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_modify_call() to patch-in the
> updated branch instruction without worrying about the instructions
> surrounding the ftrace location. Note that we continue to ensure we
> have the expected branch instruction at the ftrace location before
> patching it with the updated branch destination.
>
> Signed-off-by: Naveen N Rao <nav...@kernel.org>
Reviewed-by: Christophe Leroy <christophe.le...@csgroup.eu>
> ---
> arch/powerpc/kernel/trace/ftrace.c | 161 ++++-------------------------
> 1 file changed, 21 insertions(+), 140 deletions(-)
>
> diff --git a/arch/powerpc/kernel/trace/ftrace.c
> b/arch/powerpc/kernel/trace/ftrace.c
> index 6ea8b90246a540..c37e22c6c26521 100644
> --- a/arch/powerpc/kernel/trace/ftrace.c
> +++ b/arch/powerpc/kernel/trace/ftrace.c
> @@ -89,33 +89,11 @@ static inline int ftrace_modify_code(unsigned long ip,
> ppc_inst_t old, ppc_inst_
> return ret;
> }
>
> -/*
> - * Helper functions that are the same for both PPC64 and PPC32.
> - */
> -static int test_24bit_addr(unsigned long ip, unsigned long addr)
> -{
> - addr = ppc_function_entry((void *)addr);
> -
> - return is_offset_in_branch_range(addr - ip);
> -}
> -
> static int is_bl_op(ppc_inst_t op)
> {
> return (ppc_inst_val(op) & ~PPC_LI_MASK) == PPC_RAW_BL(0);
> }
>
> -static unsigned long find_bl_target(unsigned long ip, ppc_inst_t op)
> -{
> - int offset;
> -
> - offset = PPC_LI(ppc_inst_val(op));
> - /* make it signed */
> - if (offset & 0x02000000)
> - offset |= 0xfe000000;
> -
> - return ip + (long)offset;
> -}
> -
> static unsigned long find_ftrace_tramp(unsigned long ip)
> {
> int i;
> @@ -130,115 +108,16 @@ static unsigned long find_ftrace_tramp(unsigned long
> ip)
> }
>
> #ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
> -#ifdef CONFIG_MODULES
> -static int
> -__ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr,
> - unsigned long addr)
> +int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr,
> unsigned long addr)
> {
> - ppc_inst_t op;
> - unsigned long ip = rec->ip;
> - unsigned long entry, ptr, tramp;
> - struct module *mod = rec->arch.mod;
> -
> - /* If we never set up ftrace trampolines, then bail */
> - if (!mod->arch.tramp || !mod->arch.tramp_regs) {
> - pr_err("No ftrace trampoline\n");
> - return -EINVAL;
> - }
> -
> - /* 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);
> - entry = ppc_global_function_entry((void *)old_addr);
> -
> - pr_devel("ip:%lx jumps to %lx", ip, tramp);
> -
> - if (tramp != entry) {
> - /* old_addr is not within range, so we must have used a
> trampoline */
> - if (module_trampoline_target(mod, tramp, &ptr)) {
> - pr_err("Failed to get trampoline target\n");
> - return -EFAULT;
> - }
> -
> - pr_devel("trampoline target %lx", ptr);
> -
> - /* This should match what was called */
> - if (ptr != entry) {
> - pr_err("addr %lx does not match expected %lx\n", ptr,
> entry);
> - return -EINVAL;
> - }
> - }
> -
> - /* The new target may be within range */
> - if (test_24bit_addr(ip, addr)) {
> - /* within range */
> - if (patch_branch((u32 *)ip, addr, BRANCH_SET_LINK)) {
> - pr_err("REL24 out of range!\n");
> - return -EINVAL;
> - }
> -
> - return 0;
> - }
> -
> - if (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((u32 *)ip, tramp, BRANCH_SET_LINK)) {
> - pr_err("REL24 out of range!\n");
> - return -EINVAL;
> - }
> -
> - return 0;
> -}
> -#else
> -static int __ftrace_modify_call(struct dyn_ftrace *rec, unsigned long
> old_addr, unsigned long addr)
> -{
> - return 0;
> -}
> -#endif
> -
> -int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr,
> - unsigned long addr)
> -{
> - unsigned long ip = rec->ip;
> + unsigned long tramp, tramp_old, ip = rec->ip;
> ppc_inst_t old, new;
> + struct module *mod;
>
> - /*
> - * 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) && test_24bit_addr(ip, old_addr)) {
> - /* within range */
> - old = ftrace_call_replace(ip, old_addr, 1);
> - new = ftrace_call_replace(ip, addr, 1);
> + 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)) {
> /*
> @@ -246,20 +125,22 @@ int ftrace_modify_call(struct dyn_ftrace *rec, unsigned
> long old_addr,
> * variant, so there is nothing to do here
> */
> return 0;
> - } else if (!IS_ENABLED(CONFIG_MODULES)) {
> - /* We should not get here without modules */
> - return -EINVAL;
> + } 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);
> }
>
> - /*
> - * Out of range jumps are called from modules.
> - */
> - if (!rec->arch.mod) {
> - pr_err("No module loaded\n");
> - return -EINVAL;
> - }
> -
> - return __ftrace_modify_call(rec, old_addr, addr);
> + return -EINVAL;
> }
> #endif
>
