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-rw-r--r--arch/arm64/kernel/compat_alignment.c383
1 files changed, 383 insertions, 0 deletions
diff --git a/arch/arm64/kernel/compat_alignment.c b/arch/arm64/kernel/compat_alignment.c
new file mode 100644
index 000000000..deff21bfa
--- /dev/null
+++ b/arch/arm64/kernel/compat_alignment.c
@@ -0,0 +1,383 @@
+// SPDX-License-Identifier: GPL-2.0-only
+// based on arch/arm/mm/alignment.c
+
+#include <linux/compiler.h>
+#include <linux/errno.h>
+#include <linux/kernel.h>
+#include <linux/init.h>
+#include <linux/perf_event.h>
+#include <linux/uaccess.h>
+
+#include <asm/exception.h>
+#include <asm/ptrace.h>
+#include <asm/traps.h>
+
+/*
+ * 32-bit misaligned trap handler (c) 1998 San Mehat (CCC) -July 1998
+ *
+ * Speed optimisations and better fault handling by Russell King.
+ */
+#define CODING_BITS(i) (i & 0x0e000000)
+
+#define LDST_P_BIT(i) (i & (1 << 24)) /* Preindex */
+#define LDST_U_BIT(i) (i & (1 << 23)) /* Add offset */
+#define LDST_W_BIT(i) (i & (1 << 21)) /* Writeback */
+#define LDST_L_BIT(i) (i & (1 << 20)) /* Load */
+
+#define LDST_P_EQ_U(i) ((((i) ^ ((i) >> 1)) & (1 << 23)) == 0)
+
+#define LDSTHD_I_BIT(i) (i & (1 << 22)) /* double/half-word immed */
+
+#define RN_BITS(i) ((i >> 16) & 15) /* Rn */
+#define RD_BITS(i) ((i >> 12) & 15) /* Rd */
+#define RM_BITS(i) (i & 15) /* Rm */
+
+#define REGMASK_BITS(i) (i & 0xffff)
+
+#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))
+
+union offset_union {
+ unsigned long un;
+ signed long sn;
+};
+
+#define TYPE_ERROR 0
+#define TYPE_FAULT 1
+#define TYPE_LDST 2
+#define TYPE_DONE 3
+
+static void
+do_alignment_finish_ldst(unsigned long addr, u32 instr, struct pt_regs *regs,
+ union offset_union offset)
+{
+ if (!LDST_U_BIT(instr))
+ offset.un = -offset.un;
+
+ if (!LDST_P_BIT(instr))
+ addr += offset.un;
+
+ if (!LDST_P_BIT(instr) || LDST_W_BIT(instr))
+ regs->regs[RN_BITS(instr)] = addr;
+}
+
+static int
+do_alignment_ldrdstrd(unsigned long addr, u32 instr, struct pt_regs *regs)
+{
+ unsigned int rd = RD_BITS(instr);
+ unsigned int rd2;
+ int load;
+
+ 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)) {
+ return TYPE_ERROR;
+ } else {
+ load = ((instr & 0xf0) == 0xd0);
+ rd2 = rd + 1;
+ }
+
+ if (load) {
+ unsigned int val, val2;
+
+ if (get_user(val, (u32 __user *)addr) ||
+ get_user(val2, (u32 __user *)(addr + 4)))
+ return TYPE_FAULT;
+ regs->regs[rd] = val;
+ regs->regs[rd2] = val2;
+ } else {
+ if (put_user(regs->regs[rd], (u32 __user *)addr) ||
+ put_user(regs->regs[rd2], (u32 __user *)(addr + 4)))
+ return TYPE_FAULT;
+ }
+ return TYPE_LDST;
+}
+
+/*
+ * LDM/STM alignment handler.
