mobile-shell / mobile-shell/mosh
Investigate -pie vs -Wl,-pie on OS X
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- Dominant language
- C++
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Description
[from a blog comment]
I believe for Mac OS X you need to use -Wl,-pie even with gcc. If you use gcc -v when linking on Mac OS X you won't see -pie being passed to the linker. Here's the output of otool -h on an executable built with -pie in LDFLAGS on Mac OS X 10.6:
Mach header
magic cputype cpusubtype caps filetype ncmds sizeofcmds flags
0xfeedfacf 16777223 3 0x80 2 11 1776 0x00000085
Compare that to one built with -Wl,-pie
Mach header
magic cputype cpusubtype caps filetype ncmds sizeofcmds flags
0xfeedfacf 16777223 3 0x80 2 11 1776 0x00200085
In /usr/include/mach-o/loader.h we find this:
#define MH_PIE 0x200000 /* When this bit is set, the OS will
load the main executable at a
random address. Only used in
MH_EXECUTE filetypes. */
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First steps
- Read the whole issue, then the project's contributing guide.
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Research direction
Reproduce the two linking cases on OS X and compare the otool -h output, using the reported gcc -v behavior as a starting point. Read /usr/include/mach-o/loader.h for the MH_PIE definition; done means the effect of -pie versus -Wl,-pie and any required project change are established.
Written by the indexing model from the issue text.
Assessment
- Tech stack
- cpp, macos
- Domain
- build-system, security
- Issue type
- Bug
- Difficulty
- 4/5
- Estimated time
- 3-5 days
- Activity status
- Stale
- Clarity
- Mostly clear
- Newbie friendliness
- 35/100