[lld][ELF][AVR] Add range check for R_AVR_13_PCREL (#67636)

Some large AVR programs (for devices without long jump) may exceed
128KiB, and lld should give explicit errors other than generate wrong
executables silently.

Author: benshi001

lld/ELF/Arch/AVR.cpp

@@ -231,13 +231,14 @@ 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, 7, rel);
+    checkInt(loc, val - 2, 7, 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));
@@ -255,6 +256,7 @@ void AVR::relocate(uint8_t *loc, const Relocation &rel, uint64_t val) const {
     break;
 
   case R_AVR_CALL: {
+    checkAlignment(loc, val, 2, rel);
     uint16_t hi = val >> 17;
     uint16_t lo = val >> 1;
     write16le(loc, read16le(loc) | ((hi >> 1) << 4) | (hi & 1));

lld/test/ELF/avr-reloc-error.s

@@ -0,0 +1,53 @@
+# REQUIRES: avr
+
+# 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:     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 | \
+# RUN:     FileCheck %s --check-prefix=PCREL13
+# RUN: llvm-mc -filetype=obj -triple=avr -mcpu=atmega328 avr-abs.s -o avr-abs.o
+# RUN: not ld.lld avr-abs.o -o /dev/null -Ttext=0x1000 --defsym=callee0=0x1009 --defsym=callee1=0x1010 2>&1 | \
+# RUN:     FileCheck %s --check-prefix=ABS
+
+#--- avr-pcrel-7.s
+
+.section .LDI,"ax",@progbits
+
+.globl __start
+__start:
+
+# PCREL7-NOT: callee0
+# PCREL7:     error: {{.*}} relocation R_AVR_7_PCREL out of range: {{.*}} is not in [-64, 63]; references 'callee1'
+# PCREL7:     error: {{.*}} improper alignment for relocation R_AVR_7_PCREL: {{.*}} is not aligned to 2 bytes
+brne callee0
+breq callee1
+brlt callee2
+
+#--- avr-pcrel-13.s
+
+.section .LDI,"ax",@progbits
+
+.globl __start
+__start:
+
+# PCREL13-NOT: callee0
+# PCREL13:     error: {{.*}} relocation R_AVR_13_PCREL out of range: {{.*}} is not in [-4096, 4095]; references 'callee1'
+# PCREL13:     error: {{.*}} improper alignment for relocation R_AVR_13_PCREL: {{.*}} is not aligned to 2 bytes
+rjmp  callee0
+rcall callee1
+rjmp  callee2
+
+#--- avr-abs.s
+
+.section .LDI,"ax",@progbits
+
+.globl __start
+__start:
+
+# ABS:     error: {{.*}} improper alignment for relocation R_AVR_CALL: 0x1009 is not aligned to 2 bytes
+# ABS-NOT: 0x1010
+call callee0
+jmp  callee1