[PATCH 15/17] powerpc/ftrace: Implement ftrace_replace_code()
Christophe Leroy
christophe.leroy at csgroup.eu
Fri Jun 23 15:32:50 AEST 2023
Le 19/06/2023 à 11:47, Naveen N Rao a écrit :
> Implement ftrace_replace_code() to consolidate logic from the different
> ftrace patching routines: ftrace_make_nop(), ftrace_make_call() and
> ftrace_modify_call(). Note that ftrace_make_call() is still required
> primarily to handle patching modules during their load time. The other
> two routines should no longer be called.
>
> This lays the groundwork to enable better control in patching ftrace
> locations, including the ability to nop-out preceding profiling
> instructions when ftrace is disabled.
>
> Signed-off-by: Naveen N Rao <naveen at kernel.org>
Reviewed-by: Christophe Leroy <christophe.leroy at csgroup.eu>
> ---
> arch/powerpc/kernel/trace/ftrace.c | 173 ++++++++++++++++-------------
> 1 file changed, 96 insertions(+), 77 deletions(-)
>
> diff --git a/arch/powerpc/kernel/trace/ftrace.c b/arch/powerpc/kernel/trace/ftrace.c
> index 422dd760fbe013..cf9dce77527920 100644
> --- a/arch/powerpc/kernel/trace/ftrace.c
> +++ b/arch/powerpc/kernel/trace/ftrace.c
> @@ -94,104 +94,123 @@ static unsigned long find_ftrace_tramp(unsigned long ip)
> return 0;
> }
>
> +static int ftrace_get_call_inst(struct dyn_ftrace *rec, unsigned long addr, ppc_inst_t *call_inst)
> +{
> + unsigned long ip = rec->ip;
> + unsigned long stub;
> +
> + if (is_offset_in_branch_range(addr - ip)) {
> + /* Within range */
> + stub = addr;
> +#ifdef CONFIG_MODULES
> + } else if (rec->arch.mod) {
> + /* Module code would be going to one of the module stubs */
> + stub = (addr == (unsigned long)ftrace_caller ? rec->arch.mod->arch.tramp :
> + rec->arch.mod->arch.tramp_regs);
> +#endif
> + } else if (core_kernel_text(ip)) {
> + /* We would be branching to one of our ftrace stubs */
> + stub = find_ftrace_tramp(ip);
> + if (!stub) {
> + pr_err("0x%lx: No ftrace stubs reachable\n", ip);
> + return -EINVAL;
> + }
> + } else {
> + return -EINVAL;
> + }
> +
> + *call_inst = ftrace_create_branch_inst(ip, stub, 1);
> + return 0;
> +}
> +
> #ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
> int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr, unsigned long addr)
> {
> - unsigned long tramp, tramp_old, ip = rec->ip;
> - ppc_inst_t old, new;
> - struct module *mod;
> -
> - if (is_offset_in_branch_range(old_addr - ip) && is_offset_in_branch_range(addr - ip)) {
> - /* Within range */
> - old = ftrace_create_branch_inst(ip, old_addr, 1);
> - new = ftrace_create_branch_inst(ip, addr, 1);
> - return ftrace_modify_code(ip, old, new);
> - } else if (core_kernel_text(ip)) {
> - /*
> - * We always patch out of range locations to go to the regs
> - * variant, so there is nothing to do here
> - */
> - return 0;
> - } else if (IS_ENABLED(CONFIG_MODULES)) {
> - /* Module code would be going to one of the module stubs */
> - mod = rec->arch.mod;
> - if (addr == (unsigned long)ftrace_caller) {
> - tramp_old = mod->arch.tramp_regs;
> - tramp = mod->arch.tramp;
> - } else {
> - tramp_old = mod->arch.tramp;
> - tramp = mod->arch.tramp_regs;
> - }
> - old = ftrace_create_branch_inst(ip, tramp_old, 1);
> - new = ftrace_create_branch_inst(ip, tramp, 1);
> - return ftrace_modify_code(ip, old, new);
> - }
> -
> + /* This should never be called since we override ftrace_replace_code() */
> + WARN_ON(1);
> return -EINVAL;
> }
> #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;
> + int ret;
> +
> + /* This can only ever be called during module load */
> + if (WARN_ON(!IS_ENABLED(CONFIG_MODULES) || core_kernel_text(rec->ip)))
> + return -EINVAL;
>
> 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);
> - }
> + ret = ftrace_get_call_inst(rec, addr, &new);
> + if (ret)
> + return ret;
>
> - return -EINVAL;
> + return ftrace_modify_code(rec->ip, old, new);
> }
>
> 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;
> + /*
> + * This should never be called since we override ftrace_replace_code(),
> + * as well as ftrace_init_nop()
> + */
> + WARN_ON(1);
> + return -EINVAL;
> +}
>
> - /* 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;
> +void ftrace_replace_code(int enable)
> +{
> + ppc_inst_t old, new, call_inst, new_call_inst;
> + ppc_inst_t nop_inst = ppc_inst(PPC_RAW_NOP());
> + unsigned long ip, new_addr, addr;
> + struct ftrace_rec_iter *iter;
> + struct dyn_ftrace *rec;
> + int ret = 0, update;
> +
> + for_ftrace_rec_iter(iter) {
> + rec = ftrace_rec_iter_record(iter);
> + ip = rec->ip;
> +
> + if (rec->flags & FTRACE_FL_DISABLED && !(rec->flags & FTRACE_FL_ENABLED))
> + continue;
> +
> + addr = ftrace_get_addr_curr(rec);
> + new_addr = ftrace_get_addr_new(rec);
> + update = ftrace_update_record(rec, enable);
> +
> + switch (update) {
> + case FTRACE_UPDATE_IGNORE:
> + default:
> + continue;
> + case FTRACE_UPDATE_MODIFY_CALL:
> + ret = ftrace_get_call_inst(rec, new_addr, &new_call_inst);
> + ret |= ftrace_get_call_inst(rec, addr, &call_inst);
> + old = call_inst;
> + new = new_call_inst;
> + break;
> + case FTRACE_UPDATE_MAKE_NOP:
> + ret = ftrace_get_call_inst(rec, addr, &call_inst);
> + old = call_inst;
> + new = nop_inst;
> + break;
> + case FTRACE_UPDATE_MAKE_CALL:
> + ret = ftrace_get_call_inst(rec, new_addr, &call_inst);
> + old = nop_inst;
> + new = call_inst;
> + break;
> }
> - 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);
> +
> + if (!ret)
> + ret = ftrace_modify_code(ip, old, new);
> + if (ret)
> + goto out;
> }
>
> - return -EINVAL;
> +out:
> + if (ret)
> + ftrace_bug(ret, rec);
> + return;
> }
>
> int ftrace_init_nop(struct module *mod, struct dyn_ftrace *rec)
More information about the Linuxppc-dev
mailing list