[PATCH] tile: Fix up corner cases with signed relocations

[Chris Metcalf <cmetcalf at tilera dot com>]

Some types of relocations technically need to be signed rather than
unsigned: in particular ones that are used with moveli or movei,
or for jump and branch.  This is almost never a problem.  Jump and
branch opcodes are pretty much uniformly resolved by the static linker
(unless you omit -fpic for a shared library, which is not recommended).
The moveli and movei opcodes that need to be sign-extended generally
are for positive displacements, like the construction of the address of
main() from _start().  However, tst-pie1 ends up with main below _start
(in a different module) and the test failed due to signedness issues in
relocation handling.

This commit treats the value as signed when shifting (to preserve the
high bit) and also sign-extends the value generated from the updated
bundle when comparing with the desired bundle, which we do to make sure
no overflow occurred.  As a result, the tst-pie1 test now passes.
---
 sysdeps/tile/dl-machine.h |   40 ++++++++++++++++++++++------------------
 1 files changed, 22 insertions(+), 18 deletions(-)

This is the change I wanted to push before 2.20 froze.  It turns out
not to be a regression, so arguably the conservative thing may to wait
until after 2.21 opens.  I've done reasonable internal testing (and
will have more results by Saturday morning after a full rebuild and
test suite run) but could easily be swayed one way or the other.

diff --git a/sysdeps/tile/dl-machine.h b/sysdeps/tile/dl-machine.h
index 8be6758..ecd1eff 100644
--- a/sysdeps/tile/dl-machine.h
+++ b/sysdeps/tile/dl-machine.h
@@ -657,7 +657,7 @@ elf_machine_rela (struct link_map *map, const ElfW(Rela) *reloc,
     value += 0x8000;
 #endif
 
-  value >>= h->right_shift;
+  value = ((long) value) >> h->right_shift;
 
   switch (h->byte_size)
     {
@@ -686,13 +686,17 @@ elf_machine_rela (struct link_map *map, const ElfW(Rela) *reloc,
   tile_bundle_bits *p = (tile_bundle_bits *) reloc_addr;
   tile_bundle_bits bits = *p;
 
-#define MUNGE(func) do {                                            \
+#define MUNGE_SIGNED(func, length) do {                             \
     bits = ((bits & ~create_##func (-1)) | create_##func (value));  \
-    if (get_##func (bits) != value)                                 \
+    ElfW(Addr) result = (long) get_##func (bits)                    \
+      << (__WORDSIZE - length) >> (__WORDSIZE - length);            \
+    if (result != value)                                            \
       _dl_signal_error (0, map->l_name, NULL,                       \
                         "relocation value too large for " #func);   \
   } while (0)
 
+#define MUNGE(func) MUNGE_SIGNED(func, __WORDSIZE)
+
 #define MUNGE_NOCHECK(func)                                     \
   bits = ((bits & ~create_##func (-1)) | create_##func (value))
 
