Linker script refactoring, see details:

- Added separate relro "segment" (introduced by [17.0.0+])
- Reordered sections to better reflect official layout
- Fixed handling of TLS segment alignment

nx/source/internal.h

@@ -23,6 +23,21 @@ typedef struct {
     void* tls_tp; // !! Offset needs to be TLS+0x1F8 for __aarch64_read_tp !!
 } ThreadVars;
 
+extern const u8 __tdata_lma[];
+extern const u8 __tdata_lma_end[];
+extern u8 __tls_start[];
+extern u8 __tls_end[];
+extern size_t __tls_align;
+
 static inline ThreadVars* getThreadVars(void) {
     return (ThreadVars*)((u8*)armGetTls() + 0x200 - sizeof(ThreadVars));
 }
+
+NX_INLINE size_t getTlsStartOffset(void)
+{
+    // TLS region begins with the Thread Control Block (TCB), which is intended
+    // to contain two pointers. The actual tdata/tbss segment follows the TCB,
+    // however if it requires special alignment the offset is rounded up.
+    size_t tcb_sz = 2*sizeof(void*);
+    return __tls_align > tcb_sz ? __tls_align : tcb_sz;
+}

nx/source/kernel/thread.c

@@ -16,11 +16,6 @@
 #define USER_TLS_END   (0x200 - sizeof(ThreadVars))
 #define NUM_TLS_SLOTS ((USER_TLS_END - USER_TLS_BEGIN) / sizeof(void*))
 
-extern const u8 __tdata_lma[];
-extern const u8 __tdata_lma_end[];
-extern u8 __tls_start[];
-extern u8 __tls_end[];
-
 static Mutex g_threadMutex;
 static Thread* g_threadList;
 
@@ -45,7 +40,7 @@ static void _EntryWrap(ThreadEntryArgs* args) {
     tv->magic      = THREADVARS_MAGIC;
     tv->thread_ptr = args->t;
     tv->reent      = args->reent;
-    tv->tls_tp     = (u8*)args->tls-2*sizeof(void*); // subtract size of Thread Control Block (TCB)
+    tv->tls_tp     = (u8*)args->tls-getTlsStartOffset();
     tv->handle     = args->t->handle;
 
     // Initialize thread info
@@ -94,28 +89,35 @@ Result threadCreate(
     Thread* t, ThreadFunc entry, void* arg, void* stack_mem, size_t stack_sz,
     int prio, int cpuid)
 {
-
-    const size_t tls_sz = (__tls_end-__tls_start+0xF) &~ 0xF;
     const size_t reent_sz = (sizeof(struct _reent)+0xF) &~ 0xF;
+    const size_t tls_sz = (__tls_end-__tls_start+0xF) &~ 0xF;
+
+    // Verify stack size alignment
+    if (stack_sz & 0xFFF) {
+        return MAKERESULT(Module_Libnx, LibnxError_BadInput);
+    }
 
     bool owns_stack_mem;
     if (stack_mem == NULL) {
-        // Allocate new memory, stack then reent then tls.
+        // Allocate new memory for the stack, tls and reent.
-        stack_mem = __libnx_aligned_alloc(0x1000, stack_sz + reent_sz + tls_sz);
+        stack_mem = __libnx_aligned_alloc(0x1000, stack_sz + tls_sz + reent_sz);
 
         owns_stack_mem = true;
     } else {
-        // Use provided memory for stack, reent, and tls.
+        // Verify alignment of provided memory.
-        if (((uintptr_t)stack_mem & 0xFFF) || (stack_sz & 0xFFF)) {
+        if ((uintptr_t)stack_mem & 0xFFF) {
             return MAKERESULT(Module_Libnx, LibnxError_BadInput);
         }
 
         // Ensure we don't go out of bounds.
-        if (stack_sz <= tls_sz + reent_sz) {
+        size_t align_mask = getTlsStartOffset()-1;
+        size_t needed_sz = (tls_sz + reent_sz + align_mask) &~ align_mask;
+        if (stack_sz <= needed_sz + sizeof(ThreadEntryArgs)) {
             return MAKERESULT(Module_Libnx, LibnxError_OutOfMemory);
         }
 
-        stack_sz -= tls_sz + reent_sz;
+        // Use provided memory for the stack, tls and reent.
+        stack_sz -= needed_sz;
         owns_stack_mem = false;
     }
 
@@ -123,9 +125,9 @@ Result threadCreate(
         return MAKERESULT(Module_Libnx, LibnxError_OutOfMemory);
     }
 
