From: Josh Poimboeuf jpoimboe@redhat.com
commit fd35c88b74170d9335530d9abf271d5d73eb5401 upstream.
With GCC 8, some issues were found with the objtool switch table detection.
1) In the .rodata section, immediately after the switch table, there can be another object which contains a pointer to the function which had the switch statement. In this case objtool wrongly considers the function pointer to be part of the switch table. Fix it by:
a) making sure there are no pointers to the beginning of the function; and
b) making sure there are no gaps in the switch table.
Only the former was needed, the latter adds additional protection for future optimizations.
2) In find_switch_table(), case 1 and case 2 are missing the check to ensure that the .rodata switch table data is anonymous, i.e. that it isn't already associated with an ELF symbol. Fix it by adding the same find_symbol_containing() check which is used for case 3.
This fixes the following warnings with GCC 8:
drivers/block/virtio_blk.o: warning: objtool: virtio_queue_rq()+0x0: stack state mismatch: cfa1=7+8 cfa2=7+72 net/ipv6/icmp.o: warning: objtool: icmpv6_rcv()+0x0: stack state mismatch: cfa1=7+8 cfa2=7+64 drivers/usb/core/quirks.o: warning: objtool: quirks_param_set()+0x0: stack state mismatch: cfa1=7+8 cfa2=7+48 drivers/mtd/nand/raw/nand_hynix.o: warning: objtool: hynix_nand_decode_id()+0x0: stack state mismatch: cfa1=7+8 cfa2=7+24 drivers/mtd/nand/raw/nand_samsung.o: warning: objtool: samsung_nand_decode_id()+0x0: stack state mismatch: cfa1=7+8 cfa2=7+32 drivers/gpu/drm/nouveau/nvkm/subdev/top/gk104.o: warning: objtool: gk104_top_oneinit()+0x0: stack state mismatch: cfa1=7+8 cfa2=7+64
Reported-by: Arnd Bergmann arnd@arndb.de Reported-by: kbuild test robot lkp@intel.com Signed-off-by: Josh Poimboeuf jpoimboe@redhat.com Acked-by: Peter Zijlstra (Intel) peterz@infradead.org Cc: David Laight David.Laight@ACULAB.COM Cc: Greg KH gregkh@linuxfoundation.org Cc: Linus Torvalds torvalds@linux-foundation.org Cc: Peter Zijlstra peterz@infradead.org Cc: Randy Dunlap rdunlap@infradead.org Cc: Thomas Gleixner tglx@linutronix.de Cc: damian damian.tometzki@icloud.com Link: http://lkml.kernel.org/r/20180510224849.xwi34d6tzheb5wgw@treble Signed-off-by: Ingo Molnar mingo@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- tools/objtool/check.c | 24 ++++++++++++++++++++++-- 1 file changed, 22 insertions(+), 2 deletions(-)
diff --git a/tools/objtool/check.c b/tools/objtool/check.c index 3126760180c4..063afbdec42d 100644 --- a/tools/objtool/check.c +++ b/tools/objtool/check.c @@ -805,17 +805,28 @@ static int add_switch_table(struct objtool_file *file, struct instruction *insn, struct rela *rela = table; struct instruction *alt_insn; struct alternative *alt; + struct symbol *pfunc = insn->func->pfunc; + unsigned int prev_offset = 0;
list_for_each_entry_from(rela, &file->rodata->rela->rela_list, list) { if (rela == next_table) break;
+ /* Make sure the switch table entries are consecutive: */ + if (prev_offset && rela->offset != prev_offset + 8) + break; + + /* Detect function pointers from contiguous objects: */ + if (rela->sym->sec == pfunc->sec && + rela->addend == pfunc->offset) + break; + alt_insn = find_insn(file, rela->sym->sec, rela->addend); if (!alt_insn) break;
/* Make sure the jmp dest is in the function or subfunction: */ - if (alt_insn->func->pfunc != insn->func->pfunc) + if (alt_insn->func->pfunc != pfunc) break;
alt = malloc(sizeof(*alt)); @@ -826,6 +837,13 @@ static int add_switch_table(struct objtool_file *file, struct instruction *insn,
alt->insn = alt_insn; list_add_tail(&alt->list, &insn->alts); + prev_offset = rela->offset; + } + + if (!prev_offset) { + WARN_FUNC("can't find switch jump table", + insn->sec, insn->offset); + return -1; }
return 0; @@ -882,7 +900,9 @@ static struct rela *find_switch_table(struct objtool_file *file, struct instruction *orig_insn = insn;
text_rela = find_rela_by_dest_range(insn->sec, insn->offset, insn->len); - if (text_rela && text_rela->sym == file->rodata->sym) { + if (text_rela && text_rela->sym == file->rodata->sym && + !find_symbol_containing(file->rodata, text_rela->addend)) { + /* case 1 */ rodata_rela = find_rela_by_dest(file->rodata, text_rela->addend);