relocate a program interpreter to the map_start

This commit makes a system call that dereferences a NULL pointer fail.

executer/include/uprotocol.h

@@ -80,6 +80,7 @@ struct program_load_desc {
 	unsigned long envs_len;
 	unsigned long rlimit_stack_cur;
 	unsigned long rlimit_stack_max;
+	unsigned long interp_align;
 	struct program_image_section sections[0];
 };
 

executer/user/mcexec.c

@@ -248,6 +248,7 @@ struct program_load_desc *load_interp(struct program_load_desc *desc0, FILE *fp)
 	int i, j, nhdrs = 0;
 	struct program_load_desc *desc = desc0;
 	size_t newsize;
+	unsigned long align;
 
 	if (fread(&hdr, sizeof(hdr), 1, fp) < 1) {
 		__eprint("Cannot read Ehdr.\n");
@@ -278,6 +279,7 @@ struct program_load_desc *load_interp(struct program_load_desc *desc0, FILE *fp)
 	}
 
 	fseek(fp, hdr.e_phoff, SEEK_SET);
+	align = 1;
 	j = desc->num_sections;
 	for (i = 0; i < hdr.e_phnum; i++) {
 		if (fread(&phdr, sizeof(phdr), 1, fp) < 1) {
@@ -301,6 +303,10 @@ struct program_load_desc *load_interp(struct program_load_desc *desc0, FILE *fp)
 			desc->sections[j].prot |= (phdr.p_flags & PF_W)? PROT_WRITE: 0;
 			desc->sections[j].prot |= (phdr.p_flags & PF_X)? PROT_EXEC: 0;
 
+			if (phdr.p_align > align) {
+				align = phdr.p_align;
+			}
+
 			__dprintf("%d: (%s) %lx, %lx, %lx, %lx, %x\n",
 				  j, (phdr.p_type == PT_LOAD ? "PT_LOAD" : "PT_TLS"),
 				  desc->sections[j].vaddr,
@@ -314,6 +320,7 @@ struct program_load_desc *load_interp(struct program_load_desc *desc0, FILE *fp)
 	desc->num_sections = j;
 
 	desc->entry = hdr.e_entry;
+	desc->interp_align = align;
 
 	return desc;
 }

kernel/host.c

@@ -67,6 +67,8 @@ static int process_msg_prepare_process(unsigned long rphys)
 	int range_npages;
 	void *up_v;
 	unsigned long flags;
+	uintptr_t interp_obase = -1;
+	uintptr_t interp_nbase = -1;
 
 	sz = sizeof(struct program_load_desc)
 		+ sizeof(struct program_image_section) * 16;
@@ -100,6 +102,8 @@ static int process_msg_prepare_process(unsigned long rphys)
 	proc->tid = pn->pid;
 	proc->vm->region.user_start = pn->user_start;
 	proc->vm->region.user_end = pn->user_end;
+	proc->vm->region.map_start = (USER_END / 3) & LARGE_PAGE_MASK;
+	proc->vm->region.map_end = proc->vm->region.map_start;
 	proc->rlimit_stack.rlim_cur = pn->rlimit_stack_cur;
 	proc->rlimit_stack.rlim_max = pn->rlimit_stack_max;
 
@@ -107,6 +111,18 @@ static int process_msg_prepare_process(unsigned long rphys)
 	cpu_local_var(scp).post_idx = 0;
 
 	for (i = 0; i < n; i++) {
+		if (pn->sections[i].interp && (interp_nbase == (uintptr_t)-1)) {
+			interp_obase = pn->sections[i].vaddr;
+			interp_obase -= (interp_obase % pn->interp_align);
+			interp_nbase = proc->vm->region.map_start;
+			interp_nbase = (interp_nbase + pn->interp_align - 1)
+				& ~(pn->interp_align - 1);
+		}
+		if (pn->sections[i].interp) {
+			pn->sections[i].vaddr -= interp_obase;
+			pn->sections[i].vaddr += interp_nbase;
+			p->sections[i].vaddr = pn->sections[i].vaddr;
+		}
 		s = (pn->sections[i].vaddr) & PAGE_MASK;
 		e = (pn->sections[i].vaddr + pn->sections[i].len
 		     + PAGE_SIZE - 1) & PAGE_MASK;
@@ -153,7 +169,7 @@ static int process_msg_prepare_process(unsigned long rphys)
 
 		/* TODO: Maybe we need flag */
 		if (pn->sections[i].interp) {
-			/* nothing to do */
+			proc->vm->region.map_end = e;
 		}
 		else if (i == 0) {
 			proc->vm->region.text_start = s;
@@ -171,6 +187,13 @@ static int process_msg_prepare_process(unsigned long rphys)
 		}
 	}
 	
+	if (interp_nbase != (uintptr_t)-1) {
+		pn->entry -= interp_obase;
+		pn->entry += interp_nbase;
+		p->entry = pn->entry;
+		ihk_mc_modify_user_context(proc->uctx, IHK_UCR_PROGRAM_COUNTER, pn->entry);
+	}
+
 #if 1
     /*
       Fix for the problem where brk grows to hit .bss section
@@ -188,8 +211,6 @@ static int process_msg_prepare_process(unsigned long rphys)
 	proc->vm->region.brk_start = proc->vm->region.brk_end =
 		proc->vm->region.data_end;
 #endif
-	proc->vm->region.map_start = proc->vm->region.map_end = 
-		(USER_END / 3) & LARGE_PAGE_MASK;
 
 	/* Map system call stuffs */
 	flags = VR_RESERVED | VR_PROT_READ | VR_PROT_WRITE;

kernel/include/syscall.h

@@ -122,6 +122,7 @@ struct program_load_desc {
 	unsigned long envs_len;
 	unsigned long rlimit_stack_cur;
 	unsigned long rlimit_stack_max;
+	unsigned long interp_align;
 	struct program_image_section sections[0];
 };