[lld] r361090 - [ARM][AArch64] Revert Android Bionic PT_TLS overaligning hack
Fangrui Song via llvm-commits
llvm-commits at lists.llvm.org
Fri May 17 20:16:00 PDT 2019
Author: maskray
Date: Fri May 17 20:16:00 2019
New Revision: 361090
URL: http://llvm.org/viewvc/llvm-project?rev=361090&view=rev
Log:
[ARM][AArch64] Revert Android Bionic PT_TLS overaligning hack
This reverts D53906.
D53906 increased p_align of PT_TLS on ARM/AArch64 to 32/64 to make the
static TLS layout compatible with Android Bionic's ELF TLS. However,
this may cause glibc ARM/AArch64 programs to crash (see PR41527).
The faulty PT_TLS in the executable satisfies p_vaddr%p_align != 0. The
remainder is normally 0 but may be non-zero with the hack in place. The
problem is that we increase PT_TLS's p_align after OutputSections'
addresses are fixed (assignAddress()). It is possible that
p_vaddr%old_p_align = 0 while p_vaddr%new_p_align != 0.
For a thread local variable defined in the executable, lld computed TLS
offset (local exec) is different from glibc computed TLS offset from
another module (initial exec/generic dynamic). Note: PR41527 said the
bug affects initial exec but actually generic dynamic is affected as
well.
(glibc is correct in that it compute offsets that satisfy
`offset%p_align == p_vaddr%p_align`, which is a basic ELF requirement.
This hack appears to work on FreeBSD rtld, musl<=1.1.22, and Bionic, but
that is just because they (and lld) incorrectly compute offsets that
satisfy `offset%p_align = 0` instead.)
Android developers are fine to revert this patch, carry this patch in
their tree before figuring out a long-term solution (e.g. a dummy .tdata
with sh_addralign=64 sh_size={0,1} in crtbegin*.o files. The overhead is
now insignificant after D62059).
Reviewed By: rprichard, srhines
Differential Revision: https://reviews.llvm.org/D62055
Modified:
lld/trunk/ELF/InputSection.cpp
lld/trunk/ELF/Writer.cpp
lld/trunk/test/ELF/aarch64-cortex-a53-843419-tlsrelax.s
lld/trunk/test/ELF/aarch64-tls-gdle.s
lld/trunk/test/ELF/aarch64-tls-iele.s
lld/trunk/test/ELF/aarch64-tls-le.s
lld/trunk/test/ELF/aarch64-tlsld-ldst.s
lld/trunk/test/ELF/arm-tls-le32.s
lld/trunk/test/ELF/arm-tls-norelax-ie-le.s
Modified: lld/trunk/ELF/InputSection.cpp
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/InputSection.cpp?rev=361090&r1=361089&r2=361090&view=diff
==============================================================================
--- lld/trunk/ELF/InputSection.cpp (original)
+++ lld/trunk/ELF/InputSection.cpp Fri May 17 20:16:00 2019
@@ -590,10 +590,6 @@ static int64_t getTlsTpOffset() {
// Variant 1. The thread pointer points to a TCB with a fixed 2-word size,
// followed by a variable amount of alignment padding, followed by the TLS
// segment.
- //
- // NB: While the ARM/AArch64 ABI formally has a 2-word TCB size, lld
- // effectively increases the TCB size to 8 words for Android compatibility.
- // It accomplishes this by increasing the segment's alignment.
return alignTo(Config->Wordsize * 2, Out::TlsPhdr->p_align);
case EM_386:
case EM_X86_64:
Modified: lld/trunk/ELF/Writer.cpp
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/Writer.cpp?rev=361090&r1=361089&r2=361090&view=diff
==============================================================================
--- lld/trunk/ELF/Writer.cpp (original)
+++ lld/trunk/ELF/Writer.cpp Fri May 17 20:16:00 2019
@@ -2190,19 +2190,6 @@ template <class ELFT> void Writer<ELFT>:
// rounds up.
P->p_memsz = alignTo(P->p_memsz, Config->CommonPageSize);
}
-
- if (P->p_type == PT_TLS && P->p_memsz) {
- if (!Config->Shared &&
- (Config->EMachine == EM_ARM || Config->EMachine == EM_AARCH64)) {
- // On ARM/AArch64, reserve extra space (8 words) between the thread
- // pointer and an executable's TLS segment by overaligning the segment.
- // This reservation is needed for backwards compatibility with Android's
- // TCB, which allocates several slots after the thread pointer (e.g.
