[PATCH v3 06/25] openrisc: add l.lwa/l.swa emulation

From: Stafford Horne
Date: Tue Feb 21 2017 - 14:19:49 EST

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From: Stefan Kristiansson <stefan.kristiansson@xxxxxxxxxxxxx>

This adds an emulation layer for implementations
that lack the l.lwa and l.swa instructions.
It handles these instructions both in kernel space and
user space.

Signed-off-by: Stefan Kristiansson <stefan.kristiansson@xxxxxxxxxxxxx>
[shorne@xxxxxxxxx: Added delay slot pc adjust logic]
Signed-off-by: Stafford Horne <shorne@xxxxxxxxx>
---
arch/openrisc/kernel/entry.S | 22 ++++-
arch/openrisc/kernel/process.c | 3 +
arch/openrisc/kernel/traps.c | 183 +++++++++++++++++++++++++++++++++++++++++
3 files changed, 206 insertions(+), 2 deletions(-)

diff --git a/arch/openrisc/kernel/entry.S b/arch/openrisc/kernel/entry.S
index aac0bde..ba1a361 100644
--- a/arch/openrisc/kernel/entry.S
+++ b/arch/openrisc/kernel/entry.S
@@ -173,6 +173,11 @@ handler: ;\
l.j _ret_from_exception ;\
l.nop

+/* clobbers 'reg' */
+#define CLEAR_LWA_FLAG(reg) \
+ l.movhi reg,hi(lwa_flag) ;\
+ l.ori reg,reg,lo(lwa_flag) ;\
+ l.sw 0(reg),r0
/*
* NOTE: one should never assume that SPR_EPC, SPR_ESR, SPR_EEAR
* contain the same values as when exception we're handling
@@ -193,6 +198,7 @@ EXCEPTION_ENTRY(_tng_kernel_start)
/* ---[ 0x200: BUS exception ]------------------------------------------- */

EXCEPTION_ENTRY(_bus_fault_handler)
+ CLEAR_LWA_FLAG(r3)
/* r4: EA of fault (set by EXCEPTION_HANDLE) */
l.jal do_bus_fault
l.addi r3,r1,0 /* pt_regs */
@@ -202,11 +208,13 @@ EXCEPTION_ENTRY(_bus_fault_handler)

/* ---[ 0x300: Data Page Fault exception ]------------------------------- */
EXCEPTION_ENTRY(_dtlb_miss_page_fault_handler)
+ CLEAR_LWA_FLAG(r3)
l.and r5,r5,r0
l.j 1f
l.nop

EXCEPTION_ENTRY(_data_page_fault_handler)
+ CLEAR_LWA_FLAG(r3)
/* set up parameters for do_page_fault */
l.ori r5,r0,0x300 // exception vector
1:
@@ -282,11 +290,13 @@ EXCEPTION_ENTRY(_data_page_fault_handler)

/* ---[ 0x400: Insn Page Fault exception ]------------------------------- */
EXCEPTION_ENTRY(_itlb_miss_page_fault_handler)
+ CLEAR_LWA_FLAG(r3)
l.and r5,r5,r0
l.j 1f
l.nop

EXCEPTION_ENTRY(_insn_page_fault_handler)
+ CLEAR_LWA_FLAG(r3)
/* set up parameters for do_page_fault */
l.ori r5,r0,0x400 // exception vector
1:
@@ -304,6 +314,7 @@ EXCEPTION_ENTRY(_insn_page_fault_handler)
/* ---[ 0x500: Timer exception ]----------------------------------------- */

EXCEPTION_ENTRY(_timer_handler)
+ CLEAR_LWA_FLAG(r3)
l.jal timer_interrupt
l.addi r3,r1,0 /* pt_regs */

@@ -313,6 +324,7 @@ EXCEPTION_ENTRY(_timer_handler)
/* ---[ 0x600: Aligment exception ]-------------------------------------- */

