We write an address then a ',' to addr2line. With inline data we
generally get back (// are my comments):
0x1234    // address
foo       // function name
foo.c:123 // filename:line
bar       // function name
bar.c:123 // filename:line
0x000000000000000 // sentinel address created by ','
??        // unknown function name
??:0      // unknown filename:line

The code was assuming the inline data also had the address, which is
incorrect. This means the first inline function name (bar above) needs
to be checked to see if it is the sentinel, otherwise to be treated as
a function name. The regression was caused by the addition of
addresses as the kernel is reporting a symbol at address 0 (used by
GNU binutils when it interprets ',').

Committer testing:

Using:

  # perf trace --call-graph=dwarf -e lock:contention_*
  <SNIP>
  1244.615 TaskCon~ller #/2645281 lock:contention_begin(lock_addr: 0xffff8e6748da5ab0, flags: 2)
                                       __preempt_count_dec_and_test (inlined)
                                       trace_contention_begin (inlined)
                                       trace_contention_begin (inlined)
                                       rwsem_down_read_slowpath ([kernel.kallsyms])
                                       __preempt_count_dec_and_test (inlined)
                                       trace_contention_begin (inlined)
                                       trace_contention_begin (inlined)
                                       rwsem_down_read_slowpath ([kernel.kallsyms])
                                       __down_read_common (inlined)
                                       __down_read (inlined)
                                       down_read ([kernel.kallsyms])
                                       arch_static_branch (inlined)
                                       static_key_false (inlined)
                                       __mmap_lock_trace_acquire_returned (inlined)
                                       mmap_read_lock (inlined)
                                       do_user_addr_fault ([kernel.kallsyms])
                                       arch_local_irq_disable (inlined)
                                       handle_page_fault (inlined)
                                       exc_page_fault ([kernel.kallsyms])
                                       asm_exc_page_fault ([kernel.kallsyms])
                                       [0x4def008] (/usr/lib64/firefox/libxul.so)
  1244.619 TaskCon~ller #/2645281 lock:contention_end(lock_addr: 0xffff8e6748da5ab0)
                                       __preempt_count_dec_and_test (inlined)
                                       trace_contention_end (inlined)
                                       trace_contention_end (inlined)
                                       rwsem_down_read_slowpath ([kernel.kallsyms])
                                       __preempt_count_dec_and_test (inlined)
                                       trace_contention_end (inlined)
                                       trace_contention_end (inlined)
                                       rwsem_down_read_slowpath ([kernel.kallsyms])
                                       __down_read_common (inlined)
                                       __down_read (inlined)
                                       down_read ([kernel.kallsyms])
                                       arch_static_branch (inlined)
                                       static_key_false (inlined)
                                       __mmap_lock_trace_acquire_returned (inlined)
                                       mmap_read_lock (inlined)
                                       do_user_addr_fault ([kernel.kallsyms])
                                       arch_local_irq_disable (inlined)
                                       handle_page_fault (inlined)
                                       exc_page_fault ([kernel.kallsyms])
                                       asm_exc_page_fault ([kernel.kallsyms])
  <SNIP>

Fixes: 8dc26b6f ("perf srcline: Make sentinel reading for binutils addr2line more robust")
Reported-by: Arnaldo Carvalho de Melo <acme@kernel.org>
Signed-off-by: Ian Rogers <irogers@google.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: llvm@lists.linux.dev
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Nathan Chancellor <nathan@kernel.org>
Cc: Nick Desaulniers <ndesaulniers@google.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Tom Rix <trix@redhat.com>
Link: https://lore.kernel.org/r/20230615025041.1982072-1-irogers@google.comSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>