-    // Stack size may be unaligned in either case.
+    // Total allocation size may be unaligned in either case.
     virtmemLock();
-    const size_t aligned_stack_sz = (stack_sz + tls_sz + reent_sz +0xFFF) & ~0xFFF;
+    const size_t aligned_stack_sz = (stack_sz + tls_sz + reent_sz + 0xFFF) & ~0xFFF;
     void* stack_mirror = virtmemFindStack(aligned_stack_sz, 0x4000);
     Result rc = svcMapMemory(stack_mirror, stack_mem, aligned_stack_sz);
     virtmemUnlock();
@@ -134,8 +136,9 @@ Result threadCreate(
     {
         uintptr_t stack_top = (uintptr_t)stack_mirror + stack_sz - sizeof(ThreadEntryArgs);
         ThreadEntryArgs* args = (ThreadEntryArgs*) stack_top;
-        void *reent = (void*)((uintptr_t)stack_mirror + stack_sz);
+        void *tls = (void*)((uintptr_t)stack_mirror + stack_sz);
-        void *tls = (void*)((uintptr_t)reent + reent_sz);
+        void *reent = (void*)((uintptr_t)tls + tls_sz);
+
         Handle handle;
 
         t->handle = INVALID_HANDLE;

nx/source/runtime/newlib.c

@@ -30,10 +30,6 @@ struct __pthread_t
 
 void __attribute__((weak)) NORETURN __libnx_exit(int rc);
 
-extern const u8 __tdata_lma[];
-extern const u8 __tdata_lma_end[];
-extern u8 __tls_start[];
-
 /// TimeType passed to timeGetCurrentTime() during time initialization. If that fails and __nx_time_type isn't TimeType_Default, timeGetCurrentTime() will be called again with TimeType_Default.
 __attribute__((weak)) TimeType __nx_time_type = TimeType_Default;
 
@@ -438,7 +434,7 @@ void newlibSetup(void)
     tv->reent      = _impure_ptr;
 #pragma GCC diagnostic push
 #pragma GCC diagnostic ignored "-Warray-bounds"
-    tv->tls_tp     = __tls_start-2*sizeof(void*); // subtract size of Thread Control Block (TCB)
+    tv->tls_tp     = __tls_start-getTlsStartOffset();
 #pragma GCC diagnostic pop
     tv->handle     = envGetMainThreadHandle();
 

nx/switch.ld

@@ -11,10 +11,11 @@ PHDRS
 
 SECTIONS
 {
+	PROVIDE_HIDDEN( __start__ = 0x0 );
+
 	/* =========== CODE section =========== */
-	PROVIDE(__start__ = 0x0);
 	. = __start__;
-	__code_start = . ;
+	PROVIDE_HIDDEN( __code_start = . );
 
 	.text :
 	{
@@ -48,111 +49,143 @@ SECTIONS
 
 	/* =========== RODATA section =========== */
 	. = ALIGN(0x1000);
-	__rodata_start = . ;
+	PROVIDE_HIDDEN( __rodata_start = . );
 
 	.nx-module-name : { KEEP (*(.nx-module-name)) } :rodata
 
+	.rela.dyn : { *(.rela.*) } :rodata
+	.relr.dyn : { *(.relr.*) } :rodata
+
+	.hash     : { *(.hash) } :rodata
+	.gnu.hash : { *(.gnu.hash) } :rodata
+
+	.dynsym   : { *(.dynsym) } :rodata
+	.dynstr   : { *(.dynstr) } :rodata
+
 	.rodata :
 	{
 		*(.rodata .rodata.* .gnu.linkonce.r.*)
 		. = ALIGN(8);
 	} :rodata
 
