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main: Correct the pointer value of strtab on riscv/mips architectures

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Glibc defines `d_ptr`/`d_val` to be a relocated address on most
architectures, except for riscv and mips where it is just an offset from
the binary load address. So we need to convert `strtab` from an offset
into a pointer for riscv and mips.

Internally within glibc there is the `D_PTR` macro for doing this, which
relies on private data hidden in an ABI-unstable part of `link_map`. So
we can't use the same conditional logic as glibc does internally.

Our solution is to detect when `strtab` is unreasonably low (below the
address of our binary) and so it must be an unrelocated offset. In that
case we just do the relocation manually.

Fixes: https://gitlab.gnome.org/GNOME/gnome-shell/-/issues/6528
Part-of: <https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/2718>
This commit is contained in:
Daniel van Vugt 2023-03-23 17:51:46 +08:00 committed by Marge Bot
parent a95addd772
commit 65cde18786
1 changed files with 20 additions and 0 deletions
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20
src/main.c
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@ -1,5 +1,7 @@
/* -*- mode: C; c-file-style: "gnu"; indent-tabs-mode: nil; -*- */ /* -*- mode: C; c-file-style: "gnu"; indent-tabs-mode: nil; -*- */
#define _GNU_SOURCE
#include "config.h" #include "config.h"
#if defined (HAVE_MALLINFO) || defined (HAVE_MALLINFO2) #if defined (HAVE_MALLINFO) || defined (HAVE_MALLINFO2)
@ -20,6 +22,7 @@
#include <link.h> #include <link.h>
#ifdef HAVE_EXE_INTROSPECTION #ifdef HAVE_EXE_INTROSPECTION
#include <dlfcn.h>
#include <elf.h> #include <elf.h>
#endif #endif
@ -140,6 +143,8 @@ maybe_add_rpath_introspection_paths (void)
g_auto (GStrv) paths = NULL; g_auto (GStrv) paths = NULL;
g_autofree char *exe_dir = NULL; g_autofree char *exe_dir = NULL;
GStrv str; GStrv str;
Dl_info dl_info;
struct link_map *link_map = NULL;
for (dyn = _DYNAMIC; dyn->d_tag != DT_NULL; dyn++) for (dyn = _DYNAMIC; dyn->d_tag != DT_NULL; dyn++)
{ {
@ -154,6 +159,21 @@ maybe_add_rpath_introspection_paths (void)
if ((!rpath && !runpath) || !strtab) if ((!rpath && !runpath) || !strtab)
return; return;
if (dladdr1 (_DYNAMIC, &dl_info, (void **) &link_map, RTLD_DL_LINKMAP))
{
/* Sanity check */
g_return_if_fail ((void *) _DYNAMIC == (void *) link_map->l_ld);
/* strtab should be at an offset above our load address. If it's not
* then this is a special architecture (riscv, mips) that has a
* readonly _DYNAMIC section that's not relocated. So in that case
* strtab is currently an offset rather than an address. Let's make it
* an address...
*/
if (strtab < (const char *) link_map->l_addr)
strtab += link_map->l_addr;
}
if (rpath) if (rpath)
paths = g_strsplit (strtab + rpath->d_un.d_val, ":", -1); paths = g_strsplit (strtab + rpath->d_un.d_val, ":", -1);
else else