On Wed, Jun 26, 2019 at 5:38 PM Josh Poimboeuf <[email protected]> wrote: > > Objtool doesn't know how to read C jump tables, so it has to whitelist > functions which use them, causing missing ORC unwinder data for such > functions, e.g. ___bpf_prog_run(). > > C jump tables are very similar to GCC switch jump tables, which objtool > already knows how to read. So adding support for C jump tables is easy. > It just needs to be able to find the tables and distinguish them from > other data. > > To allow the jump tables to be found, create a standard: objtool will > automatically recognize any static local jump table named "jump_table". > > Signed-off-by: Josh Poimboeuf <[email protected]> > Acked-by: Peter Zijlstra (Intel) <[email protected]> > --- > tools/objtool/check.c | 16 ++++++++++++++-- > 1 file changed, 14 insertions(+), 2 deletions(-) > > diff --git a/tools/objtool/check.c b/tools/objtool/check.c > index 172f99195726..8341c2fff14f 100644 > --- a/tools/objtool/check.c > +++ b/tools/objtool/check.c > @@ -18,6 +18,8 @@ > > #define FAKE_JUMP_OFFSET -1 > > +#define JUMP_TABLE_SYM_PREFIX "jump_table." > + > struct alternative { > struct list_head list; > struct instruction *insn; > @@ -997,6 +999,7 @@ static struct rela *find_switch_table(struct objtool_file > *file, > struct instruction *orig_insn = insn; > struct section *rodata_sec; > unsigned long table_offset; > + struct symbol *sym; > > /* > * Backward search using the @first_jump_src links, these help avoid > @@ -1035,9 +1038,18 @@ static struct rela *find_switch_table(struct > objtool_file *file, > > /* > * Make sure the .rodata address isn't associated with a > - * symbol. gcc jump tables are anonymous data. > + * symbol. GCC jump tables are anonymous data. > + * > + * Also support C jump tables which are in the same format as > + * switch jump tables. Each jump table should be a static > + * local const array named "jump_table" for objtool to > + * recognize it.
Nacked-by: Alexei Starovoitov <[email protected]> It's not acceptable for objtool to dictate kernel naming convention.