-	.eh_frame_hdr     : { __eh_frame_hdr_start = .; *(.eh_frame_hdr) *(.eh_frame_entry .eh_frame_entry.*) __eh_frame_hdr_end = .; } :rodata
+	.tls.align :
-	.eh_frame         : ONLY_IF_RO { KEEP (*(.eh_frame)) *(.eh_frame.*) } :rodata
+	{
-	.gcc_except_table : ONLY_IF_RO { *(.gcc_except_table .gcc_except_table.*) } :rodata
+		QUAD( MAX( ALIGNOF(.tdata), ALIGNOF(.tbss) ) )
-	.gnu_extab        : ONLY_IF_RO { *(.gnu_extab*) } : rodata
+	} :rodata
+
+	PROVIDE_HIDDEN( __tls_align = ADDR(.tls.align) );
+
+	.gcc_except_table  : { *(.gcc_except_table .gcc_except_table.*) } :rodata
+	.eh_frame_hdr      : { *(.eh_frame_hdr) *(.eh_frame_entry .eh_frame_entry.*) } :rodata
+	.eh_frame          : { KEEP (*(.eh_frame)) *(.eh_frame.*) } :rodata
+	.gnu_extab         : { *(.gnu_extab*) } : rodata
+	.exception_ranges  : { *(.exception_ranges .exception_ranges*) } :rodata
+
+	PROVIDE_HIDDEN( __eh_frame_hdr_start = ADDR(.eh_frame_hdr)                         );
+	PROVIDE_HIDDEN( __eh_frame_hdr_end   = ADDR(.eh_frame_hdr) + SIZEOF(.eh_frame_hdr) );
 
-	.dynamic           : { *(.dynamic) } :rodata :dyn
-	.dynsym            : { *(.dynsym) } :rodata
-	.dynstr            : { *(.dynstr) } :rodata
-	.rela.dyn          : { *(.rela.*) } :rodata
-	.interp            : { *(.interp) } :rodata
-	.hash              : { *(.hash) } :rodata
-	.gnu.hash          : { *(.gnu.hash) } :rodata
 	.gnu.version       : { *(.gnu.version) } :rodata
 	.gnu.version_d     : { *(.gnu.version_d) } :rodata
 	.gnu.version_r     : { *(.gnu.version_r) } :rodata
+
 	.note.gnu.build-id : { *(.note.gnu.build-id) } :rodata
 
+	/* =========== RELRO section =========== */
+	. = ALIGN(0x1000);
+	PROVIDE_HIDDEN( __relro_start = . );
+
+	.preinit_array :
+	{
+		PROVIDE_HIDDEN( __preinit_array_start = . );
+		KEEP (*(.preinit_array))
+		PROVIDE_HIDDEN( __preinit_array_end = . );
+	} :data
+
+	.init_array :
+	{
+		PROVIDE_HIDDEN( __init_array_start = . );
+		KEEP( *(SORT_BY_INIT_PRIORITY(.init_array.*) SORT_BY_INIT_PRIORITY(.ctors.*)) )
+		KEEP( *(.init_array .ctors) )
+		PROVIDE_HIDDEN( __init_array_end = . );
+	} :data
+
+	.fini_array :
+	{
+		PROVIDE_HIDDEN( __fini_array_start = . );
+		KEEP( *(SORT_BY_INIT_PRIORITY(.fini_array.*) SORT_BY_INIT_PRIORITY(.dtors.*)) )
+		KEEP( *(.fini_array .dtors) )
+		PROVIDE_HIDDEN( __fini_array_end = . );
+	} :data
+
+	.data.rel.ro :
+	{
+		*(.data.rel.ro.local* .gnu.linkonce.d.rel.ro.local.*)
+		*(.data.rel.ro .data.rel.ro.* .gnu.linkonce.d.rel.ro.*)
+		. = ALIGN(8);
+	} :data
+
+	.dynamic : { *(.dynamic) } :data :dyn
+
+	.got     : { *(.got) *(.igot) } :data
+	.got.plt : { *(.got.plt)  *(.igot.plt) } :data
+
+	PROVIDE_HIDDEN( __got_start__ = ADDR(.got)                        );
+	PROVIDE_HIDDEN( __got_end__   = ADDR(.got.plt) + SIZEOF(.got.plt) );
+
 	/* =========== DATA section =========== */
 	. = ALIGN(0x1000);
-	__data_start = . ;
+	PROVIDE_HIDDEN( __data_start = . );
 