- // TLS_SLOT_STACK_GUARD==5). For simplicity, this overalignment is also
- // done on other operating systems.
- P->p_align = std::max<uint64_t>(P->p_align, Config->Wordsize * 8);
- }
- }
}
}
Modified: lld/trunk/test/ELF/aarch64-cortex-a53-843419-tlsrelax.s
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/test/ELF/aarch64-cortex-a53-843419-tlsrelax.s?rev=361090&r1=361089&r2=361090&view=diff
==============================================================================
--- lld/trunk/test/ELF/aarch64-cortex-a53-843419-tlsrelax.s (original)
+++ lld/trunk/test/ELF/aarch64-cortex-a53-843419-tlsrelax.s Fri May 17 20:16:00 2019
@@ -26,9 +26,9 @@ _start:
// CHECK: _start:
// CHECK-NEXT: 210ff8: 41 d0 3b d5 mrs x1, TPIDR_EL0
// CHECK-NEXT: 210ffc: 00 00 a0 d2 movz x0, #0, lsl #16
-// CHECK-NEXT: 211000: 01 08 80 f2 movk x1, #64
+// CHECK-NEXT: 211000: 01 02 80 f2 movk x1, #16
// CHECK-NEXT: 211004: 00 00 a0 d2 movz x0, #0, lsl #16
-// CHECK-NEXT: 211008: 01 08 80 f2 movk x1, #64
+// CHECK-NEXT: 211008: 01 02 80 f2 movk x1, #16
// CHECK-NEXT: 21100c: c0 03 5f d6 ret
.type v, at object
Modified: lld/trunk/test/ELF/aarch64-tls-gdle.s
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/test/ELF/aarch64-tls-gdle.s?rev=361090&r1=361089&r2=361090&view=diff
==============================================================================
--- lld/trunk/test/ELF/aarch64-tls-gdle.s (original)
+++ lld/trunk/test/ELF/aarch64-tls-gdle.s Fri May 17 20:16:00 2019
@@ -9,12 +9,12 @@
#RELOC: Relocations [
#RELOC-NEXT: ]
-# TCB size = 64 and foo is first element from TLS register.
+# TCB size = 0x16 and foo is first element from TLS register.
# CHECK: Disassembly of section .text:
# CHECK-EMPTY:
# CHECK: _start:
# CHECK: 210000: 00 00 a0 d2 movz x0, #0, lsl #16
-# CHECK: 210004: 00 08 80 f2 movk x0, #64
+# CHECK: 210004: 00 02 80 f2 movk x0, #16
# CHECK: 210008: 1f 20 03 d5 nop
# CHECK: 21000c: 1f 20 03 d5 nop
Modified: lld/trunk/test/ELF/aarch64-tls-iele.s
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/test/ELF/aarch64-tls-iele.s?rev=361090&r1=361089&r2=361090&view=diff
==============================================================================
--- lld/trunk/test/ELF/aarch64-tls-iele.s (original)
+++ lld/trunk/test/ELF/aarch64-tls-iele.s Fri May 17 20:16:00 2019
@@ -9,14 +9,14 @@
# RELOC: Relocations [
# RELOC-NEXT: ]
-# TCB size = 64 and foo is first element from TLS register.
+# TCB size = 0x16 and foo is first element from TLS register.
# CHECK: Disassembly of section .text:
# CHECK-EMPTY:
# CHECK: _start:
# CHECK-NEXT: 210000: 00 00 a0 d2 movz x0, #0, lsl #16
-# CHECK-NEXT: 210004: 80 08 80 f2 movk x0, #68
+# CHECK-NEXT: 210004: 80 02 80 f2 movk x0, #20
# CHECK-NEXT: 210008: 00 00 a0 d2 movz x0, #0, lsl #16
-# CHECK-NEXT: 21000c: 00 08 80 f2 movk x0, #64
+# CHECK-NEXT: 21000c: 00 02 80 f2 movk x0, #16
.section .tdata
.align 2
Modified: lld/trunk/test/ELF/aarch64-tls-le.s
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/test/ELF/aarch64-tls-le.s?rev=361090&r1=361089&r2=361090&view=diff
==============================================================================
--- lld/trunk/test/ELF/aarch64-tls-le.s (original)
+++ lld/trunk/test/ELF/aarch64-tls-le.s Fri May 17 20:16:00 2019
@@ -17,12 +17,12 @@ _start:
add x0, x0, :tprel_hi12:v2
add x0, x0, :tprel_lo12_nc:v2
-# TCB size = 64 and foo is first element from TLS register.
