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[src/trunk]: src/external/gpl3/binutils/dist Add a fix-loongson2f-btb option ...
details: https://anonhg.NetBSD.org/src/rev/a018bb407673
branches: trunk
changeset: 768774:a018bb407673
user: bouyer <bouyer%NetBSD.org@localhost>
date: Sat Aug 27 13:19:39 2011 +0000
description:
Add a fix-loongson2f-btb option to gas, from OpenBSD.
This works around a bug in the branch prediction logic of the
CPU which can cause a hard hang. The existing fix-loongson2f-jump
works around the same bug, but by 'fixing' the jump target to be within the
same 256MB region as the kernel. This will (silently) cause a jump
to the wrong address if the jump is intentionally to some other
region (e.g. a call to pmon).
fix-loongson2f-btb instead works around the issue by adding an explicit flush
of the branch target buffer (via a write to a cop0 register) before every
jump register instruction.
diffstat:
external/gpl3/binutils/dist/gas/config/tc-mips.c | 81 ++++++++++++++++++++++-
external/gpl3/binutils/dist/gas/doc/c-mips.texi | 8 ++
external/gpl3/binutils/dist/include/opcode/mips.h | 4 +
external/gpl3/binutils/dist/opcodes/mips-opc.c | 4 +
4 files changed, 95 insertions(+), 2 deletions(-)
diffs (213 lines):
diff -r 6828efedff51 -r a018bb407673 external/gpl3/binutils/dist/gas/config/tc-mips.c
--- a/external/gpl3/binutils/dist/gas/config/tc-mips.c Sat Aug 27 12:59:16 2011 +0000
+++ b/external/gpl3/binutils/dist/gas/config/tc-mips.c Sat Aug 27 13:19:39 2011 +0000
@@ -778,6 +778,8 @@
efficient expansion. */
static int mips_relax_branch;
+
+static int mips_fix_loongson2f_btb;
/* The expansion of many macros depends on the type of symbol that
they refer to. For example, when generating position-dependent code,
@@ -1051,6 +1053,7 @@
static void mips16_macro_build
(expressionS *, const char *, const char *, va_list);
static void load_register (int, expressionS *, int);
+static void macro_build (expressionS *, const char *, const char *, ...);
static void macro_start (void);
static void macro_end (void);
static void macro (struct mips_cl_insn * ip);
@@ -3584,6 +3587,41 @@
r[i] = (bfd_reloc_code_real_type) va_arg (*args, int);
}
+/* Fix jump through register issue on loongson2f processor for kernel code:
+ force a BTB clear before the jump to prevent it from being incorrectly
+ prefetched by the branch prediction engine. */
+
+static void
+macro_build_jrpatch (expressionS *ep, unsigned int sreg)
+{
+ if (!mips_fix_loongson2f_btb)
+ return;
+
+ if (sreg == ZERO || sreg == KT0 || sreg == KT1 || sreg == AT)
+ return;
+
+ if (!mips_opts.at)
+ {
+ as_warn (_("unable to apply loongson2f BTB workaround when .set noat"));
+ return;
+ }
+
+ /* li $at, COP_0_BTB_CLEAR | COP_0_RAS_DISABLE */
+ ep->X_op = O_constant;
+ ep->X_add_number = 3;
+ macro_build (ep, "ori", "t,r,i", AT, ZERO, BFD_RELOC_LO16);
+
+ /* dmtc0 $at, COP_0_DIAG */
+ macro_build (NULL, "dmtc0", "t,G", AT, 22);
+
+ /* Hide these two instructions to avoid getting a ``macro expanded into
+ multiple instructions'' warning. */
+ if (mips_relax.sequence != 2)
+ mips_macro_warning.sizes[0] -= 2 * 4;
+ if (mips_relax.sequence != 1)
+ mips_macro_warning.sizes[1] -= 2 * 4;
+}
+
/* Build an instruction created by a macro expansion. This is passed
