From: Josh Poimboeuf jpoimboe@redhat.com
commit 6f5ec2993b1f39aed12fa6fd56e8dc2272ee8a33 upstream.
Typically a switch table can be found by detecting a .rodata access followed an indirect jump:
1969: 4a 8b 0c e5 00 00 00 mov 0x0(,%r12,8),%rcx 1970: 00 196d: R_X86_64_32S .rodata+0x438 1971: e9 00 00 00 00 jmpq 1976 <dispc_runtime_suspend+0xb6a> 1972: R_X86_64_PC32 __x86_indirect_thunk_rcx-0x4
Randy Dunlap reported a case (seen with GCC 4.8) where the .rodata access uses RIP-relative addressing:
19bd: 48 8b 3d 00 00 00 00 mov 0x0(%rip),%rdi # 19c4 <dispc_runtime_suspend+0xbb8> 19c0: R_X86_64_PC32 .rodata+0x45c 19c4: e9 00 00 00 00 jmpq 19c9 <dispc_runtime_suspend+0xbbd> 19c5: R_X86_64_PC32 __x86_indirect_thunk_rdi-0x4
In this case the relocation addend needs to be adjusted accordingly in order to find the location of the switch table.
The fix is for case 3 (as described in the comments), but also make the existing case 1 & 2 checks more precise by only adjusting the addend for R_X86_64_PC32 relocations.
This fixes the following warnings:
drivers/video/fbdev/omap2/omapfb/dss/dispc.o: warning: objtool: dispc_runtime_suspend()+0xbb8: sibling call from callable instruction with modified stack frame drivers/video/fbdev/omap2/omapfb/dss/dispc.o: warning: objtool: dispc_runtime_resume()+0xcc5: sibling call from callable instruction with modified stack frame
Reported-by: Randy Dunlap rdunlap@infradead.org Signed-off-by: Josh Poimboeuf jpoimboe@redhat.com Cc: Linus Torvalds torvalds@linux-foundation.org Cc: Peter Zijlstra peterz@infradead.org Cc: Thomas Gleixner tglx@linutronix.de Link: http://lkml.kernel.org/r/b6098294fd67afb69af8c47c9883d7a68bf0f8ea.1526305958... Signed-off-by: Ingo Molnar mingo@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- tools/objtool/check.c | 33 ++++++++++++++++++--------------- 1 file changed, 18 insertions(+), 15 deletions(-)
diff --git a/tools/objtool/check.c b/tools/objtool/check.c index 063afbdec42d..27c79e4d274c 100644 --- a/tools/objtool/check.c +++ b/tools/objtool/check.c @@ -898,24 +898,24 @@ static struct rela *find_switch_table(struct objtool_file *file, { struct rela *text_rela, *rodata_rela; struct instruction *orig_insn = insn; + unsigned long table_offset;
+ /* case 1 & 2 */ text_rela = find_rela_by_dest_range(insn->sec, insn->offset, insn->len); 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); - if (rodata_rela) - return rodata_rela; + table_offset = text_rela->addend; + if (text_rela->type == R_X86_64_PC32) { + /* case 2 */ + table_offset += 4; + file->ignore_unreachables = true; + }
- /* case 2 */ - rodata_rela = find_rela_by_dest(file->rodata, - text_rela->addend + 4); + rodata_rela = find_rela_by_dest(file->rodata, table_offset); if (!rodata_rela) return NULL;
- file->ignore_unreachables = true; return rodata_rela; }
@@ -949,18 +949,21 @@ static struct rela *find_switch_table(struct objtool_file *file, if (!text_rela || text_rela->sym != file->rodata->sym) continue;
+ table_offset = text_rela->addend; + if (text_rela->type == R_X86_64_PC32) + table_offset += 4; + /* * Make sure the .rodata address isn't associated with a * symbol. gcc jump tables are anonymous data. */ - if (find_symbol_containing(file->rodata, text_rela->addend)) - continue; - - rodata_rela = find_rela_by_dest(file->rodata, text_rela->addend); - if (!rodata_rela) + if (find_symbol_containing(file->rodata, table_offset)) continue;
- return rodata_rela; + /* mov [rodata addr], %reg */ + rodata_rela = find_rela_by_dest(file->rodata, table_offset); + if (rodata_rela) + return rodata_rela; }
return NULL;