w6l: purge dead elf branches; pin rx extent

cmd/w6l/dyn.c

@@ -23,7 +23,6 @@
 /* Versym special values: 0 = local, 1 = base/global. */
 #define VER_NDX_LOCAL		0
 #define VER_NDX_GLOBAL		1
-#define VER_FLG_BASE		1
 #define VERSYM_HIDDEN		0x8000
 #define VERSYM_VERSION		0x7fff
 
@@ -208,16 +207,6 @@ l_load_so(Lnk *l, const char *path)
 			} else if (verdef_names != NULL
 			    && (int)vidx <= verdef_max
 			    && verdef_names[vidx] != NULL) {
-				/* index 1 in glibc's Verdef is the SONAME with
-				 * VER_FLG_BASE — we skip its export entries
-				 * as a side effect of vidx==1 mapping to the
-				 * BASE name (e.g. "libc.so.6"), which never
-				 * appears as a reference target. Treat any
-				 * lookup that lands on the BASE entry as
-				 * unversioned. */
-				if (vidx == 1)
-					vername = NULL;
-				else
 				vername = verdef_names[vidx];
 			}
 		}

cmd/w6l/dynout.c

@@ -376,7 +376,6 @@ l_emit_dyn_elf(Lnk *l, FILE *f, u64 base, u64 entry)
 	const u64 gotplt_va  = base + gotplt_off;
 	const u64 dynamic_va = base + dynamic_off;
 	const u64 data_va    = base + data_off;
-	(void)dynstr_va; (void)hash_va; (void)plt_va;
 
 	/* Now that the dyn layout pins text_va/data_va, apply
 	 * relocations. main.c defers this; the static path runs it from
@@ -587,6 +586,8 @@ l_emit_dyn_elf(Lnk *l, FILE *f, u64 base, u64 entry)
 	ph[0].p_vaddr  = base;
 	ph[0].p_paddr  = base;
 	ph[0].p_filesz = rx_end;
+	/* The loader page-rounds mappings; gotplt_off independently starts
+	 * the next page, so padding is not part of the R+X extent. */
 	ph[0].p_memsz  = rx_end;
 	ph[0].p_align  = page;
 

cmd/w6l/out.c

@@ -80,8 +80,6 @@ l_emit_elf(Lnk *l, FILE *f, u64 base, u64 entry)
 			bsslen++;
 	}
 	const u64 data_file_len = l->datalen - bsslen;
-	const u64 file_end = has_data ? (data_off + data_file_len) : rx_end;
-	(void)data_va;
 
 	Ehdr eh = {0};
 	memcpy(eh.e_ident, "\x7f""ELF", 4);
@@ -104,6 +102,8 @@ l_emit_elf(Lnk *l, FILE *f, u64 base, u64 entry)
 	phx.p_vaddr = base;
 	phx.p_paddr = base;
 	phx.p_filesz = rx_end;
+	/* The loader page-rounds mappings; when present, data_off starts
+	 * independently on the next page, so padding is not R+X extent. */
 	phx.p_memsz = rx_end;
 	phx.p_align = page;
 
@@ -133,7 +133,6 @@ l_emit_elf(Lnk *l, FILE *f, u64 base, u64 entry)
 		for (long i = here; i < (long)data_off; i++) fputc(0, f);
 		fwrite(l->data, 1, data_file_len, f);
 	}
-	(void)file_end;
 
 	return 0;
 }

selfhost/cmd/w6l/dyn.ww

@@ -315,10 +315,7 @@ export fn loadso(l: *lnk, path: *u8) i32 = {
 					switch (vidx) {
 					case VER_NDX_LOCAL_C:
 						keep = 0;	// not exported
-					case VER_NDX_GLOBAL_C,1u16:
+					case VER_NDX_GLOBAL_C:
-						// glibc's BASE entry (vidx==1): treat as
-						// unversioned. (The C version notes that
-						// vidx==1 in Verdef maps to the SONAME BASE.)
 						vernamecs = nil;
 					case:
 						if (verstr != nil) {

selfhost/cmd/w6l/dynout.ww

@@ -668,6 +668,8 @@ export fn emitdynelf(l: *lnk, fd: i32, base: u64, entry: u64) i32 = {
 	dwr64(filebuf.ptr, p0 + 16u64, base);
 	dwr64(filebuf.ptr, p0 + 24u64, base);
 	dwr64(filebuf.ptr, p0 + 32u64, rxend);
+	// The loader page-rounds mappings; gotpltoff independently starts
+	// the next page, so padding is not part of the R+X extent.
 	dwr64(filebuf.ptr, p0 + 40u64, rxend);
 	dwr64(filebuf.ptr, p0 + 48u64, PAGE);
 

selfhost/cmd/w6l/obj.ww

@@ -14,8 +14,8 @@ def SHT_SYMTAB:    i32 = 2;
 def SHT_STRTAB:    i32 = 3;
 def SHT_RELA:      i32 = 4;
 
