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authorBjörn Gustavsson <[email protected]>2017-09-19 06:33:06 +0200
committerBjörn Gustavsson <[email protected]>2017-10-05 12:37:56 +0200
commit22d2a00aebf0eef878af95d8b7598adbfca06e7e (patch)
treef5598c7bd2d965fa9416d4e0e1ec11925e71a173 /erts
parente1c9772ffdacae4007209ac5a82758b8e0d3cec4 (diff)
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Use 32-bits pointers to C code
On a 64-bit machine, we only need 32 bits to store a pointer to the C code that implements a BEAM instruction. Refactor the code to only use the lower 32 bits of each instruction word, and take care to preserve the high 32 bits.
Diffstat (limited to 'erts')
-rw-r--r--erts/configure.in33
-rw-r--r--erts/emulator/beam/beam_bp.c19
-rw-r--r--erts/emulator/beam/beam_emu.c30
-rw-r--r--erts/emulator/beam/erl_vm.h11
4 files changed, 77 insertions, 16 deletions
diff --git a/erts/configure.in b/erts/configure.in
index 85e167b93b..508e99a415 100644
--- a/erts/configure.in
+++ b/erts/configure.in
@@ -3774,6 +3774,39 @@ dnl
LM_FIND_EMU_CC
dnl
+dnl Test whether code pointers are always short (32 bits).
+dnl
+
+AC_MSG_CHECKING([whether the code model is small])
+saved_LDFLAGS="$LDFLAGS"
+LDFLAGS="$LDFLAGS $HIPEBEAMLDFLAGS"
+AC_TRY_RUN([
+ #include <stdlib.h>
+ int main() {
+ if ((unsigned long long)&main < (1ull << 32)) {
+ exit(0);
+ }
+ exit(1);
+ }
+],
+erl_code_model_small=yes,
+erl_code_model_small=no,
+erl_code_model_small=no)
+AC_MSG_RESULT([$erl_code_model_small])
+LDFLAGS="$saved_LDFLAGS"
+case $erl_code_model_small in
+ yes)
+ AC_DEFINE(CODE_MODEL_SMALL,[1],
+ [Define if the code model is small (code fits below 2Gb)])
+ CODE_MODEL=small
+ ;;
+ no)
+ CODE_MODEL=unknown
+ ;;
+esac
+AC_SUBST(CODE_MODEL)
+
+dnl
dnl DTrace & LTTNG
dnl
case $DYNAMIC_TRACE_FRAMEWORK in
diff --git a/erts/emulator/beam/beam_bp.c b/erts/emulator/beam/beam_bp.c
index c81380c14d..871670e8c3 100644
--- a/erts/emulator/beam/beam_bp.c
+++ b/erts/emulator/beam/beam_bp.c
@@ -419,9 +419,11 @@ erts_install_breakpoints(BpFunctions* f)
for (i = 0; i < n; i++) {
ErtsCodeInfo* ci = f->matching[i].ci;
- BeamInstr *pc = erts_codeinfo_to_code(ci);
GenericBp* g = ci->u.gen_bp;
- if (*pc != br && g) {
+ BeamInstr volatile *pc = erts_codeinfo_to_code(ci);
+ BeamInstr instr = *pc;
+
+ if (!BeamIsOpCode(instr, op_i_generic_breakpoint) && g) {
Module* modp = f->matching[i].mod;
/*
@@ -435,11 +437,16 @@ erts_install_breakpoints(BpFunctions* f)
/*
* The following write is not protected by any lock. We
* assume that the hardware guarantees that a write of an
- * aligned word-size (or half-word) writes is atomic
- * (i.e. that other processes executing this code will not
- * see a half pointer).
+ * aligned word-size writes is atomic (i.e. that other
+ * processes executing this code will not see a half
+ * pointer).
+ *
+ * The contents of *pc is marked 'volatile' to ensure that
+ * the compiler will do a single full-word write, and not
+ * try any fancy optimizations to write a half word.