a pointer to the count of instructions created so far, an
expression, the name of the instruction to build, an operand format
@@ -3985,6 +4023,7 @@
frag_grow (8);
f = frag_more (0);
}
+ macro_build_jrpatch (ep, PIC_CALL_REG);
macro_build (NULL, "jalr", "d,s", RA, PIC_CALL_REG);
if (HAVE_NEWABI)
fix_new_exp (frag_now, f - frag_now->fr_literal,
@@ -6167,6 +6206,26 @@
/* AT is not used, just return */
return;
+ case M_JR_S:
+ macro_build_jrpatch (&expr1, sreg);
+ macro_build (NULL, "jr", "s", sreg);
+ return; /* didn't modify $at */
+
+ case M_J_S:
+ macro_build_jrpatch (&expr1, sreg);
+ macro_build (NULL, "j", "s", sreg);
+ return; /* didn't modify $at */
+
+ case M_JALR_S:
+ macro_build_jrpatch (&expr1, sreg);
+ macro_build (NULL, "jalr", "s", sreg);
+ return; /* didn't modify $at */
+
+ case M_JALR_DS:
+ macro_build_jrpatch (&expr1, sreg);
+ macro_build (NULL, "jalr", "d,s", dreg, sreg);
+ return; /* didn't modify $at */
+
case M_J_A:
/* The j instruction may not be used in PIC code, since it
requires an absolute address. We convert it to a b
@@ -6185,12 +6244,16 @@
/* Fall through. */
case M_JAL_2:
if (mips_pic == NO_PIC)
- macro_build (NULL, "jalr", "d,s", dreg, sreg);
+ {
+ macro_build_jrpatch (&expr1, sreg);
+ macro_build (NULL, "jalr", "d,s", dreg, sreg);
+ }
else
{
if (sreg != PIC_CALL_REG)
as_warn (_("MIPS PIC call to register other than $25"));
+ macro_build_jrpatch (&expr1, sreg);
macro_build (NULL, "jalr", "d,s", dreg, sreg);
if (mips_pic == SVR4_PIC && !HAVE_NEWABI)
{
@@ -11324,9 +11387,14 @@
#define OPTION_NO_FIX_LOONGSON2F_NOP (OPTION_FIX_BASE + 9)
{"mfix-loongson2f-nop", no_argument, NULL, OPTION_FIX_LOONGSON2F_NOP},
{"mno-fix-loongson2f-nop", no_argument, NULL, OPTION_NO_FIX_LOONGSON2F_NOP},
+#define OPTION_FIX_LOONGSON2F_BTB (OPTION_FIX_BASE + 10)
+#define OPTION_NO_FIX_LOONGSON2F_BTB (OPTION_FIX_BASE + 11)
+ {"mfix-loongson2f-btb", no_argument, NULL, OPTION_FIX_LOONGSON2F_BTB},
+ {"mno-fix-loongson2f-btb", no_argument, NULL, OPTION_NO_FIX_LOONGSON2F_BTB},
+
/* Miscellaneous options. */
-#define OPTION_MISC_BASE (OPTION_FIX_BASE + 10)
+#define OPTION_MISC_BASE (OPTION_FIX_BASE + 12)
#define OPTION_TRAP (OPTION_MISC_BASE + 0)
{"trap", no_argument, NULL, OPTION_TRAP},
{"no-break", no_argument, NULL, OPTION_TRAP},
@@ -11645,6 +11713,14 @@
mips_fix_vr4130 = 0;
break;
+ case OPTION_FIX_LOONGSON2F_BTB:
+ mips_fix_loongson2f_btb = 1;
+ break;
+
+ case OPTION_NO_FIX_LOONGSON2F_BTB:
+ mips_fix_loongson2f_btb = 0;
+ break;
+
case OPTION_RELAX_BRANCH:
mips_relax_branch = 1;
break;
@@ -15590,6 +15666,7 @@
-mfix-loongson2f-nop work around Loongson2F NOP errata\n\
-mfix-vr4120 work around certain VR4120 errata\n\
-mfix-vr4130 work around VR4130 mflo/mfhi errata\n\
+-mfix-loongson2f-btb work around Loongson2F BTB errata\n\
-mgp32 use 32-bit GPRs, regardless of the chosen ISA\n\
-mfp32 use 32-bit FPRs, regardless of the chosen ISA\n\
-msym32 assume all symbols have 32-bit values\n\
diff -r 6828efedff51 -r a018bb407673 external/gpl3/binutils/dist/gas/doc/c-mips.texi
--- a/external/gpl3/binutils/dist/gas/doc/c-mips.texi Sat Aug 27 12:59:16 2011 +0000
+++ b/external/gpl3/binutils/dist/gas/doc/c-mips.texi Sat Aug 27 13:19:39 2011 +0000
@@ -182,6 +182,14 @@
@itemx -no-mfix-vr4130
Insert nops to work around the VR4130 @samp{mflo}/@samp{mfhi} errata.
