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linux/arch/powerpc/kernel/align.c
Paul Mackerras fab5db97e4 [PATCH] powerpc: Implement support for setting little-endian mode via prctl 
This adds the PowerPC part of the code to allow processes to change
their endian mode via prctl.

This also extends the alignment exception handler to be able to fix up
alignment exceptions that occur in little-endian mode, both for
"PowerPC" little-endian and true little-endian.

We always enter signal handlers in big-endian mode -- the support for
little-endian mode does not amount to the creation of a little-endian
user/kernel ABI.  If the signal handler returns, the endian mode is
restored to what it was when the signal was delivered.

We have two new kernel CPU feature bits, one for PPC little-endian and
one for true little-endian.  Most of the classic 32-bit processors
support PPC little-endian, and this is reflected in the CPU feature
table.  There are two corresponding feature bits reported to userland
in the AT_HWCAP aux vector entry.

This is based on an earlier patch by Anton Blanchard.

Signed-off-by: Paul Mackerras <paulus@samba.org>
2006-06-09 21:24:15 +10:00

578 lines
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/* align.c - handle alignment exceptions for the Power PC.
*
* Copyright (c) 1996 Paul Mackerras <paulus@cs.anu.edu.au>
* Copyright (c) 1998-1999 TiVo, Inc.
* PowerPC 403GCX modifications.
* Copyright (c) 1999 Grant Erickson <grant@lcse.umn.edu>
* PowerPC 403GCX/405GP modifications.
* Copyright (c) 2001-2002 PPC64 team, IBM Corp
* 64-bit and Power4 support
* Copyright (c) 2005 Benjamin Herrenschmidt, IBM Corp
* <benh@kernel.crashing.org>
* Merge ppc32 and ppc64 implementations
*
* 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.
*/
#include <linux/kernel.h>
#include <linux/mm.h>
#include <asm/processor.h>
#include <asm/uaccess.h>
#include <asm/system.h>
#include <asm/cache.h>
#include <asm/cputable.h>
struct aligninfo {
unsigned char len;
unsigned char flags;
};
#define IS_XFORM(inst) (((inst) >> 26) == 31)
#define IS_DSFORM(inst) (((inst) >> 26) >= 56)
#define INVALID { 0, 0 }
/* Bits in the flags field */
#define LD 0 /* load */
#define ST 1 /* store */
#define SE 2 /* sign-extend value */
#define F 4 /* to/from fp regs */
#define U 8 /* update index register */
#define M 0x10 /* multiple load/store */
#define SW 0x20 /* byte swap */
#define S 0x40 /* single-precision fp or... */
#define SX 0x40 /* ... byte count in XER */
#define HARD 0x80 /* string, stwcx. */
/* DSISR bits reported for a DCBZ instruction: */
#define DCBZ 0x5f /* 8xx/82xx dcbz faults when cache not enabled */
#define SWAP(a, b) (t = (a), (a) = (b), (b) = t)
/*
* The PowerPC stores certain bits of the instruction that caused the
* alignment exception in the DSISR register. This array maps those
* bits to information about the operand length and what the
* instruction would do.
