02e17ca917
On x86, the kernel gets the current task using the current macro like
below:
#define current get_current()
static __always_inline struct task_struct *get_current(void)
{
return this_cpu_read_stable(pcpu_hot.current_task);
}
So it returns the current_task field of struct pcpu_hot which is the
first member. On my build, it's located at 0x32940.
$ nm vmlinux | grep pcpu_hot
0000000000032940 D pcpu_hot
And the current macro generates the instructions like below:
mov %gs:0x32940, %rcx
So the %gs segment register points to the beginning of the per-cpu
region of this cpu and it points the variable with a constant.
Let's update the instruction location info to have a segment register
and handle %gs in kernel to look up a global variable. Pretend it as
a global variable by changing the register number to DWARF_REG_PC.
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/20240319055115.4063940-18-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.