diff --git a/hbasm/src/lib.rs b/hbasm/src/lib.rs
index 75a5731..391b251 100644
--- a/hbasm/src/lib.rs
+++ b/hbasm/src/lib.rs
@@ -21,11 +21,11 @@ macros::impl_both!(
         => [LD, ST],
     bbd(p0: R, p1: R, p2: I)
         => [ADDI, MULI, ANDI, ORI, XORI, SLI, SRI, SRSI, CMPI, CMPUI,
-            BMC, JEQ, JNE, JLT, JGT, JLTU, JGTU, ADDFI, MULFI],
+            BMC, JAL, JEQ, JNE, JLT, JGT, JLTU, JGTU, ADDFI, MULFI],
     bb(p0: R, p1: R)
         => [NEG, NOT, CP, SWA, NEGF, ITF, FTI],
     bd(p0: R, p1: I)
-        => [LI, JMP],
+        => [LI],
     n()
         => [NOP, ECALL],
 );
diff --git a/hbbytecode/src/lib.rs b/hbbytecode/src/lib.rs
index 19f4648..9b4f60b 100644
--- a/hbbytecode/src/lib.rs
+++ b/hbbytecode/src/lib.rs
@@ -54,7 +54,7 @@ constmod!(pub opcode(u8) {
     BMC = 30, "BBD; [#0] ← [#1], imm #2 bytes";
     BRC = 31, "BBB; #0 ← #1, imm #2 registers";
 
-    JMP   = 32, "BD;  Unconditional jump [#0 + imm #1]";
+    JAL   = 32, "BD;  Copy PC to #0 and unconditional jump [#1 + imm #2]";
     JEQ   = 33, "BBD; if #0 = #1 → jump imm #2";
     JNE   = 34, "BBD; if #0 ≠ #1 → jump imm #2";
     JLT   = 35, "BBD; if #0 < #1 → jump imm #2";
diff --git a/hbvm/src/validate.rs b/hbvm/src/validate.rs
index 52f726f..d75306b 100644
--- a/hbvm/src/validate.rs
+++ b/hbvm/src/validate.rs
@@ -50,8 +50,8 @@ pub fn validate(mut program: &[u8]) -> Result<(), Error> {
             | [DIR | DIRF, _, _, _, _, rest @ ..]
             | [ADD..=CMPU | BRC | ADDF..=MULF, _, _, _, rest @ ..]
             | [NEG..=NOT | CP..=SWA | NEGF..=FTI, _, _, rest @ ..]
-            | [LI | JMP, _, _, _, _, _, _, _, _, _, rest @ ..]
-            | [ADDI..=CMPUI | BMC | JEQ..=JGTU | ADDFI..=MULFI, _, _, _, _, _, _, _, _, _, _, rest @ ..]
+            | [LI, _, _, _, _, _, _, _, _, _, rest @ ..]
+            | [ADDI..=CMPUI | BMC | JAL..=JGTU | ADDFI..=MULFI, _, _, _, _, _, _, _, _, _, _, rest @ ..]
             | [LD..=ST, _, _, _, _, _, _, _, _, _, _, _, _, rest @ ..] => rest,
             _ => {
                 return Err(Error {
diff --git a/hbvm/src/vm/mem/mod.rs b/hbvm/src/vm/mem/mod.rs
index 901c41c..8609515 100644
--- a/hbvm/src/vm/mem/mod.rs
+++ b/hbvm/src/vm/mem/mod.rs
@@ -64,6 +64,25 @@ impl Memory {
         }
     }
 
+    /// Maps host's memory into VM's memory
+    ///
+    /// # Safety
+    /// Who knows.
+    pub unsafe fn map(
+        &mut self,
+        mut host: *mut u8,
+        target: usize,
+        pagesize: PageSize,
+        count: usize,
+    ) {
+        todo!()
+    }
+
+    /// Unmaps pages from VM's memory
+    pub fn unmap(&mut self, addr: usize, count: usize) {
+        todo!()
+    }
+
     /// Load value from an address
     ///
     /// # Safety
@@ -215,11 +234,11 @@ impl Memory {
         action: fn(*mut u8, *mut u8, usize),
         traph: &mut impl HandlePageFault,
     ) -> Result<(), u64> {
-        let mut pspl = AddrSplitter::new(src, len, self.root_pt);
+        let mut pspl = AddrPageLookuper::new(src, len, self.root_pt);
         loop {
             match pspl.next() {
                 // Page found
-                Some(Ok(AddrSplitOk {
+                Some(Ok(AddrPageLookupOk {
                     vaddr,
                     ptr,
                     size,
@@ -233,7 +252,7 @@ impl Memory {
                     action(ptr, dst, size);
                     dst = unsafe { dst.add(size) };
                 }
-                Some(Err(AddrSplitError { addr, size })) => {
+                Some(Err(AddrPageLookupError { addr, size })) => {
                     // Execute page fault handler
                     if traph.page_fault(reason, self, addr, size, dst) {
                         // Shift the splitter address
@@ -252,7 +271,7 @@ impl Memory {
 }
 
