summaryrefslogtreecommitdiff
diff options
context:
space:
mode:
Diffstat
-rw-r--r--arch/mips/Kconfig1
-rw-r--r--arch/mips/include/asm/dsemul.h92
-rw-r--r--arch/mips/include/asm/fpu_emulator.h17
-rw-r--r--arch/mips/include/asm/mmu.h9
-rw-r--r--arch/mips/include/asm/mmu_context.h6
-rw-r--r--arch/mips/include/asm/processor.h18
-rw-r--r--arch/mips/kernel/mips-r2-to-r6-emul.c8
-rw-r--r--arch/mips/kernel/process.c14
-rw-r--r--arch/mips/kernel/signal.c8
-rw-r--r--arch/mips/kernel/vdso.c10
-rw-r--r--arch/mips/math-emu/cp1emu.c8
-rw-r--r--arch/mips/math-emu/dsemul.c333
12 files changed, 391 insertions, 133 deletions
diff --git a/arch/mips/Kconfig b/arch/mips/Kconfig
index 286893da4855..3953bb14795e 100644
--- a/arch/mips/Kconfig
+++ b/arch/mips/Kconfig
@@ -64,6 +64,7 @@ config MIPS
select GENERIC_TIME_VSYSCALL
select ARCH_CLOCKSOURCE_DATA
select HANDLE_DOMAIN_IRQ
+ select HAVE_EXIT_THREAD
menu "Machine selection"
diff --git a/arch/mips/include/asm/dsemul.h b/arch/mips/include/asm/dsemul.h
new file mode 100644
index 000000000000..a6e067801f23
--- /dev/null
+++ b/arch/mips/include/asm/dsemul.h
@@ -0,0 +1,92 @@
+/*
+ * Copyright (C) 2016 Imagination Technologies
+ * Author: Paul Burton <paul.burton@imgtec.com>
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the
+ * Free Software Foundation; either version 2 of the License, or (at your
+ * option) any later version.
+ */
+
+#ifndef __MIPS_ASM_DSEMUL_H__
+#define __MIPS_ASM_DSEMUL_H__
+
+#include <asm/break.h>
+#include <asm/inst.h>
+
+/* Break instruction with special math emu break code set */
+#define BREAK_MATH(micromips) (((micromips) ? 0x7 : 0xd) | (BRK_MEMU << 16))
+
+/* When used as a frame index, indicates the lack of a frame */
+#define BD_EMUFRAME_NONE ((int)BIT(31))
+
+struct mm_struct;
+struct pt_regs;
+struct task_struct;
+
+/**
+ * mips_dsemul() - 'Emulate' an instruction from a branch delay slot
+ * @regs: User thread register context.
+ * @ir: The instruction to be 'emulated'.
+ * @branch_pc: The PC of the branch instruction.
+ * @cont_pc: The PC to continue at following 'emulation'.
+ *
+ * Emulate or execute an arbitrary MIPS instruction within the context of
+ * the current user thread. This is used primarily to handle instructions
+ * in the delay slots of emulated branch instructions, for example FP
+ * branch instructions on systems without an FPU.
+ *
+ * Return: Zero on success, negative if ir is a NOP, signal number on failure.
+ */
+extern int mips_dsemul(struct pt_regs *regs, mips_instruction ir,
+ unsigned long branch_pc, unsigned long cont_pc);
+
+/**
+ * do_dsemulret() - Return from a delay slot 'emulation' frame
+ * @xcp: User thread register context.
+ *
+ * Call in response to the BRK_MEMU break instruction used to return to
+ * the kernel from branch delay slot 'emulation' frames following a call
+ * to mips_dsemul(). Restores the user thread PC to the value that was
+ * passed as the cpc parameter to mips_dsemul().
+ *
+ * Return: True if an emulation frame was returned from, else false.
+ */
+extern bool do_dsemulret(struct pt_regs *xcp);
+
+/**
+ * dsemul_thread_cleanup() - Cleanup thread 'emulation' frame
+ * @tsk: The task structure associated with the thread
+ *
+ * If the thread @tsk has a branch delay slot 'emulation' frame
+ * allocated to it then free that frame.
+ *
+ * Return: True if a frame was freed, else false.
