1 files changed, 107 insertions, 0 deletions
diff --git a/src/ldso/dlstart.c b/src/ldso/dlstart.c
new file mode 100644
index 00000000..5bd2a080
--- /dev/null
+++ b/src/ldso/dlstart.c
@@ -0,0 +1,107 @@
+#include <stddef.h>
+#include "dynlink.h"
+
+#ifdef SHARED
+
+#ifndef START
+#define START "_dlstart"
+#endif
+
+#include "crt_arch.h"
+
+void _dlstart_c(size_t *sp, size_t *dynv)
+{
+	size_t i, aux[AUX_CNT], dyn[DYN_CNT];
+
+	int argc = *sp;
+	char **argv = (void *)(sp+1);
+
+	for (i=argc+1; argv[i]; i++);
+	size_t *auxv = (void *)(argv+i+1);
+
+	for (i=0; i<AUX_CNT; i++) aux[i] = 0;
+	for (i=0; auxv[i]; i+=2) if (auxv[i]<AUX_CNT)
+		aux[auxv[i]] = auxv[i+1];
+
+	for (i=0; i<DYN_CNT; i++) dyn[i] = 0;
+	for (i=0; dynv[i]; i+=2) if (dynv[i]<DYN_CNT)
+		dyn[dynv[i]] = dynv[i+1];
+
+	/* If the dynamic linker is invoked as a command, its load
+	 * address is not available in the aux vector. Instead, compute
+	 * the load address as the difference between &_DYNAMIC and the
+	 * virtual address in the PT_DYNAMIC program header. */
+	unsigned char *base = (void *)aux[AT_BASE];
+	if (!base) {
+		size_t phnum = aux[AT_PHNUM];
+		size_t phentsize = aux[AT_PHENT];
+		Phdr *ph = (void *)aux[AT_PHDR];
+		for (i=phnum; i--; ph = (void *)((char *)ph + phentsize)) {
+			if (ph->p_type == PT_DYNAMIC) {
+				base = (void *)((size_t)dynv - ph->p_vaddr);
+				break;
+			}
+		}
+	}
+
+	/* MIPS uses an ugly packed form for GOT relocations. Since we
+	 * can't make function calls yet and the code is tiny anyway,
+	 * it's simply inlined here. */
+	if (NEED_MIPS_GOT_RELOCS) {
+		size_t local_cnt = 0;
+		size_t *got = (void *)(base + dyn[DT_PLTGOT]);
+		for (i=0; dynv[i]; i+=2) if (dynv[i]==DT_MIPS_LOCAL_GOTNO)
+			local_cnt = dynv[i+1];
+		for (i=0; i<local_cnt; i++) got[i] += (size_t)base;
+	}
+
+	/* The use of the reloc_info structure and nested loops is a trick
+	 * to work around the fact that we can't necessarily make function
+	 * calls yet. Each struct in the array serves like the arguments
+	 * to a function call. */
+	struct {
+		void *rel;
+		size_t size;
+		size_t stride;
+	} reloc_info[] = {
+		{ base+dyn[DT_JMPREL], dyn[DT_PLTRELSZ], 2+(dyn[DT_PLTREL]==DT_RELA) },
+		{ base+dyn[DT_REL], dyn[DT_RELSZ], 2 },
+		{ base+dyn[DT_RELA], dyn[DT_RELASZ], 3 },
+		{ 0, 0, 0 }
+	};
+
+	for (i=0; reloc_info[i].stride; i++) {
+		size_t *rel = reloc_info[i].rel;
+		size_t rel_size = reloc_info[i].size;
+		size_t stride = reloc_info[i].stride;
+		for (; rel_size; rel+=stride, rel_size-=stride*sizeof(size_t)) {
+			if (!IS_RELATIVE(rel[1])) continue;
+			size_t *rel_addr = (void *)(base + rel[0]);
+			size_t addend = stride==3 ? rel[2] : *rel_addr;
+			*rel_addr = (size_t)base + addend;
+		}
+	}
+
+	const char *strings = (void *)(base + dyn[DT_STRTAB]);
+	const Sym *syms = (void *)(base + dyn[DT_SYMTAB]);
+
+	/* Call dynamic linker stage-2, __dls2 */
+	for (i=0; ;i++) {
+		const char *s = strings + syms[i].st_name;
+		if (s[0]=='_' && s[1]=='_' && s[2]=='d'
+		 && s[3]=='l' && s[4]=='s' && s[5]=='2' && !s[6])
+			break;
+	}
+	((stage2_func)(base + syms[i].st_value))(base);
+
+	/* Call dynamic linker stage-3, __dls3 */
+	for (i=0; ;i++) {
+		const char *s = strings + syms[i].st_name;
+		if (s[0]=='_' && s[1]=='_' && s[2]=='d'
+		 && s[3]=='l' && s[4]=='s' && s[5]=='3' && !s[6])
+			break;
+	}
+	((stage3_func)(base + syms[i].st_value))(sp);
+}
+
+#endif