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cmSystemTools, elf: handle DT_MIPS_RLD_REL_MAP in RemoveRPath

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This commit is contained in:
James Cowgill 2016-10-05 17:20:58 +01:00 committed by Brad King
parent b8b1d15186
commit cd4f573ae9
3 changed files with 31 additions and 1 deletions
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6
Source/cmELF.cxx
View File

@ -700,6 +700,12 @@ cmELF::StringEntry const* cmELFInternalImpl<Types>::GetDynamicSectionString(
const long cmELF::TagRPath = DT_RPATH;
const long cmELF::TagRunPath = DT_RUNPATH;
#ifdef DT_MIPS_RLD_MAP_REL
const long cmELF::TagMipsRldMapRel = DT_MIPS_RLD_MAP_REL;
#else
const long cmELF::TagMipsRldMapRel = 0;
#endif
cmELF::cmELF(const char* fname)
: Internal(CM_NULLPTR)
{

2
Source/cmELF.h
View File

@ -107,7 +107,7 @@ public:
/** Interesting dynamic tags.
If the tag is 0, it does not exist in the host ELF implementation */
static const long TagRPath, TagRunPath;
static const long TagRPath, TagRunPath, TagMipsRldMapRel;
private:
friend class cmELFInternal;

24
Source/cmSystemTools.cxx
View File

@ -2536,6 +2536,10 @@ bool cmSystemTools::RemoveRPath(std::string const& file, std::string* emsg,
zeroSize[i] = se[i]->Size;
}
// Get size of one DYNAMIC entry
unsigned long const sizeof_dentry =
elf.GetDynamicEntryPosition(1) - elf.GetDynamicEntryPosition(0);
// Adjust the entry list as necessary to remove the run path
unsigned long entriesErased = 0;
for (cmELF::DynamicEntryList::iterator it = dentries.begin();
@ -2545,6 +2549,26 @@ bool cmSystemTools::RemoveRPath(std::string const& file, std::string* emsg,
entriesErased++;
continue;
} else {
if (cmELF::TagMipsRldMapRel != 0 &&
it->first == cmELF::TagMipsRldMapRel) {
// Background: debuggers need to know the "linker map" which contains
// the addresses each dynamic object is loaded at. Most arches use
// the DT_DEBUG tag which the dynamic linker writes to (directly) and
// contain the location of the linker map, however on MIPS the
// .dynamic section is always read-only so this is not possible. MIPS
// objects instead contain a DT_MIPS_RLD_MAP tag which contains the
// address where the dyanmic linker will write to (an indirect
// version of DT_DEBUG). Since this doesn't work when using PIE, a
// relative equivalent was created - DT_MIPS_RLD_MAP_REL. Since this
// version contains a relative offset, moving it changes the
// calculated address. This may cause the dyanmic linker to write
// into memory it should not be changing.
//
// To fix this, we adjust the value of DT_MIPS_RLD_MAP_REL here. If
// we move it up by n bytes, we add n bytes to the value of this tag.
it->second += entriesErased * sizeof_dentry;
}
it++;
}
}