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[LLD][ELF][ARM][AArch64] Only round up ThunkSection Size when large OS. In D71281 a fix was put in to round up the size of a ThunkSection to the nearest 4KiB when performing errata patching. This fixed a problem with a very large instrumented program that had thunks and patches mutually trigger each other. Unfortunately it triggers an assertion failure in an AArch64 allyesconfig build of the kernel. There is a specific assertion preventing an InputSectionDescription being larger than 4KiB. This will always trigger if there is at least one Thunk needed in that InputSectionDescription, which is possible for an allyesconfig build. Abstractly the problem case is: .text : { *(.text) ; ... . = ALIGN(SZ_4K); __idmap_text_start = .; *(.idmap.text) __idmap_text_end = .; ... } The assertion checks that __idmap_text_end - __idmap_start is < 4 KiB. Note that there is more than one InputSectionDescription in the OutputSection so we can't just restrict the fix to OutputSections smaller than 4 KiB. The fix presented here limits the D71281 to InputSectionDescriptions that meet the following conditions: 1.) The OutputSection is bigger than the thunkSectionSpacing so adding thunks will affect the addresses of following code. 2.) The InputSectionDescription is larger than 4 KiB. This will prevent any assertion failures that an InputSectionDescription is < 4 KiB in size. We do this at ThunkSection creation time as at this point we know that the addresses are stable and up to date prior to adding the thunks as assignAddresses() will have been called immediately prior to thunk generation. The fix reverts the two tests affected by D71281 to their original state as they no longer need the 4KiB size roundup. I've added simpler tests to check for D71281 when the OutputSection size is larger than the ThunkSection spacing. Fixes https://github.com/ClangBuiltLinux/linux/issues/812 Differential Revision: https://reviews.llvm.org/D72344
2020-01-07 23:22:09 +08:00
// REQUIRES: arm
// RUN: llvm-mc -filetype=obj -triple=armv7a-linux-gnueabihf --arm-add-build-attributes %s -o %t.o
// RUN: ld.lld --fix-cortex-a8 --shared %t.o -o %t2
// RUN: llvm-objdump -d --no-show-raw-insn %t2 | FileCheck %s
/// Test case that for an OutputSection larger than the ThunkSectionSpacing
/// --fix-cortex-a8 will cause the size of the ThunkSection to be rounded up to
/// the nearest 4KiB
.thumb
.section .text.01, "ax", %progbits
.balign 4096
.globl _start
.type _start, %function
_start:
/// state change thunk required
b.w arm_func
thumb_target:
.space 4096 - 10
/// erratum patch needed
nop.w
b.w thumb_target
/// Expect thunk and patch to be inserted here
[ELF][ARM] Increase default max-page-size from 4096 to 6536 See http://lists.llvm.org/pipermail/llvm-dev/2020-April/140549.html For the record, GNU ld changed to 64k max page size in 2014 https://sourceware.org/git/?p=binutils-gdb.git;a=commit;h=7572ca8989ead4c3425a1500bc241eaaeffa2c89 "[RFC] ld/ARM: Increase maximum page size to 64kB" Android driver forced 4k page size in AArch64 (D55029) and ARM (D77746). A binary linked with max-page-size=4096 does not run on a system with a higher page size configured. There are some systems out there that do this and it leads to the binary getting `Killed!` by the kernel. In the non-linker-script cases, when linked with -z noseparate-code (default), the max-page-size increase should not cause any size difference. There may be some VMA usage differences, though. Reviewed By: psmith, MaskRay Differential Revision: https://reviews.llvm.org/D77330
2020-04-18 23:06:37 +08:00
// CHECK: 00012004 <__ThumbV7PILongThunk_arm_func>:
// CHECK-NEXT: 12004: movw r12, #4088
// CHECK-NEXT: movt r12, #256
// CHECK-NEXT: add r12, pc
// CHECK-NEXT: bx r12
// CHECK: 00013004 <__CortexA8657417_11FFE>:
// CHECK-NEXT: 13004: b.w #-8196
[LLD][ELF][ARM][AArch64] Only round up ThunkSection Size when large OS. In D71281 a fix was put in to round up the size of a ThunkSection to the nearest 4KiB when performing errata patching. This fixed a problem with a very large instrumented program that had thunks and patches mutually trigger each other. Unfortunately it triggers an assertion failure in an AArch64 allyesconfig build of the kernel. There is a specific assertion preventing an InputSectionDescription being larger than 4KiB. This will always trigger if there is at least one Thunk needed in that InputSectionDescription, which is possible for an allyesconfig build. Abstractly the problem case is: .text : { *(.text) ; ... . = ALIGN(SZ_4K); __idmap_text_start = .; *(.idmap.text) __idmap_text_end = .; ... } The assertion checks that __idmap_text_end - __idmap_start is < 4 KiB. Note that there is more than one InputSectionDescription in the OutputSection so we can't just restrict the fix to OutputSections smaller than 4 KiB. The fix presented here limits the D71281 to InputSectionDescriptions that meet the following conditions: 1.) The OutputSection is bigger than the thunkSectionSpacing so adding thunks will affect the addresses of following code. 2.) The InputSectionDescription is larger than 4 KiB. This will prevent any assertion failures that an InputSectionDescription is < 4 KiB in size. We do this at ThunkSection creation time as at this point we know that the addresses are stable and up to date prior to adding the thunks as assignAddresses() will have been called immediately prior to thunk generation. The fix reverts the two tests affected by D71281 to their original state as they no longer need the 4KiB size roundup. I've added simpler tests to check for D71281 when the OutputSection size is larger than the ThunkSection spacing. Fixes https://github.com/ClangBuiltLinux/linux/issues/812 Differential Revision: https://reviews.llvm.org/D72344
2020-01-07 23:22:09 +08:00
.section .text.02
/// Take us over thunk section spacing
.space 16 * 1024 * 1024
.section .text.03, "ax", %progbits
.arm
.balign 4
.type arm_func, %function
arm_func:
bx lr