 /// Result from address split
-struct AddrSplitOk {
+struct AddrPageLookupOk {
     /// Virtual address
     vaddr: u64,
 
@@ -266,7 +285,7 @@ struct AddrSplitOk {
     perm: Permission,
 }
 
-struct AddrSplitError {
+struct AddrPageLookupError {
     /// Address of failure
     addr: u64,
 
@@ -275,7 +294,7 @@ struct AddrSplitError {
 }
 
 /// Address splitter into pages
-struct AddrSplitter {
+struct AddrPageLookuper {
     /// Current address
     addr: u64,
 
@@ -286,7 +305,7 @@ struct AddrSplitter {
     pagetable: *const PageTable,
 }
 
-impl AddrSplitter {
+impl AddrPageLookuper {
     /// Create a new page splitter
     pub const fn new(addr: u64, size: usize, pagetable: *const PageTable) -> Self {
         Self {
@@ -303,8 +322,8 @@ impl AddrSplitter {
     }
 }
 
-impl Iterator for AddrSplitter {
-    type Item = Result<AddrSplitOk, AddrSplitError>;
+impl Iterator for AddrPageLookuper {
+    type Item = Result<AddrPageLookupOk, AddrPageLookupError>;
 
     fn next(&mut self) -> Option<Self::Item> {
         // The end, everything is fine
@@ -328,7 +347,7 @@ impl Iterator for AddrSplitter {
                     match entry.permission() {
                         // No page → page fault
                         Permission::Empty => {
-                            return Some(Err(AddrSplitError {
+                            return Some(Err(AddrPageLookupError {
                                 addr: self.addr,
                                 size: PageSize::from_lvl(lvl)?,
                             }))
@@ -358,7 +377,7 @@ impl Iterator for AddrSplitter {
         let avail = (size as usize - offset).clamp(0, self.size);
         self.bump(size);
 
-        Some(Ok(AddrSplitOk {
+        Some(Ok(AddrPageLookupOk {
             vaddr: self.addr,
             ptr: unsafe { base.add(offset) }, // Return pointer to the start of region
             size: avail,
diff --git a/hbvm/src/vm/mod.rs b/hbvm/src/vm/mod.rs
index d9937a3..1fcee80 100644
--- a/hbvm/src/vm/mod.rs
+++ b/hbvm/src/vm/mod.rs
@@ -259,8 +259,9 @@ impl<'a, PfHandler: HandlePageFault, const TIMER_QUOTIENT: usize>
                             usize::from(count),
                         );
                     }
-                    JMP => {
-                        let ParamBD(reg, offset) = param!(self, ParamBD);
+                    JAL => {
+                        let ParamBBD(save, reg, offset) = param!(self, ParamBBD);
+                        self.write_reg(save, self.pc as u64);
                         self.pc = (self.read_reg(reg).as_u64() + offset) as usize;
                     }
                     JEQ => cond_jump!(self, int, Equal),
diff --git a/spec.md b/spec.md
index b9adf17..55c3aaa 100644
--- a/spec.md
+++ b/spec.md
@@ -166,11 +166,11 @@
 ## Control flow
 
 ### Unconditional jump
-- Type BD
+- Type BBD
 
-| Opcode | Name |        Action         |
-|:------:|:----:|:---------------------:|
-|   32   | JMP  | Jump at `#0 + imm #1` |
+| Opcode | Name |                      Action                       |
+|:------:|:----:|:-------------------------------------------------:|
+|   32   | JAL  | Save current PC to `#0` and jump at `#1 + imm #2` |
 
 ### Conditional jumps
 - Type BBD