perf annotate-arm64: Support per-cpu variable access tracking

Extend update_insn_state_arm64() to handle per-cpu variable addressing.

On arm64, per-cpu variables are accessed by adding a per-cpu offset
(typically from the '__per_cpu_offset' array) to the address of a global
variable or a structure field with '__percpu' modifier (e.g.,
's32 __percpu *counters' in struct percpu_counter). This results in
instruction patterns like:

  ldr   x0, [x6, x5]   // Pattern A: direct load per-cpu instance
  add   x0, x6, x5     // Pattern B: compute per-cpu address

where x6 holds the per-cpu offset retrieved from:

  adrp  x4, <page>
  add   x4, x4, #offset          // x4 = &__per_cpu_offset
  ldr   x6, [x4, w0, sxtw #3]    // x6 = __per_cpu_offset[cpu]

And x5 holds the base address being offset, which can come from one of
two cases:

  Case 1: global variable
    adrp  x5, <page>
    add   x5, x5, #offset        // x5 = &global_var

  Case 2: '__percpu' field embedded in a structure
    ldr   x5, [x25, #32]         // x5 = &percpu_field

To handle such cases:

1. Identify per-cpu base initialization: Detect 'adrp + ldr' pairs that
   resolve to the '__per_cpu_offset' symbol and mark the destination
   register as TSR_KIND_PERCPU_BASE.
2. Propagate type information: During subsequent 'ldr' or 'add'
   instructions, if one register is TSR_KIND_PERCPU_BASE, attempt to
   resolve the type from the other register.

A real-world example is shown below:

  ffff8000808f2d28 <cppc_set_perf>:
  ffff8000808f2d38:  adrp  x2, ffff800082033000
  ffff8000808f2d3c:  add   x5, x2, #0x3f8         // x5 = &__per_cpu_offset
  ffff8000808f2d44:  adrp  x2, ffff800081f73000
  ffff8000808f2d48:  add   x2, x2, #0x6b8         // x2 = &cpu_pcc_subspace_idx
  ffff8000808f2d6c:  ldr   x5, [x5, w0, sxtw #3]  // x5 = __per_cpu_offset[cpu]
* ffff8000808f2d80:  ldr   w23, [x5, x2]          // per_cpu_var(cpu_pcc_subspace_idx)

Before this commit, the tracker could not link x5 back to a per-cpu
context, resulting in an incorrect data type resolution:

  adrp [10] global addr=0xffff800082033000 -> reg2
  add [14] global 0x3f8(reg2) -> reg5
  adrp [1c] global addr=0xffff800081f73000 -> reg2
  add [20] global 0x6b8(reg2) -> reg2
  ldr [44] global (reg5, reg0) -> reg5 type='long unsigned int[]' size=0x1000
  chk [58] reg5 offset=0 ok=1 kind=1 (long unsigned int[]) : Good!
  found by insn track: 0(reg5, reg2) type-offset=0
  final result:  type='long unsigned int' size=0x8

After this commit, the tracker correctly identifies the per-cpu flow and
resolves the actual variable type:

  ldr [44] global (reg5, reg0) -> reg5 percpu base
  chk [58] reg5 offset=0 ok=1 kind=2 percpu var : retry
  chk [58] reg2 offset=0 ok=1 kind=7 global addr : Good!
  found by insn track: 0(reg5, reg2) type-offset=0
  final result:  type='int' size=0x4

Reviewed-by: Namhyung Kim <namhyung@kernel.org>
Signed-off-by: Tengda Wu <wutengda@huaweicloud.com>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

0 files changed, 0 insertions, 0 deletions