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Namhyung Kim
eb9190afae
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>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.