From: pengdonglin <pengdonglin@xiaomi.com>

The current funcgraph-retval implementation has two limitations:

1. It prints a return value even when the traced function returns void.
2. When the return type is narrower than a register, the printed value may
   be incorrect because high bits can contain undefined data.

Both issues are addressed by using BTF to obtain the precise return type
of each traced function:

- Return values are now printed only for functions whose return type is
  not void.
- The value is truncated to the actual width of the return type, ensuring
  correct representation.

These changes make the funcgraph-retval output more accurate and remove
noise from void functions.

pengdonglin (2):
  fgraph: use BTF to trim and filter return values
  tracing: Update funcgraph-retval documentation

 Documentation/trace/ftrace.rst       | 74 +++++++++++++++-------------
 kernel/trace/trace_functions_graph.c | 64 ++++++++++++++++++++----
 2 files changed, 94 insertions(+), 44 deletions(-)

-- 
2.34.1