From 3676e57417390c2facae30407f4b71fe68c7abc1 Mon Sep 17 00:00:00 2001 From: Andrii Nakryiko Date: Thu, 21 Nov 2024 14:45:58 -0800 Subject: [PATCH] libbpf: don't adjust USDT semaphore address if .stapsdt.base addr is missing [ Upstream commit 98ebe5ef6f5c4517ba92fb3e56f95827ebea83fd ] USDT ELF note optionally can record an offset of .stapsdt.base, which is used to make adjustments to USDT target attach address. Currently, libbpf will do this address adjustment unconditionally if it finds .stapsdt.base ELF section in target binary. But there is a corner case where .stapsdt.base ELF section is present, but specific USDT note doesn't reference it. In such case, libbpf will basically just add base address and end up with absolutely incorrect USDT target address. This adjustment has to be done only if both .stapsdt.sema section is present and USDT note is recording a reference to it. Fixes: 74cc6311cec9 ("libbpf: Add USDT notes parsing and resolution logic") Signed-off-by: Andrii Nakryiko Acked-by: Jiri Olsa Link: https://lore.kernel.org/r/20241121224558.796110-1-andrii@kernel.org Signed-off-by: Alexei Starovoitov Signed-off-by: Sasha Levin --- tools/lib/bpf/usdt.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/tools/lib/bpf/usdt.c b/tools/lib/bpf/usdt.c index 93794f01bb67..6ff28e7bf5e3 100644 --- a/tools/lib/bpf/usdt.c +++ b/tools/lib/bpf/usdt.c @@ -659,7 +659,7 @@ static int collect_usdt_targets(struct usdt_manager *man, Elf *elf, const char * * [0] https://sourceware.org/systemtap/wiki/UserSpaceProbeImplementation */ usdt_abs_ip = note.loc_addr; - if (base_addr) + if (base_addr && note.base_addr) usdt_abs_ip += base_addr - note.base_addr; /* When attaching uprobes (which is what USDTs basically are)