+ */
+extern bool dsemul_thread_cleanup(struct task_struct *tsk);
+
+/**
+ * dsemul_thread_rollback() - Rollback from an 'emulation' frame
+ * @regs: User thread register context.
+ *
+ * If the current thread, whose register context is represented by @regs,
+ * is executing within a delay slot 'emulation' frame then exit that
+ * frame. The PC will be rolled back to the branch if the instruction
+ * that was being 'emulated' has not yet executed, or advanced to the
+ * continuation PC if it has.
+ *
+ * Return: True if a frame was exited, else false.
+ */
+extern bool dsemul_thread_rollback(struct pt_regs *regs);
+
+/**
+ * dsemul_mm_cleanup() - Cleanup per-mm delay slot 'emulation' state
+ * @mm: The struct mm_struct to cleanup state for.
+ *
+ * Cleanup state for the given @mm, ensuring that any memory allocated
+ * for delay slot 'emulation' book-keeping is freed. This is to be called
+ * before @mm is freed in order to avoid memory leaks.
+ */
+extern void dsemul_mm_cleanup(struct mm_struct *mm);
+
+#endif /* __MIPS_ASM_DSEMUL_H__ */
diff --git a/arch/mips/include/asm/fpu_emulator.h b/arch/mips/include/asm/fpu_emulator.h
index 3225c3c0724b..355dc25172e7 100644
--- a/arch/mips/include/asm/fpu_emulator.h
+++ b/arch/mips/include/asm/fpu_emulator.h
@@ -24,7 +24,7 @@
#define _ASM_FPU_EMULATOR_H
#include <linux/sched.h>
-#include <asm/break.h>
+#include <asm/dsemul.h>
#include <asm/thread_info.h>
#include <asm/inst.h>
#include <asm/local.h>
@@ -60,27 +60,16 @@ do { \
#define MIPS_FPU_EMU_INC_STATS(M) do { } while (0)
#endif /* CONFIG_DEBUG_FS */
-extern int mips_dsemul(struct pt_regs *regs, mips_instruction ir,
- unsigned long cpc);
-extern int do_dsemulret(struct pt_regs *xcp);
extern int fpu_emulator_cop1Handler(struct pt_regs *xcp,
struct mips_fpu_struct *ctx, int has_fpu,
void *__user *fault_addr);
int process_fpemu_return(int sig, void __user *fault_addr,
unsigned long fcr31);
+int isBranchInstr(struct pt_regs *regs, struct mm_decoded_insn dec_insn,
+ unsigned long *contpc);
int mm_isBranchInstr(struct pt_regs *regs, struct mm_decoded_insn dec_insn,
unsigned long *contpc);
-/*
- * Instruction inserted following the badinst to further tag the sequence
- */
-#define BD_COOKIE 0x0000bd36 /* tne $0, $0 with baggage */
-
-/*
- * Break instruction with special math emu break code set
- */
-#define BREAK_MATH(micromips) (((micromips) ? 0x7 : 0xd) | (BRK_MEMU << 16))
-
#define SIGNALLING_NAN 0x7ff800007ff80000LL
static inline void fpu_emulator_init_fpu(void)
diff --git a/arch/mips/include/asm/mmu.h b/arch/mips/include/asm/mmu.h
index 1afa1f986df8..f6ba08d77931 100644
--- a/arch/mips/include/asm/mmu.h
+++ b/arch/mips/include/asm/mmu.h
@@ -2,11 +2,20 @@
#define __ASM_MMU_H
#include <linux/atomic.h>
+#include <linux/spinlock.h>
+#include <linux/wait.h>
typedef struct {
unsigned long asid[NR_CPUS];
void *vdso;
atomic_t fp_mode_switching;
+
