Le 19/06/2023 à 11:47, Naveen N Rao a écrit : > 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 <nav...@kernel.org>
Reviewed-by: Christophe Leroy <christophe.le...@csgroup.eu> > --- > arch/powerpc/kernel/trace/ftrace.c | 220 +++++------------------------ > 1 file changed, 32 insertions(+), 188 deletions(-) > > diff --git a/arch/powerpc/kernel/trace/ftrace.c > b/arch/powerpc/kernel/trace/ftrace.c > index 98bd099c428ee0..05153a1038fdff 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 <tramp> > - * 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;