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645af3fb62
In match_var_offset(), it checks the offset range with the target type
only for non-pointer types. But it also needs to check the pointer
types with the target type.
This is because there can be more than one pointer variable located in
the same register. Let's look at the following example. It's looking
up a variable for reg3 at tcp_get_info+0x62. It found "sk" variable but
it wasn't the right one since it accesses beyond the target type (struct
'sock' in this case) size.
-----------------------------------------------------------
find data type for 0x7bc(reg3) at tcp_get_info+0x62
CU for net/ipv4/tcp.c (die:0x7b5f516)
frame base: cfa=0 fbreg=6
offset: 1980 is bigger than size: 760
check variable "sk" failed (die: 0x7b92b2c)
variable location: reg3
type='struct sock' size=0x2f8 (die:0x7b63c3a)
Actually there was another variable "tp" in the function and it's
located at the same (reg3) because it's just type-casted like below.
void tcp_get_info(struct sock *sk, struct tcp_info *info)
{
const struct tcp_sock *tp = tcp_sk(sk);
...
The 'struct tcp_sock' contains the 'struct sock' at offset 0 so it can
just use the same address as a pointer to tcp_sock. That means it
should match variables correctly by checking the offset and size.
Actually it cannot distinguish if the offset was smaller than the size
of the original struct sock. But I think it's fine as they are the same
at that part.
So let's check the target type size and retry if it doesn't match.
Now it succeeded to find the correct variable.
-----------------------------------------------------------
find data type for 0x7bc(reg3) at tcp_get_info+0x62
CU for net/ipv4/tcp.c (die:0x7b5f516)
frame base: cfa=0 fbreg=6
found "tp" in scope=1/1 (die: 0x7b92b16) type_offset=0x7bc
variable location: reg3
type='struct tcp_sock' size=0xa68 (die:0x7b81380)
Fixes: bc10db8eb8 ("perf annotate-data: Support stack variables")
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: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://lore.kernel.org/r/20240412183310.2518474-3-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.