There are different patterns for percpu variable access using a constant
value added to the base.
2aeb: mov -0x7da0f7e0(,%rax,8),%r14 # r14 = __per_cpu_offset[cpu]
2af3: mov $0x34740,%rax # rax = address of runqueues
* 2afa: add %rax,%r14 # r14 = &per_cpu(runqueues, cpu)
2bfd: cmpl $0x0,0x10(%r14) # cpu_rq(cpu)->has_blocked_load
2b03: je 0x2b36
At the first instruction, r14 has the __per_cpu_offset. And then rax
has an immediate value and then added to r14 to calculate the address of
a per-cpu variable. So it needs to track the immediate values and ADD
instructions.
Similar but a little different case is to use "this_cpu_off" instead of
"__per_cpu_offset" for the current CPU. This time the variable address
comes with PC-rel addressing.
89: mov $0x34740,%rax # rax = address of runqueues
* 90: add %gs:0x7f015f60(%rip),%rax # 19a78 <this_cpu_off>
98: incl 0xd8c(%rax) # cpu_rq(cpu)->sched_count
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/20240319055115.4063940-21-namhyung@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
eb9190afae