Lecture 115 - Making the process_realloc function

nibblebits · nibblebits · commit 7de789dafc04 · 2025-08-13T12:27:19.000+01:00
diff --git a/PeachOS64Bit/programs/blank/blank.elf b/PeachOS64Bit/programs/blank/blank.elf
diff --git a/PeachOS64Bit/programs/shell/shell.elf b/PeachOS64Bit/programs/shell/shell.elf
diff --git a/PeachOS64Bit/programs/stdlib/build/peachos.asm.o b/PeachOS64Bit/programs/stdlib/build/peachos.asm.o
diff --git a/PeachOS64Bit/programs/stdlib/build/stdlib.o b/PeachOS64Bit/programs/stdlib/build/stdlib.o
diff --git a/PeachOS64Bit/programs/stdlib/src/peachos.asm b/PeachOS64Bit/programs/stdlib/src/peachos.asm
@@ -16,6 +16,7 @@ global peachos_fclose:function
 global peachos_fread:function
 global peachos_fseek:function
 global peachos_fstat:function
+global peachos_realloc:function
 
 ; void print(const char* filename)
 print:
@@ -131,4 +132,14 @@ peachos_fstat:
     push qword rdi  ; fd
     int 0x80        ; call kernel
     add rsp, 16     ; restore stack
+    ret
+
+; void* peachos_realloc(void* old_ptr, size_t new_size);
+peachos_realloc:
+    mov rax, 15     ; Command 15 realloc
+    push qword rsi  ; new_size
+    push qword rdi  ; old_ptr
+    int 0x80
+    add rsp, 16
+    ; RAX = new the pointer address
     ret
diff --git a/PeachOS64Bit/programs/stdlib/src/peachos.h b/PeachOS64Bit/programs/stdlib/src/peachos.h
@@ -39,4 +39,5 @@ void peachos_fclose(size_t fd);
 long peachos_fread(void* buffer, size_t size, size_t count, long fd);
 long peachos_fseek(long fd, long offset, long whence);
 long peachos_fstat(long fd, struct file_stat* file_stat_out);
+void* peachos_realloc(void* old_ptr, size_t new_size);
 #endif
diff --git a/PeachOS64Bit/programs/stdlib/src/stdlib.c b/PeachOS64Bit/programs/stdlib/src/stdlib.c
@@ -1,5 +1,6 @@
 #include "stdlib.h"
 #include "peachos.h"
+#include "memory.h"
 
 char* itoa(int i)
 {
@@ -32,6 +33,23 @@ void* malloc(size_t size)
 {
     return peachos_malloc(size);
 }
+void* calloc(size_t n_memb, size_t size)
+{
+   size_t b_size = n_memb * size;
+   void* ptr = malloc(b_size);
+   if (!ptr)
+   {
+        return NULL;
+   }   
+
+   memset(ptr, 0, b_size);
+   return ptr;
+}
+
+void* realloc(void* ptr, size_t new_size)
+{
+    return peachos_realloc(ptr, new_size);
+}
 
 void free(void* ptr)
 {
diff --git a/PeachOS64Bit/programs/stdlib/src/stdlib.h b/PeachOS64Bit/programs/stdlib/src/stdlib.h
@@ -2,6 +2,8 @@
 #define PEACHOS_STDLIB_H
 #include <stddef.h>
 
+void* calloc(size_t n_memb, size_t size);
+void* realloc(void* ptr, size_t new_size);
 void* malloc(size_t size);
 void free(void* ptr);
 char* itoa(int i);
diff --git a/PeachOS64Bit/programs/stdlib/stdlib.elf b/PeachOS64Bit/programs/stdlib/stdlib.elf
diff --git a/PeachOS64Bit/src/isr80h/heap.c b/PeachOS64Bit/src/isr80h/heap.c
@@ -2,6 +2,16 @@
 #include "task/task.h"
 #include "task/process.h"
 #include <stddef.h>
+
+void* isr80h_command15_realloc(struct interrupt_frame* frame)
+{
+    void* userland_virt_addr = (void*) task_get_stack_item(task_current(), 0);
+    void* new_alloc_addr = NULL;
+    size_t new_ptr_size = (size_t) task_get_stack_item(task_current(), 1);
+    new_alloc_addr = process_realloc(task_current()->process, userland_virt_addr, new_ptr_size);
+    return new_alloc_addr;
+}
+
 void* isr80h_command4_malloc(struct interrupt_frame* frame)
 {
     size_t size = (uintptr_t)task_get_stack_item(task_current(), 0);
diff --git a/PeachOS64Bit/src/isr80h/heap.h b/PeachOS64Bit/src/isr80h/heap.h
@@ -2,6 +2,8 @@
 #define ISR80H_HEAP_H
 