+# TCB size = 0x16 and foo is first element from TLS register.
#CHECK: Disassembly of section .text:
#CHECK: _start:
#CHECK: 210000: 40 d0 3b d5 mrs x0, TPIDR_EL0
#CHECK: 210004: 00 00 40 91 add x0, x0, #0, lsl #12
-#CHECK: 210008: 00 00 01 91 add x0, x0, #64
+#CHECK: 210008: 00 40 00 91 add x0, x0, #16
#CHECK: 21000c: 40 d0 3b d5 mrs x0, TPIDR_EL0
#CHECK: 210010: 00 fc 7f 91 add x0, x0, #4095, lsl #12
#CHECK: 210014: 00 e0 3f 91 add x0, x0, #4088
@@ -36,9 +36,9 @@ v1:
.word 0
.size v1, 4
-# The current offset from the thread pointer is 68. Raise it to just below the
+# The current offset from the thread pointer is 20. Raise it to just below the
# 24-bit limit.
-.space (0xfffff8 - 68)
+.space (0xfffff8 - 20)
.type v2, at object
.globl v2
Modified: lld/trunk/test/ELF/aarch64-tlsld-ldst.s
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/test/ELF/aarch64-tlsld-ldst.s?rev=361090&r1=361089&r2=361090&view=diff
==============================================================================
--- lld/trunk/test/ELF/aarch64-tlsld-ldst.s (original)
+++ lld/trunk/test/ELF/aarch64-tlsld-ldst.s Fri May 17 20:16:00 2019
@@ -26,27 +26,27 @@ _start: mrs x8, TPIDR_EL0
// CHECK: _start:
// CHECK-NEXT: 210000: 48 d0 3b d5 mrs x8, TPIDR_EL0
-// 0x0 + c40 = 0xc40 = tcb (64-bytes) + var0
-// CHECK-NEXT: 210004: 08 01 40 91 add x8, x8, #0, lsl #12
-// CHECK-NEXT: 210008: 14 11 c3 3d ldr q20, [x8, #3136]
-// 0x1000 + 0x850 = 0x1850 = tcb + var1
-// CHECK-NEXT: 21000c: 08 05 40 91 add x8, x8, #1, lsl #12
-// CHECK-NEXT: 210010: 00 29 44 f9 ldr x0, [x8, #2128]
-// 0x2000 + 0x458 = 0x2458 = tcb + var2
-// CHECK-NEXT: 210014: 08 09 40 91 add x8, x8, #2, lsl #12
-// CHECK-NEXT: 210018: 00 59 44 b9 ldr w0, [x8, #1112]
-// 0x3000 + 0x5c = 0x305c = tcb + var3
-// CHECK-NEXT: 21001c: 08 0d 40 91 add x8, x8, #3, lsl #12
-// CHECK-NEXT: 210020: 00 b9 40 79 ldrh w0, [x8, #92]
-// 0x3000 + 0xc5e = 0x3c5e = tcb + var4
-// CHECK-NEXT: 210024: 08 0d 40 91 add x8, x8, #3, lsl #12
-// CHECK-NEXT: 210028: 00 79 71 39 ldrb w0, [x8, #3166]
+// 0x0 + c10 = 0xc10 = tcb (16-bytes) + var0
+// CHECK-NEXT: 210004: 08 01 40 91 add x8, x8, #0, lsl #12
+// CHECK-NEXT: 210008: 14 05 c3 3d ldr q20, [x8, #3088]
+// 0x1000 + 0x820 = 0x1820 = tcb + var1
+// CHECK-NEXT: 21000c: 08 05 40 91 add x8, x8, #1, lsl #12
+// CHECK-NEXT: 210010: 00 11 44 f9 ldr x0, [x8, #2080]
+// 0x2000 + 0x428 = 0x2428 = tcb + var2
+// CHECK-NEXT: 210014: 08 09 40 91 add x8, x8, #2, lsl #12
+// CHECK-NEXT: 210018: 00 29 44 b9 ldr w0, [x8, #1064]
+// 0x3000 + 0x2c = 0x302c = tcb + var3
+// CHECK-NEXT: 21001c: 08 0d 40 91 add x8, x8, #3, lsl #12
+// CHECK-NEXT: 210020: 00 59 40 79 ldrh w0, [x8, #44]
+// 0x3000 + 0xc2e = 0x32ce = tcb + var4
+// CHECK-NEXT: 210024: 08 0d 40 91 add x8, x8, #3, lsl #12
+// CHECK-NEXT: 210028: 00 b9 70 39 ldrb w0, [x8, #3118]
-// CHECK-SYMS: 0000000000000c00 16 TLS GLOBAL DEFAULT 2 var0
