[RFC][PATCH v5 00/16] Proof-of-Concept implementation of RTLD_SHARED for dlmopen
Vivek Das Mohapatra
vivek@collabora.com
Wed Jun 17 14:00:08 GMT 2020
This is a revision of a previous patchset that I posted here
regarding https://sourceware.org/bugzilla/show_bug.cgi?id=22745
I will recap the previous introduction here:
=======================================================================
As discussed in the URL above dlmopen requires a mechanism for
[optionally] sharing some objects between more than one namespace.
The following patchset attempts an implementation for this: If an
object is loaded with the new RTLD_SHARED flag we instead ensure
that a "master" copy exists (and is flagged as no-delete) in the
main namespace and a thin wrapper or clone is placed in the target
namespace.
This patch series should address all the comments received on the
earlier (v1) series, and fixes a bug in the previous (v2) series
which left the r_debug struct in an inconsistent state when creating
a proxy triggered the initial load of a DSO into the main namespace.
=======================================================================
In addition this patch series now mplements the following:
- dlmopen will implicitly apply RTLD_SHARED to the libc/libpthread group
(requires a patched binutils/ld so that the libc family of DSOs can
be flagged as requiring this behaviour)
- LD_AUDIT paths will not apply this implict sharing rule, so audit libraries
will continue to be completely isolated.
- The mechanism for tagging DSOs as implicitly shared has been changed
from a DT_FLAGS_1 flag to a DT_VALRNGHI/LO range dynamic tag.
(Based on feedback on the binutils side of this patch series).
- A flag RTLD_ISOLATE which is used inernally to suppress RTLD_SHARED
behaviour when audit libraries are being loaded, and is also made available
to users who really want a completely separate copy of glibc in their new
namespace.
- Tests for most of the new dlmopen behaviour (to be added to if
this patch series is acceptable)
I have not yet implemented, but plan to address once this series is
accepted/acceptable:
- Sensible RTLD_GLOBAL semantics for dlmopened DSOs in non-base namespaces
- dl_iterate_ns_phdr (cf dl_iterate_phdr but taking a namespace argument)
Vivek Das Mohapatra (16):
Declare and describe the dlmopen RTLD_SHARED flag
include/link.h: Update the link_map struct to allow proxies
elf/dl-object.c: Implement a helper function to proxy link_map entries
elf/dl-load.c, elf-dl-open.c: Implement RTLD_SHARED dlmopen proxying
elf/dl-fini.c: Handle proxy link_map entries in the shutdown path
elf/dl-init.c: Skip proxied link map entries in the dl init path
Define a new dynamic section tag - DT_GNU_UNIQUE
Abstract the loaded-DSO search code into a private helper function
Compare loaded DSOs by file ID and check for DF_1_UNIQUE
Use the new DSO finder helper function since we have it
Use the DSO search helper to check for preloaded DT_GNU_UNIQUE DSOs
When loading DSOs into alternate namespaces check for DT_GNU_UNIQUE
Suppress inter-namespace DSO sharing for audit libraries
dlsym, dlvsym should be able to look up symbols via DSO proxies
Add a DT_GNU_UNIQUE dynamic section to the glibc cluster DSOs
Add dlmopen / RTLD_SHARED tests
Makeconfig | 1 +
Makerules | 2 +-
bits/dlfcn.h | 10 +
elf/Makefile | 42 +-
elf/dl-close.c | 43 +-
elf/dl-fini.c | 6 +-
elf/dl-init.c | 4 +-
elf/dl-load.c | 204 +++++++--
elf/dl-object.c | 84 ++++
elf/dl-open.c | 99 ++++-
elf/dl-sym.c | 14 +
elf/elf.h | 3 +-
elf/rtld.c | 2 +-
elf/tst-dlmopen-common.h | 15 +
elf/tst-dlmopen-main.h | 899 +++++++++++++++++++++++++++++++++++++++
elf/tst-dlmopen-modules.h | 3 +
elf/tst-dlmopen-rtld-shared1.c | 74 ++++
elf/tst-dlmopen-rtld-shared2.c | 76 ++++
elf/tst-dlmopen-rtld-shared3.c | 53 +++
elf/tst-dlmopen-rtld-shared4.c | 24 ++
elf/tst-dlmopen-rtld-shared5.c | 35 ++
elf/tst-dlmopen-rtld-shared6.c | 46 ++
elf/tst-dlmopen-rtld-unique1.c | 96 +++++
elf/tst-dlmopen-rtld-unique2.c | 35 ++
elf/tst-dlmopen-rtld-unique3.c | 23 +
elf/tst-dlmopen-rtld-unique4.c | 24 ++
elf/tst-dlmopen-sharedmod-norm.c | 11 +
elf/tst-dlmopen-sharedmod-uniq.c | 11 +
elf/tst-dlmopen-std-do-test.h | 11 +
iconvdata/Makefile | 1 +
include/link.h | 6 +-
nptl/Makefile | 2 +-
sysdeps/generic/ldsodefs.h | 9 +
sysdeps/mips/bits/dlfcn.h | 10 +
34 files changed, 1922 insertions(+), 56 deletions(-)
create mode 100644 elf/tst-dlmopen-common.h
create mode 100644 elf/tst-dlmopen-main.h
create mode 100644 elf/tst-dlmopen-modules.h
create mode 100644 elf/tst-dlmopen-rtld-shared1.c
create mode 100644 elf/tst-dlmopen-rtld-shared2.c
create mode 100644 elf/tst-dlmopen-rtld-shared3.c
create mode 100644 elf/tst-dlmopen-rtld-shared4.c
create mode 100644 elf/tst-dlmopen-rtld-shared5.c
create mode 100644 elf/tst-dlmopen-rtld-shared6.c
create mode 100644 elf/tst-dlmopen-rtld-unique1.c
create mode 100644 elf/tst-dlmopen-rtld-unique2.c
create mode 100644 elf/tst-dlmopen-rtld-unique3.c
create mode 100644 elf/tst-dlmopen-rtld-unique4.c
create mode 100644 elf/tst-dlmopen-sharedmod-norm.c
create mode 100644 elf/tst-dlmopen-sharedmod-uniq.c
create mode 100644 elf/tst-dlmopen-std-do-test.h
--
2.11.0
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