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b7d4aacfc8
I sometimes see ("unknown type") in the result and it was because it
didn't check the type of stack variables properly during the instruction
tracking. The stack can carry constant values (without type info) and
if the target instruction is accessing the stack location, it resulted
in the "unknown type".
Maybe we could pick one of integer types for the constant, but it
doesn't really mean anything useful. Let's just drop the stack slot if
it doesn't have a valid type info.
Here's an example how it got the unknown type.
Note that 0xffffff48 = -0xb8.
-----------------------------------------------------------
find data type for 0xffffff48(reg6) at ...
CU for ...
frame base: cfa=0 fbreg=6
scope: [2/2] (die:11cb97f)
bb: [37 - 3a]
var [37] reg15 type='int' size=0x4 (die:0x1180633)
bb: [40 - 4b]
mov [40] imm=0x1 -> reg13
var [45] reg8 type='sigset_t*' size=0x8 (die:0x11a39ee)
mov [45] imm=0x1 -> reg2 <--- here reg2 has a constant
bb: [215 - 237]
mov [218] reg2 -> -0xb8(stack) constant <--- and save it to the stack
mov [225] reg13 -> -0xc4(stack) constant
call [22f] find_task_by_vgpid
call [22f] return -> reg0 type='struct task_struct*' size=0x8 (die:0x11881e8)
bb: [5c8 - 5cf]
bb: [2fb - 302]
mov [2fb] -0xc4(stack) -> reg13 constant
bb: [13b - 14d]
mov [143] 0xd50(reg3) -> reg5 type='struct task_struct*' size=0x8 (die:0xa31f3c)
bb: [153 - 153]
chk [153] reg6 offset=0xffffff48 ok=0 kind=0 fbreg <--- access here
found by insn track: 0xffffff48(reg6) type-offset=0
type='G<EF>^K<F6><AF>U' size=0 (die:0xffffffffffffffff)
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: Kan Liang <kan.liang@linux.intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://lore.kernel.org/r/20240502060011.1838090-7-namhyung@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
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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.