[ARM] 5540/1: 32-bit Thumb-2 {ld,st}{m,rd} alignment fault fixup support
From: Min Zhang <mzhang@mvista.com>
Add alignment fault fixup support for 32-bit Thumb-2 LDM, LDRD, POP,
PUSH, STM and STRD instructions. Alignment fault fixup support for
the remaining 32-bit Thumb-2 load/store instruction cases is not
included since ARMv6 and later processors include hardware support
for loads and stores of unaligned words and halfwords.
Signed-off-by: Min Zhang <mzhang@mvista.com>
Signed-off-by: George G. Davis <gdavis@mvista.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
diff --git a/arch/arm/mm/alignment.c b/arch/arm/mm/alignment.c
index 3a398be..03cd27d 100644
--- a/arch/arm/mm/alignment.c
+++ b/arch/arm/mm/alignment.c
@@ -62,6 +62,12 @@
#define SHIFT_ASR 0x40
#define SHIFT_RORRRX 0x60
+#define BAD_INSTR 0xdeadc0de
+
+/* Thumb-2 32 bit format per ARMv7 DDI0406A A6.3, either f800h,e800h,f800h */
+#define IS_T32(hi16) \
+ (((hi16) & 0xe000) == 0xe000 && ((hi16) & 0x1800))
+
static unsigned long ai_user;
static unsigned long ai_sys;
static unsigned long ai_skipped;
@@ -332,38 +338,48 @@
struct pt_regs *regs)
{
unsigned int rd = RD_BITS(instr);
+ unsigned int rd2;
+ int load;
- if (((rd & 1) == 1) || (rd == 14))
+ if ((instr & 0xfe000000) == 0xe8000000) {
+ /* ARMv7 Thumb-2 32-bit LDRD/STRD */
+ rd2 = (instr >> 8) & 0xf;
+ load = !!(LDST_L_BIT(instr));
+ } else if (((rd & 1) == 1) || (rd == 14))
goto bad;
+ else {
+ load = ((instr & 0xf0) == 0xd0);
+ rd2 = rd + 1;
+ }
ai_dword += 1;
if (user_mode(regs))
goto user;
- if ((instr & 0xf0) == 0xd0) {
+ if (load) {
unsigned long val;
get32_unaligned_check(val, addr);
regs->uregs[rd] = val;
get32_unaligned_check(val, addr + 4);
- regs->uregs[rd + 1] = val;
+ regs->uregs[rd2] = val;
} else {
put32_unaligned_check(regs->uregs[rd], addr);
- put32_unaligned_check(regs->uregs[rd + 1], addr + 4);
+ put32_unaligned_check(regs->uregs[rd2], addr + 4);
}
return TYPE_LDST;
user:
- if ((instr & 0xf0) == 0xd0) {
+ if (load) {
unsigned long val;
get32t_unaligned_check(val, addr);
regs->uregs[rd] = val;
get32t_unaligned_check(val, addr + 4);
- regs->uregs[rd + 1] = val;
+ regs->uregs[rd2] = val;
} else {
put32t_unaligned_check(regs->uregs[rd], addr);
- put32t_unaligned_check(regs->uregs[rd + 1], addr + 4);
+ put32t_unaligned_check(regs->uregs[rd2], addr + 4);
}
return TYPE_LDST;
@@ -616,10 +632,74 @@
/* Else fall through for illegal instruction case */
default:
- return 0xdeadc0de;
+ return BAD_INSTR;
}
}
+/*
+ * Convert Thumb-2 32 bit LDM, STM, LDRD, STRD to equivalent instruction
+ * handlable by ARM alignment handler, also find the corresponding handler,
+ * so that we can reuse ARM userland alignment fault fixups for Thumb.
+ *
+ * @pinstr: original Thumb-2 instruction; returns new handlable instruction
+ * @regs: register context.
+ * @poffset: return offset from faulted addr for later writeback
+ *
+ * NOTES:
+ * 1. Comments below refer to ARMv7 DDI0406A Thumb Instruction sections.