+ /* lock to be held whilst modifying fp_bd_emupage_allocmap */
+ spinlock_t bd_emupage_lock;
+ /* bitmap tracking allocation of fp_bd_emupage */
+ unsigned long *bd_emupage_allocmap;
+ /* wait queue for threads requiring an emuframe */
+ wait_queue_head_t bd_emupage_queue;
} mm_context_t;
#endif /* __ASM_MMU_H */
diff --git a/arch/mips/include/asm/mmu_context.h b/arch/mips/include/asm/mmu_context.h
index fc57e135cb0a..ddd57ade1aa8 100644
--- a/arch/mips/include/asm/mmu_context.h
+++ b/arch/mips/include/asm/mmu_context.h
@@ -16,6 +16,7 @@
#include <linux/smp.h>
#include <linux/slab.h>
#include <asm/cacheflush.h>
+#include <asm/dsemul.h>
#include <asm/hazards.h>
#include <asm/tlbflush.h>
#include <asm-generic/mm_hooks.h>
@@ -128,6 +129,10 @@ init_new_context(struct task_struct *tsk, struct mm_struct *mm)
atomic_set(&mm->context.fp_mode_switching, 0);
+ mm->context.bd_emupage_allocmap = NULL;
+ spin_lock_init(&mm->context.bd_emupage_lock);
+ init_waitqueue_head(&mm->context.bd_emupage_queue);
+
return 0;
}
@@ -162,6 +167,7 @@ static inline void switch_mm(struct mm_struct *prev, struct mm_struct *next,
*/
static inline void destroy_context(struct mm_struct *mm)
{
+ dsemul_mm_cleanup(mm);
}
#define deactivate_mm(tsk, mm) do { } while (0)
diff --git a/arch/mips/include/asm/processor.h b/arch/mips/include/asm/processor.h
index 7e78b6208d7d..0d36c87acbe2 100644
--- a/arch/mips/include/asm/processor.h
+++ b/arch/mips/include/asm/processor.h
@@ -11,12 +11,14 @@
#ifndef _ASM_PROCESSOR_H
#define _ASM_PROCESSOR_H
+#include <linux/atomic.h>
#include <linux/cpumask.h>
#include <linux/threads.h>
#include <asm/cachectl.h>
#include <asm/cpu.h>
#include <asm/cpu-info.h>
+#include <asm/dsemul.h>
#include <asm/mipsregs.h>
#include <asm/prefetch.h>
@@ -78,7 +80,11 @@ extern unsigned int vced_count, vcei_count;
#endif
-#define STACK_TOP (TASK_SIZE & PAGE_MASK)
+/*
+ * One page above the stack is used for branch delay slot "emulation".
+ * See dsemul.c for details.
+ */
+#define STACK_TOP ((TASK_SIZE & PAGE_MASK) - PAGE_SIZE)
/*
* This decides where the kernel will search for a free chunk of vm
@@ -256,6 +262,12 @@ struct thread_struct {
/* Saved fpu/fpu emulator stuff. */
struct mips_fpu_struct fpu FPU_ALIGN;
+ /* Assigned branch delay slot 'emulation' frame */
+ atomic_t bd_emu_frame;
+ /* PC of the branch from a branch delay slot 'emulation' */
+ unsigned long bd_emu_branch_pc;
+ /* PC to continue from following a branch delay slot 'emulation' */
+ unsigned long bd_emu_cont_pc;
#ifdef CONFIG_MIPS_MT_FPAFF
/* Emulated instruction count */
unsigned long emulated_fp;
@@ -323,6 +335,10 @@ struct thread_struct {
* FPU affinity state (null if not FPAFF) \
*/ \
FPAFF_INIT \
+ /* Delay slot emulation */ \
+ .bd_emu_frame = ATOMIC_INIT(BD_EMUFRAME_NONE), \
+ .bd_emu_branch_pc = 0, \
+ .bd_emu_cont_pc = 0, \
/* \
* Saved DSP stuff \
*/ \
diff --git a/arch/mips/kernel/mips-r2-to-r6-emul.c b/arch/mips/kernel/mips-r2-to-r6-emul.c
