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https://sourceware.org/git/glibc.git
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elf: Introduce rtld_setup_main_map
This function collects most of the processing needed to initialize the link map for the main executable. Reviewed-by: H.J. Lu <hjl.tools@gmail.com>
This commit is contained in:
Florian Weimer
parent
0eb230ccce
commit
b4d4ff8963
303
elf/rtld.c
303
elf/rtld.c
@ -1129,17 +1129,172 @@ rtld_chain_load (struct link_map *main_map, char *argv0)
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rtld_soname, pathname, errcode);
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rtld_soname, pathname, errcode);
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}
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}
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/* Called to complete the initialization of the link map for the main
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executable. Returns true if there is a PT_INTERP segment. */
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static bool
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rtld_setup_main_map (struct link_map *main_map)
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{
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/* This have already been filled in right after _dl_new_object, or
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as part of _dl_map_object. */
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const ElfW(Phdr) *phdr = main_map->l_phdr;
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ElfW(Word) phnum = main_map->l_phnum;
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bool has_interp = false;
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main_map->l_map_end = 0;
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main_map->l_text_end = 0;
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/* Perhaps the executable has no PT_LOAD header entries at all. */
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main_map->l_map_start = ~0;
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/* And it was opened directly. */
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++main_map->l_direct_opencount;
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/* Scan the program header table for the dynamic section. */
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for (const ElfW(Phdr) *ph = phdr; ph < &phdr[phnum]; ++ph)
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switch (ph->p_type)
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{
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case PT_PHDR:
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/* Find out the load address. */
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main_map->l_addr = (ElfW(Addr)) phdr - ph->p_vaddr;
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break;
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case PT_DYNAMIC:
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/* This tells us where to find the dynamic section,
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which tells us everything we need to do. */
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main_map->l_ld = (void *) main_map->l_addr + ph->p_vaddr;
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main_map->l_ld_readonly = (ph->p_flags & PF_W) == 0;
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break;
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case PT_INTERP:
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/* This "interpreter segment" was used by the program loader to
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find the program interpreter, which is this program itself, the
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dynamic linker. We note what name finds us, so that a future
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dlopen call or DT_NEEDED entry, for something that wants to link
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against the dynamic linker as a shared library, will know that
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the shared object is already loaded. */
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_dl_rtld_libname.name = ((const char *) main_map->l_addr
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+ ph->p_vaddr);
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/* _dl_rtld_libname.next = NULL; Already zero. */
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GL(dl_rtld_map).l_libname = &_dl_rtld_libname;
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/* Ordinarilly, we would get additional names for the loader from
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our DT_SONAME. This can't happen if we were actually linked as
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a static executable (detect this case when we have no DYNAMIC).
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If so, assume the filename component of the interpreter path to
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be our SONAME, and add it to our name list. */
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if (GL(dl_rtld_map).l_ld == NULL)
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{
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const char *p = NULL;
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const char *cp = _dl_rtld_libname.name;
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/* Find the filename part of the path. */
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while (*cp != '\0')
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if (*cp++ == '/')
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p = cp;
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if (p != NULL)
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{
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_dl_rtld_libname2.name = p;
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/* _dl_rtld_libname2.next = NULL; Already zero. */
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_dl_rtld_libname.next = &_dl_rtld_libname2;
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}
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}
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has_interp = true;
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break;
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case PT_LOAD:
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{
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ElfW(Addr) mapstart;
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ElfW(Addr) allocend;
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/* Remember where the main program starts in memory. */
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mapstart = (main_map->l_addr
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+ (ph->p_vaddr & ~(GLRO(dl_pagesize) - 1)));
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if (main_map->l_map_start > mapstart)
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main_map->l_map_start = mapstart;
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/* Also where it ends. */
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allocend = main_map->l_addr + ph->p_vaddr + ph->p_memsz;
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if (main_map->l_map_end < allocend)
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main_map->l_map_end = allocend;
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if ((ph->p_flags & PF_X) && allocend > main_map->l_text_end)
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main_map->l_text_end = allocend;
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}
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break;
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case PT_TLS:
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if (ph->p_memsz > 0)
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{
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/* Note that in the case the dynamic linker we duplicate work
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here since we read the PT_TLS entry already in
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_dl_start_final. But the result is repeatable so do not
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check for this special but unimportant case. */
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main_map->l_tls_blocksize = ph->p_memsz;
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main_map->l_tls_align = ph->p_align;
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if (ph->p_align == 0)
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main_map->l_tls_firstbyte_offset = 0;
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else
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main_map->l_tls_firstbyte_offset = (ph->p_vaddr
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& (ph->p_align - 1));
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main_map->l_tls_initimage_size = ph->p_filesz;
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main_map->l_tls_initimage = (void *) ph->p_vaddr;
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/* This image gets the ID one. */
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GL(dl_tls_max_dtv_idx) = main_map->l_tls_modid = 1;
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}
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break;
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case PT_GNU_STACK:
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GL(dl_stack_flags) = ph->p_flags;
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break;
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case PT_GNU_RELRO:
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main_map->l_relro_addr = ph->p_vaddr;
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main_map->l_relro_size = ph->p_memsz;
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break;
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}
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/* Process program headers again, but scan them backwards so
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that PT_NOTE can be skipped if PT_GNU_PROPERTY exits. */
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for (const ElfW(Phdr) *ph = &phdr[phnum]; ph != phdr; --ph)
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switch (ph[-1].p_type)
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{
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case PT_NOTE:
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_dl_process_pt_note (main_map, -1, &ph[-1]);
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break;
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case PT_GNU_PROPERTY:
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_dl_process_pt_gnu_property (main_map, -1, &ph[-1]);
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break;
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}
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/* Adjust the address of the TLS initialization image in case
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the executable is actually an ET_DYN object. */
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if (main_map->l_tls_initimage != NULL)
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main_map->l_tls_initimage
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= (char *) main_map->l_tls_initimage + main_map->l_addr;
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if (! main_map->l_map_end)
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main_map->l_map_end = ~0;
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if (! main_map->l_text_end)
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main_map->l_text_end = ~0;
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if (! GL(dl_rtld_map).l_libname && GL(dl_rtld_map).l_name)
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{
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/* We were invoked directly, so the program might not have a
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PT_INTERP. */
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_dl_rtld_libname.name = GL(dl_rtld_map).l_name;
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/* _dl_rtld_libname.next = NULL; Already zero. */
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GL(dl_rtld_map).l_libname = &_dl_rtld_libname;
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}
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else
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assert (GL(dl_rtld_map).l_libname); /* How else did we get here? */
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return has_interp;
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}
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static void
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static void
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dl_main (const ElfW(Phdr) *phdr,
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dl_main (const ElfW(Phdr) *phdr,
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ElfW(Word) phnum,
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ElfW(Word) phnum,
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ElfW(Addr) *user_entry,
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ElfW(Addr) *user_entry,
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ElfW(auxv_t) *auxv)
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ElfW(auxv_t) *auxv)
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{
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{
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const ElfW(Phdr) *ph;
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struct link_map *main_map;
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struct link_map *main_map;
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size_t file_size;
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size_t file_size;
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char *file;
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char *file;
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bool has_interp = false;
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unsigned int i;
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unsigned int i;
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bool prelinked = false;
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bool prelinked = false;
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bool rtld_is_main = false;
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bool rtld_is_main = false;
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@ -1353,7 +1508,7 @@ dl_main (const ElfW(Phdr) *phdr,
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load the program below unless it has a PT_GNU_STACK indicating
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load the program below unless it has a PT_GNU_STACK indicating
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nonexecutable stack is ok. */
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nonexecutable stack is ok. */
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for (ph = phdr; ph < &phdr[phnum]; ++ph)
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for (const ElfW(Phdr) *ph = phdr; ph < &phdr[phnum]; ++ph)
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if (ph->p_type == PT_GNU_STACK)
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if (ph->p_type == PT_GNU_STACK)
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{
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{
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GL(dl_stack_flags) = ph->p_flags;
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GL(dl_stack_flags) = ph->p_flags;
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@ -1472,147 +1627,7 @@ dl_main (const ElfW(Phdr) *phdr,
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information for the program. */
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information for the program. */
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}
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}
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main_map->l_map_end = 0;
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bool has_interp = rtld_setup_main_map (main_map);
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main_map->l_text_end = 0;
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/* Perhaps the executable has no PT_LOAD header entries at all. */
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main_map->l_map_start = ~0;
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/* And it was opened directly. */
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++main_map->l_direct_opencount;
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/* Scan the program header table for the dynamic section. */
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for (ph = phdr; ph < &phdr[phnum]; ++ph)
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switch (ph->p_type)
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{
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case PT_PHDR:
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/* Find out the load address. */
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main_map->l_addr = (ElfW(Addr)) phdr - ph->p_vaddr;
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break;
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case PT_DYNAMIC:
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/* This tells us where to find the dynamic section,
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which tells us everything we need to do. */
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main_map->l_ld = (void *) main_map->l_addr + ph->p_vaddr;
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main_map->l_ld_readonly = (ph->p_flags & PF_W) == 0;
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break;
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case PT_INTERP:
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/* This "interpreter segment" was used by the program loader to
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find the program interpreter, which is this program itself, the
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dynamic linker. We note what name finds us, so that a future
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dlopen call or DT_NEEDED entry, for something that wants to link
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against the dynamic linker as a shared library, will know that
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the shared object is already loaded. */
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_dl_rtld_libname.name = ((const char *) main_map->l_addr
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+ ph->p_vaddr);
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/* _dl_rtld_libname.next = NULL; Already zero. */
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GL(dl_rtld_map).l_libname = &_dl_rtld_libname;
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/* Ordinarilly, we would get additional names for the loader from
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our DT_SONAME. This can't happen if we were actually linked as
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a static executable (detect this case when we have no DYNAMIC).