+ * 2. Register name Rt from ARMv7 is same as Rd from ARMv6 (Rd is Rt)
+ */
+static void *
+do_alignment_t32_to_handler(unsigned long *pinstr, struct pt_regs *regs,
+ union offset_union *poffset)
+{
+ unsigned long instr = *pinstr;
+ u16 tinst1 = (instr >> 16) & 0xffff;
+ u16 tinst2 = instr & 0xffff;
+ poffset->un = 0;
+
+ switch (tinst1 & 0xffe0) {
+ /* A6.3.5 Load/Store multiple */
+ case 0xe880: /* STM/STMIA/STMEA,LDM/LDMIA, PUSH/POP T2 */
+ case 0xe8a0: /* ...above writeback version */
+ case 0xe900: /* STMDB/STMFD, LDMDB/LDMEA */
+ case 0xe920: /* ...above writeback version */
+ /* no need offset decision since handler calculates it */
+ return do_alignment_ldmstm;
+
+ case 0xf840: /* POP/PUSH T3 (single register) */
+ if (RN_BITS(instr) == 13 && (tinst2 & 0x09ff) == 0x0904) {
+ u32 L = !!(LDST_L_BIT(instr));
+ const u32 subset[2] = {
+ 0xe92d0000, /* STMDB sp!,{registers} */
+ 0xe8bd0000, /* LDMIA sp!,{registers} */
+ };
+ *pinstr = subset[L] | (1<<RD_BITS(instr));
+ return do_alignment_ldmstm;
+ }
+ /* Else fall through for illegal instruction case */
+ break;
+
+ /* A6.3.6 Load/store double, STRD/LDRD(immed, lit, reg) */
+ case 0xe860:
+ case 0xe960:
+ case 0xe8e0:
+ case 0xe9e0:
+ poffset->un = (tinst2 & 0xff) << 2;
+ case 0xe940:
+ case 0xe9c0:
+ return do_alignment_ldrdstrd;
+
+ /*
+ * No need to handle load/store instructions up to word size
+ * since ARMv6 and later CPUs can perform unaligned accesses.
+ */
+ default:
+ break;
+ }
+ return NULL;
+}
+
static int
do_alignment(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
{
@@ -630,6 +710,8 @@
mm_segment_t fs;
unsigned int fault;
u16 tinstr = 0;
+ int isize = 4;
+ int thumb2_32b = 0;
instrptr = instruction_pointer(regs);
@@ -637,8 +719,19 @@
set_fs(KERNEL_DS);
if (thumb_mode(regs)) {
fault = __get_user(tinstr, (u16 *)(instrptr & ~1));
- if (!(fault))
- instr = thumb2arm(tinstr);
+ if (!fault) {
+ if (cpu_architecture() >= CPU_ARCH_ARMv7 &&
+ IS_T32(tinstr)) {
+ /* Thumb-2 32-bit */
+ u16 tinst2 = 0;
+ fault = __get_user(tinst2, (u16 *)(instrptr+2));
+ instr = (tinstr << 16) | tinst2;
+ thumb2_32b = 1;
+ } else {
+ isize = 2;
+ instr = thumb2arm(tinstr);
+ }
+ }
} else
fault = __get_user(instr, (u32 *)instrptr);
set_fs(fs);
@@ -655,7 +748,7 @@
fixup:
- regs->ARM_pc += thumb_mode(regs) ? 2 : 4;
+ regs->ARM_pc += isize;
switch (CODING_BITS(instr)) {
case 0x00000000: /* 3.13.4 load/store instruction extensions */
@@ -714,18 +807,25 @@
handler = do_alignment_ldrstr;
break;
- case 0x08000000: /* ldm or stm */
- handler = do_alignment_ldmstm;
+ case 0x08000000: /* ldm or stm, or thumb-2 32bit instruction */
+ if (thumb2_32b)
+ handler = do_alignment_t32_to_handler(&instr, regs, &offset);
+ else
+ handler = do_alignment_ldmstm;
break;
default:
goto bad;
}
+ if (!handler)
+ goto bad;
type = handler(addr, instr, regs);
- if (type == TYPE_ERROR || type == TYPE_FAULT)
+ if (type == TYPE_ERROR || type == TYPE_FAULT) {
+ regs->ARM_pc -= isize;
goto bad_or_fault;
+ }
if (type == TYPE_LDST)
do_alignment_finish_ldst(addr, instr, regs, offset);
@@ -735,7 +835,6 @@
bad_or_fault:
if (type == TYPE_ERROR)
goto bad;
- regs->ARM_pc -= thumb_mode(regs) ? 2 : 4;
/*
* We got a fault - fix it up, or die.
*/
@@ -751,8 +850,8 @@
*/
printk(KERN_ERR "Alignment trap: not handling instruction "
"%0*lx at [<%08lx>]\n",
- thumb_mode(regs) ? 4 : 8,
- thumb_mode(regs) ? tinstr : instr, instrptr);
+ isize << 1,
+ isize == 2 ? tinstr : instr, instrptr);
ai_skipped += 1;
return 1;
@@ -763,8 +862,8 @@
printk("Alignment trap: %s (%d) PC=0x%08lx Instr=0x%0*lx "
"Address=0x%08lx FSR 0x%03x\n", current->comm,
task_pid_nr(current), instrptr,
- thumb_mode(regs) ? 4 : 8,
- thumb_mode(regs) ? tinstr : instr,
+ isize << 1,
+ isize == 2 ? tinstr : instr,
addr, fsr);
if (ai_usermode & UM_FIXUP)