*/
static struct aligninfo aligninfo[128] = {
{ 4, LD }, /* 00 0 0000: lwz / lwarx */
INVALID, /* 00 0 0001 */
{ 4, ST }, /* 00 0 0010: stw */
INVALID, /* 00 0 0011 */
{ 2, LD }, /* 00 0 0100: lhz */
{ 2, LD+SE }, /* 00 0 0101: lha */
{ 2, ST }, /* 00 0 0110: sth */
{ 4, LD+M }, /* 00 0 0111: lmw */
{ 4, LD+F+S }, /* 00 0 1000: lfs */
{ 8, LD+F }, /* 00 0 1001: lfd */
{ 4, ST+F+S }, /* 00 0 1010: stfs */
{ 8, ST+F }, /* 00 0 1011: stfd */
INVALID, /* 00 0 1100 */
{ 8, LD }, /* 00 0 1101: ld/ldu/lwa */
INVALID, /* 00 0 1110 */
{ 8, ST }, /* 00 0 1111: std/stdu */
{ 4, LD+U }, /* 00 1 0000: lwzu */
INVALID, /* 00 1 0001 */
{ 4, ST+U }, /* 00 1 0010: stwu */
INVALID, /* 00 1 0011 */
{ 2, LD+U }, /* 00 1 0100: lhzu */
{ 2, LD+SE+U }, /* 00 1 0101: lhau */
{ 2, ST+U }, /* 00 1 0110: sthu */
{ 4, ST+M }, /* 00 1 0111: stmw */
{ 4, LD+F+S+U }, /* 00 1 1000: lfsu */
{ 8, LD+F+U }, /* 00 1 1001: lfdu */
{ 4, ST+F+S+U }, /* 00 1 1010: stfsu */
{ 8, ST+F+U }, /* 00 1 1011: stfdu */
INVALID, /* 00 1 1100 */
INVALID, /* 00 1 1101 */
INVALID, /* 00 1 1110 */
INVALID, /* 00 1 1111 */
{ 8, LD }, /* 01 0 0000: ldx */
INVALID, /* 01 0 0001 */
{ 8, ST }, /* 01 0 0010: stdx */
INVALID, /* 01 0 0011 */
INVALID, /* 01 0 0100 */
{ 4, LD+SE }, /* 01 0 0101: lwax */
INVALID, /* 01 0 0110 */
INVALID, /* 01 0 0111 */
{ 4, LD+M+HARD+SX }, /* 01 0 1000: lswx */
{ 4, LD+M+HARD }, /* 01 0 1001: lswi */
{ 4, ST+M+HARD+SX }, /* 01 0 1010: stswx */
{ 4, ST+M+HARD }, /* 01 0 1011: stswi */
INVALID, /* 01 0 1100 */
{ 8, LD+U }, /* 01 0 1101: ldu */
INVALID, /* 01 0 1110 */
{ 8, ST+U }, /* 01 0 1111: stdu */
{ 8, LD+U }, /* 01 1 0000: ldux */
INVALID, /* 01 1 0001 */
{ 8, ST+U }, /* 01 1 0010: stdux */
INVALID, /* 01 1 0011 */
INVALID, /* 01 1 0100 */
{ 4, LD+SE+U }, /* 01 1 0101: lwaux */
INVALID, /* 01 1 0110 */
INVALID, /* 01 1 0111 */
INVALID, /* 01 1 1000 */
INVALID, /* 01 1 1001 */
INVALID, /* 01 1 1010 */
INVALID, /* 01 1 1011 */
INVALID, /* 01 1 1100 */
INVALID, /* 01 1 1101 */
INVALID, /* 01 1 1110 */
INVALID, /* 01 1 1111 */
INVALID, /* 10 0 0000 */
INVALID, /* 10 0 0001 */
INVALID, /* 10 0 0010: stwcx. */
INVALID, /* 10 0 0011 */
INVALID, /* 10 0 0100 */
INVALID, /* 10 0 0101 */
INVALID, /* 10 0 0110 */
INVALID, /* 10 0 0111 */
{ 4, LD+SW }, /* 10 0 1000: lwbrx */
INVALID, /* 10 0 1001 */
{ 4, ST+SW }, /* 10 0 1010: stwbrx */
INVALID, /* 10 0 1011 */
{ 2, LD+SW }, /* 10 0 1100: lhbrx */
{ 4, LD+SE }, /* 10 0 1101 lwa */
{ 2, ST+SW }, /* 10 0 1110: sthbrx */
INVALID, /* 10 0 1111 */
INVALID, /* 10 1 0000 */
INVALID, /* 10 1 0001 */
INVALID, /* 10 1 0010 */
INVALID, /* 10 1 0011 */
INVALID, /* 10 1 0100 */
INVALID, /* 10 1 0101 */
INVALID, /* 10 1 0110 */
INVALID, /* 10 1 0111 */
INVALID, /* 10 1 1000 */
INVALID, /* 10 1 1001 */
INVALID, /* 10 1 1010 */
INVALID, /* 10 1 1011 */
INVALID, /* 10 1 1100 */
INVALID, /* 10 1 1101 */
INVALID, /* 10 1 1110 */
{ 0, ST+HARD }, /* 10 1 1111: dcbz */
{ 4, LD }, /* 11 0 0000: lwzx */
INVALID, /* 11 0 0001 */
{ 4, ST }, /* 11 0 0010: stwx */
INVALID, /* 11 0 0011 */
{ 2, LD }, /* 11 0 0100: lhzx */
{ 2, LD+SE }, /* 11 0 0101: lhax */
{ 2, ST }, /* 11 0 0110: sthx */
INVALID, /* 11 0 0111 */
{ 4, LD+F+S }, /* 11 0 1000: lfsx */
{ 8, LD+F }, /* 11 0 1001: lfdx */
{ 4, ST+F+S }, /* 11 0 1010: stfsx */
{ 8, ST+F }, /* 11 0 1011: stfdx */
INVALID, /* 11 0 1100 */
{ 8, LD+M }, /* 11 0 1101: lmd */
INVALID, /* 11 0 1110 */
{ 8, ST+M }, /* 11 0 1111: stmd */
{ 4, LD+U }, /* 11 1 0000: lwzux */
INVALID, /* 11 1 0001 */
