Messages in this thread | | | Date | Tue, 21 Mar 2023 10:31:21 +0800 | Subject | Re: [PATCH v5 2/2] tracing: Add documentation for funcgraph-retval and graph_retval_hex | From | Ding Hui <> |
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On 2023/3/20 21:16, Donglin Peng wrote:
> +There are some limitations when using the funcgraph-retval currently: > + > +- Even if the function return type is void, a return value will still > + be printed, and you can just ignore it. > + > +- Even if the return value is not an error code actually, it may be > + displayed as an error code. You should read the code to check. > + For example, both 0xfe and 0xfffe are be interpreted as -2.
For char and short types, displaying as signed decimal may be not appropriate, because they are rarely used to store error code.
So in "smart" mode (graph_retval_hex=0), I suggest just smart convert error value stored in int or pointer to signed decimal.
> +- Only the value of the first return register will be recorded and > + printed even if the return values may be stored in two registers > + actually. For example, both the eax and edx are used to store a > + 64 bit return value in the x86 architecture, and the eax stores > + the low 32 bit, the edx stores the high 32 bit, however only the > + value stored in eax will be recorded and printed. > + > You can put some comments on specific functions by using > trace_printk() For example, if you want to put a comment inside > the __might_sleep() function, you just have to include
-- Thanks, - Ding Hui
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