index 7ff2a557f4aa..ef23c61c1e28 100644
--- a/arch/mips/kernel/mips-r2-to-r6-emul.c
+++ b/arch/mips/kernel/mips-r2-to-r6-emul.c
@@ -283,7 +283,7 @@ static int jr_func(struct pt_regs *regs, u32 ir)
err = mipsr6_emul(regs, nir);
if (err > 0) {
regs->cp0_epc = nepc;
- err = mips_dsemul(regs, nir, cepc);
+ err = mips_dsemul(regs, nir, epc, cepc);
if (err == SIGILL)
err = SIGEMT;
MIPS_R2_STATS(dsemul);
@@ -1033,7 +1033,7 @@ repeat:
if (nir) {
err = mipsr6_emul(regs, nir);
if (err > 0) {
- err = mips_dsemul(regs, nir, cpc);
+ err = mips_dsemul(regs, nir, epc, cpc);
if (err == SIGILL)
err = SIGEMT;
MIPS_R2_STATS(dsemul);
@@ -1082,7 +1082,7 @@ repeat:
if (nir) {
err = mipsr6_emul(regs, nir);
if (err > 0) {
- err = mips_dsemul(regs, nir, cpc);
+ err = mips_dsemul(regs, nir, epc, cpc);
if (err == SIGILL)
err = SIGEMT;
MIPS_R2_STATS(dsemul);
@@ -1149,7 +1149,7 @@ repeat:
if (nir) {
err = mipsr6_emul(regs, nir);
if (err > 0) {
- err = mips_dsemul(regs, nir, cpc);
+ err = mips_dsemul(regs, nir, epc, cpc);
if (err == SIGILL)
err = SIGEMT;
MIPS_R2_STATS(dsemul);
diff --git a/arch/mips/kernel/process.c b/arch/mips/kernel/process.c
index 813ed7829c61..7429ad09fbe3 100644
--- a/arch/mips/kernel/process.c
+++ b/arch/mips/kernel/process.c
@@ -30,6 +30,7 @@
#include <asm/asm.h>
#include <asm/bootinfo.h>
#include <asm/cpu.h>
+#include <asm/dsemul.h>
#include <asm/dsp.h>
#include <asm/fpu.h>
#include <asm/msa.h>
@@ -68,11 +69,22 @@ void start_thread(struct pt_regs * regs, unsigned long pc, unsigned long sp)
lose_fpu(0);
clear_thread_flag(TIF_MSA_CTX_LIVE);
clear_used_math();
+ atomic_set(&current->thread.bd_emu_frame, BD_EMUFRAME_NONE);
init_dsp();
regs->cp0_epc = pc;
regs->regs[29] = sp;
}
+void exit_thread(struct task_struct *tsk)
+{
+ /*
+ * User threads may have allocated a delay slot emulation frame.
+ * If so, clean up that allocation.
+ */
+ if (!(current->flags & PF_KTHREAD))
+ dsemul_thread_cleanup(tsk);
+}
+
int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src)
{
/*
@@ -159,6 +171,8 @@ int copy_thread(unsigned long clone_flags, unsigned long usp,
clear_tsk_thread_flag(p, TIF_FPUBOUND);
#endif /* CONFIG_MIPS_MT_FPAFF */
+ atomic_set(&p->thread.bd_emu_frame, BD_EMUFRAME_NONE);
+
if (clone_flags & CLONE_SETTLS)
ti->tp_value = regs->regs[7];
diff --git a/arch/mips/kernel/signal.c b/arch/mips/kernel/signal.c
index ae4231452115..938363554c24 100644
--- a/arch/mips/kernel/signal.c
+++ b/arch/mips/kernel/signal.c
@@ -772,6 +772,14 @@ static void handle_signal(struct ksignal *ksig, struct pt_regs *regs)
struct mips_abi *abi = current->thread.abi;
void *vdso = current->mm->context.vdso;
+ /*
+ * If we were emulating a delay slot instruction, exit that frame such
+ * that addresses in the sigframe are as expected for userland and we
+ * don't have a problem if we reuse the thread's frame for an
+ * instruction within the signal handler.
