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perf annotate-arm64: Support 'mrs' instruction to track 'current' pointer

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Extend update_insn_state_arm64() to handle the 'mrs' instruction,
enabling the tracking of the 'current' task pointer in the kernel.

On arm64, the kernel uses the 'sp_el0' system register to store the
address of the currently executing 'struct task_struct'. This is
typically accessed via the 'get_current()' inline function, resulting
in the instruction 'mrs xN, sp_el0'.

To resolve the data type of the target register, first verify the
access is to 'sp_el0' within a kernel DSO. Then, locate the
'get_current()' inline function's DWARF Die at the current PC and
extract its return type (which should be 'struct task_struct*').

A real-world example is shown below:

  ffff8000800deee8 <kthread_blkcg>:
  ffff8000800deef0:  mrs  x0, sp_el0    // x0 = current
* ffff8000800deef4:  ldr  w1, [x0, #44]

Before this commit, the type flow starts with no information:

  chk [c] reg0 offset=0x2c ok=0 kind=0 cfa : no type information
  final result: no type information

After this commit, the tracker identifies the 'current' pointer
from the system register:

  mrs [8] sp_el0 -> reg0 type='struct task_struct*'
  chk [c] reg0 offset=0x2c ok=1 kind=1 (struct task_struct*) : Good!
  found by insn track: 0x2c(reg0) type-offset=0x2c
  final result: type='struct task_struct'

Reviewed-by: Ian Rogers <irogers@google.com>
Reviewed-by: Namhyung Kim <namhyung@kernel.org>
Signed-off-by: Li Huafei <lihuafei1@huawei.com>
Signed-off-by: Tengda Wu <wutengda@huaweicloud.com>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
This commit is contained in:
Tengda Wu 2026-10-20 13:45:11 +00:00 committed by Arnaldo Carvalho de Melo
parent b61eb0fd4e
commit 645d694dd0
1 changed files with 71 additions and 0 deletions
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71
tools/perf/util/annotate-arch/annotate-arm64.c
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@ -4,6 +4,7 @@
#include <inttypes.h>
#include <stdlib.h>
#include <string.h>
#include <strings.h>
#include <linux/ctype.h>
#include <linux/string.h>
#include <linux/zalloc.h>
@ -15,6 +16,7 @@
#include "../dso.h"
#include "../map.h"
#include "../symbol.h"
#include "../strbuf.h"
struct arch_arm64 {
struct arch arch;
@ -1114,6 +1116,73 @@ static void update_adrp_insn_state(struct type_state *state,
insn_offset, tsr->imm_value, dreg);
}
static void update_mrs_insn_state(struct type_state *state,
struct data_loc_info *dloc, Dwarf_Die *cu_die,
struct disasm_line *dl,
struct annotated_op_loc *dst)
{
struct type_state_reg *tsr;
Dwarf_Die type_die;
u32 insn_offset = dl->al.offset;
int dreg = dst->reg1;
Dwarf_Die func_die;
Dwarf_Attribute attr;
u64 ip, pc;
struct strbuf sb;
char *type_name;
if (!has_reg_type(state, dreg))
return;
tsr = &state->regs[dreg];
tsr->copied_from = -1;
/* Handle case difference: LLVM (SP_EL0) vs objdump (sp_el0) */
if (!dso__kernel(map__dso(dloc->ms->map)) ||
strcasecmp(dl->ops.source.raw, "sp_el0")) {
invalidate_reg_state(tsr);
return;
}
ip = dloc->ms->sym->start + dl->al.offset;
pc = map__rip_2objdump(dloc->ms->map, ip);
/*
* Find the inline function 'get_current()' Dwarf_Die and obtain its
* return value data type, which should be 'struct task_struct*'.
*/
if (!die_find_inlinefunc(cu_die, pc, &func_die) ||
!die_compare_name(&func_die, "get_current") ||
!dwarf_attr_integrate(&func_die, DW_AT_type, &attr) ||
!dwarf_formref_die(&attr, &type_die)) {
invalidate_reg_state(tsr);
return;
}
strbuf_init(&sb, 32);
die_get_typename_from_type(&type_die, &sb);
type_name = strbuf_detach(&sb, NULL);
if (!type_name || strcmp(type_name, "struct task_struct*")) {
invalidate_reg_state(tsr);
goto out_free;
}
tsr->type = type_die;
tsr->kind = TSR_KIND_TYPE;
tsr->offset = 0;
tsr->imm_value = 0;
tsr->lifetime_active = false;
tsr->lifetime_end = 0;
tsr->ok = true;
pr_debug_dtp("mrs [%x] sp_el0 -> reg%d", insn_offset, dreg);
pr_debug_type_name(&type_die, tsr->kind);
out_free:
free(type_name);
}
static void update_insn_state_arm64(struct type_state *state,
struct data_loc_info *dloc, Dwarf_Die *cu_die,
struct disasm_line *dl)
@ -1130,6 +1199,8 @@ static void update_insn_state_arm64(struct type_state *state,
if (ins__is_call(&dl->ins))
update_call_insn_state(state, dloc, cu_die, dl);
else if (!strcmp(dl->ins.name, "mrs"))
update_mrs_insn_state(state, dloc, cu_die, dl, dst);
else if (!strcmp(dl->ins.name, "adrp"))
update_adrp_insn_state(state, dl, dst);
else if (!strcmp(dl->ins.name, "add"))