EXCEPTION_ENTRY(_alignment_handler)
+ CLEAR_LWA_FLAG(r3)
/* r4: EA of fault (set by EXCEPTION_HANDLE) */
l.jal do_unaligned_access
l.addi r3,r1,0 /* pt_regs */
@@ -509,6 +521,7 @@ EXCEPTION_ENTRY(_external_irq_handler)
// l.sw PT_SR(r1),r4
1:
#endif
+ CLEAR_LWA_FLAG(r3)
l.addi r3,r1,0
l.movhi r8,hi(do_IRQ)
l.ori r8,r8,lo(do_IRQ)
@@ -556,8 +569,12 @@ ENTRY(_sys_call_handler)
* they should be clobbered, otherwise
*/
l.sw PT_GPR3(r1),r3
- /* r4 already saved */
- /* r4 holds the EEAR address of the fault, load the original r4 */
+ /*
+ * r4 already saved
+ * r4 holds the EEAR address of the fault, use it as screatch reg and
+ * then load the original r4
+ */
+ CLEAR_LWA_FLAG(r4)
l.lwz r4,PT_GPR4(r1)
l.sw PT_GPR5(r1),r5
l.sw PT_GPR6(r1),r6
@@ -776,6 +793,7 @@ UNHANDLED_EXCEPTION(_vector_0xd00,0xd00)
/* ---[ 0xe00: Trap exception ]------------------------------------------ */

EXCEPTION_ENTRY(_trap_handler)
+ CLEAR_LWA_FLAG(r3)
/* r4: EA of fault (set by EXCEPTION_HANDLE) */
l.jal do_trap
l.addi r3,r1,0 /* pt_regs */
diff --git a/arch/openrisc/kernel/process.c b/arch/openrisc/kernel/process.c
index d7990df..c49350b 100644
--- a/arch/openrisc/kernel/process.c
+++ b/arch/openrisc/kernel/process.c
@@ -226,6 +226,7 @@ int dump_fpu(struct pt_regs *regs, elf_fpregset_t * fpu)

extern struct thread_info *_switch(struct thread_info *old_ti,
struct thread_info *new_ti);
+extern int lwa_flag;

struct task_struct *__switch_to(struct task_struct *old,
struct task_struct *new)
@@ -243,6 +244,8 @@ struct task_struct *__switch_to(struct task_struct *old,
new_ti = new->stack;
old_ti = old->stack;

+ lwa_flag = 0;
+
current_thread_info_set[smp_processor_id()] = new_ti;
last = (_switch(old_ti, new_ti))->task;

diff --git a/arch/openrisc/kernel/traps.c b/arch/openrisc/kernel/traps.c
index a4574cb..7907b6c 100644
--- a/arch/openrisc/kernel/traps.c
+++ b/arch/openrisc/kernel/traps.c
@@ -40,6 +40,8 @@
extern char _etext, _stext;

int kstack_depth_to_print = 0x180;
+int lwa_flag;
+unsigned long __user *lwa_addr;

static inline int valid_stack_ptr(struct thread_info *tinfo, void *p)
{
@@ -334,10 +336,191 @@ asmlinkage void do_bus_fault(struct pt_regs *regs, unsigned long address)
}
}

