git-riscv64-gnu-ifunc

commit 306b8dbac917ef7f499044551df9bf051ca78fa4
Author: Vincent Chen <vincent.chen@sifive.com>
Date:   Tue Dec 15 17:16:40 2020 +0800

    riscv: Initialize $gp before resolving the IRELATIVE relocation

    The $gp register may be used to access the global variable in
    the PDE program, so the $gp register should be initialized before
    executing the IFUNC resolver of PDE program to avoid unexpected
    error occurs.

commit 963f5858750635876d849878fd1df9eac1a6cd6a
Author: Vincent Chen <vincent.chen@sifive.com>
Date:   Tue Dec 15 17:16:39 2020 +0800

    riscv: support GNU indirect function

    Enable riscv glibc to support GNU indirect function

Gbp-Pq: Topic riscv64
Gbp-Pq: Name git-riscv64-gnu-ifunc.diff

diff --git a/libc-abis b/libc-abis
index e702f6ae245c1528f5a608df8cfae4f037809de2..70b154de4b02cba2c399b07613f4617a833f136c 100644 (file)
--- a/libc-abis
+++ b/libc-abis
@@ -48,3 +48,4 @@ IFUNC         sparc64-*-linux*
 IFUNC          sparc-*-linux*
 # Absolute (SHN_ABS) symbols working correctly.
 ABSOLUTE
+IFUNC          riscv*-linux*

diff --git a/sysdeps/riscv/dl-irel.h b/sysdeps/riscv/dl-irel.h
new file mode 100644 (file)
index 0000000..cad9cc8
--- /dev/null
+++ b/sysdeps/riscv/dl-irel.h
@@ -0,0 +1,56 @@
+/* Machine-dependent ELF indirect relocation inline functions.
+   RISC-V version.
+   Copyright (C) 2020 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#ifndef _DL_IREL_H
+#define _DL_IREL_H
+
+#include <stdio.h>
+#include <unistd.h>
+#include <ldsodefs.h>
+#include <sysdep.h>
+
+#define ELF_MACHINE_IRELA      1
+
+static inline ElfW(Addr)
+__attribute ((always_inline))
+elf_ifunc_invoke (ElfW(Addr) addr)
+{
+  /* The second argument is a void pointer to preserve the extension
+     fexibility.  */
+  return ((ElfW(Addr) (*) (uint64_t, void *)) (addr))
+        (GLRO(dl_hwcap), NULL);
+}
+
+static inline void
+__attribute ((always_inline))
+elf_irela (const ElfW(Rela) *reloc)
+{
+  ElfW(Addr) *const reloc_addr = (void *) reloc->r_offset;
+  const unsigned long int r_type = ELFW(R_TYPE) (reloc->r_info);
+
+  if (__glibc_likely (r_type == R_RISCV_IRELATIVE))
+    {
+      ElfW(Addr) value = elf_ifunc_invoke (reloc->r_addend);
+      *reloc_addr = value;
+    }
+  else
+    __libc_fatal ("Unexpected reloc type in static binary.\n");
+}
+
+#endif

diff --git a/sysdeps/riscv/dl-machine.h b/sysdeps/riscv/dl-machine.h
index 03db94aebafc8f2f7e19d84e19910cf5c13eed19..c1cf8849010d93f8fbcda40ce10d3ba5daac895e 100644 (file)
--- a/sysdeps/riscv/dl-machine.h
+++ b/sysdeps/riscv/dl-machine.h
@@ -25,6 +25,7 @@
 #include <elf/elf.h>
 #include <sys/asm.h>
 #include <dl-tls.h>
+#include <dl-irel.h>
 
 #ifndef _RTLD_PROLOGUE
 # define _RTLD_PROLOGUE(entry)                                         \
@@ -174,6 +175,13 @@ elf_machine_rela (struct link_map *map, const ElfW(Rela) *reloc,
   if (sym_map != NULL)
     value = SYMBOL_ADDRESS (sym_map, sym, true) + reloc->r_addend;
 
+  if (sym != NULL
+      && __glibc_unlikely (ELFW(ST_TYPE) (sym->st_info) == STT_GNU_IFUNC)
+      && __glibc_likely (sym->st_shndx != SHN_UNDEF)
+      && __glibc_likely (!skip_ifunc))
+    value = elf_ifunc_invoke (value);
+
+
   switch (r_type)
     {
 #ifndef RTLD_BOOTSTRAP
@@ -249,6 +257,13 @@ elf_machine_rela (struct link_map *map, const ElfW(Rela) *reloc,
     }
 #endif
 
+    case R_RISCV_IRELATIVE:
+      value = map->l_addr + reloc->r_addend;
+      if (__glibc_likely (!skip_ifunc))
+        value = elf_ifunc_invoke (value);
+      *addr_field = value;
+      break;
+
     case R_RISCV_JUMP_SLOT:
     case __WORDSIZE == 64 ? R_RISCV_64 : R_RISCV_32:
       *addr_field = value;
@@ -290,6 +305,13 @@ elf_machine_lazy_rel (struct link_map *map, ElfW(Addr) l_addr,
       else
        *reloc_addr = map->l_mach.plt;
     }
+  else if (__glibc_unlikely (r_type == R_RISCV_IRELATIVE))
+    {
+      ElfW(Addr) value = map->l_addr + reloc->r_addend;
+      if (__glibc_likely (!skip_ifunc))
+        value = elf_ifunc_invoke (value);
+      *reloc_addr = value;
+    }
   else
     _dl_reloc_bad_type (map, r_type, 1);
 }
@@ -315,8 +337,28 @@ elf_machine_runtime_setup (struct link_map *l, int lazy, int profile)
       gotplt[0] = (ElfW(Addr)) &_dl_runtime_resolve;
       gotplt[1] = (ElfW(Addr)) l;
     }
-#endif
 
+  if (l->l_type == lt_executable)
+    {
+      /* The __global_pointer$ may not be defined by the linker if the
+        $gp register does not be used to access the global variable
+        in the executable program. Therefore, the search symbol is
+        set to a weak symbol to avoid we error out if the
+        __global_pointer$ is not found.  */
+      ElfW(Sym) gp_sym = { 0 };
+      gp_sym.st_info = (unsigned char) ELFW (ST_INFO (STB_WEAK, STT_NOTYPE));
+
+      const ElfW(Sym) *ref = &gp_sym;
+      _dl_lookup_symbol_x ("__global_pointer$", l, &ref,
+                          l->l_scope, NULL, 0, 0, NULL);
+      if (ref)
+        asm (
+          "mv gp, %0\n"
+          :
+          : "r" (ref->st_value)
+        );
+    }
+#endif
   return lazy;
 }