Re: [PATCH] elf: Replace tst-p_alignmod1-editX with a python script

[Adhemerval Zanella <adhemerval.zanella@linaro.org>]

On 26/01/2022 13:11, H.J. Lu wrote:
> On Wed, Jan 26, 2022 at 7:54 AM Adhemerval Zanella
> <adhemerval.zanella@linaro.org> wrote:
>>
>>
>>
>> On 26/01/2022 12:46, H.J. Lu wrote:
>>> On Wed, Jan 26, 2022 at 7:45 AM Adhemerval Zanella
>>> <adhemerval.zanella@linaro.org> wrote:
>>>>
>>>>
>>>>
>>>> On 26/01/2022 12:35, H.J. Lu wrote:
>>>>> On Wed, Jan 26, 2022 at 4:10 AM Adhemerval Zanella
>>>>> <adhemerval.zanella@linaro.org> wrote:
>>>>>>
>>>>>>
>>>>>>
>>>>>> On 26/01/2022 07:09, Florian Weimer wrote:
>>>>>>> * Adhemerval Zanella via Libc-alpha:
>>>>>>>
>>>>>>>> diff --git a/scripts/tst-elf-edit.py b/scripts/tst-elf-edit.py
>>>>>>>> new file mode 100644
>>>>>>>> index 0000000000..1fb9b8e0fe
>>>>>>>> --- /dev/null
>>>>>>>> +++ b/scripts/tst-elf-edit.py
>>>>>>>> @@ -0,0 +1,206 @@
>>>>>>>
>>>>>>>> +class Elf_Ehdr:
>>>>>>>> +    def __init__(self, e_ident):
>>>>>>>> +        endian, addr, off = elf_types_fmts(e_ident)
>>>>>>>> +        self.fmt = '{0}HHI{1}{2}{2}IHHHHHH'.format(endian, addr, off)
>>>>>>>> +        self.len = struct.calcsize(self.fmt)
>>>>>>>> +
>>>>>>>> +    def read(self, f):
>>>>>>>> +        buf = f.read(self.len)
>>>>>>>> +        if not buf:
>>>>>>>> +            error('{}: header too small'.format(f.name))
>>>>>>>
>>>>>>> I think you need to check len(buf) < self.len.
>>>>>>
>>>>>> Ack.
>>>>>>
>>>>>>>
>>>>>>>> +class Elf_Phdr:
>>>>>>>> +    def __init__(self, e_ident):
>>>>>>>> +        endian, addr, off = elf_types_fmts(e_ident)
>>>>>>>> +        self.ei_class = e_ident[EI_CLASS]
>>>>>>>> +        if self.ei_class == ELFCLASS32:
>>>>>>>> +            self.fmt = '{0}I{2}{1}{1}IIII'.format(endian, addr, off)
>>>>>>>> +        else:
>>>>>>>> +            self.fmt = '{0}II{2}{1}{1}QQQ'.format(endian, addr, off)
>>>>>>>> +        self.len = struct.calcsize(self.fmt)
>>>>>>>> +
>>>>>>>> +    def read(self, f):
>>>>>>>> +        buf = f.read(self.len)
>>>>>>>> +        if not buf:
>>>>>>>> +            error('{}: program header too small'.format(f.name))
>>>>>>>
>>>>>>> Here as well.
>>>>>>
>>>>>> Ack.
>>>>>>
>>>>>>>
>>>>>>> Rest looks okay.
>>>>>>
>>>>>> Thanks, I push it upstream with the above fixes installed.
>>>>>
>>>>> I got
>>>>>
>>>>> FAIL: elf/tst-p_align3
>>>>>
>>>>> [hjl@gnu-tgl-2 build-x86_64-linux]$ cat elf/tst-p_align3.out
>>>>> /export/build/gnu/tools-build/glibc-cet-gitlab/build-x86_64-linux/elf/tst-p_align3:
>>>>> error while loading shared libraries:
>>>>> /export/build/gnu/tools-build/glibc-cet-gitlab/build-x86_64-linux/elf/tst-p_alignmod3.so:
>>>>> cannot change memory protections
>>>>> [hjl@gnu-tgl-2 build-x86_64-linux]$
>>>>>
>>>>> Only p_align should be changed to 0x100.  But I  saw
>>>>
>>>> I am not sure if this is related because tst-p_align3 and tst-alignmod3.so uses
>>>> LDFLAGS instead:
>>>>
>>>> 1644 $(objpfx)tst-align3: $(objpfx)tst-alignmod3.so
>>>> 1645 ifeq (yes,$(have-fpie))
>>>> 1646 CFLAGS-tst-align3.c += $(PIE-ccflag)
>>>> 1647 endif
>>>> 1648 LDFLAGS-tst-align3 += -Wl,-z,max-page-size=0x200000
>>>> 1649 LDFLAGS-tst-alignmod3.so += -Wl,-z,max-page-size=0x200000
>>>> 1650 $(objpfx)tst-alignmod3.so: $(libsupport)
>>>>
>>>> And the patch only changed the way tst-p_align1 and tst-p_align2 modules were
>>>> changed.
>>>
>>> It is tst-p_alignmod3.so, not tst-alignmod3.so.
>>>             ^^
>> My confusion here. But even though the script in not involved:
>>
>> 2622 LDFLAGS-tst-p_alignmod3.so += -Wl,-z,max-page-size=0x100,-z,common-page-size=0x100
>> 2623
>> 2624 $(objpfx)tst-p_align3: $(objpfx)tst-p_alignmod3.so
>> 2625 $(objpfx)tst-p_align3.out: tst-p_align3.sh $(objpfx)tst-p_align3
>> 2626         $(SHELL) $< $(common-objpfx) '$(test-program-prefix)'; \
>> 2627         $(evaluate-test)
>>
>> That's why it is puzzling me that it start to fail now.
> 
> This test checks the invalid p_align handling.   You have to edit the
> binary to change p_align to 0x100 which is invalid.
> 