{ 4, ST+U }, /* 11 1 0010: stwux */
INVALID, /* 11 1 0011 */
{ 2, LD+U }, /* 11 1 0100: lhzux */
{ 2, LD+SE+U }, /* 11 1 0101: lhaux */
{ 2, ST+U }, /* 11 1 0110: sthux */
INVALID, /* 11 1 0111 */
{ 4, LD+F+S+U }, /* 11 1 1000: lfsux */
{ 8, LD+F+U }, /* 11 1 1001: lfdux */
{ 4, ST+F+S+U }, /* 11 1 1010: stfsux */
{ 8, ST+F+U }, /* 11 1 1011: stfdux */
INVALID, /* 11 1 1100 */
INVALID, /* 11 1 1101 */
INVALID, /* 11 1 1110 */
INVALID, /* 11 1 1111 */
};
/*
* Create a DSISR value from the instruction
*/
static inline unsigned make_dsisr(unsigned instr)
{
unsigned dsisr;
/* bits 6:15 --> 22:31 */
dsisr = (instr & 0x03ff0000) >> 16;
if (IS_XFORM(instr)) {
/* bits 29:30 --> 15:16 */
dsisr |= (instr & 0x00000006) << 14;
/* bit 25 --> 17 */
dsisr |= (instr & 0x00000040) << 8;
/* bits 21:24 --> 18:21 */
dsisr |= (instr & 0x00000780) << 3;
} else {
/* bit 5 --> 17 */
dsisr |= (instr & 0x04000000) >> 12;
/* bits 1: 4 --> 18:21 */
dsisr |= (instr & 0x78000000) >> 17;
/* bits 30:31 --> 12:13 */
if (IS_DSFORM(instr))
dsisr |= (instr & 0x00000003) << 18;
}
return dsisr;
}
/*
* The dcbz (data cache block zero) instruction
* gives an alignment fault if used on non-cacheable
* memory. We handle the fault mainly for the
* case when we are running with the cache disabled
* for debugging.
*/
static int emulate_dcbz(struct pt_regs *regs, unsigned char __user *addr)
{
long __user *p;
int i, size;
#ifdef __powerpc64__
size = ppc64_caches.dline_size;
#else
size = L1_CACHE_BYTES;
#endif
p = (long __user *) (regs->dar & -size);
if (user_mode(regs) && !access_ok(VERIFY_WRITE, p, size))
return -EFAULT;
for (i = 0; i < size / sizeof(long); ++i)
if (__put_user(0, p+i))
return -EFAULT;
return 1;
}
/*
* Emulate load & store multiple instructions
* On 64-bit machines, these instructions only affect/use the
* bottom 4 bytes of each register, and the loads clear the
* top 4 bytes of the affected register.
*/
#ifdef CONFIG_PPC64
#define REG_BYTE(rp, i) *((u8 *)((rp) + ((i) >> 2)) + ((i) & 3) + 4)
#else
#define REG_BYTE(rp, i) *((u8 *)(rp) + (i))
#endif
#define SWIZ_PTR(p) ((unsigned char __user *)((p) ^ swiz))
static int emulate_multiple(struct pt_regs *regs, unsigned char __user *addr,
unsigned int reg, unsigned int nb,
unsigned int flags, unsigned int instr,
unsigned long swiz)
{
unsigned long *rptr;
unsigned int nb0, i, bswiz;
unsigned long p;
/*
* We do not try to emulate 8 bytes multiple as they aren't really
* available in our operating environments and we don't try to
* emulate multiples operations in kernel land as they should never
* be used/generated there at least not on unaligned boundaries
*/
if (unlikely((nb > 4) || !user_mode(regs)))
return 0;
/* lmw, stmw, lswi/x, stswi/x */
nb0 = 0;
if (flags & HARD) {
if (flags & SX) {
nb = regs->xer & 127;
if (nb == 0)
return 1;
} else {
unsigned long pc = regs->nip ^ (swiz & 4);
if (__get_user(instr, (unsigned int __user *)pc))
return -EFAULT;
if (swiz == 0 && (flags & SW))
instr = cpu_to_le32(instr);
nb = (instr >> 11) & 0x1f;
if (nb == 0)
nb = 32;
}
if (nb + reg * 4 > 128) {
nb0 = nb + reg * 4 - 128;
nb = 128 - reg * 4;
}
} else {
/* lwm, stmw */
nb = (32 - reg) * 4;
}
if (!access_ok((flags & ST ? VERIFY_WRITE: VERIFY_READ), addr, nb+nb0))
return -EFAULT; /* bad address */
rptr = &regs->gpr[reg];
p = (unsigned long) addr;
bswiz = (flags & SW)? 3: 0;
if (!(flags & ST)) {
/*
* This zeroes the top 4 bytes of the affected registers
* in 64-bit mode, and also zeroes out any remaining
* bytes of the last register for lsw*.
