[glibc/maskray/unnest] elf: Copy l_addr/l_ld when adding ld.so to a new namespace

[glibc/maskray/unnest] elf: Copy l_addr/l_ld when adding ld.so to a new namespace

[Fangrui Song]

https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=88361b408b9dbd313f15413cc2e6be0f1cafb01a

commit 88361b408b9dbd313f15413cc2e6be0f1cafb01a
Author: H.J. Lu <hjl.tools@gmail.com>
Date:   Tue Aug 17 19:36:04 2021 -0700

    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.
    
    Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>

Diff:
---
 elf/dl-load.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/elf/dl-load.c b/elf/dl-load.c
index 6ea71077af..99c5ab83b3 100644
--- a/elf/dl-load.c
+++ b/elf/dl-load.c
@@ -1026,6 +1026,10 @@ _dl_map_object_from_fd (const char *name, const char *origname, int fd,
       /* Refer to the real descriptor.  */
       l->l_real = &GL(dl_rtld_map);
 
+      /* Copy l_addr and l_ld to avoid a GDB warning with dlmopen().  */
+      l->l_addr = l->l_real->l_addr;
+      l->l_ld = l->l_real->l_ld;
+
       /* No need to bump the refcount of the real object, ld.so will
 	 never be unloaded.  */
       __close_nocancel (fd);