+static inline int in_delay_slot(struct pt_regs *regs)
+{
+#ifdef CONFIG_OPENRISC_NO_SPR_SR_DSX
+ /* No delay slot flag, do the old way */
+ unsigned int op, insn;
+
+ insn = *((unsigned int *)regs->pc);
+ op = insn >> 26;
+ switch (op) {
+ case 0x00: /* l.j */
+ case 0x01: /* l.jal */
+ case 0x03: /* l.bnf */
+ case 0x04: /* l.bf */
+ case 0x11: /* l.jr */
+ case 0x12: /* l.jalr */
+ return 1;
+ default:
+ return 0;
+ }
+#else
+ return regs->sr & SPR_SR_DSX;
+#endif
+}
+
+static inline void adjust_pc(struct pt_regs *regs, unsigned long address)
+{
+ int displacement;
+ unsigned int rb, op, jmp;
+
+ if (unlikely(in_delay_slot(regs))) {
+ /* In delay slot, instruction at pc is a branch, simulate it */
+ jmp = *((unsigned int *)regs->pc);
+
+ displacement = sign_extend32(((jmp) & 0x3ffffff) << 2, 27);
+ rb = (jmp & 0x0000ffff) >> 11;
+ op = jmp >> 26;
+
+ switch (op) {
+ case 0x00: /* l.j */
+ regs->pc += displacement;
+ return;
+ case 0x01: /* l.jal */
+ regs->pc += displacement;
+ regs->gpr[9] = regs->pc + 8;
+ return;
+ case 0x03: /* l.bnf */
+ if (regs->sr & SPR_SR_F)
+ regs->pc += 8;
+ else
+ regs->pc += displacement;
+ return;
+ case 0x04: /* l.bf */
+ if (regs->sr & SPR_SR_F)
+ regs->pc += displacement;
+ else
+ regs->pc += 8;
+ return;
+ case 0x11: /* l.jr */
+ regs->pc = regs->gpr[rb];
+ return;
+ case 0x12: /* l.jalr */
+ regs->pc = regs->gpr[rb];
+ regs->gpr[9] = regs->pc + 8;
+ return;
+ default:
+ break;
+ }
+ } else {
+ regs->pc += 4;
+ }
+}
+
+static inline void simulate_lwa(struct pt_regs *regs, unsigned long address,
+ unsigned int insn)
+{
+ unsigned int ra, rd;
+ unsigned long value;
+ unsigned long orig_pc;
+ long imm;
+
+ const struct exception_table_entry *entry;
+
+ orig_pc = regs->pc;
+ adjust_pc(regs, address);
+
+ ra = (insn >> 16) & 0x1f;
+ rd = (insn >> 21) & 0x1f;
+ imm = (short)insn;
+ lwa_addr = (unsigned long __user *)(regs->gpr[ra] + imm);
+
+ if ((unsigned long)lwa_addr & 0x3) {
+ do_unaligned_access(regs, address);
+ return;
+ }
+
+ if (get_user(value, lwa_addr)) {
+ if (user_mode(regs)) {
+ force_sig(SIGSEGV, current);
+ return;
+ }
+
+ if ((entry = search_exception_tables(orig_pc))) {
+ regs->pc = entry->fixup;
+ return;
+ }
+
+ /* kernel access in kernel space, load it directly */
+ value = *((unsigned long *)lwa_addr);
+ }
+
+ lwa_flag = 1;
+ regs->gpr[rd] = value;
+}
+
+static inline void simulate_swa(struct pt_regs *regs, unsigned long address,
+ unsigned int insn)
+{
+ unsigned long __user *vaddr;
+ unsigned long orig_pc;
+ unsigned int ra, rb;
+ long imm;
+
+ const struct exception_table_entry *entry;
+
+ orig_pc = regs->pc;
+ adjust_pc(regs, address);
+
+ ra = (insn >> 16) & 0x1f;
+ rb = (insn >> 11) & 0x1f;
+ imm = (short)(((insn & 0x2200000) >> 10) | (insn & 0x7ff));
+ vaddr = (unsigned long __user *)(regs->gpr[ra] + imm);
+
+ if (!lwa_flag || vaddr != lwa_addr) {
+ regs->sr &= ~SPR_SR_F;
+ return;
+ }
+
+ if ((unsigned long)vaddr & 0x3) {
+ do_unaligned_access(regs, address);
+ return;
+ }
+
+ if (put_user(regs->gpr[rb], vaddr)) {
+ if (user_mode(regs)) {
+ force_sig(SIGSEGV, current);
+ return;
+ }
+
+ if ((entry = search_exception_tables(orig_pc))) {
+ regs->pc = entry->fixup;
+ return;
+ }
+
+ /* kernel access in kernel space, store it directly */
+ *((unsigned long *)vaddr) = regs->gpr[rb];
+ }
+
+ lwa_flag = 0;
+ regs->sr |= SPR_SR_F;
+}
+
+#define INSN_LWA 0x1b
+#define INSN_SWA 0x33
+
asmlinkage void do_illegal_instruction(struct pt_regs *regs,
unsigned long address)
{
siginfo_t info;
+ unsigned int op;
+ unsigned int insn = *((unsigned int *)address);
+
+ op = insn >> 26;
+
+ switch (op) {
+ case INSN_LWA:
+ simulate_lwa(regs, address, insn);
+ return;
+
+ case INSN_SWA:
+ simulate_swa(regs, address, insn);
+ return;
+
+ default:
+ break;
+ }

if (user_mode(regs)) {
/* Send a SIGILL */
--
2.9.3

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