*/
- *pc = br;
+ instr = BeamSetCodeAddr(instr, br);
+ *pc = instr;
modp->curr.num_breakpoints++;
}
}
diff --git a/erts/emulator/beam/beam_emu.c b/erts/emulator/beam/beam_emu.c
index 9a77c63390..6a45087a34 100644
--- a/erts/emulator/beam/beam_emu.c
+++ b/erts/emulator/beam/beam_emu.c
@@ -50,14 +50,14 @@
#if defined(NO_JUMP_TABLE)
# define OpCase(OpCode) case op_##OpCode
# define CountCase(OpCode) case op_count_##OpCode
-# define IsOpCode(InstrWord, OpCode) ((InstrWord) == (BeamInstr)op_##OpCode)
-# define Goto(Rel) {Go = (Rel); goto emulator_loop;}
+# define IsOpCode(InstrWord, OpCode) (BeamCodeAddr(InstrWord) == (BeamInstr)op_##OpCode)
+# define Goto(Rel) {Go = BeamCodeAddr(Rel); goto emulator_loop;}
#else
# define OpCase(OpCode) lb_##OpCode
# define CountCase(OpCode) lb_count_##OpCode
-# define IsOpCode(InstrWord, OpCode) ((InstrWord) == (BeamInstr)&&lb_##OpCode)
-# define Goto(Rel) goto *((void *)Rel)
-# define LabelAddr(Label) &&Label
+# define IsOpCode(InstrWord, OpCode) (BeamCodeAddr(InstrWord) == (BeamInstr)&&lb_##OpCode)
+# define Goto(Rel) goto *((void *)BeamCodeAddr(Rel))
+# define LabelAddr(Label) &&Label
#endif
#ifdef ERTS_ENABLE_LOCK_CHECK
@@ -131,11 +131,11 @@ do { \
/* We don't check the range if an ordinary switch is used */
#ifdef NO_JUMP_TABLE
-#define VALID_INSTR(IP) ((UWord)(IP) < (NUMBER_OF_OPCODES*2+10))
+# define VALID_INSTR(IP) (BeamCodeAddr(IP) < (NUMBER_OF_OPCODES*2+10))
#else
-#define VALID_INSTR(IP) \
- ((SWord)LabelAddr(emulator_loop) <= (SWord)(IP) && \
- (SWord)(IP) < (SWord)LabelAddr(end_emulator_loop))
+# define VALID_INSTR(IP) \
+ ((BeamInstr)LabelAddr(emulator_loop) <= BeamCodeAddr(IP) && \
+ BeamCodeAddr(IP) < (BeamInstr)LabelAddr(end_emulator_loop))
#endif /* NO_JUMP_TABLE */
#define SET_CP(p, ip) \
@@ -1006,6 +1006,18 @@ init_emulator_finish(void)
int i;
Export* ep;
+#if defined(ARCH_64) && defined(CODE_MODEL_SMALL)
+ for (i = 0; i < NUMBER_OF_OPCODES; i++) {
+ BeamInstr instr = BeamOpCodeAddr(i);
+ if (instr >= (1ull << 32)) {
+ erts_exit(ERTS_ERROR_EXIT,
+ "This run-time was supposed be compiled with all code below 2Gb,\n"
+ "but the instruction '%s' is located at %016lx.\n",
+ opc[i].name, instr);
+ }
+ }
+#endif
+
beam_apply[0] = BeamOpCodeAddr(op_i_apply);
beam_apply[1] = BeamOpCodeAddr(op_normal_exit);
beam_exit[0] = BeamOpCodeAddr(op_error_action_code);
diff --git a/erts/emulator/beam/erl_vm.h b/erts/emulator/beam/erl_vm.h
index 661538eadd..76980b5871 100644
--- a/erts/emulator/beam/erl_vm.h
+++ b/erts/emulator/beam/erl_vm.h
@@ -209,6 +209,15 @@ extern void** beam_ops;
# define BeamOpCodeAddr(OpCode) ((BeamInstr)beam_ops[(OpCode)])
#endif
-#define BeamIsOpCode(InstrWord, OpCode) ((InstrWord) == BeamOpCodeAddr(OpCode))
+#if defined(ARCH_64) && defined(CODE_MODEL_SMALL)
+# define BeamCodeAddr(InstrWord) ((BeamInstr)(Uint32)(InstrWord))
+# define BeamSetCodeAddr(InstrWord, Addr) (((InstrWord) & ~((1ull << 32)-1)) | (Addr))
+# define BeamExtraData(InstrWord) ((InstrWord) >> 32)
+#else
+# define BeamCodeAddr(InstrWord) ((BeamInstr)(InstrWord))
+# define BeamSetCodeAddr(InstrWord, Addr) (Addr)
+#endif
+
+#define BeamIsOpCode(InstrWord, OpCode) (BeamCodeAddr(InstrWord) == BeamOpCodeAddr(OpCode))
#endif /* __ERL_VM_H__ */