-// w6a/w6l use straight LE on amd64. Reading via byte offsets keeps us off
+// ELF64/x86-64 is little-endian; bytewise decoding also avoids alignment
-// the cgen's u16 field-load story for now (MOVZBQ exists; MOVZWQ doesn't).
+// and host-layout assumptions about input buffers.
 
 fn rdu16(p: *u8, off: u64) u16 = {
 	let b0: u16 = p[off]: u16;
@@ -507,9 +507,8 @@ fn loadimage(l: *lnk, path: *u8, buf: *u8, len: u64) i32 = {
 		};
 	};
 
-	// We don't keep a per-object map[] of *lsym. Instead the reloc
+	// Rewalking avoids retaining an nsyms-sized per-object map solely
-	// loop re-walks symtab and re-interns by name. Simpler than
+	// for relocation lookup.
-	// dancing around the cgen's u64-shift gaps.
 	let si: u64 = 1u64;	// skip index 0 (always undef sentinel)
 	for (si < nsyms) {
 		let symp: u64 = symoff + si * SYM_SIZE;
@@ -526,7 +525,6 @@ fn loadimage(l: *lnk, path: *u8, buf: *u8, len: u64) i32 = {
 				if (idxdata >= 0) {
 					indt = (stshndx: i32) == idxdata;
 				};
-				if (intext && indt) { indt = false; };
 				if (intext) {
 					if (gs.defined != 0) {
 						let m: str = "w6l: duplicate symbol\n";

selfhost/cmd/w6l/out.ww

@@ -111,6 +111,8 @@ export fn emitelf(l: *lnk, fd: i32, base: u64, entry: u64) i32 = {
 	wru64(hdr.ptr, 80u64, base);		// p_vaddr
 	wru64(hdr.ptr, 88u64, base);		// p_paddr
 	wru64(hdr.ptr, 96u64, rxend);		// p_filesz
+	// The loader page-rounds mappings; when present, dataoff starts
+	// independently on the next page, so padding is not R+X extent.
 	wru64(hdr.ptr, 104u64, rxend);		// p_memsz
 	wru64(hdr.ptr, 112u64, TEXT_OFF);		// p_align
 

test/object/link_test.ww

@@ -14,7 +14,8 @@ package link_test;
 //
 // twoloads (620) — a DATAW input links to exactly 2 program headers,
 // both PT_LOAD, exactly one R+X and one R+W (exact p_flags equality;
-// any other combination fails).
+// any other combination fails). R+X filesz/memsz stop at content rather
+// than absorbing the page padding before R+W.
 //
 // nodatasingleload (620) — an input without DATAW keeps the single
 // PT_LOAD layout; test 992 (selfhost w6l diff, the terminal bootstrap
@@ -169,6 +170,9 @@ fn runexit(td: str, tag: str, exe: str) i32 = {
 	if (phnum(o) != 2) { fail("twoloads", "e_phnum != 2"); };
 	let sawrx: bool = false;
 	let sawrw: bool = false;
+	let rxfilesz: u64 = 0u64;
+	let rxmemsz: u64 = 0u64;
+	let rwoff: u64 = 0u64;
 	let i: i32 = 0;
 	for (i < 2) {
 		let ph: i32 = phoff(o, i);
@@ -176,8 +180,14 @@ fn runexit(td: str, tag: str, exe: str) i32 = {
 			fail("twoloads", "phdr not PT_LOAD");
 		};
 		let flags: u64 = testenv.leu32(o, ph + 4);
-		if (flags == 5u64) { sawrx = true; }
+		if (flags == 5u64) {
-		else if (flags == 6u64) { sawrw = true; }
+			sawrx = true;
+			rxfilesz = testenv.leu64(o, ph + 32);
+			rxmemsz = testenv.leu64(o, ph + 40);
+		} else if (flags == 6u64) {
+			sawrw = true;
+			rwoff = testenv.leu64(o, ph + 8);
+		}
 		else {
 			fail("twoloads", "phdr flags not exactly R+X or R+W");
 		};
@@ -185,6 +195,12 @@ fn runexit(td: str, tag: str, exe: str) i32 = {
 	};
 	if (!sawrx) { fail("twoloads", "missing R+X PT_LOAD"); };
 	if (!sawrw) { fail("twoloads", "missing R+W PT_LOAD"); };
+	if (rxfilesz != rxmemsz) {
+		fail("twoloads", "R+X filesz != memsz");
+	};
+	if (rxmemsz >= rwoff) {
+		fail("twoloads", "R+X memsz includes page padding");
+	};
 	testenv.clean(td);
 };