*/
memset(rptr, 0, ((nb + 3) / 4) * sizeof(unsigned long));
if (nb0 > 0)
memset(&regs->gpr[0], 0,
((nb0 + 3) / 4) * sizeof(unsigned long));
for (i = 0; i < nb; ++i, ++p)
if (__get_user(REG_BYTE(rptr, i ^ bswiz), SWIZ_PTR(p)))
return -EFAULT;
if (nb0 > 0) {
rptr = &regs->gpr[0];
addr += nb;
for (i = 0; i < nb0; ++i, ++p)
if (__get_user(REG_BYTE(rptr, i ^ bswiz),
SWIZ_PTR(p)))
return -EFAULT;
}
} else {
for (i = 0; i < nb; ++i, ++p)
if (__put_user(REG_BYTE(rptr, i ^ bswiz), SWIZ_PTR(p)))
return -EFAULT;
if (nb0 > 0) {
rptr = &regs->gpr[0];
addr += nb;
for (i = 0; i < nb0; ++i, ++p)
if (__put_user(REG_BYTE(rptr, i ^ bswiz),
SWIZ_PTR(p)))
return -EFAULT;
}
}
return 1;
}
/*
* Called on alignment exception. Attempts to fixup
*
* Return 1 on success
* Return 0 if unable to handle the interrupt
* Return -EFAULT if data address is bad
*/
int fix_alignment(struct pt_regs *regs)
{
unsigned int instr, nb, flags;
unsigned int reg, areg;
unsigned int dsisr;
unsigned char __user *addr;
unsigned long p, swiz;
int ret, t;
union {
u64 ll;
double dd;
unsigned char v[8];
struct {
unsigned hi32;
int low32;
} x32;
struct {
unsigned char hi48[6];
short low16;
} x16;
} data;
/*
* We require a complete register set, if not, then our assembly
* is broken
*/
CHECK_FULL_REGS(regs);
dsisr = regs->dsisr;
/* Some processors don't provide us with a DSISR we can use here,
* let's make one up from the instruction
*/
if (cpu_has_feature(CPU_FTR_NODSISRALIGN)) {
unsigned long pc = regs->nip;
if (cpu_has_feature(CPU_FTR_PPC_LE) && (regs->msr & MSR_LE))
pc ^= 4;
if (unlikely(__get_user(instr, (unsigned int __user *)pc)))
return -EFAULT;
if (cpu_has_feature(CPU_FTR_REAL_LE) && (regs->msr & MSR_LE))
instr = cpu_to_le32(instr);
dsisr = make_dsisr(instr);
}
/* extract the operation and registers from the dsisr */
reg = (dsisr >> 5) & 0x1f; /* source/dest register */
areg = dsisr & 0x1f; /* register to update */
instr = (dsisr >> 10) & 0x7f;
instr |= (dsisr >> 13) & 0x60;
/* Lookup the operation in our table */
nb = aligninfo[instr].len;
flags = aligninfo[instr].flags;
/* Byteswap little endian loads and stores */
swiz = 0;
if (regs->msr & MSR_LE) {
flags ^= SW;
/*
* So-called "PowerPC little endian" mode works by
* swizzling addresses rather than by actually doing
* any byte-swapping. To emulate this, we XOR each
* byte address with 7. We also byte-swap, because
* the processor's address swizzling depends on the
* operand size (it xors the address with 7 for bytes,
* 6 for halfwords, 4 for words, 0 for doublewords) but
* we will xor with 7 and load/store each byte separately.
