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authorLeonid Yegoshin <Leonid.Yegoshin@imgtec.com>2013-03-25 13:08:40 -0500
committerRalf Baechle <ralf@linux-mips.org>2013-05-09 17:55:18 +0200
commitfb6883e5809c08e43de23581759af4570ca91b0f (patch)
tree2bf479748d969f85c79cb8880a1573b2ca7c61ee /arch
parent2a0b24f56c2492b932f1aed617ae80fb23500d21 (diff)
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MIPS: microMIPS: Support handling of delay slots.
Add logic needed to properly calculate exceptions for delay slots when in microMIPS mode. Signed-off-by: Leonid Yegoshin <Leonid.Yegoshin@imgtec.com> Signed-off-by: Steven J. Hill <Steven.Hill@imgtec.com>
Diffstat (limited to 'arch')
-rw-r--r--arch/mips/include/asm/branch.h22
-rw-r--r--arch/mips/kernel/branch.c85
2 files changed, 102 insertions, 5 deletions
diff --git a/arch/mips/include/asm/branch.h b/arch/mips/include/asm/branch.h
index 888766ae1f85..40bb9ebcc7aa 100644
--- a/arch/mips/include/asm/branch.h
+++ b/arch/mips/include/asm/branch.h
@@ -11,6 +11,13 @@
#include <asm/ptrace.h>
#include <asm/inst.h>
+extern int __isa_exception_epc(struct pt_regs *regs);
+extern int __compute_return_epc(struct pt_regs *regs);
+extern int __compute_return_epc_for_insn(struct pt_regs *regs,
+ union mips_instruction insn);
+extern int __microMIPS_compute_return_epc(struct pt_regs *regs);
+
+
static inline int delay_slot(struct pt_regs *regs)
{
return regs->cp0_cause & CAUSEF_BD;
@@ -18,20 +25,25 @@ static inline int delay_slot(struct pt_regs *regs)
static inline unsigned long exception_epc(struct pt_regs *regs)
{
- if (!delay_slot(regs))
+ if (likely(!delay_slot(regs)))
return regs->cp0_epc;
+ if (get_isa16_mode(regs->cp0_epc))
+ return __isa_exception_epc(regs);
+
return regs->cp0_epc + 4;
}
#define BRANCH_LIKELY_TAKEN 0x0001
-extern int __compute_return_epc(struct pt_regs *regs);
-extern int __compute_return_epc_for_insn(struct pt_regs *regs,
- union mips_instruction insn);
-
static inline int compute_return_epc(struct pt_regs *regs)
{
+ if (get_isa16_mode(regs->cp0_epc)) {
+ if (cpu_has_mmips)
+ return __microMIPS_compute_return_epc(regs);
+ return regs->cp0_epc;
+ }
+
if (!delay_slot(regs)) {
regs->cp0_epc += 4;
return 0;
diff --git a/arch/mips/kernel/branch.c b/arch/mips/kernel/branch.c
index 83ffe950f710..a03836b5b683 100644
--- a/arch/mips/kernel/branch.c
+++ b/arch/mips/kernel/branch.c
@@ -14,10 +14,93 @@
#include <asm/cpu.h>
#include <asm/cpu-features.h>
#include <asm/fpu.h>
+#include <asm/fpu_emulator.h>
#include <asm/inst.h>
#include <asm/ptrace.h>
#include <asm/uaccess.h>
+/*
+ * Calculate and return exception PC in case of branch delay
+ * slot for microMIPS. It does not clear the ISA mode bit.
+ */
+int __isa_exception_epc(struct pt_regs *regs)
+{
+ long epc = regs->cp0_epc;
+ unsigned short inst;
+
+ /* Calculate exception PC in branch delay slot. */
+ if (__get_user(inst, (u16 __user *) msk_isa16_mode(epc))) {
+ /* This should never happen because delay slot was checked. */
+ force_sig(SIGSEGV, current);
+ return epc;
+ }
+
+ if (mm_insn_16bit(inst))
+ epc += 2;
+ else
+ epc += 4;
+
+ return epc;
+}
+
+/*
+ * Compute return address and emulate branch in microMIPS mode after an
+ * exception only. It does not handle compact branches/jumps and cannot
+ * be used in interrupt context. (Compact branches/jumps do not cause
+ * exceptions.)
+ */
+int __microMIPS_compute_return_epc(struct pt_regs *regs)
+{
+ u16 __user *pc16;
+ u16 halfword;
+ unsigned int word;
+ unsigned long contpc;
+ struct mm_decoded_insn mminsn = { 0 };
+
+ mminsn.micro_mips_mode = 1;
+
+ /* This load never faults. */
+ pc16 = (unsigned short __user *)msk_isa16_mode(regs->cp0_epc);
+ __get_user(halfword, pc16);
+ pc16++;
+ contpc = regs->cp0_epc + 2;
+ word = ((unsigned int)halfword << 16);
+ mminsn.pc_inc = 2;
+
+ if (!mm_insn_16bit(halfword)) {
+ __get_user(halfword, pc16);
+ pc16++;
+ contpc = regs->cp0_epc + 4;
+ mminsn.pc_inc = 4;
+ word |= halfword;
+ }
+ mminsn.insn = word;
+
+ if (get_user(halfword, pc16))
+ goto sigsegv;
+ mminsn.next_pc_inc = 2;
+ word = ((unsigned int)halfword << 16);
+
+ if (!mm_insn_16bit(halfword)) {
+ pc16++;
+ if (get_user(halfword, pc16))
+ goto sigsegv;
+ mminsn.next_pc_inc = 4;
+ word |= halfword;
+ }
+ mminsn.next_insn = word;
+
+ mm_isBranchInstr(regs, mminsn, &contpc);
+
+ regs->cp0_epc = contpc;
+
+ return 0;
+
+sigsegv:
+ force_sig(SIGSEGV, current);
+ return -EFAULT;
+}
+
/**
* __compute_return_epc_for_insn - Computes the return address and do emulate
* branch simulation, if required.
@@ -129,6 +212,8 @@ int __compute_return_epc_for_insn(struct pt_regs *regs,
epc <<= 28;
epc |= (insn.j_format.target << 2);
regs->cp0_epc = epc;
+ if (insn.i_format.opcode == jalx_op)
+ set_isa16_mode(regs->cp0_epc);
break;
/*