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bd98c81346
This fixes objtool for both a GCC issue and a Clang issue:
1) GCC issue:
kernel/bpf/core.o: warning: objtool: ___bpf_prog_run()+0x8d5: sibling call from callable instruction with modified stack frame
With CONFIG_RETPOLINE=n, GCC is doing the following optimization in
___bpf_prog_run().
Before:
select_insn:
jmp *jumptable(,%rax,8)
...
ALU64_ADD_X:
...
jmp select_insn
ALU_ADD_X:
...
jmp select_insn
After:
select_insn:
jmp *jumptable(, %rax, 8)
...
ALU64_ADD_X:
...
jmp *jumptable(, %rax, 8)
ALU_ADD_X:
...
jmp *jumptable(, %rax, 8)
This confuses objtool. It has never seen multiple indirect jump
sites which use the same jump table.
For GCC switch tables, the only way of detecting the size of a table
is by continuing to scan for more tables. The size of the previous
table can only be determined after another switch table is found, or
when the scan reaches the end of the function.
That logic was reused for C jump tables, and was based on the
assumption that each jump table only has a single jump site. The
above optimization breaks that assumption.
2) Clang issue:
drivers/usb/misc/sisusbvga/sisusb.o: warning: objtool: sisusb_write_mem_bulk()+0x588: can't find switch jump table
With clang 9, code can be generated where a function contains two
indirect jump instructions which use the same switch table.
The fix is the same for both issues: split the jump table parsing into
two passes.
In the first pass, locate the heads of all switch tables for the
function and mark their locations.
In the second pass, parse the switch tables and add them.
Fixes: e55a73251d ("bpf: Fix ORC unwinding in non-JIT BPF code")
Reported-by: Randy Dunlap <rdunlap@infradead.org>
Reported-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Jann Horn <jannh@google.com>
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Nick Desaulniers <ndesaulniers@google.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/e995befaada9d4d8b2cf788ff3f566ba900d2b4d.1563413318.git.jpoimboe@redhat.com
Co-developed-by: Josh Poimboeuf <jpoimboe@redhat.com>
98 lines
2.4 KiB
C
98 lines
2.4 KiB
C
/* SPDX-License-Identifier: GPL-2.0-or-later */
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/*
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* Copyright (C) 2015 Josh Poimboeuf <jpoimboe@redhat.com>
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*/
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#ifndef _OBJTOOL_ELF_H
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#define _OBJTOOL_ELF_H
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#include <stdio.h>
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#include <gelf.h>
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#include <linux/list.h>
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#include <linux/hashtable.h>
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#ifdef LIBELF_USE_DEPRECATED
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# define elf_getshdrnum elf_getshnum
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# define elf_getshdrstrndx elf_getshstrndx
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#endif
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/*
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* Fallback for systems without this "read, mmaping if possible" cmd.
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*/
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#ifndef ELF_C_READ_MMAP
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#define ELF_C_READ_MMAP ELF_C_READ
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#endif
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struct section {
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struct list_head list;
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GElf_Shdr sh;
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struct list_head symbol_list;
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DECLARE_HASHTABLE(symbol_hash, 8);
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struct list_head rela_list;
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DECLARE_HASHTABLE(rela_hash, 16);
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struct section *base, *rela;
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struct symbol *sym;
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Elf_Data *data;
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char *name;
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int idx;
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unsigned int len;
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bool changed, text, rodata;
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};
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struct symbol {
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struct list_head list;
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struct hlist_node hash;
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GElf_Sym sym;
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struct section *sec;
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char *name;
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unsigned int idx;
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unsigned char bind, type;
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unsigned long offset;
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unsigned int len;
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struct symbol *pfunc, *cfunc, *alias;
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bool uaccess_safe;
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};
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struct rela {
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struct list_head list;
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struct hlist_node hash;
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GElf_Rela rela;
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struct section *sec;
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struct symbol *sym;
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unsigned int type;
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unsigned long offset;
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int addend;
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bool jump_table_start;
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};
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struct elf {
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Elf *elf;
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GElf_Ehdr ehdr;
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int fd;
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char *name;
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struct list_head sections;
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DECLARE_HASHTABLE(rela_hash, 16);
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};
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struct elf *elf_read(const char *name, int flags);
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struct section *find_section_by_name(struct elf *elf, const char *name);
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struct symbol *find_symbol_by_offset(struct section *sec, unsigned long offset);
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struct symbol *find_symbol_by_name(struct elf *elf, const char *name);
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struct symbol *find_symbol_containing(struct section *sec, unsigned long offset);
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struct rela *find_rela_by_dest(struct section *sec, unsigned long offset);
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struct rela *find_rela_by_dest_range(struct section *sec, unsigned long offset,
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unsigned int len);
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struct symbol *find_containing_func(struct section *sec, unsigned long offset);
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struct section *elf_create_section(struct elf *elf, const char *name, size_t
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entsize, int nr);
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struct section *elf_create_rela_section(struct elf *elf, struct section *base);
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int elf_rebuild_rela_section(struct section *sec);
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int elf_write(struct elf *elf);
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void elf_close(struct elf *elf);
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#define for_each_sec(file, sec) \
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list_for_each_entry(sec, &file->elf->sections, list)
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#endif /* _OBJTOOL_ELF_H */
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