PR/59296 CVS commit: [netbsd-10] src

["Martin Husemann" <martin%netbsd.org@localhost>]

The following reply was made to PR port-mips/59296; it has been noted by GNATS.

From: "Martin Husemann" <martin%netbsd.org@localhost>
To: gnats-bugs%gnats.NetBSD.org@localhost
Cc: 
Subject: PR/59296 CVS commit: [netbsd-10] src
Date: Fri, 9 Oct 2026 15:01:12 +0000

 Module Name:	src
 Committed By:	martin
 Date:		Fri Oct  9 15:01:12 UTC 2026
 
 Modified Files:
 	src/libexec/ld.elf_so [netbsd-10]: headers.c
 	src/sys/arch/mips/include [netbsd-10]: elf_machdep.h
 	src/tests/libexec/ld.elf_so [netbsd-10]: t_dlinfo.c t_rtld_r_debug.c
 
 Log Message:
 Pull up following revision(s) (requested by riastradh in ticket #1354):
 
 	libexec/ld.elf_so/headers.c: revision 1.73
 	tests/libexec/ld.elf_so/t_rtld_r_debug.c: revision 1.4
 	tests/libexec/ld.elf_so/t_rtld_r_debug.c: revision 1.5
 	tests/libexec/ld.elf_so/t_rtld_r_debug.c: revision 1.7
 	tests/libexec/ld.elf_so/t_rtld_r_debug.c: revision 1.8
 	tests/libexec/ld.elf_so/t_rtld_r_debug.c: revision 1.9
 	tests/libexec/ld.elf_so/t_dlinfo.c: revision 1.7
 	tests/libexec/ld.elf_so/t_rtld_r_debug.c: revision 1.10
 	tests/libexec/ld.elf_so/t_dlinfo.c: revision 1.8
 	tests/libexec/ld.elf_so/t_rtld_r_debug.c: revision 1.11
 	sys/arch/mips/include/elf_machdep.h: revision 1.21
 
 rtld tests: Don't use RZ for dlinfo.
 
 Use
         ATF_REQUIRE_EQ_MSG(dlinfo(...), 0, "dlinfo: %s", dlerror())
 instead, in order to accurately report the error on failure.  RZ is
 only for functions like pthread_create(3) that return zero on success
 and errno(3) code on failure, but dlinfo returns -1 on failure and
 sets dlerror() to report the nature of the error.
 
 t_dlinfo, t_rtld_r_debug: Audit ATF_REQUIRE/CHECK, sprinkle messages.
 
 Make sure to use ATF_REQUIRE when the subsequent code doesn't work if
 the check fails.
 
 t_rtld_r_debug: Use ATF_REQUIRE where we can't proceed on failure.
 
 Not helpful for the test program to crash with SIGSEGV on null
 pointer dereference -- just make it stop when we detect the null
 pointer.
 
 t_rtld_r_debug: Print some diagnostics as we go.
 
 t_rtld_r_debug: Mark this xfail on mips.
 PR port-mips/59296: t_rtld_r_debug test is failing
 
 t_rtld_r_debug: Fix xfail on mips.
 There was an earlier assertion, oops.
 Add __RCSID while here.
 
 PR port-mips/59296: t_rtld_r_debug test is failing
 
 ld.elf_so: Teach this to handle MIPS PIE rtld debug data.
 Adapt t_rtld_r_debug to handle the two MIPS cases too.
 XXX t_rtld_r_debug should be tested both as PIE and non-PIE to
 exercise both cases.
 
 Context:
 
 The value of a DT_DEBUG .dynamic entry is initialized at load-time,
 by ld.elf_so, to a pointer to a data structure set up by ld.elf_so
 describing the shared objects loaded by the executable, so debuggers
 can find them from, e.g., core dumps.  None of this is really
 documented anywhere that I can find.  Best reference is this post on
 the gdb mailing list from a quarter century ago saying there's no
 real documentation:
 https://web.archive.org/web/20250414021320/https://sourceware.org/pipermail/gdb/2000-April/004509.html
 
 However, on MIPS, the .dynamic section is mapped read-only, so
 ld.elf_so can't properly modify it (I imagine technically it could
 with some mprotect shenanigans but that's not how it's done on MIPS).
 
 Instead, the linker reserves a location in read/write memory and uses
 a DT_MIPS_RLD_MAP entry with a pointer to that location.
 
 However, in position-independent executables, the .dynamic entry
 can't have an absolute pointer to that location because it's not
 known up front.  Instead, the the linker uses a DT_MIPS_RLD_MAP_REL
 entry with the relative offset to that location from the Elf_Dyn
 entry itself.
 
 I would add a reference for this but it's basically a matter of UTSL
 plus some oblique mentions on the web and mailing list discussions:
 https://web.archive.org/web/20250414024823/https://cygwin.com/legacy-ml/binutils/2016-04/msg00244.html
 https://web.archive.org/web/20250403151803/https://maskray.me/blog/2023-09-04-toolchain-notes-on-mips
 https://web.archive.org/web/20211024050833/https://reviews.llvm.org/D12794?id=34533
 https://web.archive.org/web/20250407052145/https://wiki.debian.org/MIPSPort
 https://web.archive.org/web/20250414024924/https://reviews.freebsd.org/D17867?id=50122
 
 PR port-mips/59296: t_rtld_r_debug test is failing
 
 
 To generate a diff of this commit:
 cvs rdiff -u -r1.70.2.2 -r1.70.2.3 src/libexec/ld.elf_so/headers.c
 cvs rdiff -u -r1.20 -r1.20.34.1 src/sys/arch/mips/include/elf_machdep.h
 cvs rdiff -u -r1.6 -r1.6.10.1 src/tests/libexec/ld.elf_so/t_dlinfo.c
 cvs rdiff -u -r1.3 -r1.3.6.1 src/tests/libexec/ld.elf_so/t_rtld_r_debug.c
 
 Please note that diffs are not public domain; they are subject to the
 copyright notices on the relevant files.