+ */
+ dsemul_thread_rollback(regs);
+
if (regs->regs[0]) {
switch(regs->regs[2]) {
case ERESTART_RESTARTBLOCK:
diff --git a/arch/mips/kernel/vdso.c b/arch/mips/kernel/vdso.c
index 54e1663ce639..9abe447a4b48 100644
--- a/arch/mips/kernel/vdso.c
+++ b/arch/mips/kernel/vdso.c
@@ -107,6 +107,16 @@ int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
if (down_write_killable(&mm->mmap_sem))
return -EINTR;
+ /* Map delay slot emulation page */
+ base = mmap_region(NULL, STACK_TOP, PAGE_SIZE,
+ VM_READ|VM_WRITE|VM_EXEC|
+ VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC,
+ 0);
+ if (IS_ERR_VALUE(base)) {
+ ret = base;
+ goto out;
+ }
+
/*
* Determine total area size. This includes the VDSO data itself, the
* data page, and the GIC user page if present. Always create a mapping
diff --git a/arch/mips/math-emu/cp1emu.c b/arch/mips/math-emu/cp1emu.c
index d96e912b9d44..8afa090f9536 100644
--- a/arch/mips/math-emu/cp1emu.c
+++ b/arch/mips/math-emu/cp1emu.c
@@ -434,8 +434,8 @@ static int microMIPS32_to_MIPS32(union mips_instruction *insn_ptr)
* a single subroutine should be used across both
* modules.
*/
-static int isBranchInstr(struct pt_regs *regs, struct mm_decoded_insn dec_insn,
- unsigned long *contpc)
+int isBranchInstr(struct pt_regs *regs, struct mm_decoded_insn dec_insn,
+ unsigned long *contpc)
{
union mips_instruction insn = (union mips_instruction)dec_insn.insn;
unsigned int fcr31;
@@ -1268,7 +1268,7 @@ branch_common:
* instruction in the dslot.
*/
sig = mips_dsemul(xcp, ir,
- contpc);
+ bcpc, contpc);
if (sig < 0)
break;
if (sig)
@@ -1323,7 +1323,7 @@ branch_common:
* Single step the non-cp1
* instruction in the dslot
*/
- sig = mips_dsemul(xcp, ir, contpc);
+ sig = mips_dsemul(xcp, ir, bcpc, contpc);
if (sig < 0)
break;
if (sig)
diff --git a/arch/mips/math-emu/dsemul.c b/arch/mips/math-emu/dsemul.c
index 47074887e64c..72a4642eee2c 100644
--- a/arch/mips/math-emu/dsemul.c
+++ b/arch/mips/math-emu/dsemul.c
@@ -1,3 +1,6 @@
+#include <linux/err.h>
+#include <linux/slab.h>
+
#include <asm/branch.h>
#include <asm/cacheflush.h>
#include <asm/fpu_emulator.h>
@@ -5,43 +8,211 @@
#include <asm/mipsregs.h>
#include <asm/uaccess.h>
-#include "ieee754.h"
-
-/*
- * Emulate the arbitrary instruction ir at xcp->cp0_epc. Required when
- * we have to emulate the instruction in a COP1 branch delay slot. Do
- * not change cp0_epc due to the instruction
+/**
+ * struct emuframe - The 'emulation' frame structure
+ * @emul: The instruction to 'emulate'.
+ * @badinst: A break instruction to cause a return to the kernel.
*
- * According to the spec:
- * 1) it shouldn't be a branch :-)
- * 2) it can be a COP instruction :-(
- * 3) if we are tring to run a protected memory space we must take
- * special care on memory access instructions :-(
- */
-
-/*
- * "Trampoline" return routine to catch exception following
- * execution of delay-slot instruction execution.
+ * This structure defines the frames placed within the delay slot emulation
+ * page in response to a call to mips_dsemul(). Each thread may be allocated
+ * only one frame at any given time. The kernel stores within it the
+ * instruction to be 'emulated' followed by a break instruction, then
+ * executes the frame in user mode. The break causes a trap to the kernel
+ * which leads to do_dsemulret() being called unless the instruction in
+ * @emul causes a trap itself, is a branch, or a signal is delivered to
+ * the thread. In these cases the allocated frame will either be reused by
+ * a subsequent delay slot 'emulation', or be freed during signal delivery or
+ * upon thread exit.
+ *
+ * This approach is used because:
+ *
+ * - Actually emulating all instructions isn't feasible. We would need to
+ * be able to handle instructions from all revisions of the MIPS ISA,
+ * all ASEs & all vendor instruction set extensions. This would be a
+ * whole lot of work & continual maintenance burden as new instructions
+ * are introduced, and in the case of some vendor extensions may not
+ * even be possible. Thus we need to take the approach of actually
+ * executing the instruction.
