From 4617721c502b2ddaa4e324e86da4997edf738fa5 Mon Sep 17 00:00:00 2001 From: Steven Rostedt Date: Wed, 2 Sep 2026 09:55:01 -0400 Subject: ftrace: Synchronize the initialization of ftrace_ops There's some internal state that ftrace_ops needs to have set, but since it can be declared outside of the ftrace.c code, it calls ftrace_ops_init() on the ops in every global function. The issue is that if two tasks call it on the same ops at the same time it is possible to have the initialization of one corrupt the initialization of the other call. Create a ops_mutex to use to synchronize every initialization of the ftrace_ops. The mutex is taken within checking the ftrace_ops flag that states it was initializied but the flag is checked again after the mutex has been taken. Checking first outside the mutex allows it to shortcut having to take the mutex. But then the check needs to be done again after the mute is taken in case of races. Cc: stable@vger.kernel.org Link: https://patch.msgid.link/20260902095501.6b59af20@gandalf.local.home Fixes: f04f24fb7e48d ("ftrace, kprobes: Fix a deadlock on ftrace_regex_lock") Reported-by: sashiko-bot@kernel.org Close: https://lore.kernel.org/all/20260829025528.49A831F000E9@smtp.kernel.org/ Signed-off-by: Steven Rostedt --- tools/objtool/special.c | 169 ++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 169 insertions(+) create mode 100644 tools/objtool/special.c (limited to 'tools/objtool/special.c') diff --git a/tools/objtool/special.c b/tools/objtool/special.c new file mode 100644 index 000000000..2a533afbc --- /dev/null +++ b/tools/objtool/special.c @@ -0,0 +1,169 @@ +// SPDX-License-Identifier: GPL-2.0-or-later +/* + * Copyright (C) 2015 Josh Poimboeuf + */ + +/* + * This file reads all the special sections which have alternate instructions + * which can be patched in or redirected to at runtime. + */ + +#include +#include + +#include +#include +#include +#include + +struct special_entry { + const char *sec; + bool group, jump_or_nop; + unsigned char size, orig, new; + unsigned char orig_len, new_len; /* group only */ + unsigned char feature; /* ALTERNATIVE macro CPU feature */ + unsigned char key; /* jump_label key */ +}; + +static const struct special_entry entries[] = { + { + .sec = ".altinstructions", + .group = true, + .size = ALT_ENTRY_SIZE, + .orig = ALT_ORIG_OFFSET, + .orig_len = ALT_ORIG_LEN_OFFSET, + .new = ALT_NEW_OFFSET, + .new_len = ALT_NEW_LEN_OFFSET, + .feature = ALT_FEATURE_OFFSET, + }, + { + .sec = "__jump_table", + .jump_or_nop = true, + .size = JUMP_ENTRY_SIZE, + .orig = JUMP_ORIG_OFFSET, + .new = JUMP_NEW_OFFSET, + .key = JUMP_KEY_OFFSET, + }, + { + .sec = "__ex_table", + .size = EX_ENTRY_SIZE, + .orig = EX_ORIG_OFFSET, + .new = EX_NEW_OFFSET, + }, + {}, +}; + +void __weak arch_handle_alternative(struct special_alt *alt) +{ +} + +static void reloc_to_sec_off(struct reloc *reloc, struct section **sec, + unsigned long *off) +{ + *sec = reloc->sym->sec; + *off = reloc->sym->offset + reloc_addend(reloc); +} + +static int get_alt_entry(struct elf *elf, const struct special_entry *entry, + struct section *sec, int idx, + struct special_alt *alt) +{ + struct reloc *orig_reloc, *new_reloc; + unsigned long offset; + + offset = idx * entry->size; + + alt->group = entry->group; + alt->jump_or_nop = entry->jump_or_nop; + + if (alt->group) { + alt->orig_len = *(unsigned char *)(sec->data->d_buf + offset + + entry->orig_len); + alt->new_len = *(unsigned char *)(sec->data->d_buf + offset + + entry->new_len); + alt->feature = *(unsigned int *)(sec->data->d_buf + offset + + entry->feature); + } + + orig_reloc = find_reloc_by_dest(elf, sec, offset + entry->orig); + if (!orig_reloc) { + ERROR_FUNC(sec, offset + entry->orig, "can't find orig reloc"); + return -1; + } + + reloc_to_sec_off(orig_reloc, &alt->orig_sec, &alt->orig_off); + + arch_handle_alternative(alt); + + if (!entry->group || alt->new_len) { + new_reloc = find_reloc_by_dest(elf, sec, offset + entry->new); + if (!new_reloc) { + ERROR_FUNC(sec, offset + entry->new, "can't find new reloc"); + return -1; + } + + reloc_to_sec_off(new_reloc, &alt->new_sec, &alt->new_off); + + /* _ASM_EXTABLE_EX hack */ + if (alt->new_off >= 0x7ffffff0) + alt->new_off -= 0x7ffffff0; + } + + if (entry->key) { + struct reloc *key_reloc; + + key_reloc = find_reloc_by_dest(elf, sec, offset + entry->key); + if (!key_reloc) { + ERROR_FUNC(sec, offset + entry->key, "can't find key reloc"); + return -1; + } + alt->key_addend = reloc_addend(key_reloc); + } + + return 0; +} + +/* + * Read all the special sections and create a list of special_alt structs which + * describe all the alternate instructions which can be patched in or + * redirected to at runtime. + */ +int special_get_alts(struct elf *elf, struct list_head *alts) +{ + const struct special_entry *entry; + struct section *sec; + unsigned int nr_entries; + struct special_alt *alt; + int idx; + + INIT_LIST_HEAD(alts); + + for (entry = entries; entry->sec; entry++) { + sec = find_section_by_name(elf, entry->sec); + if (!sec) + continue; + + if (sec_size(sec) % entry->size != 0) { + ERROR("%s size not a multiple of %d", sec->name, entry->size); + return -1; + } + + nr_entries = sec_size(sec) / entry->size; + + for (idx = 0; idx < nr_entries; idx++) { + alt = malloc(sizeof(*alt)); + if (!alt) { + ERROR_GLIBC("malloc failed"); + return -1; + } + memset(alt, 0, sizeof(*alt)); + + if (get_alt_entry(elf, entry, sec, idx, alt)) + return -1; + + list_add_tail(&alt->list, alts); + } + } + + return 0; +} -- cgit v1.3.1