+ *
+ * There are 4 variants of this instruction:
+ *
+ * B = rn pointer before instruction, A = rn pointer after instruction
+ * ------ increasing address ----->
+ * | | r0 | r1 | ... | rx | |
+ * PU = 01 B A
+ * PU = 11 B A
+ * PU = 00 A B
+ * PU = 10 A B
+ */
+static int
+do_alignment_ldmstm(unsigned long addr, u32 instr, struct pt_regs *regs)
+{
+ unsigned int rd, rn, nr_regs, regbits;
+ unsigned long eaddr, newaddr;
+ unsigned int val;
+
+ /* count the number of registers in the mask to be transferred */
+ nr_regs = hweight16(REGMASK_BITS(instr)) * 4;
+
+ rn = RN_BITS(instr);
+ newaddr = eaddr = regs->regs[rn];
+
+ if (!LDST_U_BIT(instr))
+ nr_regs = -nr_regs;
+ newaddr += nr_regs;
+ if (!LDST_U_BIT(instr))
+ eaddr = newaddr;
+
+ if (LDST_P_EQ_U(instr)) /* U = P */
+ eaddr += 4;
+
+ for (regbits = REGMASK_BITS(instr), rd = 0; regbits;
+ regbits >>= 1, rd += 1)
+ if (regbits & 1) {
+ if (LDST_L_BIT(instr)) {
+ if (get_user(val, (u32 __user *)eaddr))
+ return TYPE_FAULT;
+ if (rd < 15)
+ regs->regs[rd] = val;
+ else
+ regs->pc = val;
+ } else {
+ /*
+ * The PC register has a bias of +8 in ARM mode
+ * and +4 in Thumb mode. This means that a read
+ * of the value of PC should account for this.
+ * Since Thumb does not permit STM instructions
+ * to refer to PC, just add 8 here.
+ */
+ val = (rd < 15) ? regs->regs[rd] : regs->pc + 8;
+ if (put_user(val, (u32 __user *)eaddr))
+ return TYPE_FAULT;
+ }
+ eaddr += 4;
+ }
+
+ if (LDST_W_BIT(instr))
+ regs->regs[rn] = newaddr;
+
+ return TYPE_DONE;
+}
+
+/*
+ * Convert Thumb multi-word load/store instruction forms to equivalent ARM
+ * instructions so we can reuse ARM userland alignment fault fixups for Thumb.
+ *
+ * This implementation was initially based on the algorithm found in
+ * gdb/sim/arm/thumbemu.c. It is basically just a code reduction of same
+ * to convert only Thumb ld/st instruction forms to equivalent ARM forms.
+ *
+ * NOTES:
+ * 1. Comments below refer to ARM ARM DDI0100E Thumb Instruction sections.
+ * 2. If for some reason we're passed an non-ld/st Thumb instruction to
+ * decode, we return 0xdeadc0de. This should never happen under normal
+ * circumstances but if it does, we've got other problems to deal with
+ * elsewhere and we obviously can't fix those problems here.
+ */
+
+static unsigned long thumb2arm(u16 tinstr)
+{
+ u32 L = (tinstr & (1<<11)) >> 11;
+
+ switch ((tinstr & 0xf800) >> 11) {
+ /* 6.6.1 Format 1: */
+ case 0xc000 >> 11: /* 7.1.51 STMIA */
+ case 0xc800 >> 11: /* 7.1.25 LDMIA */
+ {
+ u32 Rn = (tinstr & (7<<8)) >> 8;
+ u32 W = ((L<<Rn) & (tinstr&255)) ? 0 : 1<<21;
+
+ return 0xe8800000 | W | (L<<20) | (Rn<<16) |
+ (tinstr&255);
+ }
+
+ /* 6.6.1 Format 2: */
+ case 0xb000 >> 11: /* 7.1.48 PUSH */
+ case 0xb800 >> 11: /* 7.1.47 POP */
+ if ((tinstr & (3 << 9)) == 0x0400) {
+ static const u32 subset[4] = {
+ 0xe92d0000, /* STMDB sp!,{registers} */
+ 0xe92d4000, /* STMDB sp!,{registers,lr} */
