[Bug dynamic-link/31799] New: -static-pie -Wl,-Ttext-segment=0x50000 doesn't work

[Bug dynamic-link/31799] New: -static-pie -Wl,-Ttext-segment=0x50000 doesn't work

[hjl.tools at gmail dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=31799

            Bug ID: 31799
           Summary: -static-pie -Wl,-Ttext-segment=0x50000 doesn't work
           Product: glibc
           Version: 2.40
            Status: NEW
          Severity: normal
          Priority: P2
         Component: dynamic-link
          Assignee: unassigned at sourceware dot org
          Reporter: hjl.tools at gmail dot com
  Target Milestone: ---

[hjl@gnu-cfl-3 tmp]$ cat x.c
int
main ()
{
  return 0;
}
[hjl@gnu-cfl-3 tmp]$ gcc -fPIE -static-pie -Wl,-Ttext-segment=0x50000 x.c
[hjl@gnu-cfl-3 tmp]$ readelf -h a.out 
ELF Header:
  Magic:   7f 45 4c 46 02 01 01 03 00 00 00 00 00 00 00 00 
  Class:                             ELF64
  Data:                              2's complement, little endian
  Version:                           1 (current)
  OS/ABI:                            UNIX - GNU
  ABI Version:                       0
  Type:                              EXEC (Executable file)
  Machine:                           Advanced Micro Devices X86-64
  Version:                           0x1
  Entry point address:               0x57750
  Start of program headers:          64 (bytes into file)
  Start of section headers:          824960 (bytes into file)
  Flags:                             0x0
  Size of this header:               64 (bytes)
  Size of program headers:           56 (bytes)
  Number of program headers:         12
  Size of section headers:           64 (bytes)
  Number of section headers:         37
  Section header string table index: 36
[hjl@gnu-cfl-3 tmp]$ ./a.out 
Segmentation fault (core dumped)
[hjl@gnu-cfl-3 tmp]$ 

Static PIE is marked ET_EXEC if its load address isn't 0.  It is done to sure
that -Wl,-Ttext-segment=0x50000 works.

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[Bug dynamic-link/31799] -static-pie -Wl,-Ttext-segment=0x50000 doesn't work

[hjl.tools at gmail dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=31799

H.J. Lu <hjl.tools at gmail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|---                         |2.40
           Assignee|unassigned at sourceware dot org   |hjl.tools at gmail dot com
             Status|NEW                         |ASSIGNED

--- Comment #1 from H.J. Lu <hjl.tools at gmail dot com> ---
This works:

diff --git a/elf/dl-reloc-static-pie.c b/elf/dl-reloc-static-pie.c
index 10c23d0bf0..939113f688 100644
--- a/elf/dl-reloc-static-pie.c
+++ b/elf/dl-reloc-static-pie.c
@@ -32,16 +32,20 @@

 /* Relocate static executable with PIE.  */

+extern const ElfW(Ehdr) __ehdr_start attribute_hidden;
+
 void
 _dl_relocate_static_pie (void)
 {
   struct link_map *main_map = _dl_get_dl_main_map ();

   /* Figure out the run-time load address of static PIE.  */
-  main_map->l_addr = elf_machine_load_address ();
+  ElfW(Addr) l_addr = elf_machine_load_address ();
+  if (__ehdr_start.e_type == ET_DYN)
+    main_map->l_addr = l_addr;

   /* Read our own dynamic section and fill in the info array.  */
-  main_map->l_ld = ((void *) main_map->l_addr + elf_machine_dynamic ());
+  main_map->l_ld = ((void *) l_addr + elf_machine_dynamic ());

   const ElfW(Phdr) *ph, *phdr = GL(dl_phdr);
   size_t phnum = GL(dl_phnum);

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[Bug dynamic-link/31799] -static-pie -Wl,-Ttext-segment=0x50000 doesn't work

[hjl.tools at gmail dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=31799

H.J. Lu <hjl.tools at gmail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           See Also|                            |https://sourceware.org/bugz
                   |                            |illa/show_bug.cgi?id=31795

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[Bug dynamic-link/31799] -static-pie -Wl,-Ttext-segment=0x50000 doesn't work

[hjl.tools at gmail dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=31799

--- Comment #2 from H.J. Lu <hjl.tools at gmail dot com> ---
For static PIE, its dynamic section entries contain the relocated values for
the
load address.  We can't relocate them again.

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[Bug dynamic-link/31799] -static-pie -Wl,-Ttext-segment=0x50000 doesn't work

[i at maskray dot me]

https://sourceware.org/bugzilla/show_bug.cgi?id=31799

Fangrui Song <i at maskray dot me> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |i at maskray dot me

--- Comment #3 from Fangrui Song <i at maskray dot me> ---
> Static PIE is marked ET_EXEC if its load address isn't 0.  It is done to sure that -Wl,-Ttext-segment=0x50000 works.

I think we should revisit the 2013 GNU ld special case.
See https://sourceware.org/bugzilla/show_bug.cgi?id=31795#c37 : the --no-pie
option added in 2021 makes the special case unnecessary.

musl supports the first PT_LOAD having a non-zero p_vaddr.
Fixing the segfault is desired.
However, there is probably no requirement that loaders (kernel / rtld) should
make the image base >= p_vaddr.

```
% ~/musl/out/debug/obj/musl-gcc -fpie a.c -static-pie -fuse-ld=lld
-Wl,--image-base=0x50000 -o a
% ./a
0x7f036cf6b599

% gcc -fpie a.c -static-pie -fuse-ld=lld -Wl,--image-base=0x50000 -o a
% ./a
[1]    2347408 segmentation fault  ./a
```

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[Bug dynamic-link/31799] -static-pie -Wl,-Ttext-segment=0x50000 doesn't work

[fweimer at redhat dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=31799

Florian Weimer <fweimer at redhat dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
              Flags|                            |security-
                 CC|                            |fweimer at redhat dot com

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