backtrace: print function name instead of addr

Thx to the ELF header given by the bootloader

core/main.c

@@ -159,6 +159,9 @@ void kmain(unsigned long magic, unsigned long addr)
             }
         }
 
+        if (CHECK_FLAG(mbi->flags, 5)) {
+            stackSymbolSetup(mbi);
+        }
         if (CHECK_FLAG(mbi->flags, 6)) {
             memMapAvailable = 1;
         }

core/stack.c

@@ -1,7 +1,94 @@
 #include "stack.h"
+#include "elf.h"
 #include "klibc.h"
+#include "paging.h"
 #include "types.h"
 
+/** Defined in linker.ld script  **/
+extern char __multiboot_data_start;
+extern char __multiboot_data_end;
+static size_t multibootDataSize;
+static size_t multibootUsage;
+
+/** Initialized at 'StackSymbolSetup'. */
+static Elf32_Sym_t *elfSymtab;
+static size_t elfSymtabSize;
+
+static const char *elfStrtab;
+static size_t elfStrtabSize;
+
+static void *stackSaveSection(const void *addr, size_t size, const char *sectionName)
+{
+    if (size > (multibootDataSize - multibootUsage)) {
+        printf("No enough room to store %s (%d/%d). Increase multiboot_data section size",
+               sectionName, size, (multibootDataSize - multibootUsage));
+        return NULL;
+    }
+    void *destAddr = (void *)&__multiboot_data_start + multibootUsage;
+
+    memcpy((void *)destAddr, addr, size);
+    multibootUsage += size;
+
+    return destAddr;
+}
+
+/**
+ * Copy the symbols table and string table from a multiboot information.
+ * We need to copy them as they are loaded by the bootloader and could be override as soon
+ * as we play with memory around our loaded kernel.
+ * As special ELF section is allocated for this purpose.
+ */
+void stackSymbolSetup(multiboot_info_t *mbi)
+{
+    /** Get the section header table as an array of section headers. */
+    Elf32_Shdr_t *sht = (Elf32_Shdr_t *)mbi->u.elf_sec.addr;
+    size_t sec_len    = (size_t)mbi->u.elf_sec.num;
+    assert(mbi->u.elf_sec.size == sizeof(Elf32_Shdr_t));
+    multibootDataSize = &__multiboot_data_end - &__multiboot_data_start;
+    multibootUsage    = 0;
+
+    /**
+     * The section header at index 'shndx' in the table is a meta section
+     * header. It contains a list of section header names in the table. We
+     * should look for section header names ".symtab" & ".strtab".
+     */
+    const char *sh_names = (const char *)sht[mbi->u.elf_sec.shndx].sh_addr;
+
+    /** Loop through the table and look for ".symtab" & ".strtab". */
+    for (size_t i = 0; i < sec_len; ++i) {
+        const char *name = sh_names + sht[i].sh_name;
+
+        if (strcmp(name, ".symtab") == 0) {
+            assert(sht[i].sh_type == SHT_SYMTAB);
+            elfSymtab = stackSaveSection((void *)sht[i].sh_addr, sht[i].sh_size, name);
+            if (elfSymtab)
+                elfSymtabSize = sht[i].sh_size;
+
+        } else if (strcmp(name, ".strtab") == 0) {
+            assert(sht[i].sh_type == SHT_STRTAB);
+            elfStrtab = stackSaveSection((void *)sht[i].sh_addr, sht[i].sh_size, name);
+            if (elfStrtab)
+                elfStrtabSize = sht[i].sh_size;
+        }
+    }
+}
+
+/** Look up an address in symbols map and return its function name or NULL. */
+static const char *lookupSymbolName(uint32_t addr)
+{
+    size_t symtab_len = elfSymtabSize / sizeof(Elf32_Sym_t);
+
+    for (size_t i = 0; i < symtab_len; ++i) {
+        if ((ELF_SYM_TYPE(elfSymtab[i].st_info) == ELF_SYM_TYPE_FUNC) &&
+            (addr >= elfSymtab[i].st_value) &&
+            (addr <= elfSymtab[i].st_value + elfSymtab[i].st_size)) {
+            return elfStrtab + elfSymtab[i].st_name;
+        }
+    }
+
+    return NULL;
+}
+
 void printStackTrace(unsigned int maxFrames)
 {
 #ifdef DEBUG
@@ -21,7 +108,12 @@ void printStackTrace(unsigned int maxFrames)
             break;
         }
         unsigned int *arguments = ebp + 2;
-        printf("[%d] 0x%x (", frame, eip);
+        const char *functionName = lookupSymbolName(eip);
+        if (functionName != NULL) {
+            printf("[%d] %s (", frame, functionName);
+        } else {
+            printf("[%d] 0x%x (", frame, eip);
+        }
         int nbArg = 0;
         do {
             if ((_stack_bottom <= (vaddr_t)arguments) && ((vaddr_t)arguments <= _stack_top)) {

core/stack.h

@@ -1,6 +1,8 @@
 #pragma once
+#include "multiboot.h"
 
 #include "types.h"
 extern vaddr_t _stack_bottom;
 extern vaddr_t _stack_top;
 void printStackTrace(unsigned int maxFrame);
+void stackSymbolSetup(multiboot_info_t *mbi);

linker.ld

@@ -39,6 +39,12 @@ SECTIONS
 		*(.bss)
 	}
 
+	.multiboot_data : {
+		__multiboot_data_size = 48k;
+		__multiboot_data_start = .;
+		. = . + __multiboot_data_size;
+		__multiboot_data_end = .;
+	}
    __ld_kernel_end = .;
 
 	/* The compiler may produce other sections, by default it will put them in