+ 0xe8bd0000, /* LDMIA sp!,{registers} */
+ 0xe8bd8000 /* LDMIA sp!,{registers,pc} */
+ };
+ return subset[(L<<1) | ((tinstr & (1<<8)) >> 8)] |
+ (tinstr & 255); /* register_list */
+ }
+ fallthrough; /* for illegal instruction case */
+
+ default:
+ 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(u32 *pinstr, struct pt_regs *regs,
+ union offset_union *poffset)
+{
+ u32 instr = *pinstr;
+ u16 tinst1 = (instr >> 16) & 0xffff;
+ u16 tinst2 = instr & 0xffff;
+
+ 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;
+ fallthrough;
+
+ 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 alignment_get_arm(struct pt_regs *regs, __le32 __user *ip, u32 *inst)
+{
+ __le32 instr = 0;
+ int fault;
+
+ fault = get_user(instr, ip);
+ if (fault)
+ return fault;
+
+ *inst = __le32_to_cpu(instr);
+ return 0;
+}
+
+static int alignment_get_thumb(struct pt_regs *regs, __le16 __user *ip, u16 *inst)
+{
+ __le16 instr = 0;
+ int fault;
+
+ fault = get_user(instr, ip);
+ if (fault)
+ return fault;
+
+ *inst = __le16_to_cpu(instr);
+ return 0;
+}
+
+int do_compat_alignment_fixup(unsigned long addr, struct pt_regs *regs)
+{
+ union offset_union offset;
+ unsigned long instrptr;
+ int (*handler)(unsigned long addr, u32 instr, struct pt_regs *regs);
+ unsigned int type;
+ u32 instr = 0;
+ int isize = 4;
+ int thumb2_32b = 0;
+
+ instrptr = instruction_pointer(regs);
+
+ if (compat_thumb_mode(regs)) {
+ __le16 __user *ptr = (__le16 __user *)(instrptr & ~1);
+ u16 tinstr, tinst2;
+
+ if (alignment_get_thumb(regs, ptr, &tinstr))
+ return 1;
+
+ if (IS_T32(tinstr)) { /* Thumb-2 32-bit */
+ if (alignment_get_thumb(regs, ptr + 1, &tinst2))
+ return 1;
+ instr = ((u32)tinstr << 16) | tinst2;
+ thumb2_32b = 1;
+ } else {
+ isize = 2;
+ instr = thumb2arm(tinstr);
+ }
+ } else {
+ if (alignment_get_arm(regs, (__le32 __user *)instrptr, &instr))
+ return 1;
+ }
+
+ switch (CODING_BITS(instr)) {
+ case 0x00000000: /* 3.13.4 load/store instruction extensions */
+ if (LDSTHD_I_BIT(instr))
+ offset.un = (instr & 0xf00) >> 4 | (instr & 15);
+ else
+ offset.un = regs->regs[RM_BITS(instr)];
+
+ if ((instr & 0x001000f0) == 0x000000d0 || /* LDRD */
+ (instr & 0x001000f0) == 0x000000f0) /* STRD */
+ handler = do_alignment_ldrdstrd;
+ else
+ return 1;
+ break;
+
+ case 0x08000000: /* ldm or stm, or thumb-2 32bit instruction */
+ if (thumb2_32b) {
+ offset.un = 0;
+ handler = do_alignment_t32_to_handler(&instr, regs, &offset);
+ } else {
+ offset.un = 0;
+ handler = do_alignment_ldmstm;
+ }
+ break;
+
+ default:
+ return 1;
+ }
+
+ type = handler(addr, instr, regs);
+
+ if (type == TYPE_ERROR || type == TYPE_FAULT)
+ return 1;
+
+ if (type == TYPE_LDST)
+ do_alignment_finish_ldst(addr, instr, regs, offset);
+
+ perf_sw_event(PERF_COUNT_SW_ALIGNMENT_FAULTS, 1, regs, regs->pc);
+ arm64_skip_faulting_instruction(regs, isize);
+
+ return 0;
+}
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