https://sourceware.org/bugzilla/show_bug.cgi?id=26312
Bug ID: 26312
Summary: ld produces broken PLT on aarch64 with BTI+PAC
Product: binutils
Version: 2.35
Status: NEW
Severity: normal
Priority: P2
Component: ld
Assignee: unassigned at sourceware dot org
Reporter: fweimer at redhat dot com
Target Milestone: ---
Target: aarch64
Building glibc 2.32 on Fedora rawhide with GCC 10.2,
-mbranch-protection=standard, and binutils 2.35 results in a libc.so.6 which
lacks PAC support, possibly due to missing PAC in libgcc.a for the outline
atomics. (We build with -moutline-atomics as well.) This in itself should not
be a problem.
However, catgets/gencat is mislinked. The PLT is corrupted because its entry
size is not constant (32 bytes for the first entry, 24 bytes for subsequent
entryes, section table says 24 bytes):
Disassembly of section .plt:
0000000000401140 <.plt>:
401140: d503245f bti c
401144: a9bf7bf0 stp x16, x30, [sp, #-16]!
401148: d00000f0 adrp x16, 41f000 <__FRAME_END__+0x1abd4>
40114c: f9474a11 ldr x17, [x16, #3728]
401150: 913a4210 add x16, x16, #0xe90
401154: d61f0220 br x17
401158: d503201f nop
40115c: d503201f nop
0000000000401160 <memcpy@plt>:
401160: d503245f bti c
401164: d00000f0 adrp x16, 41f000 <__FRAME_END__+0x1abd4>
401168: f9474e11 ldr x17, [x16, #3736]
40116c: 913a6210 add x16, x16, #0xe98
401170: d61f0220 br x17
401174: d503201f nop
0000000000401178 <strlen@plt>:
401178: d503245f bti c
40117c: d00000f0 adrp x16, 41f000 <__FRAME_END__+0x1abd4>
401180: f9475211 ldr x17, [x16, #3744]
401184: 913a8210 add x16, x16, #0xea0
401188: d61f0220 br x17
40118c: d503201f nop
I mentioned the lack of PAC earlier because ld seems to be confused about the
PAC status. It only sets DT_AARCH64_BTI_PLT:
Dynamic section at offset 0xfc60 contains 29 entries:
Tag Type Name/Value
0x0000000000000001 (NEEDED) Shared library: [libc.so.6]
0x0000000000000001 (NEEDED) Shared library:
[ld-linux-aarch64.so.1]
0x000000000000000c (INIT) 0x401120
0x000000000000000d (FINI) 0x403868
0x0000000000000019 (INIT_ARRAY) 0x41fc40
0x000000000000001b (INIT_ARRAYSZ) 8 (bytes)
0x000000000000001a (FINI_ARRAY) 0x41fc48
0x000000000000001c (FINI_ARRAYSZ) 8 (bytes)
0x0000000000000004 (HASH) 0x400330
0x000000006ffffef5 (GNU_HASH) 0x400498
0x0000000000000005 (STRTAB) 0x400990
0x0000000000000006 (SYMTAB) 0x4004e0
0x000000000000000a (STRSZ) 575 (bytes)
0x000000000000000b (SYMENT) 24 (bytes)
0x0000000000000015 (DEBUG) 0x0
0x0000000000000003 (PLTGOT) 0x41fe80
0x0000000000000002 (PLTRELSZ) 1008 (bytes)
0x0000000000000014 (PLTREL) RELA
0x0000000000000017 (JMPREL) 0x400d30
0x0000000000000007 (RELA) 0x400c88
0x0000000000000008 (RELASZ) 168 (bytes)
0x0000000000000009 (RELAENT) 24 (bytes)
0x0000000070000001 (AARCH64_BTI_PLT)
0x0000000000000018 (BIND_NOW)
0x000000006ffffffb (FLAGS_1) Flags: NOW
0x000000006ffffffe (VERNEED) 0x400c38
0x000000006fffffff (VERNEEDNUM) 2
0x000000006ffffff0 (VERSYM) 0x400bd0
0x0000000000000000 (NULL) 0x0
But the note says it has both:
Displaying notes found in: .note.gnu.property
Owner Data size Description
GNU 0x00000010 NT_GNU_PROPERTY_TYPE_0
Properties: AArch64 feature: BTI, PAC
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