Alan Maguire 8543ac4923 libbpf: Btf dedup identical struct test needs check for nested structs/arrays ... [ Upstream commit f3c51fe02c ] When examining module BTF, it is common to see core kernel structures such as sk_buff, net_device duplicated in the module. After adding debug messaging to BTF it turned out that much of the problem was down to the identical struct test failing during deduplication; sometimes the compiler adds identical structs. However it turns out sometimes that type ids of identical struct members can also differ, even when the containing structs are still identical. To take an example, for struct sk_buff, debug messaging revealed that the identical struct matching was failing for the anon struct "headers"; specifically for the first field: __u8 __pkt_type_offset[0]; /* 128 0 */ Looking at the code in BTF deduplication, we have code that guards against the possibility of identical struct definitions, down to type ids, and identical array definitions. However in this case we have a struct which is being defined twice but does not have identical type ids since each duplicate struct has separate type ids for the above array member. A similar problem (though not observed) could occur for struct-in-struct. The solution is to make the "identical struct" test check members not just for matching ids, but to also check if they in turn are identical structs or arrays. The results of doing this are quite dramatic (for some modules at least); I see the number of type ids drop from around 10000 to just over 1000 in one module for example. For testing use latest pahole or apply [1], otherwise dedups can fail for the reasons described there. Also fix return type of btf_dedup_identical_arrays() as suggested by Andrii to match boolean return type used elsewhere. Fixes: efdd3eb801 ("libbpf: Accommodate DWARF/compiler bug with duplicated structs") Signed-off-by: Alan Maguire <alan.maguire@oracle.com> Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Link: https://lore.kernel.org/bpf/1666622309-22289-1-git-send-email-alan.maguire@oracle.com [1] https://lore.kernel.org/bpf/1666364523-9648-1-git-send-email-alan.maguire Signed-off-by: Sasha Levin <sashal@kernel.org>		2022-12-31 13:32:04 +01:00
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accounting	…
arch	x86/cpu: Restore AMD's DE_CFG MSR after resume	2022-11-15 10:15:58 -08:00
bootconfig	…
bpf	bpftool: Fix NULL pointer dereference when pin {PROG, MAP, LINK} without FILE	2022-11-02 12:05:42 +01:00
build	perf bpf: Fix build with libbpf 0.7.0 by checking if bpf_program__set_insns() is available	2022-10-25 17:40:48 -03:00
certs	…
cgroup	…
counter	…
debugging	…
edid	…
firewire	…
firmware	…
gpio	…
hv	…
iio	tools: iio: iio_generic_buffer: Fix read size	2022-11-01 08:48:13 +00:00
include	bpf-for-netdev	2022-11-03 19:51:02 -07:00
io_uring	…
kvm/kvm_stat	tools/kvm_stat: update exit reasons for vmx/svm/aarch64/userspace	2022-11-09 12:26:52 -05:00
laptop	…
leds	…
lib	libbpf: Btf dedup identical struct test needs check for nested structs/arrays	2022-12-31 13:32:04 +01:00
memory-model	…
objtool	objtool, kcsan: Add volatile read/write instrumentation to whitelist	2022-12-31 13:31:48 +01:00
pci	…
pcmcia	…
perf	perf tools: Add the include/perf/ directory to .gitignore	2022-11-08 18:54:41 -03:00
power	pm-graph v5.10	2022-10-25 17:46:15 +02:00
rcu	…
scripts	…
spi	…
testing	selftests/bpf: fix missing BPF object files	2022-12-31 13:32:03 +01:00
thermal	…
time	…
tracing	…
usb	…
verification	rv/dot2c: Make automaton definition static	2022-10-20 16:02:45 -04:00
virtio	…
vm	tools/vm/slabinfo-gnuplot: use "grep -E" instead of "egrep"	2022-11-30 14:49:41 -08:00
wmi	…
Makefile	…