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Add a supplementary explanation to function get_syscall_fnname #2593

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Nov 13, 2019
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Add a supplementary explanation to function get_syscall_fnname #2593

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3281e29
add a supplementary explanation to function `get_syscall_fnname`.
wwyf Nov 13, 2019
0aa9428
fix the contents
wwyf Nov 13, 2019
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18 changes: 18 additions & 0 deletions docs/reference_guide.md
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Expand Up @@ -86,6 +86,7 @@ This guide is incomplete. If something feels missing, check the bcc and kernel s
- [2. ksymname()](#2-ksymname)
- [3. sym()](#3-sym)
- [4. num_open_kprobes()](#4-num_open_kprobes)
- [5. get_syscall_fnname()](#5-get_syscall_fnname)

- [BPF Errors](#bpf-errors)
- [1. Invalid mem access](#1-invalid-mem-access)
Expand Down Expand Up @@ -1593,6 +1594,23 @@ Examples in situ:
[search /examples](https://github.com/iovisor/bcc/search?q=num_open_kprobes+path%3Aexamples+language%3Apython&type=Code),
[search /tools](https://github.com/iovisor/bcc/search?q=num_open_kprobes+path%3Atools+language%3Apython&type=Code)

### 5. get_syscall_fnname()

Syntax: ```BPF.get_syscall_fnname(name : str)```

Return the corresponding kernel function name of the syscall. This helper function will try different prefixes and use the right one to concatenate with the syscall name. Note that the return value may vary in different versions of linux kernel and sometimes it will causing trouble. (see [#2590](https://github.com/iovisor/bcc/issues/2590))

Example:

```Python
print("The function name of %s in kernel is %s" % ("clone", b.get_syscall_fnname("clone")))
# sys_clone or __x64_sys_clone or ...
```

Examples in situ:
[search /examples](https://github.com/iovisor/bcc/search?q=get_syscall_fnname+path%3Aexamples+language%3Apython&type=Code),
[search /tools](https://github.com/iovisor/bcc/search?q=get_syscall_fnname+path%3Atools+language%3Apython&type=Code)

# BPF Errors

See the "Understanding eBPF verifier messages" section in the kernel source under Documentation/networking/filter.txt.
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