This is a supporting change for a kernel RFC that should allow using
uapi headers with vmlinux.h. For this it is necessary to add
`#ifndef GUARD ... #ifdef` brackets around some types if those types
originate from uapi kernel headers.
For example:
include/uapi/linux/tcp.h:
#ifndef _UAPI_LINUX_TCP_H
#define _UAPI_LINUX_TCP_H
...
union tcp_word_hdr {
struct tcphdr hdr;
__be32 words[5];
};
...
#endif /* _UAPI_LINUX_TCP_H */
vmlinux.h:
...
#ifndef _UAPI_LINUX_TCP_H
union tcp_word_hdr {
struct tcphdr hdr;
__be32 words[5];
};
#endif
...
The information about the GUARD names has to be encoded in BTF to
allow `bpftool` to generate it for a specific kernel binary.
This is achieved by adding a parameter `--header_guards_db` to pahole.
This parameter should point to a file that associates header file
names with names of a C pre-processor variables used as a double
include guards (dubbed as "header guard"s).
For each emitted type the DWARF attribute DW_AT_decl_file is checked,
when the file name is present in the header guards DB a fake
BTF_KIND_DECL_TAG record of the following form is emitted:
- type: the id of the emitted type;
- name_off: a string "header_guard:<guard>".
I'd like to cover this thing with a few unit tests but I don't see any
tests in the dwarves repository ([1]), could you please suggest the
right location?
I'm going to use a lore link to this thread in the kernel RFC email.
I will post a link to the kernel RFC as a reply in this thread as soon
as I have one. The change is not useful on it's own, so if kernel RFC
will not be accepted this one should not be accepted either.
Thanks,
Eduard
[1] https://github.com/acmel/dwarves
Eduard Zingerman (1):
pahole: Save header guard names when --header_guards_db is passed
btf_encoder.c | 103 ++++++++++++++++++++++++++++++++++++++++++++++----
btf_encoder.h | 3 +-
dutil.c | 20 +++++++---
dutil.h | 1 +
dwarves.h | 1 +
pahole.c | 99 +++++++++++++++++++++++++++++++++++++++++++++++-
6 files changed, 210 insertions(+), 17 deletions(-)
--
2.34.1
