon Sep 17 00:00:00 2001 From: Naveen N Rao Date: Mon, 19 Jun 2023 15:17:29 +0530 Subject: powerpc/ftrace: Simplify ftrace_make_nop() Now that we validate the ftrace location during initialization in ftrace_init_nop(), we can simplify ftrace_make_nop() to patch-in the nop without worrying about the instructions surrounding the ftrace location. Note that we continue to ensure that we have a bl to ftrace_[regs_]caller at the ftrace location before nop-ing it out. Signed-off-by: Naveen N Rao Reviewed-by: Christophe Leroy Signed-off-by: Michael Ellerman Link: https://msgid.link/e12ccbf28c50c3a07fb614f4d392e55f7098a729.1687166935.git.naveen@kernel.org --- arch/powerpc/kernel/trace/ftrace.c | 220 ++++++------------------------------- 1 file changed, 32 insertions(+), 188 deletions(-) (limited to 'arch/powerpc') diff --git a/arch/powerpc/kernel/trace/ftrace.c b/arch/powerpc/kernel/trace/ftrace.c index 98bd099c428e..05153a1038fd 100644 --- a/arch/powerpc/kernel/trace/ftrace.c +++ b/arch/powerpc/kernel/trace/ftrace.c @@ -116,112 +116,6 @@ static unsigned long find_bl_target(unsigned long ip, ppc_inst_t op) return ip + (long)offset; } -#ifdef CONFIG_MODULES -static int -__ftrace_make_nop(struct module *mod, - struct dyn_ftrace *rec, unsigned long addr) -{ - unsigned long entry, ptr, tramp; - unsigned long ip = rec->ip; - ppc_inst_t op, pop; - - /* read where this goes */ - if (copy_inst_from_kernel_nofault(&op, (void *)ip)) { - pr_err("Fetching opcode failed.\n"); - return -EFAULT; - } - - /* Make sure that this is still a 24bit jump */ - if (!is_bl_op(op)) { - pr_err("Not expected bl: opcode is %08lx\n", ppc_inst_as_ulong(op)); - return -EINVAL; - } - - /* lets find where the pointer goes */ - tramp = find_bl_target(ip, op); - - pr_devel("ip:%lx jumps to %lx", ip, 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 (IS_ENABLED(CONFIG_MPROFILE_KERNEL)) { - if (copy_inst_from_kernel_nofault(&op, (void *)(ip - 4))) { - pr_err("Fetching instruction at %lx failed.\n", ip - 4); - return -EFAULT; - } - - /* We expect either a mflr r0, or a std r0, LRSAVE(r1) */ - if (!ppc_inst_equal(op, ppc_inst(PPC_RAW_MFLR(_R0))) && - !ppc_inst_equal(op, ppc_inst(PPC_INST_STD_LR))) { - pr_err("Unexpected instruction %08lx around bl _mcount\n", - ppc_inst_as_ulong(op)); - return -EINVAL; - } - } else if (IS_ENABLED(CONFIG_PPC64)) { - /* - * Check what is in the next instruction. We can see ld r2,40(r1), but - * on first pass after boot we will see mflr r0. - */ - if (copy_inst_from_kernel_nofault(&op, (void *)(ip + 4))) { - pr_err("Fetching op failed.\n"); - return -EFAULT; - } - - if (!ppc_inst_equal(op, ppc_inst(PPC_INST_LD_TOC))) { - pr_err("Expected %08lx found %08lx\n", PPC_INST_LD_TOC, - ppc_inst_as_ulong(op)); - return -EINVAL; - } - } - - /* - * When using -mprofile-kernel or PPC32 there is no load to jump over. - * - * Otherwise our original call site looks like: - * - * bl - * ld r2,XX(r1) - * - * Milton Miller pointed out that we can not simply nop the branch. - * If a task was preempted when calling a trace function, the nops - * will remove the way to restore the TOC in r2 and the r2 TOC will - * get corrupted. - * - * Use a b +8 to jump over the load. - * XXX: could make PCREL depend on MPROFILE_KERNEL - * XXX: check PCREL && MPROFILE_KERNEL calling sequence - */ - if (IS_ENABLED(CONFIG_MPROFILE_KERNEL) || IS_ENABLED(CONFIG_PPC32)) - pop = ppc_inst(PPC_RAW_NOP()); - else - pop = ppc_inst(PPC_RAW_BRANCH(8)); /* b +8 */ - - if (patch_instruction((u32 *)ip, pop)) { - pr_err("Patching NOP failed.