libbpf: don't adjust USDT semaphore address if .stapsdt.base addr is missing

JIRA: https://issues.redhat.com/browse/RHEL-78201

commit 98ebe5e
Author: Andrii Nakryiko <andrii@kernel.org>
Date:   Thu Nov 21 14:45:58 2024 -0800

    libbpf: don't adjust USDT semaphore address if .stapsdt.base addr is missing

    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: 74cc631 ("libbpf: Add USDT notes parsing and resolution logic")
    Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
    Acked-by: Jiri Olsa <jolsa@kernel.org>
    Link: https://lore.kernel.org/r/20241121224558.796110-1-andrii@kernel.org
    Signed-off-by: Alexei Starovoitov <ast@kernel.org>

Signed-off-by: Jerome Marchand <jmarchan@redhat.com>

Author: jeromemarchand

tools/lib/bpf/usdt.c

@@ -661,7 +661,7 @@ 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)