LibCoreDump: Don't subtract one from the first stack frame's EIP

The first stack frame represents the current instruction pointer
rather than the return address so we shouldn't subtract one
from it.

Fixes #8162.

2 files changed, 12 insertions, 2 deletions

diff --git a/Userland/Libraries/LibCoreDump/Backtrace.cpp b/Userland/Libraries/LibCoreDump/Backtrace.cpp
index c91922a3e2..ad542e7668 100644
--- a/Userland/Libraries/LibCoreDump/Backtrace.cpp
+++ b/Userland/Libraries/LibCoreDump/Backtrace.cpp
@@ -53,11 +53,16 @@ Backtrace::Backtrace(const Reader& coredump, const ELF::Core::ThreadInfo& thread
 {
     uint32_t* ebp = (uint32_t*)m_thread_info.regs.ebp;
     uint32_t* eip = (uint32_t*)m_thread_info.regs.eip;
+    bool first_frame = true;
     while (ebp && eip) {
         // We use eip - 1 because the return address from a function frame
         // is the instruction that comes after the 'call' instruction.
+        // However, because the first frame represents the faulting
+        // instruction rather than the return address we don't subtract
+        // 1 there.
         VERIFY((FlatPtr)eip > 0);
-        add_entry(coredump, (FlatPtr)eip - 1);
+        add_entry(coredump, (FlatPtr)eip - (first_frame ? 0 : 1));
+        first_frame = false;
         auto next_eip = coredump.peek_memory((FlatPtr)(ebp + 1));
         auto next_ebp = coredump.peek_memory((FlatPtr)(ebp));
         if (!next_eip.has_value() || !next_ebp.has_value())
diff --git a/Userland/Libraries/LibSymbolication/Symbolication.cpp b/Userland/Libraries/LibSymbolication/Symbolication.cpp
index c331e568d1..5f17a60951 100644
--- a/Userland/Libraries/LibSymbolication/Symbolication.cpp
+++ b/Userland/Libraries/LibSymbolication/Symbolication.cpp
@@ -148,6 +148,7 @@ Vector<Symbol> symbolicate_thread(pid_t pid, pid_t tid)
     }
 
     Vector<Symbol> symbols;
+    bool first_frame = true;
 
     for (auto address : stack) {
         const RegionWithSymbols* found_region = nullptr;
@@ -171,7 +172,11 @@ Vector<Symbol> symbolicate_thread(pid_t pid, pid_t tid)
 
         // We're subtracting 1 from the address because this is the return address,
         // i.e. it is one instruction past the call instruction.
-        auto result = symbolicate(found_region->path, adjusted_address - 1);
+        // However, because the first frame represents the current
+        // instruction pointer rather than the return address we don't
+        // subtract 1 for that.
+        auto result = symbolicate(found_region->path, adjusted_address - (first_frame ? 0 : 1));
+        first_frame = false;
         if (!result.has_value()) {
             symbols.append(Symbol {
                 .address = address,