+@item -mfix-loongson2f-btb
+@itemx -mno-fix-loongson2f-btb
+Clear the Branch Target Buffer before any jump through a register. This
+option is intended to be used on kernel code for the Loongson 2F processor
+only; userland code compiled with this option will fault, and kernel code
+compiled with this option run on another processor than Loongson 2F will
+yield unpredictable results.
+
@item -m4010
@itemx -no-m4010
Generate code for the LSI @sc{r4010} chip. This tells the assembler to
diff -r 6828efedff51 -r a018bb407673 external/gpl3/binutils/dist/include/opcode/mips.h
--- a/external/gpl3/binutils/dist/include/opcode/mips.h Sat Aug 27 12:59:16 2011 +0000
+++ b/external/gpl3/binutils/dist/include/opcode/mips.h Sat Aug 27 13:19:39 2011 +0000
@@ -762,7 +762,11 @@
M_DSUB_I,
M_DSUBU_I,
M_DSUBU_I_2,
+ M_JR_S,
+ M_J_S,
M_J_A,
+ M_JALR_S,
+ M_JALR_DS,
M_JAL_1,
M_JAL_2,
M_JAL_A,
diff -r 6828efedff51 -r a018bb407673 external/gpl3/binutils/dist/opcodes/mips-opc.c
--- a/external/gpl3/binutils/dist/opcodes/mips-opc.c Sat Aug 27 12:59:16 2011 +0000
+++ b/external/gpl3/binutils/dist/opcodes/mips-opc.c Sat Aug 27 13:19:39 2011 +0000
@@ -712,10 +712,12 @@
{"floor.w.s", "D,S", 0x4600000f, 0xffff003f, WR_D|RD_S|FP_S, 0, I2 },
{"hibernate","", 0x42000023, 0xffffffff, 0, 0, V1 },
{"ins", "t,r,+A,+B", 0x7c000004, 0xfc00003f, WR_t|RD_s, 0, I33 },
+{"jr", "s", 0, (int) M_JR_S, INSN_MACRO, 0, I1 },
{"jr", "s", 0x00000008, 0xfc1fffff, UBD|RD_s, 0, I1 },
/* jr.hb is officially MIPS{32,64}R2, but it works on R1 as jr with
the same hazard barrier effect. */
{"jr.hb", "s", 0x00000408, 0xfc1fffff, UBD|RD_s, 0, I32 },
+{"j", "s", 0, (int) M_J_S, INSN_MACRO, 0, I1 },
{"j", "s", 0x00000008, 0xfc1fffff, UBD|RD_s, 0, I1 }, /* jr */
/* SVR4 PIC code requires special handling for j, so it must be a
macro. */
@@ -724,7 +726,9 @@
assembler, but will never match user input (because the line above
will match first). */
{"j", "a", 0x08000000, 0xfc000000, UBD, 0, I1 },
+{"jalr", "s", 0, (int) M_JALR_S, INSN_MACRO, 0, I1 },
{"jalr", "s", 0x0000f809, 0xfc1fffff, UBD|RD_s|WR_d, 0, I1 },
+{"jalr", "d,s", 0, (int) M_JALR_DS, INSN_MACRO, 0, I1 },
{"jalr", "d,s", 0x00000009, 0xfc1f07ff, UBD|RD_s|WR_d, 0, I1 },
/* jalr.hb is officially MIPS{32,64}R2, but it works on R1 as jalr
with the same hazard barrier effect. */
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