\n"); - return -EPERM; - } - - return 0; -} -#else -static int __ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec, unsigned long addr) -{ - return 0; -} -#endif /* CONFIG_MODULES */ - static unsigned long find_ftrace_tramp(unsigned long ip) { int i; @@ -235,88 +129,6 @@ static unsigned long find_ftrace_tramp(unsigned long ip) return 0; } -static int __ftrace_make_nop_kernel(struct dyn_ftrace *rec, unsigned long addr) -{ - unsigned long tramp, ip = rec->ip; - ppc_inst_t op; - - /* Read where this goes */ - if (copy_inst_from_kernel_nofault(&op, (void *)ip)) { - pr_err("Fetching opcode failed.\n"); - return -EFAULT; - } - - /* Make sure that this is still a 24bit jump */ - if (!is_bl_op(op)) { - pr_err("Not expected bl: opcode is %08lx\n", ppc_inst_as_ulong(op)); - return -EINVAL; - } - - /* Let's find where the pointer goes */ - tramp = find_bl_target(ip, op); - - pr_devel("ip:%lx jumps to %lx", ip, tramp); - - /* Are ftrace trampolines reachable? */ - if (!find_ftrace_tramp(ip)) { - pr_err("No ftrace trampolines reachable from %ps\n", (void *)ip); - return -EINVAL; - } - - if (patch_instruction((u32 *)ip, ppc_inst(PPC_RAW_NOP()))) { - pr_err("Patching NOP failed.\n"); - return -EPERM; - } - - return 0; -} - -int ftrace_make_nop(struct module *mod, - 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 = ftrace_call_replace(ip, addr, 1); - new = ppc_inst(PPC_RAW_NOP()); - return ftrace_modify_code(ip, old, new); - } else if (core_kernel_text(ip)) { - return __ftrace_make_nop_kernel(rec, addr); - } else if (!IS_ENABLED(CONFIG_MODULES)) { - return -EINVAL; - } - - /* - * Out of range jumps are called from modules. - * We should either already have a pointer to the module - * or it has been passed in. - */ - if (!rec->arch.mod) { - if (!mod) { - pr_err("No module loaded addr=%lx\n", addr); - return -EFAULT; - } - rec->arch.mod = mod; - } else if (mod) { - if (mod != rec->arch.mod) { - pr_err("Record mod %p not equal to passed in mod %p\n", - rec->arch.mod, mod); - return -EINVAL; - } - /* nothing to do if mod == rec->arch.mod */ - } else - mod = rec->arch.mod; - - return __ftrace_make_nop(mod, rec, addr); -} - #ifdef CONFIG_MODULES /* * Examine the existing instructions for __ftrace_make_call. @@ -607,6 +419,38 @@ int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr, } #endif +int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec, unsigned long addr) +{ + unsigned long tramp, ip = rec->ip; + ppc_inst_t old, new; + + /* Nop-out the ftrace location */ + new = ppc_inst(PPC_RAW_NOP()); + if (is_offset_in_branch_range(addr - ip)) { + /* Within range */ + old = 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; + } + old = 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 */ + if (!mod) + mod = rec->arch.mod; + tramp = (addr == (unsigned long)ftrace_caller ? mod->arch.tramp : mod->arch.tramp_regs); + old = ftrace_create_branch_inst(ip, tramp, 1); + return ftrace_modify_code(ip, old, new); + } + + return -EINVAL; +} + int ftrace_init_nop(struct module *mod, struct dyn_ftrace *rec) { unsigned long addr, ip = rec->ip; -- cgit v1.2.3