-	.eh_frame : ONLY_IF_RW { KEEP (*(.eh_frame)) *(.eh_frame.*) } :data
+	.data :
-	.gcc_except_table : ONLY_IF_RW { *(.gcc_except_table .gcc_except_table.*) } :data
-	.gnu_extab : ONLY_IF_RW { *(.gnu_extab*) } : data
-	.exception_ranges : ONLY_IF_RW { *(.exception_ranges .exception_ranges*) } :data
-
-	.tdata ALIGN(8) :
-	{
-		__tdata_lma = .;
-		*(.tdata .tdata.* .gnu.linkonce.td.*)
-		. = ALIGN(8);
-		__tdata_lma_end = .;
-	} :data
-
-	.tbss ALIGN(8) :
-	{
-		*(.tbss .tbss.* .gnu.linkonce.tb.*) *(.tcommon)
-		. = ALIGN(8);
-	} :data
-
-	.preinit_array ALIGN(8) :
-	{
-		PROVIDE (__preinit_array_start = .);
-		KEEP (*(.preinit_array))
-		PROVIDE (__preinit_array_end = .);
-	} :data
-
-	.init_array ALIGN(8) :
-	{
-		PROVIDE (__init_array_start = .);
-		KEEP( *(SORT_BY_INIT_PRIORITY(.init_array.*) SORT_BY_INIT_PRIORITY(.ctors.*)) )
-		KEEP( *(.init_array .ctors) )
-		PROVIDE (__init_array_end = .);
-	} :data
-
-	.fini_array ALIGN(8) :
-	{
-		PROVIDE (__fini_array_start = .);
-		KEEP( *(SORT_BY_INIT_PRIORITY(.fini_array.*) SORT_BY_INIT_PRIORITY(.dtors.*)) )
-		KEEP( *(.fini_array .dtors) )
-		PROVIDE (__fini_array_end = .);
-	} :data
-
-	__got_start__ = .;
-
-	.got            : { *(.got) *(.igot) } :data
-	.got.plt        : { *(.got.plt)  *(.igot.plt) } :data
-
-	__got_end__ = .;
-
-	.data ALIGN(8) :
 	{
 		*(.data .data.* .gnu.linkonce.d.*)
 		SORT(CONSTRUCTORS)
+		. = ALIGN(8);
 	} :data
 
-	.bss ALIGN(8) :
+	.tdata :
+	{
+		*(.tdata .tdata.* .gnu.linkonce.td.*)
+		. = ALIGN(8);
+	} :data
+
+	PROVIDE_HIDDEN( __tdata_lma     = ADDR(.tdata)                  );
+	PROVIDE_HIDDEN( __tdata_lma_end = ADDR(.tdata) + SIZEOF(.tdata) );
+
+	.tbss :
+	{
+		*(.tbss .tbss.* .gnu.linkonce.tb.*)
+		*(.tcommon)
+		. = ALIGN(8);
+	} :data
+
+	.bss :
 	{
 		*(.dynbss)
 		*(.bss .bss.* .gnu.linkonce.b.*)
 		*(COMMON)
 		. = ALIGN(8);
+	} :data
 
-		/* Reserve space for the TLS segment of the main thread */
+	/* Reserve space for the TLS segment of the main thread */
-		__tls_start = .;
+	.main.tls ALIGN(MAX(ALIGNOF(.tdata),ALIGNOF(.tbss))) :
-		. += + SIZEOF(.tdata) + SIZEOF(.tbss);
+	{
-		__tls_end = .;
+		. += SIZEOF(.tdata);
-	} : data
+		. = ALIGN(ALIGNOF(.tbss));
-	__bss_start__ = ADDR(.bss);
+		. += SIZEOF(.tbss);
-	__bss_end__ = ADDR(.bss) + SIZEOF(.bss);
+	} :data
 
-	__end__ = ABSOLUTE(.) ;
+	PROVIDE_HIDDEN( __tls_start   = ADDR(.main.tls)                     );
+	PROVIDE_HIDDEN( __tls_end     = ADDR(.main.tls) + SIZEOF(.main.tls) );
 
+	PROVIDE_HIDDEN( __bss_start__ = ADDR(.bss) );
+	PROVIDE_HIDDEN( __bss_end__   = __tls_end  );
+
+	PROVIDE_HIDDEN( __end__ = ABSOLUTE(.) );
+
+	/* =========== Argument buffer =========== */
 	. = ALIGN(0x1000);
-	__argdata__ = ABSOLUTE(.) ;
+	PROVIDE_HIDDEN( __argdata__ = ABSOLUTE(.) );
 
 	/* ==================
 	   ==== Metadata ====

nx/switch.specs

@@ -1,8 +1,5 @@
-%rename link                old_link
-
 *link:
-%(old_link) -T %:getenv(DEVKITPRO /libnx/switch.ld) -pie --no-dynamic-linker --spare-dynamic-tags=0 --gc-sections -z text -z nodynamic-undefined-weak --build-id=sha1 --nx-module-name
++ -T %:getenv(DEVKITPRO /libnx/switch.ld) -pie --no-dynamic-linker --spare-dynamic-tags=0 --gc-sections -z text -z now -z nodynamic-undefined-weak --build-id=sha1 --nx-module-name
 
 *startfile:
 crti%O%s crtbegin%O%s --require-defined=main
-