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If so, assume the filename component of the interpreter path to
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be our SONAME, and add it to our name list. */
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if (GL(dl_rtld_map).l_ld == NULL)
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{
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const char *p = NULL;
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const char *cp = _dl_rtld_libname.name;
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/* Find the filename part of the path. */
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while (*cp != '\0')
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if (*cp++ == '/')
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p = cp;
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if (p != NULL)
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{
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_dl_rtld_libname2.name = p;
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/* _dl_rtld_libname2.next = NULL; Already zero. */
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_dl_rtld_libname.next = &_dl_rtld_libname2;
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}
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}
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has_interp = true;
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break;
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case PT_LOAD:
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{
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ElfW(Addr) mapstart;
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ElfW(Addr) allocend;
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/* Remember where the main program starts in memory. */
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mapstart = (main_map->l_addr
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+ (ph->p_vaddr & ~(GLRO(dl_pagesize) - 1)));
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if (main_map->l_map_start > mapstart)
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main_map->l_map_start = mapstart;
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/* Also where it ends. */
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allocend = main_map->l_addr + ph->p_vaddr + ph->p_memsz;
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if (main_map->l_map_end < allocend)
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main_map->l_map_end = allocend;
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if ((ph->p_flags & PF_X) && allocend > main_map->l_text_end)
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main_map->l_text_end = allocend;
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}
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break;
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case PT_TLS:
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if (ph->p_memsz > 0)
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{
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/* Note that in the case the dynamic linker we duplicate work
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here since we read the PT_TLS entry already in
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_dl_start_final. But the result is repeatable so do not
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check for this special but unimportant case. */
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main_map->l_tls_blocksize = ph->p_memsz;
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main_map->l_tls_align = ph->p_align;
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if (ph->p_align == 0)
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main_map->l_tls_firstbyte_offset = 0;
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else
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main_map->l_tls_firstbyte_offset = (ph->p_vaddr
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& (ph->p_align - 1));
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main_map->l_tls_initimage_size = ph->p_filesz;
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main_map->l_tls_initimage = (void *) ph->p_vaddr;
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/* This image gets the ID one. */
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GL(dl_tls_max_dtv_idx) = main_map->l_tls_modid = 1;
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}
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break;
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case PT_GNU_STACK:
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GL(dl_stack_flags) = ph->p_flags;
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break;
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case PT_GNU_RELRO:
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main_map->l_relro_addr = ph->p_vaddr;
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main_map->l_relro_size = ph->p_memsz;
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break;
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}
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/* Process program headers again, but scan them backwards so
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that PT_NOTE can be skipped if PT_GNU_PROPERTY exits. */
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for (ph = &phdr[phnum]; ph != phdr; --ph)
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switch (ph[-1].p_type)
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{
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case PT_NOTE:
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_dl_process_pt_note (main_map, -1, &ph[-1]);
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break;
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case PT_GNU_PROPERTY:
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_dl_process_pt_gnu_property (main_map, -1, &ph[-1]);
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break;
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}
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/* Adjust the address of the TLS initialization image in case
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the executable is actually an ET_DYN object. */
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if (main_map->l_tls_initimage != NULL)
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main_map->l_tls_initimage
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= (char *) main_map->l_tls_initimage + main_map->l_addr;
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if (! main_map->l_map_end)
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main_map->l_map_end = ~0;
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if (! main_map->l_text_end)
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main_map->l_text_end = ~0;
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if (! GL(dl_rtld_map).l_libname && GL(dl_rtld_map).l_name)
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{
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/* We were invoked directly, so the program might not have a
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PT_INTERP. */
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_dl_rtld_libname.name = GL(dl_rtld_map).l_name;
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/* _dl_rtld_libname.next = NULL; Already zero. */
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GL(dl_rtld_map).l_libname = &_dl_rtld_libname;
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}
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else
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assert (GL(dl_rtld_map).l_libname); /* How else did we get here? */
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/* If the current libname is different from the SONAME, add the
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/* If the current libname is different from the SONAME, add the
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latter as well. */
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latter as well. */
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