ldso: lazy binding support for RISC-V

* added assembler invocation path for jump slot relocations
* fix GOT initialization (jmp_slot pointer goes to GOT[0] not GOT[2] on
  RISC-V)

Fixes #3339

repos/base/src/lib/ldso/include/relocation_generic.h

@@ -31,7 +31,7 @@ extern "C" void _jmp_slot(void);
 
 namespace Linker
 {
-	struct Plt_got;
+	template <unsigned JUMP_INDEX = 2> struct Plt_got_generic;
 	template <typename REL, unsigned TYPE, bool DIV> class Reloc_jmpslot_generic;
 	template <typename REL, unsigned TYPE, unsigned JMPSLOT> struct Reloc_plt_generic;
 	template <typename REL, unsigned TYPE> struct Reloc_bind_now_generic;
@@ -43,15 +43,15 @@ namespace Linker
  * Set 2nd and 3rd GOT entry (see: SYSTEM V APPLICATION BINARY INTERFACE
  * Intel386 Architecture Processor Supplement - 5.9
  */
-struct Linker::Plt_got
+template <unsigned JUMP_INDEX> struct Linker::Plt_got_generic
 {
-	Plt_got(Dependency const &dep, Elf::Addr *pltgot)
+	Plt_got_generic(Dependency const &dep, Elf::Addr *pltgot)
 	{
 		if (verbose_relocation)
 			log("OBJ: ", dep.obj().name(), " (", &dep, ")");
 
-		pltgot[1] = (Elf::Addr) &dep;       /* ELF object */
+		pltgot[1]          = (Elf::Addr) &dep;       /* ELF object */
-		pltgot[2] = (Elf::Addr) &_jmp_slot; /* Linker entry */
+		pltgot[JUMP_INDEX] = (Elf::Addr) &_jmp_slot; /* Linker entry */
 	}
 };
 

repos/base/src/lib/ldso/spec/arm/relocation.h

@@ -29,6 +29,7 @@ namespace Linker {
 
 	class Reloc_non_plt;
 
+	typedef Plt_got_generic<2>                             Plt_got;
 	typedef Reloc_plt_generic<Elf::Rel, DT_REL, R_JMPSLOT> Reloc_plt;
 	typedef Reloc_jmpslot_generic<Elf::Rel, DT_REL, false> Reloc_jmpslot;
 	typedef Reloc_bind_now_generic<Elf::Rel, DT_REL>       Reloc_bind_now;

repos/base/src/lib/ldso/spec/riscv/jmp_slot.s

@@ -5,7 +5,7 @@
  */
 
 /*
- * Copyright (C) 2015-2017 Genode Labs GmbH
+ * Copyright (C) 2015-2019 Genode Labs GmbH
  *
  * This file is part of the Genode OS framework, which is distributed
  * under the terms of the GNU Affero General Public License version 3.
@@ -15,9 +15,49 @@
 .globl _jmp_slot
 .type  _jmp_slot,%function
 /*
- *  stack[0] = RA
+ *  t0 = GOT[1] = Dependency
- *  ip = &GOT[n+3]
+ *  t1 = PLT offset
- *  lr = &GOT[2]
  */
 _jmp_slot:
-	jal jmp_slot
+
+	/* stack frame */
+	addi sp, sp, -(8*9)
+
+	/* save arguments and return address */
+	sd a0, (0)(sp)
+	sd a1, (1 * 8)(sp)
+	sd a2, (2 * 8)(sp)
+	sd a3, (3 * 8)(sp)
+	sd a4, (4 * 8)(sp)
+	sd a5, (5 * 8)(sp)
+	sd a6, (6 * 8)(sp)
+	sd a7, (7 * 8)(sp)
+	sd ra, (8 * 8)(sp)
+
+	/* GOT[1] = Dependency */
+	mv a0, t0 /* arg 0 */
+
+	/* calculate symbol index from PLT offset (index = offset / 8) */
+	srli a1, t1, 3 /* arg 1 */
+
+	jal  jmp_slot
+
+	/* save address of function to call */
+	mv t0, a0
+
+	/* restore arguments and return address */
+	ld a0, (0)(sp)
+	ld a1, (1 * 8)(sp)
+	ld a2, (2 * 8)(sp)
+	ld a3, (3 * 8)(sp)
+	ld a4, (4 * 8)(sp)
+	ld a5, (5 * 8)(sp)
+	ld a6, (6 * 8)(sp)
+	ld a7, (7 * 8)(sp)
+	ld ra, (8 * 8)(sp)
+
+	/* stack frame */
+	addi sp, sp,(8*9)
+
+	/* call function */
+	jr t0

repos/base/src/lib/ldso/spec/riscv/relocation.h

@@ -38,6 +38,7 @@ namespace Linker {
 
 	class Reloc_non_plt;
 
+	typedef Plt_got_generic<0>                               Plt_got;
 	typedef Reloc_plt_generic<Elf::Rela, DT_RELA, R_JMPSLOT> Reloc_plt;
 	typedef Reloc_jmpslot_generic<Elf::Rela, DT_RELA, false> Reloc_jmpslot;
 	typedef Reloc_bind_now_generic<Elf::Rela, DT_RELA>       Reloc_bind_now;
@@ -87,9 +88,9 @@ class Linker::Reloc_non_plt : public Reloc_non_plt_generic
 					log("LD: reloc: ", rel, " type: ", (int)rel->type());
 
 				switch(rel->type()) {
-					case R_JMPSLOT:  _glob_dat_64(rel, addr, false); break;
 					case R_64:       _glob_dat_64(rel, addr, true);  break;
 					case R_RELATIVE: _relative(rel, addr);           break;
+					case R_JMPSLOT:                                  break;
 
 					default:
 						if (!_dep.obj().is_linker()) {

repos/base/src/lib/ldso/spec/x86_32/relocation.h

@@ -29,6 +29,7 @@ namespace Linker {
 
 	class Reloc_non_plt;
 
+	typedef Plt_got_generic<2>                             Plt_got;
 	typedef Reloc_plt_generic<Elf::Rel, DT_REL, R_JMPSLOT> Reloc_plt;
 	typedef Reloc_jmpslot_generic<Elf::Rel, DT_REL, true>  Reloc_jmpslot;
 	typedef Reloc_bind_now_generic<Elf::Rel, DT_REL>       Reloc_bind_now;

repos/base/src/lib/ldso/spec/x86_64/relocation.h

@@ -32,6 +32,7 @@ namespace Linker {
 
 	class Reloc_non_plt;
 
+	typedef Plt_got_generic<2>                               Plt_got;
 	typedef Reloc_plt_generic<Elf::Rela, DT_RELA, R_JMPSLOT> Reloc_plt;
 	typedef Reloc_jmpslot_generic<Elf::Rela, DT_RELA, false> Reloc_jmpslot;
 	typedef Reloc_bind_now_generic<Elf::Rela, DT_RELA>       Reloc_bind_now;