From f61da8be06fdfebc598cba783e78117319231140 Mon Sep 17 00:00:00 2001
From: Ada Christine <adachristine18@gmail.com>
Date: Sun, 3 Mar 2024 08:44:42 +0000
Subject: build changes

---
 service/dynamic_x86_64.c | 139 +++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 139 insertions(+)
 create mode 100644 service/dynamic_x86_64.c

(limited to 'service/dynamic_x86_64.c')

diff --git a/service/dynamic_x86_64.c b/service/dynamic_x86_64.c
new file mode 100644
index 0000000..02538ec
--- /dev/null
+++ b/service/dynamic_x86_64.c
@@ -0,0 +1,139 @@
+#include <kc.h>
+
+#include <libc/string.h>
+#include <lib/elf.h>
+
+extern void _rtld_link(void);
+
+struct elf64_relatab
+{
+	Elf64_Rela *entries;
+	size_t size;
+	size_t entsize;
+};
+
+struct elf64_symtab
+{
+	Elf64_Sym *entries;
+	const char *strings;
+	size_t strsize;
+};
+
+struct elf64_dso_info
+{
+	char *base;
+	struct elf64_relatab jmprel;
+	struct elf64_relatab reladyn;
+	struct elf64_symtab dynsym;
+	Elf64_Addr *pltgot;
+};
+
+static struct elf64_dso_info dso_info;
+
+void kc_dynamic_init(char *base, Elf64_Dyn *dyn)
+{
+	dso_info = (struct elf64_dso_info)
+	{
+		base,
+		{
+			elf64_dt_ptr(base, dyn, DT_JMPREL),
+			elf64_dt_val(dyn, DT_PLTRELSZ),
+			elf64_dt_val(dyn, DT_PLTREL) == DT_RELA ? sizeof(Elf64_Rela) : -1 
+		},
+		{
+			elf64_dt_ptr(base, dyn, DT_RELA),
+			elf64_dt_val(dyn, DT_RELASZ),
+			elf64_dt_val(dyn, DT_RELAENT)
+		},
+		{
+			elf64_dt_ptr(base, dyn, DT_SYMTAB),
+			elf64_dt_ptr(base, dyn, DT_STRTAB),
+			elf64_dt_val(dyn, DT_STRSZ)
+		},
+		elf64_dt_ptr(base, dyn, DT_PLTGOT)
+	};
+
+	if (dso_info.pltgot != nullptr)
+	{
+		dso_info.pltgot[1] = (uintptr_t)&dso_info;
+		dso_info.pltgot[2] = (uintptr_t)_rtld_link;
+	}
+
+	kc_dynamic_reloc(base, &dso_info.jmprel);
+	kc_dynamic_reloc(base, &dso_info.reladyn);
+}
+
+void *kc_dynamic_link(struct elf64_dso_info *dso, int index)
+{
+	struct kjarna_interface *ftab = entry_params->interface;
+
+	int symindex = ELF64_R_SYM(dso->jmprel.entries[index].r_info);
+	int strindex = dso->dynsym.entries[symindex].st_name;
+	const char *name = &dso->dynsym.strings[strindex];
+	uintptr_t *fixup = (uintptr_t *)(dso->base + dso->jmprel.entries[index].r_offset);
+
+	// TODO: generate a symbol table for kjarna interface
+	// TODO: implement symbol lookup (maybe hashed too)
+	if (strcmp(name, "open") == 0)
+	{
+		*fixup = (uintptr_t)*ftab->open;
+	}
+	else if (strcmp(name, "close") == 0)
+	{
+		*fixup = (uintptr_t)*ftab->close;
+	}
+	else if (strcmp(name, "read") == 0)
+	{
+		*fixup = (uintptr_t)*ftab->read;
+	}
+	else if (strcmp(name, "write") == 0)
+	{
+		*fixup = (uintptr_t)*ftab->write;
+	}
+	else if (strcmp(name, "lseek") == 0)
+	{
+		*fixup = (uintptr_t)*ftab->lseek;
+	}
+	else if (strcmp(name, "mmap") == 0)
+	{
+		*fixup = (uintptr_t)*ftab->mmap;
+	}
+	else if (strcmp(name, "munmap") == 0)
+	{
+		*fixup = (uintptr_t)*ftab->munmap;
+	}
+	else
+	{
+		return nullptr;
+	}
+
+	return fixup;
+}
+
+static void do_rela(char *base, Elf64_Rela *rela)
+{
+	uintptr_t *fixup = (uintptr_t *)(base + rela->r_offset);
+
+    switch (ELF64_R_TYPE(rela->r_info))
+    {
+        case R_X86_64_JUMP_SLOT:
+            *fixup += (uintptr_t)base;
+            break;
+        case R_X86_64_RELATIVE:
+            *fixup = (uintptr_t)(rela->r_addend + base);
+            break;
+        default:
+            break;
+    }
+}
+
+void kc_dynamic_reloc(char *base, struct elf64_relatab *rela)
+{
+	size_t entries = rela->size / rela->entsize;
+
+    for (size_t i = 0; rela->entries && (i < entries); i++)
+    {
+        do_rela(base, &rela->entries[i]);
+    }
+}
+
-- 
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