+ *
+ * - We must execute the instruction within user context. If we were to
+ * execute the instruction in kernel mode then it would have access to
+ * kernel resources without very careful checks, leaving us with a
+ * high potential for security or stability issues to arise.
+ *
+ * - We used to place the frame on the users stack, but this requires
+ * that the stack be executable. This is bad for security so the
+ * per-process page is now used instead.
+ *
+ * - The instruction in @emul may be something entirely invalid for a
+ * delay slot. The user may (intentionally or otherwise) place a branch
+ * in a delay slot, or a kernel mode instruction, or something else
+ * which generates an exception. Thus we can't rely upon the break in
+ * @badinst always being hit. For this reason we track the index of the
+ * frame allocated to each thread, allowing us to clean it up at later
+ * points such as signal delivery or thread exit.
+ *
+ * - The user may generate a fake struct emuframe if they wish, invoking
+ * the BRK_MEMU break instruction themselves. We must therefore not
+ * trust that BRK_MEMU means there's actually a valid frame allocated
+ * to the thread, and must not allow the user to do anything they
+ * couldn't already.
*/
-
struct emuframe {
mips_instruction emul;
mips_instruction badinst;
- mips_instruction cookie;
- unsigned long epc;
};
-/*
- * Set up an emulation frame for instruction IR, from a delay slot of
- * a branch jumping to CPC. Return 0 if successful, -1 if no emulation
- * required, otherwise a signal number causing a frame setup failure.
- */
-int mips_dsemul(struct pt_regs *regs, mips_instruction ir, unsigned long cpc)
+static const int emupage_frame_count = PAGE_SIZE / sizeof(struct emuframe);
+
+static inline __user struct emuframe *dsemul_page(void)
+{
+ return (__user struct emuframe *)STACK_TOP;
+}
+
+static int alloc_emuframe(void)
+{
+ mm_context_t *mm_ctx = &current->mm->context;
+ int idx;
+
+retry:
+ spin_lock(&mm_ctx->bd_emupage_lock);
+
+ /* Ensure we have an allocation bitmap */
+ if (!mm_ctx->bd_emupage_allocmap) {
+ mm_ctx->bd_emupage_allocmap =
+ kcalloc(BITS_TO_LONGS(emupage_frame_count),
+ sizeof(unsigned long),
+ GFP_ATOMIC);
+
+ if (!mm_ctx->bd_emupage_allocmap) {
+ idx = BD_EMUFRAME_NONE;
+ goto out_unlock;
+ }
+ }
+
+ /* Attempt to allocate a single bit/frame */
+ idx = bitmap_find_free_region(mm_ctx->bd_emupage_allocmap,
+ emupage_frame_count, 0);
+ if (idx < 0) {
+ /*
+ * Failed to allocate a frame. We'll wait until one becomes
+ * available. We unlock the page so that other threads actually
+ * get the opportunity to free their frames, which means
+ * technically the result of bitmap_full may be incorrect.
+ * However the worst case is that we repeat all this and end up
+ * back here again.
