On Fri, Jun 14, 2019 at 02:09:25PM -0700, Alexei Starovoitov wrote: > On Fri, Jun 14, 2019 at 2:07 PM Josh Poimboeuf <jpoim...@redhat.com> wrote: > > > > On Fri, Jun 14, 2019 at 01:58:42PM -0700, Alexei Starovoitov wrote: > > > On Fri, Jun 14, 2019 at 12:56:41PM -0500, Josh Poimboeuf wrote: > > > > Objtool currently ignores ___bpf_prog_run() because it doesn't > > > > understand the jump table. This results in the ORC unwinder not being > > > > able to unwind through non-JIT BPF code. > > > > > > > > Luckily, the BPF jump table resembles a GCC switch jump table, which > > > > objtool already knows how to read. > > > > > > > > Add generic support for reading any static local jump table array named > > > > "jump_table", and rename the BPF variable accordingly, so objtool can > > > > generate ORC data for ___bpf_prog_run(). > > > > > > > > Fixes: d15d356887e7 ("perf/x86: Make perf callchains work without > > > > CONFIG_FRAME_POINTER") > > > > Reported-by: Song Liu <songliubrav...@fb.com> > > > > Signed-off-by: Josh Poimboeuf <jpoim...@redhat.com> > > > > Acked-by: Peter Zijlstra (Intel) <pet...@infradead.org> > > > > --- > > > > kernel/bpf/core.c | 5 ++--- > > > > tools/objtool/check.c | 16 ++++++++++++++-- > > > > 2 files changed, 16 insertions(+), 5 deletions(-) > > > > > > > > diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c > > > > index 7c473f208a10..aa546ef7dbdc 100644 > > > > --- a/kernel/bpf/core.c > > > > +++ b/kernel/bpf/core.c > > > > @@ -1299,7 +1299,7 @@ static u64 ___bpf_prog_run(u64 *regs, const > > > > struct bpf_insn *insn, u64 *stack) > > > > { > > > > #define BPF_INSN_2_LBL(x, y) [BPF_##x | BPF_##y] = &&x##_##y > > > > #define BPF_INSN_3_LBL(x, y, z) [BPF_##x | BPF_##y | BPF_##z] = > > > > &&x##_##y##_##z > > > > - static const void *jumptable[256] = { > > > > + static const void *jump_table[256] = { > > > > [0 ... 255] = &&default_label, > > > > /* Now overwrite non-defaults ... */ > > > > BPF_INSN_MAP(BPF_INSN_2_LBL, BPF_INSN_3_LBL), > > > > @@ -1315,7 +1315,7 @@ static u64 ___bpf_prog_run(u64 *regs, const > > > > struct bpf_insn *insn, u64 *stack) > > > > #define CONT_JMP ({ insn++; goto select_insn; }) > > > > > > > > select_insn: > > > > - goto *jumptable[insn->code]; > > > > + goto *jump_table[insn->code]; > > > > > > > > /* ALU */ > > > > #define ALU(OPCODE, OP) \ > > > > @@ -1558,7 +1558,6 @@ static u64 ___bpf_prog_run(u64 *regs, const > > > > struct bpf_insn *insn, u64 *stack) > > > > BUG_ON(1); > > > > return 0; > > > > } > > > > -STACK_FRAME_NON_STANDARD(___bpf_prog_run); /* jump table */ > > > > > > > > #define PROG_NAME(stack_size) __bpf_prog_run##stack_size > > > > #define DEFINE_BPF_PROG_RUN(stack_size) \ > > > > 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." > > > > > > since external tool will be looking at it should it be named > > > "bpf_jump_table." to avoid potential name conflicts? > > > Or even more unique name? > > > Like "bpf_interpreter_jump_table." ? > > > > No, the point is that it's a generic feature which can also be used any > > non-BPF code which might also have a jump table. > > and you're proposing to name all such jump tables in the kernel > as static foo jump_table[] ?
That's the idea. -- Josh