-// CHECK-SYMS-NEXT: 0000000000001810 8 TLS GLOBAL DEFAULT 2 var1
-// CHECK-SYMS-NEXT: 0000000000002418 4 TLS GLOBAL DEFAULT 2 var2
-// CHECK-SYMS-NEXT: 000000000000301c 2 TLS GLOBAL DEFAULT 2 var3
-// CHECK-SYMS-NEXT: 0000000000003c1e 1 TLS GLOBAL DEFAULT 2 var4
+// CHECK-SYMS: 0000000000000c00 0 TLS GLOBAL DEFAULT 2 var0
+// CHECK-SYMS-NEXT: 0000000000001810 4 TLS GLOBAL DEFAULT 2 var1
+// CHECK-SYMS-NEXT: 0000000000002418 2 TLS GLOBAL DEFAULT 2 var2
+// CHECK-SYMS-NEXT: 000000000000301c 1 TLS GLOBAL DEFAULT 2 var3
+// CHECK-SYMS-NEXT: 0000000000003c1e 0 TLS GLOBAL DEFAULT 2 var4
.globl var0
.globl var1
@@ -59,12 +59,12 @@ _start: mrs x8, TPIDR_EL0
.type var3, at object
.section .tbss,"awT", at nobits
- .balign 64
+ .balign 16
.space 1024 * 3
var0:
.quad 0
.quad 0
- .size var0, 16
+ .size var1, 16
.space 1024 * 3
var1:
.quad 0
@@ -72,14 +72,14 @@ var1:
.space 1024 * 3
var2:
.word 0
- .size var2, 4
+ .size var1, 4
.space 1024 * 3
var3:
.hword 0
- .size var3, 2
+ .size var2, 2
.space 1024 * 3
var4:
.byte 0
- .size var4, 1
+ .size var3, 1
.space 1024 * 3
Modified: lld/trunk/test/ELF/arm-tls-le32.s
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/test/ELF/arm-tls-le32.s?rev=361090&r1=361089&r2=361090&view=diff
==============================================================================
--- lld/trunk/test/ELF/arm-tls-le32.s (original)
+++ lld/trunk/test/ELF/arm-tls-le32.s Fri May 17 20:16:00 2019
@@ -70,9 +70,9 @@ x:
// CHECK: Disassembly of section .text:
// CHECK-EMPTY:
// CHECK-NEXT: _start:
-// offset of x from Thread pointer = (TcbSize + 0x0 = 0x20)
-// CHECK-NEXT: 11000: 20 00 00 00
-// offset of z from Thread pointer = (TcbSize + 0x8 = 0x28)
-// CHECK-NEXT: 11004: 28 00 00 00
-// offset of y from Thread pointer = (TcbSize + 0x4 = 0x24)
-// CHECK-NEXT: 11008: 24 00 00 00
+// offset of x from Thread pointer = (TcbSize + 0x0 = 0x8)
+// CHECK-NEXT: 11000: 08 00 00 00
+// offset of z from Thread pointer = (TcbSize + 0x8 = 0x10)
+// CHECK-NEXT: 11004: 10 00 00 00
+// offset of y from Thread pointer = (TcbSize + 0x4 = 0xc)
+// CHECK-NEXT: 11008: 0c 00 00 00
Modified: lld/trunk/test/ELF/arm-tls-norelax-ie-le.s
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/test/ELF/arm-tls-norelax-ie-le.s?rev=361090&r1=361089&r2=361090&view=diff
==============================================================================
--- lld/trunk/test/ELF/arm-tls-norelax-ie-le.s (original)
+++ lld/trunk/test/ELF/arm-tls-norelax-ie-le.s Fri May 17 20:16:00 2019
@@ -37,5 +37,5 @@ x2:
.type x2, %object
// CHECK: Contents of section .got:
-// x1 at offset 0x20 from TP, x2 at offset 0x24 from TP. Offsets include TCB size of 0x20
-// CHECK-NEXT: 12064 20000000 24000000
+// x1 at offset 8 from TP, x2 at offset 0xc from TP. Offsets include TCB size of 8
+// CHECK-NEXT: 12064 08000000 0c000000
More information about the llvm-commits
mailing list