 struct interrupt_frame;
+
+void* isr80h_command15_realloc(struct interrupt_frame* frame);
 void* isr80h_command4_malloc(struct interrupt_frame* frame);
 void* isr80h_command5_free(struct interrupt_frame* frame);
 
diff --git a/PeachOS64Bit/src/isr80h/isr80h.c b/PeachOS64Bit/src/isr80h/isr80h.c
@@ -22,4 +22,5 @@ void isr80h_register_commands()
     isr80h_register_command(SYSTEM_COMMAND12_FREAD, isr80h_command12_fread);
     isr80h_register_command(SYSTEM_COMMAND13_FSEEK, isr80h_command13_fseek);
     isr80h_register_command(SYSTEM_COMMAND14_FSTAT, isr80h_command14_fstat);
+    isr80h_register_command(SYSTEM_COMMAND15_REALLOC, isr80h_command15_realloc);
 }
diff --git a/PeachOS64Bit/src/isr80h/isr80h.h b/PeachOS64Bit/src/isr80h/isr80h.h
@@ -18,6 +18,7 @@ enum SystemCommands
     SYSTEM_COMMAND12_FREAD,
     SYSTEM_COMMAND13_FSEEK,
     SYSTEM_COMMAND14_FSTAT,
+    SYSTEM_COMMAND15_REALLOC
 };
 
 void isr80h_register_commands();
diff --git a/PeachOS64Bit/src/status.h b/PeachOS64Bit/src/status.h
@@ -12,5 +12,6 @@
 #define EISTKN 8
 #define EINFORMAT 9
 #define EOUTOFRANGE 10
+#define ENOTFOUND 11
 
 #endif
diff --git a/PeachOS64Bit/src/task/process.c b/PeachOS64Bit/src/task/process.c
@@ -117,6 +117,71 @@ int process_allocation_set_map(struct process *process, int allocation_entry_ind
 out:
     return res;
 }
+
+int process_allocation_exists(struct process* process, void* ptr, size_t* index_out)
+{
+    int res = -ENOTFOUND;
+    size_t total_allocations = vector_count(process->allocations);
+    for(size_t i = 0; i < total_allocations; i++)
+    {
+        struct process_allocation allocation;
+        res = vector_at(process->allocations, i, &allocation, sizeof(allocation));
+        if (res < 0)
+        {
+            break;
+        }
+
+        if (allocation.ptr == ptr)
+        {
+            if (index_out)
+            {
+                *index_out = i;
+            }
+            res = 0;
+            break;
+        }
+    }
+    return res;
+}
+void* process_realloc(struct process* process, void* old_virt_ptr, size_t new_size)
+{
+    int res = 0;
+    void* new_ptr = NULL;
+    void* old_phys_ptr = NULL;
+    size_t old_allocation_index = 0;
+    res = process_allocation_exists(process, old_virt_ptr, &old_allocation_index);
+    if (res < 0)
+    {
+        goto out;
+    }
+
+    old_phys_ptr = old_virt_ptr;
+    if (old_phys_ptr)
+    {
+        old_phys_ptr = task_virtual_address_to_physical(process->task, old_virt_ptr);
+        if (!old_phys_ptr)
+        {
+            res = -ENOMEM;
+            goto out;
+        }
+    }
+    new_ptr = krealloc(old_phys_ptr, new_size);
+    if (!new_ptr)
+    {
+        res = -ENOMEM;
+        goto out;
+    }
+
+    res = process_allocation_set_map(process, old_allocation_index, new_ptr, new_size);
+    if (res < 0)
+    {
+        goto out;
+    }
+
+out:
+    return new_ptr;
+
+}
 void *process_malloc(struct process *process, size_t size)
 {
     int res = 0;
diff --git a/PeachOS64Bit/src/task/process.h b/PeachOS64Bit/src/task/process.h
@@ -122,6 +122,7 @@ int process_load_for_slot(const char* filename, struct process** process, int pr
 struct process* process_current();
 struct process* process_get(int process_id);
 void* process_malloc(struct process* process, size_t size);
+void* process_realloc(struct process* process, void* old_virt_ptr, size_t new_size);
 void process_free(struct process* process, void* ptr);
 
 void process_get_arguments(struct process* process, int* argc, char*** argv);