+ */
+ spin_unlock(&mm_ctx->bd_emupage_lock);
+ if (!wait_event_killable(mm_ctx->bd_emupage_queue,
+ !bitmap_full(mm_ctx->bd_emupage_allocmap,
+ emupage_frame_count)))
+ goto retry;
+
+ /* Received a fatal signal - just give in */
+ return BD_EMUFRAME_NONE;
+ }
+
+ /* Success! */
+ pr_debug("allocate emuframe %d to %d\n", idx, current->pid);
+out_unlock:
+ spin_unlock(&mm_ctx->bd_emupage_lock);
+ return idx;
+}
+
+static void free_emuframe(int idx, struct mm_struct *mm)
+{
+ mm_context_t *mm_ctx = &mm->context;
+
+ spin_lock(&mm_ctx->bd_emupage_lock);
+
+ pr_debug("free emuframe %d from %d\n", idx, current->pid);
+ bitmap_clear(mm_ctx->bd_emupage_allocmap, idx, 1);
+
+ /* If some thread is waiting for a frame, now's its chance */
+ wake_up(&mm_ctx->bd_emupage_queue);
+
+ spin_unlock(&mm_ctx->bd_emupage_lock);
+}
+
+static bool within_emuframe(struct pt_regs *regs)
+{
+ unsigned long base = (unsigned long)dsemul_page();
+
+ if (regs->cp0_epc < base)
+ return false;
+ if (regs->cp0_epc >= (base + PAGE_SIZE))
+ return false;
+
+ return true;
+}
+
+bool dsemul_thread_cleanup(struct task_struct *tsk)
+{
+ int fr_idx;
+
+ /* Clear any allocated frame, retrieving its index */
+ fr_idx = atomic_xchg(&tsk->thread.bd_emu_frame, BD_EMUFRAME_NONE);
+
+ /* If no frame was allocated, we're done */
+ if (fr_idx == BD_EMUFRAME_NONE)
+ return false;
+
+ task_lock(tsk);
+
+ /* Free the frame that this thread had allocated */
+ if (tsk->mm)
+ free_emuframe(fr_idx, tsk->mm);
+
+ task_unlock(tsk);
+ return true;
+}
+
+bool dsemul_thread_rollback(struct pt_regs *regs)
+{
+ struct emuframe __user *fr;
+ int fr_idx;
+
+ /* Do nothing if we're not executing from a frame */
+ if (!within_emuframe(regs))
+ return false;
+
+ /* Find the frame being executed */
+ fr_idx = atomic_read(&current->thread.bd_emu_frame);
+ if (fr_idx == BD_EMUFRAME_NONE)
+ return false;
+ fr = &dsemul_page()[fr_idx];
+
+ /*
+ * If the PC is at the emul instruction, roll back to the branch. If
+ * PC is at the badinst (break) instruction, we've already emulated the
+ * instruction so progress to the continue PC. If it's anything else
+ * then something is amiss & the user has branched into some other area
+ * of the emupage - we'll free the allocated frame anyway.
+ */
+ if (msk_isa16_mode(regs->cp0_epc) == (unsigned long)&fr->emul)
+ regs->cp0_epc = current->thread.bd_emu_branch_pc;
+ else if (msk_isa16_mode(regs->cp0_epc) == (unsigned long)&fr->badinst)
+ regs->cp0_epc = current->thread.bd_emu_cont_pc;
+
+ atomic_set(&current->thread.bd_emu_frame, BD_EMUFRAME_NONE);
+ free_emuframe(fr_idx, current->mm);
+ return true;
+}
+
+void dsemul_mm_cleanup(struct mm_struct *mm)
+{
+ mm_context_t *mm_ctx = &mm->context;
+
+ kfree(mm_ctx->bd_emupage_allocmap);
+}
+
+int mips_dsemul(struct pt_regs *regs, mips_instruction ir,
+ unsigned long branch_pc, unsigned long cont_pc)
{
int isa16 = get_isa16_mode(regs->cp0_epc);
mips_instruction break_math;
struct emuframe __user *fr;
- int err;
+ int err, fr_idx;
/* NOP is easy */
if (ir == 0)
@@ -68,30 +239,20 @@ int mips_dsemul(struct pt_regs *regs, mips_instruction ir, unsigned long cpc)
}
}
- pr_debug("dsemul %lx %lx\n", regs->cp0_epc, cpc);
+ pr_debug("dsemul 0x%08lx cont at 0x%08lx\n", regs->cp0_epc, cont_pc);
- /*
- * The strategy is to push the instruction onto the user stack
- * and put a trap after it which we can catch and jump to
- * the required address any alternative apart from full
- * instruction emulation!!.
- *
- * Algorithmics used a system call instruction, and
- * borrowed that vector. MIPS/Linux version is a bit
- * more heavyweight in the interests of portability and
- * multiprocessor support. For Linux we use a BREAK 514
- * instruction causing a breakpoint exception.
