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In match_var_offset(), it just checked the end address of the variable with the given offset because it assumed the register holds a pointer to the data type and the offset starts from the base. But I found some cases that the stack pointer (rsp = reg7) register is used to pointer a stack variable while the frame base is maintained by a different register (rbp = reg6). In that case, it cannot simply use the stack pointer as it cannot guarantee that it points to the frame base. So it needs to check both boundaries of the variable location. Before: ----------------------------------------------------------- find data type for 0x7c(reg7) at tcp_getsockopt+0xb62 CU for net/ipv4/tcp.c (die:0x7b5f516) frame base: cfa=0 fbreg=6 no pointer or no type check variable "tss" failed (die: 0x7b95801) variable location: base reg7, offset=0x110 type='struct scm_timestamping_internal' size=0x30 (die:0x7b8c126) So the current code just checks register number for the non-PC and non-FB registers and assuming it has offset 0. But this variable has offset 0x110 so it should not match to this. After: ----------------------------------------------------------- find data type for 0x7c(reg7) at tcp_getsockopt+0xb62 CU for net/ipv4/tcp.c (die:0x7b5f516) frame base: cfa=0 fbreg=6 no pointer or no type check variable "zc" failed (die: 0x7b9580a) variable location: base=reg7, offset=0x40 type='struct tcp_zerocopy_receive' size=0x40 (die:7b947f4) Now it find the correct variable "zc". It was located at reg7 + 0x40 and the size if 0x40 which means it should cover [0x40, 0x80). And the access was for reg7 + 0x7c so it found the right one. But it still failed to use the variable and it would be handled in the next patch. 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: Peter Zijlstra <peterz@infradead.org> Link: https://lore.kernel.org/r/20240412183310.2518474-4-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.