When the alignment is larger than natural, it is very likely that the
source code was using the cacheline size. Therefore, use the cacheline
size when it would only result in increasing the alignment.
Committer tests:
This is one of the cases that this heuristic works well, 'struct Qdisc'
in the Linux kernel:
--- /tmp/btfdiff.dwarf.pXdgRU 2021-10-28 10:22:11.738200232 -0300
+++ /tmp/btfdiff.btf.bkDkdf 2021-10-28 10:22:11.925205061 -0300
@@ -107,7 +107,7 @@ struct Qdisc {
/* XXX 24 bytes hole, try to pack */
/* --- cacheline 2 boundary (128 bytes) --- */
- struct sk_buff_head gso_skb __attribute__((__aligned__(64))); /* 128 24 */
+ struct sk_buff_head gso_skb __attribute__((__aligned__(32))); /* 128 24 */
struct qdisc_skb_head q; /* 152 24 */
struct gnet_stats_basic_packed bstats; /* 176 16 */
/* --- cacheline 3 boundary (192 bytes) --- */
With this patch both DWARF and BTF generated output have the same
alignment.
Suggested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: Douglas Raillard <douglas.raillard@arm.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: dwarves@vger.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Build instructions:
1. install cmake
2. mkdir build
3. cd build
4. cmake -D__LIB=lib ..
5. make install
cmake Options:
-DBUILD_SHARED_LIBS
By default SHARED libraries are created and applications are linked to it.
Use -DBUILD_SHARED_LIBS=OFF while invoking cmake to create STATIC libraries
and link applications to it.
Ex. cmake -D__LIB=lib -DBUILD_SHARED_LIBS=OFF ..
-DCMAKE_INSTALL_PREFIX
Default is to install to /usr/local, use -DCMAKE_INSTALL_PREFIX=
when invoking cmake to specify another install location.
Known to work scenarios:
Mandriva Cooker:
cmake 2.4.5-1mdv2007.1
libelfutils1-devel 0.123-1mdv2007.1
Debian Unstable:
cmake 2.4.5-1
libdw-dev 0.123-2
Fedora Core 6:
cmake 2.4.5-2.fc6
elfutils-devel 0.126-1.fc6
696c621804