perf annotate-data: Handle this-cpu variables in kernel

On x86, the kernel gets the current task using the current macro like
below:

  #define current  get_current()

  static __always_inline struct task_struct *get_current(void)
  {
      return this_cpu_read_stable(pcpu_hot.current_task);
  }

So it returns the current_task field of struct pcpu_hot which is the
first member.  On my build, it's located at 0x32940.

  $ nm vmlinux | grep pcpu_hot
  0000000000032940 D pcpu_hot

And the current macro generates the instructions like below:

  mov  %gs:0x32940, %rcx

So the %gs segment register points to the beginning of the per-cpu
region of this cpu and it points the variable with a constant.

Let's update the instruction location info to have a segment register
and handle %gs in kernel to look up a global variable.  Pretend it as
a global variable by changing the register number to DWARF_REG_PC.

Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Link: https://lore.kernel.org/r/20240319055115.4063940-18-namhyung@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

diff --git a/tools/perf/util/annotate-data.c b/tools/perf/util/annotate-data.c
index f5329a78a97d828f9c3375fb24097800aa42c024..d57622ddd5d317ec71a29c2c7bf3cf10788e1341 100644 (file)
--- a/tools/perf/util/annotate-data.c
+++ b/tools/perf/util/annotate-data.c
@@ -790,7 +790,7 @@ static void delete_var_types(struct die_var_type *var_types)
 /* It's at the target address, check if it has a matching type */
 static bool check_matching_type(struct type_state *state,
                                struct data_loc_info *dloc, int reg,
-                               Dwarf_Die *type_die)
+                               Dwarf_Die *cu_die, Dwarf_Die *type_die)
 {
        Dwarf_Word size;
        u32 insn_offset = dloc->ip - dloc->ms->sym->start;
@@ -864,6 +864,23 @@ static bool check_matching_type(struct type_state *state,
                return true;
        }
 
+       if (map__dso(dloc->ms->map)->kernel && arch__is(dloc->arch, "x86")) {
+               u64 addr;
+               int offset;
+
+               if (dloc->op->segment == INSN_SEG_X86_GS && dloc->op->imm) {
+                       pr_debug_dtp(" this-cpu var\n");
+
+                       addr = dloc->op->offset;
+
+                       if (get_global_var_type(cu_die, dloc, dloc->ip, addr,
+                                               &offset, type_die)) {
+                               dloc->type_offset = offset;
+                               return true;
+                       }
+               }
+       }
+
        pr_debug_dtp("\n");
        return false;
 }
@@ -897,7 +914,7 @@ static bool find_data_type_insn(struct data_loc_info *dloc, int reg,
 
                        if (this_ip == dloc->ip) {
                                found = check_matching_type(&state, dloc, reg,
-                                                           type_die);
+                                                           cu_die, type_die);
                                goto out;
                        }
 

diff --git a/tools/perf/util/annotate.c b/tools/perf/util/annotate.c
index 3aa3a3b987ad84145757b5ea2790f3f566b808ff..e4121acb4f88c5305452095a1dfa0e7a8240033c 100644 (file)
--- a/tools/perf/util/annotate.c
+++ b/tools/perf/util/annotate.c
@@ -3921,6 +3921,13 @@ retry:
                                                            op_loc->offset, dl);
                }
 
+               /* This CPU access in kernel - pretend PC-relative addressing */
+               if (map__dso(ms->map)->kernel && arch__is(arch, "x86") &&
+                   op_loc->segment == INSN_SEG_X86_GS && op_loc->imm) {
+                       dloc.var_addr = op_loc->offset;
+                       op_loc->reg1 = DWARF_REG_PC;
+               }
+
                mem_type = find_data_type(&dloc);
                if (mem_type)
                        istat->good++;