*/
if (cpu_has_feature(CPU_FTR_PPC_LE))
swiz = 7;
}
/* DAR has the operand effective address */
addr = (unsigned char __user *)regs->dar;
/* A size of 0 indicates an instruction we don't support, with
* the exception of DCBZ which is handled as a special case here
*/
if (instr == DCBZ)
return emulate_dcbz(regs, addr);
if (unlikely(nb == 0))
return 0;
/* Load/Store Multiple instructions are handled in their own
* function
*/
if (flags & M)
return emulate_multiple(regs, addr, reg, nb,
flags, instr, swiz);
/* Verify the address of the operand */
if (unlikely(user_mode(regs) &&
!access_ok((flags & ST ? VERIFY_WRITE : VERIFY_READ),
addr, nb)))
return -EFAULT;
/* Force the fprs into the save area so we can reference them */
if (flags & F) {
/* userland only */
if (unlikely(!user_mode(regs)))
return 0;
flush_fp_to_thread(current);
}
/* If we are loading, get the data from user space, else
* get it from register values
*/
if (!(flags & ST)) {
data.ll = 0;
ret = 0;
p = (unsigned long) addr;
switch (nb) {
case 8:
ret |= __get_user(data.v[0], SWIZ_PTR(p++));
ret |= __get_user(data.v[1], SWIZ_PTR(p++));
ret |= __get_user(data.v[2], SWIZ_PTR(p++));
ret |= __get_user(data.v[3], SWIZ_PTR(p++));
case 4:
ret |= __get_user(data.v[4], SWIZ_PTR(p++));
ret |= __get_user(data.v[5], SWIZ_PTR(p++));
case 2:
ret |= __get_user(data.v[6], SWIZ_PTR(p++));
ret |= __get_user(data.v[7], SWIZ_PTR(p++));
if (unlikely(ret))
return -EFAULT;
}
} else if (flags & F) {
data.dd = current->thread.fpr[reg];
if (flags & S) {
/* Single-precision FP store requires conversion... */
#ifdef CONFIG_PPC_FPU
preempt_disable();
enable_kernel_fp();
cvt_df(&data.dd, (float *)&data.v[4], &current->thread);
preempt_enable();
#else
return 0;
#endif
}
} else
data.ll = regs->gpr[reg];
if (flags & SW) {
switch (nb) {
case 8:
SWAP(data.v[0], data.v[7]);
SWAP(data.v[1], data.v[6]);
SWAP(data.v[2], data.v[5]);
SWAP(data.v[3], data.v[4]);
break;
case 4:
SWAP(data.v[4], data.v[7]);
SWAP(data.v[5], data.v[6]);
break;
case 2:
SWAP(data.v[6], data.v[7]);
break;
}
}
/* Perform other misc operations like sign extension
* or floating point single precision conversion
*/
switch (flags & ~(U|SW)) {
case LD+SE: /* sign extend */
if ( nb == 2 )
data.ll = data.x16.low16;
else /* nb must be 4 */
data.ll = data.x32.low32;
break;
/* Single-precision FP load requires conversion... */
case LD+F+S:
#ifdef CONFIG_PPC_FPU
preempt_disable();
enable_kernel_fp();
cvt_fd((float *)&data.v[4], &data.dd, &current->thread);
preempt_enable();
#else
return 0;
#endif
break;
}
/* Store result to memory or update registers */
if (flags & ST) {
ret = 0;
p = (unsigned long) addr;
switch (nb) {
case 8:
ret |= __put_user(data.v[0], SWIZ_PTR(p++));
ret |= __put_user(data.v[1], SWIZ_PTR(p++));
ret |= __put_user(data.v[2], SWIZ_PTR(p++));
ret |= __put_user(data.v[3], SWIZ_PTR(p++));
case 4:
ret |= __put_user(data.v[4], SWIZ_PTR(p++));
ret |= __put_user(data.v[5], SWIZ_PTR(p++));
case 2:
ret |= __put_user(data.v[6], SWIZ_PTR(p++));
ret |= __put_user(data.v[7], SWIZ_PTR(p++));
}
if (unlikely(ret))
return -EFAULT;
} else if (flags & F)
current->thread.fpr[reg] = data.dd;
else
regs->gpr[reg] = data.ll;
/* Update RA as needed */
if (flags & U)
regs->gpr[areg] = regs->dar;
return 1;
}
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