Re: [Patch] ld: check for address space overflow

["H.J. Lu" <hjl dot tools at gmail dot com>]

On Mon, Mar 13, 2017 at 12:06 PM, H.J. Lu <hjl.tools@gmail.com> wrote:
> On Fri, Mar 10, 2017 at 6:29 AM, Tristan Gingold <gingold@adacore.com> wrote:
>> Hello,
>>
>> currently the linker allows to put a section which starts near the end of the address space and which ends past the end (so wrap around).  I think this should be flagged as an error.
>>
>> No regression on powerpc-elf
>>
>> Ok for master ?
>>
>> Tristan.
>>
>> commit 09718888d36a07cc9c71aa301a39a4299dbf8c34
>> Author: Tristan Gingold <gingold@adacore.com>
>> Date:   Fri Mar 10 15:16:19 2017 +0100
>>
>>     ld: add an error in case of address space overflow.
>>
>>     ld/
>>         * ldlang.c (lang_check_section_addresses): Check for address space
>>         overflow.
>>         * testsuite/ld-checks/checks.exp (overflow_check): New procedure
>>         * testsuite/ld-checks/over.s: New test source.
>>         * testsuite/ld-checks/over.d: New test.
>>         * testsuite/ld-checks/over2.s: New test source.
>>         * testsuite/ld-checks/over2.d: New test.
>>
>> diff --git a/ld/ChangeLog b/ld/ChangeLog
>> index 3883bcb..5387210 100644
>> --- a/ld/ChangeLog
>> +++ b/ld/ChangeLog
>> @@ -1,3 +1,13 @@
>> +2017-03-10  Tristan Gingold  <gingold@adacore.com>
>> +
>> +       * ldlang.c (lang_check_section_addresses): Check for address space
>> +       overflow.
>> +       * testsuite/ld-checks/checks.exp (overflow_check): New procedure
>> +       * testsuite/ld-checks/over.s: New test source.
>> +       * testsuite/ld-checks/over.d: New test.
>> +       * testsuite/ld-checks/over2.s: New test source.
>> +       * testsuite/ld-checks/over2.d: New test.
>> +
>>  2017-03-07  Alan Modra  <amodra@gmail.com>
>>
>>         * ldlang.c (open_input_bfds): Check that lang_assignment_statement
>> diff --git a/ld/ldlang.c b/ld/ldlang.c
>> index ff6ef39..36b6884 100644
>> --- a/ld/ldlang.c
>> +++ b/ld/ldlang.c
>> @@ -4768,6 +4768,7 @@ lang_check_section_addresses (void)
>>    asection *s, *p;
>>    struct check_sec *sections;
>>    size_t i, count;
>> +  bfd_vma addr_mask;
>>    bfd_vma s_start;
>>    bfd_vma s_end;
>>    bfd_vma p_start = 0;
>> @@ -4775,6 +4776,25 @@ lang_check_section_addresses (void)
>>    lang_memory_region_type *m;
>>    bfd_boolean overlays;
>>
>> +  /* Detect address space overflow.  */
>> +  addr_mask = ((bfd_vma) 1 <<
>> +              (bfd_arch_bits_per_address (link_info.output_bfd) - 1)) - 1;
>
> This isn't correct.  See is32bit () in bfd.c.  And it doesn't work
> for -0x80000000 with 64-bit VMA for 32-bit targets.
>
>> +  addr_mask = (addr_mask << 1) + 1;
>> +  for (s = link_info.output_bfd->sections; s != NULL; s = s->next)
>> +    {
>> +      s_end = (s->vma + s->size) & addr_mask;
>> +      if (s_end != 0 && s_end < s->vma)
>> +       einfo (_("%X%P: section %s VMA wraps around address space\n"),
>> +              s->name);
>> +      else
>> +       {
>> +         s_end = (s->lma + s->size) & addr_mask;
>> +         if (s_end != 0 && s_end < s->lma)
>> +           einfo (_("%X%P: section %s LMA wraps around address space\n"),
>> +                  s->name);
>> +       }
>> +    }

This works:

diff --git a/ld/ldlang.c b/ld/ldlang.c
index a0638ea..8c1d829 100644
--- a/ld/ldlang.c
+++ b/ld/ldlang.c
@@ -4783,13 +4783,13 @@ lang_check_section_addresses (void)
   for (s = link_info.output_bfd->sections; s != NULL; s = s->next)
     {
       s_end = (s->vma + s->size) & addr_mask;
-      if (s_end != 0 && s_end < s->vma)
+      if (s_end != 0 && s_end < (s->vma & addr_mask))
   einfo (_("%X%P: section %s VMA wraps around address space\n"),
          s->name);
       else
   {
     s_end = (s->lma + s->size) & addr_mask;
-    if (s_end != 0 && s_end < s->lma)
+    if (s_end != 0 && s_end < (s->lma & addr_mask))
       einfo (_("%X%P: section %s LMA wraps around address space\n"),
         s->name);
   }


>> +
>>    if (bfd_count_sections (link_info.output_bfd) <= 1)
>>      return;



-- 
H.J.