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FAIL: gdb.mi/mi-dlmopen.exp: still-in-use fields were all correct ... While investigating this, I stumbled on this warning emitted during the calculation of allow_dlmopen_tests: ... (gdb) run ^M Starting program: allow_dlmopen_tests.x ^M [Thread debugging using libthread_db enabled]^M Using host libthread_db library "/lib64/libthread_db.so.1".^M warning: .dynamic section for "/lib64/ld64.so.2" is not at the expected \ address (wrong library or version mismatch?)^M dlmopen debug supported.^M ... The warning is mentioned in this glibc commit 88361b408b: ... elf: Copy l_addr/l_ld when adding ld.so to a new namespace When add ld.so to a new namespace, we don't actually load ld.so. We create a new link map and refers the real one for almost everything. Copy l_addr and l_ld from the real ld.so link map to avoid GDB warning: warning: .dynamic section for ".../elf/ld-linux-x86-64.so.2" is not at \ the expected address (wrong library or version mismatch?) when handling shared library loaded by dlmopen. ... So, AFAICT the setup is: - the glibc package is based on v2.34 - it contains a backport of commit a93d9e03a3 ("Extend struct r_debug to support multiple namespaces [BZ #15971]") - it doesn't contain a backport of commit 88361b408b ("elf: Copy l_addr/l_ld when adding ld.so to a new namespace") [1] - both commits are part of v2.35 What happens is: - when probing for l_addr and l_ld in svr4_solib_ops::read_lm_info, both get the value 0 - in svr4_solib_ops::lm_addr_check, the 0 value propagates to l_dynaddr, and "l_addr = l_dynaddr - dynaddr" then underflows, and things go downhill from there, resulting in the warning and eventually the FAIL. Fix this by detecting the situation in svr4_solib_ops::read_so_list, and bailing out with a warning. Add detection of this and other "corruption" warnings in allow_dlmopen_tests to make sure the related test-cases are skipped. In more detail, before this patch we have: ... $ gdb -q -batch outputs/gdb.base/dlmopen/dlmopen -ex start -ex next \ -ex "pipe info shared | ld64" ... warning: .dynamic section for "/lib64/ld64.so.2" is not at the expected \ address (wrong library or version mismatch?) ... 0x00007ffff7f80000 0x00007ffff8000000 0 Yes /lib64/ld64.so.2 0x0000000000000160 0xffffffffffff0000 1 Yes /lib64/ld64.so.2 ... and after: ... warning: Corrupted shared library entry: zero l_addr and l_ld warning: Corrupted shared library entry: zero l_addr and l_ld ... 0x00007ffff7f80000 0x00007ffff8000000 0 Yes /lib64/ld64.so.2 ... Alternatively, we could prevent the underflow in svr4_solib_ops::lm_addr_check: ... bool l_addr_updated = false; if (l_dynaddr >= dynaddr) { l_addr = l_dynaddr - dynaddr; l_addr_updated = true; } if (l_addr_updated && (l_addr & (minpagesize - 1)) == 0 && (l_addr & align) == ((l_dynaddr - dynaddr) & align)) ... but we'd still get an incorrect range: ... warning: .dynamic section for "/lib64/ld64.so.2" is not at the expected \ address (wrong library or version mismatch?) ... 0x00007ffff7f80000 0x00007ffff8000000 0 Yes /lib64/ld64.so.2 0x0000000000060000 0x0000000000080000 1 Yes /lib64/ld64.so.2 ... FTR, in an earlier attempt I proposed to deal with the FAIL using an xfail [2]. And in an another attempt I proposed to deal with it by replicating the glibc fix in gdb [3]. Changed in v2: - fixed incorrect footnote reference - made comment more precise - use "AlmaLinux" consistently Versions: - v1 https://sourceware.org/pipermail/gdb-patches/2026-September/230275.html Tested on ppc64le-linux and x86_64-linux. Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=33662 [1] https://bugs.almalinux.org/view.php?id=667 [2] https://sourceware.org/pipermail/gdb-patches/2026-July/229073.html [3] https://sourceware.org/pipermail/gdb-patches/2026-August/229549.html --- gdb/solib-svr4.c | 23 +++++++++++++++++++++++ gdb/testsuite/lib/gdb.exp | 3 +++ 2 files changed, 26 insertions(+) diff --git a/gdb/solib-svr4.c b/gdb/solib-svr4.c index c4af1b11a4d..810b0fae7a3 100644 --- a/gdb/solib-svr4.c +++ b/gdb/solib-svr4.c @@ -1333,6 +1333,29 @@ svr4_solib_ops::read_so_list (svr4_info *info, CORE_ADDR lm, CORE_ADDR prev_lm, if (*name == '\0' || match_main (name.get ())) continue; + gdb_byte dummy; + if (li->l_addr_inferior == 0 && li->l_ld == 0 + && target_read_memory (0, &dummy, 1) != 0) + { + /* We have l_addr_inferior == 0 and l_ld == 0 (corresponding to link + map entries l_addr and l_ld). This can happen with a glibc that: + - has commit a93d9e03a3 ("Extend struct r_debug to support + multiple namespaces [BZ #15971]"), but + - misses commit 88361b408b ("elf: Copy l_addr/l_ld when adding + ld.so to a new namespace"). + This seems to be the case at least for the AlmaLinux 9.8 BaseOS + version, which uses glibc v2.34 and backports only the first + commit ( https://bugs.almalinux.org/view.php?id=667 ). + Detect this here and bail out. Otherwise, we'll present + the user with incorrect info for "info shared". + + The target_read_memory is there to detect the improbable + situation that address 0 is mapped, in which case it might be the + address of the dynamic section. */ + warning (_("Corrupted shared library entry: zero l_addr and l_ld")); + return 0; + } + sos.emplace_back (name.get (), std::move (li)); } diff --git a/gdb/testsuite/lib/gdb.exp b/gdb/testsuite/lib/gdb.exp index 9ade9a16818..bfb0e8e9273 100644 --- a/gdb/testsuite/lib/gdb.exp +++ b/gdb/testsuite/lib/gdb.exp @@ -3193,6 +3193,9 @@ gdb_caching_proc allow_dlmopen_tests {} { return 0 } gdb_expect { + -re "warning: Corrupted.*$gdb_prompt $" { + set allow_dlmopen_tests 0 + } -re "$inferior_exited_re normally.*${gdb_prompt} $" { set allow_dlmopen_tests 1 } base-commit: 196286d25ccc652dc086ae173d1cfa836bed0618 -- 2.51.0