- */
- break_math = BREAK_MATH(isa16);
-
- /* Ensure that the two instructions are in the same cache line */
- fr = (struct emuframe __user *)
- ((regs->regs[29] - sizeof(struct emuframe)) & ~0x7);
-
- /* Verify that the stack pointer is not completely insane */
- if (unlikely(!access_ok(VERIFY_WRITE, fr, sizeof(struct emuframe))))
+ /* Allocate a frame if we don't already have one */
+ fr_idx = atomic_read(&current->thread.bd_emu_frame);
+ if (fr_idx == BD_EMUFRAME_NONE)
+ fr_idx = alloc_emuframe();
+ if (fr_idx == BD_EMUFRAME_NONE)
return SIGBUS;
+ fr = &dsemul_page()[fr_idx];
+
+ /* Retrieve the appropriately encoded break instruction */
+ break_math = BREAK_MATH(isa16);
+ /* Write the instructions to the frame */
if (isa16) {
err = __put_user(ir >> 16,
(u16 __user *)(&fr->emul));
@@ -106,84 +267,36 @@ int mips_dsemul(struct pt_regs *regs, mips_instruction ir, unsigned long cpc)
err |= __put_user(break_math, &fr->badinst);
}
- err |= __put_user((mips_instruction)BD_COOKIE, &fr->cookie);
- err |= __put_user(cpc, &fr->epc);
-
if (unlikely(err)) {
MIPS_FPU_EMU_INC_STATS(errors);
+ free_emuframe(fr_idx, current->mm);
return SIGBUS;
}
+ /* Record the PC of the branch, PC to continue from & frame index */
+ current->thread.bd_emu_branch_pc = branch_pc;
+ current->thread.bd_emu_cont_pc = cont_pc;
+ atomic_set(&current->thread.bd_emu_frame, fr_idx);
+
+ /* Change user register context to execute the frame */
regs->cp0_epc = (unsigned long)&fr->emul | isa16;
+ /* Ensure the icache observes our newly written frame */
flush_cache_sigtramp((unsigned long)&fr->emul);
return 0;
}
-int do_dsemulret(struct pt_regs *xcp)
+bool do_dsemulret(struct pt_regs *xcp)
{
- int isa16 = get_isa16_mode(xcp->cp0_epc);
- struct emuframe __user *fr;
- unsigned long epc;
- u32 insn, cookie;
- int err = 0;
- u16 instr[2];
-
- fr = (struct emuframe __user *)
- (msk_isa16_mode(xcp->cp0_epc) - sizeof(mips_instruction));
-
- /*
- * If we can't even access the area, something is very wrong, but we'll
- * leave that to the default handling
- */
- if (!access_ok(VERIFY_READ, fr, sizeof(struct emuframe)))
- return 0;
-
- /*
- * Do some sanity checking on the stackframe:
- *
- * - Is the instruction pointed to by the EPC an BREAK_MATH?
- * - Is the following memory word the BD_COOKIE?
- */
- if (isa16) {
- err = __get_user(instr[0],
- (u16 __user *)(&fr->badinst));
- err |= __get_user(instr[1],
- (u16 __user *)((long)(&fr->badinst) + 2));
- insn = (instr[0] << 16) | instr[1];
- } else {
- err = __get_user(insn, &fr->badinst);
- }
- err |= __get_user(cookie, &fr->cookie);
-
- if (unlikely(err ||
- insn != BREAK_MATH(isa16) || cookie != BD_COOKIE)) {
+ /* Cleanup the allocated frame, returning if there wasn't one */
+ if (!dsemul_thread_cleanup(current)) {
MIPS_FPU_EMU_INC_STATS(errors);
- return 0;
- }
-
- /*
- * At this point, we are satisfied that it's a BD emulation trap. Yes,
- * a user might have deliberately put two malformed and useless
- * instructions in a row in his program, in which case he's in for a
- * nasty surprise - the next instruction will be treated as a
- * continuation address! Alas, this seems to be the only way that we
- * can handle signals, recursion, and longjmps() in the context of
- * emulating the branch delay instruction.
- */
-
- pr_debug("dsemulret\n");
-
- if (__get_user(epc, &fr->epc)) { /* Saved EPC */
- /* This is not a good situation to be in */
- force_sig(SIGBUS, current);
-
- return 0;
+ return false;
}
/* Set EPC to return to post-branch instruction */
- xcp->cp0_epc = epc;
- MIPS_FPU_EMU_INC_STATS(ds_emul);
- return 1;
+ xcp->cp0_epc = current->thread.bd_emu_cont_pc;
+ pr_debug("dsemulret to 0x%08lx\n", xcp->cp0_epc);
+ return true;
}