6.9-stable review patch. If anyone has any objections, please let me know.
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From: Namhyung Kim namhyung@kernel.org
[ Upstream commit 645af3fb62bf12911ce1fc79efa676dae9a8289b ]
In match_var_offset(), it checks the offset range with the target type only for non-pointer types. But it also needs to check the pointer types with the target type.
This is because there can be more than one pointer variable located in the same register. Let's look at the following example. It's looking up a variable for reg3 at tcp_get_info+0x62. It found "sk" variable but it wasn't the right one since it accesses beyond the target type (struct 'sock' in this case) size.
----------------------------------------------------------- find data type for 0x7bc(reg3) at tcp_get_info+0x62 CU for net/ipv4/tcp.c (die:0x7b5f516) frame base: cfa=0 fbreg=6 offset: 1980 is bigger than size: 760 check variable "sk" failed (die: 0x7b92b2c) variable location: reg3 type='struct sock' size=0x2f8 (die:0x7b63c3a)
Actually there was another variable "tp" in the function and it's located at the same (reg3) because it's just type-casted like below.
void tcp_get_info(struct sock *sk, struct tcp_info *info) { const struct tcp_sock *tp = tcp_sk(sk); ...
The 'struct tcp_sock' contains the 'struct sock' at offset 0 so it can just use the same address as a pointer to tcp_sock. That means it should match variables correctly by checking the offset and size. Actually it cannot distinguish if the offset was smaller than the size of the original struct sock. But I think it's fine as they are the same at that part.
So let's check the target type size and retry if it doesn't match. Now it succeeded to find the correct variable.
----------------------------------------------------------- find data type for 0x7bc(reg3) at tcp_get_info+0x62 CU for net/ipv4/tcp.c (die:0x7b5f516) frame base: cfa=0 fbreg=6 found "tp" in scope=1/1 (die: 0x7b92b16) type_offset=0x7bc variable location: reg3 type='struct tcp_sock' size=0xa68 (die:0x7b81380)
Fixes: bc10db8eb8955fbc ("perf annotate-data: Support stack variables") 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: Kan Liang kan.liang@linux.intel.com Cc: Masami Hiramatsu mhiramat@kernel.org Cc: Namhyung Kim namhyung@kernel.org Cc: Peter Zijlstra peterz@infradead.org Link: https://lore.kernel.org/r/20240412183310.2518474-3-namhyung@kernel.org Signed-off-by: Arnaldo Carvalho de Melo acme@redhat.com Signed-off-by: Sasha Levin sashal@kernel.org --- tools/perf/util/dwarf-aux.c | 28 +++++++++++++++++++++------- 1 file changed, 21 insertions(+), 7 deletions(-)
diff --git a/tools/perf/util/dwarf-aux.c b/tools/perf/util/dwarf-aux.c index 2791126069b4f..f7f7171539d3c 100644 --- a/tools/perf/util/dwarf-aux.c +++ b/tools/perf/util/dwarf-aux.c @@ -1280,7 +1280,7 @@ struct find_var_data { #define DWARF_OP_DIRECT_REGS 32
static bool match_var_offset(Dwarf_Die *die_mem, struct find_var_data *data, - u64 addr_offset, u64 addr_type) + u64 addr_offset, u64 addr_type, bool is_pointer) { Dwarf_Die type_die; Dwarf_Word size; @@ -1294,6 +1294,12 @@ static bool match_var_offset(Dwarf_Die *die_mem, struct find_var_data *data, if (die_get_real_type(die_mem, &type_die) == NULL) return false;
+ if (is_pointer && dwarf_tag(&type_die) == DW_TAG_pointer_type) { + /* Get the target type of the pointer */ + if (die_get_real_type(&type_die, &type_die) == NULL) + return false; + } + if (dwarf_aggregate_size(&type_die, &size) < 0) return false;
@@ -1361,31 +1367,38 @@ static int __die_find_var_reg_cb(Dwarf_Die *die_mem, void *arg) if (data->is_fbreg && ops->atom == DW_OP_fbreg && data->offset >= (int)ops->number && check_allowed_ops(ops, nops) && - match_var_offset(die_mem, data, data->offset, ops->number)) + match_var_offset(die_mem, data, data->offset, ops->number, + /*is_pointer=*/false)) return DIE_FIND_CB_END;
/* Only match with a simple case */ if (data->reg < DWARF_OP_DIRECT_REGS) { /* pointer variables saved in a register 0 to 31 */ if (ops->atom == (DW_OP_reg0 + data->reg) && - check_allowed_ops(ops, nops)) + check_allowed_ops(ops, nops) && + match_var_offset(die_mem, data, data->offset, 0, + /*is_pointer=*/true)) return DIE_FIND_CB_END;
/* Local variables accessed by a register + offset */ if (ops->atom == (DW_OP_breg0 + data->reg) && check_allowed_ops(ops, nops) && - match_var_offset(die_mem, data, data->offset, ops->number)) + match_var_offset(die_mem, data, data->offset, ops->number, + /*is_pointer=*/false)) return DIE_FIND_CB_END; } else { /* pointer variables saved in a register 32 or above */ if (ops->atom == DW_OP_regx && ops->number == data->reg && - check_allowed_ops(ops, nops)) + check_allowed_ops(ops, nops) && + match_var_offset(die_mem, data, data->offset, 0, + /*is_pointer=*/true)) return DIE_FIND_CB_END;
/* Local variables accessed by a register + offset */ if (ops->atom == DW_OP_bregx && data->reg == ops->number && check_allowed_ops(ops, nops) && - match_var_offset(die_mem, data, data->offset, ops->number2)) + match_var_offset(die_mem, data, data->offset, ops->number2, + /*is_poitner=*/false)) return DIE_FIND_CB_END; } } @@ -1447,7 +1460,8 @@ static int __die_find_var_addr_cb(Dwarf_Die *die_mem, void *arg) continue;
if (check_allowed_ops(ops, nops) && - match_var_offset(die_mem, data, data->addr, ops->number)) + match_var_offset(die_mem, data, data->addr, ops->number, + /*is_pointer=*/false)) return DIE_FIND_CB_END; } return DIE_FIND_CB_SIBLING;