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[ELF] Implement option to force PIC compatible Thunks
By default LLD will generate position independent Thunks when the --pie or
--shared option is used. Reference to absolute addresses is permitted in
other cases. For some embedded systems position independent thunks are
needed for code that executes before the MMU has been set up. The option
--pic-veneer is used by ld.bfd to force position independent thunks.
The patch adds --pic-veneer as the option is needed for the Linux kernel
on Arm.
fixes pr39886
Differential Revision: https://reviews.llvm.org/D55505
llvm-svn: 351326- Loading branch information
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,87 @@ | ||
| // REQUIRES: arm | ||
| // RUN: llvm-mc -arm-add-build-attributes -filetype=obj -triple=armv7a-none-linux-gnueabi %s -o %t | ||
| // RUN: echo "SECTIONS { \ | ||
| // RUN: . = SIZEOF_HEADERS; \ | ||
| // RUN: .text_low : { *(.text_low) *(.text_low2) } \ | ||
| // RUN: .text_high 0x2000000 : { *(.text_high) *(.text_high2) } \ | ||
| // RUN: } " > %t.script | ||
| // RUN: ld.lld --pic-veneer --script %t.script %t -o %t2 2>&1 | ||
| // RUN: llvm-objdump -d -triple=thumbv7a-none-linux-gnueabi %t2 | FileCheck %s | ||
|
|
||
| // Test that we can force generation of position independent thunks even when | ||
| // inputs are not pic. | ||
|
|
||
| .syntax unified | ||
| .section .text_low, "ax", %progbits | ||
| .thumb | ||
| .globl _start | ||
| _start: bx lr | ||
| .globl low_target | ||
| .type low_target, %function | ||
| low_target: | ||
| bl high_target | ||
| bl high_target2 | ||
|
|
||
| .section .text_low2, "ax", %progbits | ||
| .thumb | ||
| .globl low_target2 | ||
| .type low_target2, %function | ||
| low_target2: | ||
| bl high_target | ||
| bl high_target2 | ||
|
|
||
| // CHECK: Disassembly of section .text_low: | ||
| // CHECK-NEXT: _start: | ||
| // CHECK-NEXT: 94: 70 47 bx lr | ||
| // CHECK: low_target: | ||
| // CHECK-NEXT: 96: 00 f0 03 f8 bl #6 | ||
| // CHECK-NEXT: 9a: 00 f0 07 f8 bl #14 | ||
| // CHECK-NEXT: 9e: d4 d4 bmi #-88 | ||
| // CHECK: __ThumbV7PILongThunk_high_target: | ||
| // CHECK-NEXT: a0: 4f f6 55 7c movw r12, #65365 | ||
| // CHECK-NEXT: a4: c0 f2 ff 1c movt r12, #511 | ||
| // CHECK-NEXT: a8: fc 44 add r12, pc | ||
| // CHECK-NEXT: aa: 60 47 bx r12 | ||
| // CHECK: __ThumbV7PILongThunk_high_target2: | ||
| // CHECK-NEXT: ac: 4f f6 69 7c movw r12, #65385 | ||
| // CHECK-NEXT: b0: c0 f2 ff 1c movt r12, #511 | ||
| // CHECK-NEXT: b4: fc 44 add r12, pc | ||
| // CHECK-NEXT: b6: 60 47 bx r12 | ||
| // CHECK: low_target2: | ||
| // CHECK-NEXT: b8: ff f7 f2 ff bl #-28 | ||
| // CHECK-NEXT: bc: ff f7 f6 ff bl #-20 | ||
|
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||
|
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| .section .text_high, "ax", %progbits | ||
| .thumb | ||
| .globl high_target | ||
| .type high_target, %function | ||
| high_target: | ||
| bl low_target | ||
| bl low_target2 | ||
|
|
||
| .section .text_high2, "ax", %progbits | ||
| .thumb | ||
| .globl high_target2 | ||
| .type high_target2, %function | ||
| high_target2: | ||
| bl low_target | ||
| bl low_target2 | ||
|
|
||
| // CHECK: Disassembly of section .text_high: | ||
| // CHECK-NEXT: high_target: | ||
| // CHECK-NEXT: 2000000: 00 f0 02 f8 bl #4 | ||
| // CHECK-NEXT: 2000004: 00 f0 06 f8 bl #12 | ||
| // CHECK: __ThumbV7PILongThunk_low_target: | ||
| // CHECK-NEXT: 2000008: 40 f2 83 0c movw r12, #131 | ||
| // CHECK-NEXT: 200000c: cf f6 00 6c movt r12, #65024 | ||
| // CHECK-NEXT: 2000010: fc 44 add r12, pc | ||
| // CHECK-NEXT: 2000012: 60 47 bx r12 | ||
| // CHECK: __ThumbV7PILongThunk_low_target2: | ||
| // CHECK-NEXT: 2000014: 40 f2 99 0c movw r12, #153 | ||
| // CHECK-NEXT: 2000018: cf f6 00 6c movt r12, #65024 | ||
| // CHECK-NEXT: 200001c: fc 44 add r12, pc | ||
| // CHECK-NEXT: 200001e: 60 47 bx r12 | ||
| // CHECK: high_target2: | ||
| // CHECK-NEXT: 2000020: ff f7 f2 ff bl #-28 | ||
| // CHECK-NEXT: 2000024: ff f7 f6 ff bl #-20 |