But it is already done by the LD_FLAGS above (from elf/Makefile).  I am
still failing to understand why my patch that only changes tst-p_align1 
and tst-p_align2 objects made tst-p_align3 to fail.

Before:

$ readelf -l elf/tst-p_align3
[...]
  LOAD           0x0000000000000000 0x0000000000000000 0x0000000000000000
                 0x00000000000015c0 0x00000000000015c0  R      0x1000
  LOAD           0x0000000000002000 0x0000000000002000 0x0000000000002000
                 0x0000000000001892 0x0000000000001892  R E    0x1000
  LOAD           0x0000000000004000 0x0000000000004000 0x0000000000004000
                 0x0000000000000d58 0x0000000000000d58  R      0x1000
  LOAD           0x0000000000005cf8 0x0000000000006cf8 0x0000000000006cf8
                 0x0000000000000498 0x00000000000004d8  RW     0x1000
[...]
$ readelf -l elf/tst-p_alignmod3.so 
[....]
Program Headers:
  Type           Offset             VirtAddr           PhysAddr
                 FileSiz            MemSiz              Flags  Align
  LOAD           0x0000000000000000 0x0000000000000000 0x0000000000000000
                 0x0000000000000540 0x0000000000000540  R      0x100
  LOAD           0x0000000000000600 0x0000000000000600 0x0000000000000600
                 0x00000000000001f2 0x00000000000001f2  R E    0x100
  LOAD           0x0000000000000800 0x0000000000000800 0x0000000000000800
                 0x00000000000000d0 0x00000000000000d0  R      0x100
  LOAD           0x0000000000000930 0x0000000000000a30 0x0000000000000a30

                 0x00000000000001f8 0x0000000000000208  RW     0x100
After:

$ readelf -l elf/tst-p_align3
[...]
  LOAD           0x0000000000000000 0x0000000000000000 0x0000000000000000
                 0x00000000000015b8 0x00000000000015b8  R      0x1000
  LOAD           0x0000000000002000 0x0000000000002000 0x0000000000002000
                 0x0000000000001892 0x0000000000001892  R E    0x1000
  LOAD           0x0000000000004000 0x0000000000004000 0x0000000000004000
                 0x0000000000000d50 0x0000000000000d50  R      0x1000
  LOAD           0x0000000000005cf8 0x0000000000006cf8 0x0000000000006cf8
                 0x0000000000000498 0x00000000000004d8  RW     0x1000

$ readelf -l elf/tst-p_alignmod3.so
Elf file type is DYN (Shared object file)
[....]
Program Headers:
  Type           Offset             VirtAddr           PhysAddr
                 FileSiz            MemSiz              Flags  Align
  LOAD           0x0000000000000000 0x0000000000000000 0x0000000000000000
                 0x0000000000000540 0x0000000000000540  R      0x100
  LOAD           0x0000000000000600 0x0000000000000600 0x0000000000000600
                 0x00000000000001f2 0x00000000000001f2  R E    0x100
  LOAD           0x0000000000000800 0x0000000000000800 0x0000000000000800
                 0x00000000000000d0 0x00000000000000d0  R      0x100
  LOAD           0x0000000000000930 0x0000000000000a30 0x0000000000000a30
                 0x00000000000001f8 0x0000000000000208  RW     0x100

So PT_LOAD p_align are still strictly the same.