@@ -700,23 +704,23 @@ elf_machine_rela (struct link_map *map, const ElfW(Rela) *reloc,
     {
 #ifdef __tilegx__
     case R_TILEGX_BROFF_X1:
-      MUNGE (BrOff_X1);
+      MUNGE_SIGNED (BrOff_X1, 17);
       break;
     case R_TILEGX_JUMPOFF_X1:
     case R_TILEGX_JUMPOFF_X1_PLT:
-      MUNGE (JumpOff_X1);
+      MUNGE_SIGNED (JumpOff_X1, 27);
       break;
     case R_TILEGX_IMM8_X0:
-      MUNGE (Imm8_X0);
+      MUNGE_SIGNED (Imm8_X0, 8);
       break;
     case R_TILEGX_IMM8_Y0:
-      MUNGE (Imm8_Y0);
+      MUNGE_SIGNED (Imm8_Y0, 8);
       break;
     case R_TILEGX_IMM8_X1:
-      MUNGE (Imm8_X1);
+      MUNGE_SIGNED (Imm8_X1, 8);
       break;
     case R_TILEGX_IMM8_Y1:
-      MUNGE (Imm8_Y1);
+      MUNGE_SIGNED (Imm8_Y1, 8);
       break;
     case R_TILEGX_MT_IMM14_X1:
       MUNGE (MT_Imm14_X1);
@@ -746,7 +750,7 @@ elf_machine_rela (struct link_map *map, const ElfW(Rela) *reloc,
     case R_TILEGX_IMM16_X0_HW1_LAST_TLS_GD:
     case R_TILEGX_IMM16_X0_HW0_LAST_TLS_IE:
     case R_TILEGX_IMM16_X0_HW1_LAST_TLS_IE:
-      MUNGE (Imm16_X0);
+      MUNGE_SIGNED (Imm16_X0, 16);
       break;
     case R_TILEGX_IMM16_X1_HW0:
     case R_TILEGX_IMM16_X1_HW1:
@@ -770,7 +774,7 @@ elf_machine_rela (struct link_map *map, const ElfW(Rela) *reloc,
     case R_TILEGX_IMM16_X1_HW1_LAST_TLS_GD:
     case R_TILEGX_IMM16_X1_HW0_LAST_TLS_IE:
     case R_TILEGX_IMM16_X1_HW1_LAST_TLS_IE:
-      MUNGE (Imm16_X1);
+      MUNGE_SIGNED (Imm16_X1, 16);
       break;
     case R_TILEGX_MMSTART_X0:
       MUNGE (BFStart_X0);
@@ -792,23 +796,23 @@ elf_machine_rela (struct link_map *map, const ElfW(Rela) *reloc,
       break;
 #else
     case R_TILEPRO_BROFF_X1:
-      MUNGE (BrOff_X1);
+      MUNGE_SIGNED (BrOff_X1, 17);
       break;
     case R_TILEPRO_JOFFLONG_X1:
     case R_TILEPRO_JOFFLONG_X1_PLT:
       MUNGE_NOCHECK (JOffLong_X1);   /* holds full 32-bit value */
       break;
     case R_TILEPRO_IMM8_X0:
-      MUNGE (Imm8_X0);
+      MUNGE_SIGNED (Imm8_X0, 8);
       break;
     case R_TILEPRO_IMM8_Y0:
-      MUNGE (Imm8_Y0);
+      MUNGE_SIGNED (Imm8_Y0, 8);
       break;
     case R_TILEPRO_IMM8_X1:
-      MUNGE (Imm8_X1);
+      MUNGE_SIGNED (Imm8_X1, 8);
       break;
     case R_TILEPRO_IMM8_Y1:
-      MUNGE (Imm8_Y1);
+      MUNGE_SIGNED (Imm8_Y1, 8);
       break;
     case R_TILEPRO_MT_IMM15_X1:
       MUNGE (MT_Imm15_X1);
@@ -834,7 +838,7 @@ elf_machine_rela (struct link_map *map, const ElfW(Rela) *reloc,
     case R_TILEPRO_IMM16_X0_PCREL:
     case R_TILEPRO_IMM16_X0_TLS_GD:
     case R_TILEPRO_IMM16_X0_TLS_IE:
-      MUNGE (Imm16_X0);
+      MUNGE_SIGNED (Imm16_X0, 16);
       break;
     case R_TILEPRO_IMM16_X1_LO:
     case R_TILEPRO_IMM16_X1_HI:
@@ -854,7 +858,7 @@ elf_machine_rela (struct link_map *map, const ElfW(Rela) *reloc,
     case R_TILEPRO_IMM16_X1_PCREL:
     case R_TILEPRO_IMM16_X1_TLS_GD:
     case R_TILEPRO_IMM16_X1_TLS_IE:
-      MUNGE (Imm16_X1);
+      MUNGE_SIGNED (Imm16_X1, 16);
       break;
     case R_TILEPRO_MMSTART_X0:
       MUNGE (MMStart_X0);
-- 
1.7.1