[lld] Fix R_AVR_7_PCREL and R_AVR_13_PCREL range checking (PR #92695)

[via llvm-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-lld-elf

Author: Ayke (aykevl)

<details>
<summary>Changes</summary>

See the commit messages for detail. The first one fixes a bug I found while updating to LLVM 18 (see https://github.com/llvm/llvm-project/pull/67636#issuecomment-2118869227), the second one fixes a bug I found while fixing the first.

I'm not sure whether sending two commits in a single PR like this is allowed, but since they're related (but fix different bugs) it made sense to me to do it in one PR.

---
Full diff: https://github.com/llvm/llvm-project/pull/92695.diff


3 Files Affected:

- (modified) lld/ELF/Arch/AVR.cpp (+1-2) 
- (modified) lld/test/ELF/avr-reloc-error.s (+2-2) 
- (modified) lld/test/ELF/avr-reloc.s (+12) 


``````````diff
diff --git a/lld/ELF/Arch/AVR.cpp b/lld/ELF/Arch/AVR.cpp
index 9211eabc9669a..2275f86942871 100644
--- a/lld/ELF/Arch/AVR.cpp
+++ b/lld/ELF/Arch/AVR.cpp
@@ -231,14 +231,13 @@ void AVR::relocate(uint8_t *loc, const Relocation &rel, uint64_t val) const {
 
   // Since every jump destination is word aligned we gain an extra bit
   case R_AVR_7_PCREL: {
-    checkInt(loc, val - 2, 7, rel);
+    checkInt(loc, val - 2, 8, rel);
     checkAlignment(loc, val, 2, rel);
     const uint16_t target = (val - 2) >> 1;
     write16le(loc, (read16le(loc) & 0xfc07) | ((target & 0x7f) << 3));
     break;
   }
   case R_AVR_13_PCREL: {
-    checkInt(loc, val - 2, 13, rel);
     checkAlignment(loc, val, 2, rel);
     const uint16_t target = (val - 2) >> 1;
     write16le(loc, (read16le(loc) & 0xf000) | (target & 0xfff));
diff --git a/lld/test/ELF/avr-reloc-error.s b/lld/test/ELF/avr-reloc-error.s
index 0a30f68d168e2..4e49adfd78b7e 100644
--- a/lld/test/ELF/avr-reloc-error.s
+++ b/lld/test/ELF/avr-reloc-error.s
@@ -3,7 +3,7 @@
 # RUN: rm -rf %t && split-file %s %t && cd %t
 
 # RUN: llvm-mc -filetype=obj -triple=avr -mcpu=atmega328 avr-pcrel-7.s -o avr-pcrel-7.o
-# RUN: not ld.lld avr-pcrel-7.o -o /dev/null -Ttext=0x1000 --defsym=callee0=0x1040 --defsym=callee1=0x1044 --defsym=callee2=0x100f 2>&1 | \
+# RUN: not ld.lld avr-pcrel-7.o -o /dev/null -Ttext=0x1000 --defsym=callee0=0x1040 --defsym=callee1=0x1084 --defsym=callee2=0x100f 2>&1 | \
 # RUN:     FileCheck %s --check-prefix=PCREL7
 # RUN: llvm-mc -filetype=obj -triple=avr -mcpu=atmega328 avr-pcrel-13.s -o avr-pcrel-13.o
 # RUN: not ld.lld avr-pcrel-13.o -o /dev/null -Ttext=0x1000 --defsym=callee0=0x2000 --defsym=callee1=0x2004 --defsym=callee2=0x100f 2>&1 | \
@@ -20,7 +20,7 @@
 __start:
 
 # PCREL7-NOT: callee0
-# PCREL7:     error: {{.*}} relocation R_AVR_7_PCREL out of range: {{.*}} is not in [-64, 63]; references 'callee1'
+# PCREL7:     error: {{.*}} relocation R_AVR_7_PCREL out of range: {{.*}} is not in [-128, 127]; references 'callee1'
 # PCREL7:     error: {{.*}} improper alignment for relocation R_AVR_7_PCREL: {{.*}} is not aligned to 2 bytes
 brne callee0
 breq callee1
diff --git a/lld/test/ELF/avr-reloc.s b/lld/test/ELF/avr-reloc.s
index 172c0e03ba74b..ec088eaa149d0 100644
--- a/lld/test/ELF/avr-reloc.s
+++ b/lld/test/ELF/avr-reloc.s
@@ -82,6 +82,12 @@ sbic  b, 1    ; R_AVR_PORT5
 ; CHECK-NEXT:  rjmp .-36
 ; CHECK-NEXT:  breq .+26
 ; CHECK-NEXT:  breq .-40
+; CHECK-NEXT:  rjmp .-4096
+; CHECK-NEXT:  rjmp .+4094
+; CHECK-NEXT:  rjmp .+4094
+; CHECK-NEXT:  rjmp .-4096
+; CHECK-NEXT:  breq .-128
+; CHECK-NEXT:  breq .+126
 ; HEX-LABEL:   section .PCREL:
 ; HEX-NEXT:    0fc0eecf 69f061f3
 foo:
@@ -89,6 +95,12 @@ rjmp foo + 32  ; R_AVR_13_PCREL
 rjmp foo - 32  ; R_AVR_13_PCREL
 breq foo + 32  ; R_AVR_7_PCREL
 breq foo - 32  ; R_AVR_7_PCREL
+rjmp 1f - 4096  $ 1:  ; R_AVR_13_PCREL
+rjmp 1f + 4094  $ 1:  ; R_AVR_13_PCREL
+rjmp 1f - 4098  $ 1:  ; R_AVR_13_PCREL (overflow)
+rjmp 1f + 4096  $ 1:  ; R_AVR_13_PCREL (overflow)
+breq 1f - 128   $ 1:  ; R_AVR_7_PCREL
+breq 1f + 126   $ 1:  ; R_AVR_7_PCREL
 
 .section .LDSSTS,"ax", at progbits
 ; CHECK-LABEL: section .LDSSTS:

``````````

</details>


https://github.com/llvm/llvm-project/pull/92695