sample malloc working

Tests/isa/CPrograms/build-assembler.sh

@@ -1,6 +1,7 @@
 # Send assembler file to remote machine to run
 scp start.S home-1:/home/akilan/cheri/output/sdk/bin/
-scp main.c home-1:/home/akilan/cheri/output/sdk/bin/
+# scp main.c home-1:/home/akilan/cheri/output/sdk/bin/
+scp malloc.c home-1:/home/akilan/cheri/output/sdk/bin/
 
 # scp cheri.S home:/home/akilan/cheri/output/sdk/bin/
 
@@ -11,6 +12,9 @@ scp main.c home-1:/home/akilan/cheri/output/sdk/bin/
 
 ssh home-1 'cd /home/akilan/cheri/output/sdk/bin/ && ./clang   --target=riscv64-unknown-elf   -march=rv64gcxcheri -mabi=lp64d -nostdlib -nostartfiles   -Wl,-Ttext=0x80000000 -o testC start.S main.c'
 
+# Malloc test implementation
+ssh home-1 'cd /home/akilan/cheri/output/sdk/bin/ && ./clang   --target=riscv64-unknown-elf   -march=rv64gcxcheri -mabi=lp64d -nostdlib -nostartfiles -fno-builtin-malloc -mcmodel=medany   -Wl,-Ttext=0x80000000 -o testC start.S malloc.c'
+
 # Disassembly ouput
 ssh home-1 'cd /home/akilan/cheri/output/sdk/bin/ && ./llvm-objdump -d testC'
 

Tests/isa/CPrograms/malloc.c

@@ -0,0 +1,74 @@
+#include <cheriintrin.h>
+#include <stdint.h>
+#include <stddef.h>
+
+#define HEAP_SIZE 4096
+
+static char heap[HEAP_SIZE];
+static size_t bump = 0;
+
+// Add delta value for TLB translation
+static inline void * __capability add_delta(void * __capability cap, int offset) {
+    void * __capability result;
+
+    asm volatile (
+        "candperm %0, %1, %2"
+        : "=C" (result)  // Output: %0 (result)
+        : "C" (cap),     // Input:  %1 (original cap)
+          "r" (offset)   // Input:  %2 (offset register)
+        :                // No clobbered registers
+    );
+
+    return result;
+}
+
+
+void * __capability malloc(size_t size) {
+
+    // Align to 8 bytes (important for capability safety)
+    size = (size + 7) & ~7;
+
+    if (bump + size > HEAP_SIZE)
+        return NULL;
+
+    void * __capability base = cheri_ddc_get();
+
+    uintptr_t addr = (uintptr_t)(heap + bump);
+
+    // Create capability to this region
+    void * __capability cap = cheri_address_set(base, addr);
+
+    // Enforce bounds (this is the key CHERI feature)
+    cap = cheri_bounds_set(cap, size);
+
+    // Hard-coded delta value 
+    cap = add_delta(cap, 4);
+
+    bump += size;
+
+    return cap;
+}
+
+void bump_reset(void) {
+    bump = 0;
+}
+
+int main(void) {
+    char * __capability a = malloc(30);
+    char * __capability b = malloc(16);
+
+    if (!a || !b) return -1;
+
+    a[0] = 'A';
+    a[1] = 'C';
+    b[0] = 'B';
+
+    // This will fault (out-of-bounds)
+    // a[20] = 'X';
+
+    if (a[1] != 'C') {
+        while (1);
+    }
+
+    return 0;
+}

todo.org

@@ -0,0 +1,8 @@
+* Tasks
+
+- [ ] Design a simple cheri based bump allocator (For a C
+  bare metal program with simple MMAP calls).
+
+- [ ] Test for Paging and TLB bypass
+
+- [ ] Log CPU cycles for simple malloc and free program