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powerpc: Set regs->dar if memory access fails in emulate_step()
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This adds code to the instruction emulation code to set regs->dar
to the address of any memory access that fails.  This address is
not necessarily the same as the effective address of the instruction,
because if the memory access is unaligned, it might cross a page
boundary and fault on the second page.

Signed-off-by: Paul Mackerras <paulus@ozlabs.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
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Paul Mackerras authored and Michael Ellerman committed Sep 1, 2017
1 parent b2543f7 commit b9da9c8
Showing 1 changed file with 52 additions and 22 deletions.
74 changes: 52 additions & 22 deletions arch/powerpc/lib/sstep.c
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Original file line number Diff line number Diff line change
Expand Up @@ -103,11 +103,19 @@ static nokprobe_inline int branch_taken(unsigned int instr,
return 1;
}

static nokprobe_inline long address_ok(struct pt_regs *regs, unsigned long ea, int nb)
static nokprobe_inline long address_ok(struct pt_regs *regs,
unsigned long ea, int nb)
{
if (!user_mode(regs))
return 1;
return __access_ok(ea, nb, USER_DS);
if (__access_ok(ea, nb, USER_DS))
return 1;
if (__access_ok(ea, 1, USER_DS))
/* Access overlaps the end of the user region */
regs->dar = USER_DS.seg;
else
regs->dar = ea;
return 0;
}

/*
Expand Down Expand Up @@ -210,7 +218,8 @@ static nokprobe_inline unsigned long byterev_8(unsigned long x)
#endif

static nokprobe_inline int read_mem_aligned(unsigned long *dest,
unsigned long ea, int nb)
unsigned long ea, int nb,
struct pt_regs *regs)
{
int err = 0;
unsigned long x = 0;
Expand All @@ -233,14 +242,17 @@ static nokprobe_inline int read_mem_aligned(unsigned long *dest,
}
if (!err)
*dest = x;
else
regs->dar = ea;
return err;
}

/*
* Copy from userspace to a buffer, using the largest possible
* aligned accesses, up to sizeof(long).
*/
static int nokprobe_inline copy_mem_in(u8 *dest, unsigned long ea, int nb)
static int nokprobe_inline copy_mem_in(u8 *dest, unsigned long ea, int nb,
struct pt_regs *regs)
{
int err = 0;
int c;
Expand Down Expand Up @@ -268,8 +280,10 @@ static int nokprobe_inline copy_mem_in(u8 *dest, unsigned long ea, int nb)
break;
#endif
}
if (err)
if (err) {
regs->dar = ea;
return err;
}
dest += c;
ea += c;
}
Expand All @@ -289,7 +303,7 @@ static nokprobe_inline int read_mem_unaligned(unsigned long *dest,

u.ul = 0;
i = IS_BE ? sizeof(unsigned long) - nb : 0;
err = copy_mem_in(&u.b[i], ea, nb);
err = copy_mem_in(&u.b[i], ea, nb, regs);
if (!err)
*dest = u.ul;
return err;
Expand All @@ -306,13 +320,14 @@ static int read_mem(unsigned long *dest, unsigned long ea, int nb,
if (!address_ok(regs, ea, nb))
return -EFAULT;
if ((ea & (nb - 1)) == 0)
return read_mem_aligned(dest, ea, nb);
return read_mem_aligned(dest, ea, nb, regs);
return read_mem_unaligned(dest, ea, nb, regs);
}
NOKPROBE_SYMBOL(read_mem);

static nokprobe_inline int write_mem_aligned(unsigned long val,
unsigned long ea, int nb)
unsigned long ea, int nb,
struct pt_regs *regs)
{
int err = 0;

Expand All @@ -332,14 +347,17 @@ static nokprobe_inline int write_mem_aligned(unsigned long val,
break;
#endif
}
if (err)
regs->dar = ea;
return err;
}

/*
* Copy from a buffer to userspace, using the largest possible
* aligned accesses, up to sizeof(long).
*/
static int nokprobe_inline copy_mem_out(u8 *dest, unsigned long ea, int nb)
static int nokprobe_inline copy_mem_out(u8 *dest, unsigned long ea, int nb,
struct pt_regs *regs)
{
int err = 0;
int c;
Expand Down Expand Up @@ -367,8 +385,10 @@ static int nokprobe_inline copy_mem_out(u8 *dest, unsigned long ea, int nb)
break;
#endif
}
if (err)
if (err) {
regs->dar = ea;
return err;
}
dest += c;
ea += c;
}
Expand All @@ -387,7 +407,7 @@ static nokprobe_inline int write_mem_unaligned(unsigned long val,

u.ul = val;
i = IS_BE ? sizeof(unsigned long) - nb : 0;
return copy_mem_out(&u.b[i], ea, nb);
return copy_mem_out(&u.b[i], ea, nb, regs);
}

/*
Expand All @@ -400,7 +420,7 @@ static int write_mem(unsigned long val, unsigned long ea, int nb,
if (!address_ok(regs, ea, nb))
return -EFAULT;
if ((ea & (nb - 1)) == 0)
return write_mem_aligned(val, ea, nb);
return write_mem_aligned(val, ea, nb, regs);
return write_mem_unaligned(val, ea, nb, regs);
}
NOKPROBE_SYMBOL(write_mem);
Expand All @@ -422,7 +442,7 @@ static int do_fp_load(int rn, unsigned long ea, int nb, struct pt_regs *regs)

if (!address_ok(regs, ea, nb))
return -EFAULT;
err = copy_mem_in(u.b, ea, nb);
err = copy_mem_in(u.b, ea, nb, regs);
if (err)
return err;
preempt_disable();
Expand Down Expand Up @@ -471,7 +491,7 @@ static int do_fp_store(int rn, unsigned long ea, int nb, struct pt_regs *regs)
u.l[1] = current->thread.TS_FPR(rn);
}
preempt_enable();
return copy_mem_out(u.b, ea, nb);
return copy_mem_out(u.b, ea, nb, regs);
}
NOKPROBE_SYMBOL(do_fp_store);
#endif
Expand All @@ -491,7 +511,7 @@ static nokprobe_inline int do_vec_load(int rn, unsigned long ea,
return -EFAULT;
/* align to multiple of size */
ea &= ~(size - 1);
err = copy_mem_in(&u.b[ea & 0xf], ea, size);
err = copy_mem_in(&u.b[ea & 0xf], ea, size, regs);
if (err)
return err;

Expand Down Expand Up @@ -523,7 +543,7 @@ static nokprobe_inline int do_vec_store(int rn, unsigned long ea,
else
u.v = current->thread.vr_state.vr[rn];
preempt_enable();
return copy_mem_out(&u.b[ea & 0xf], ea, size);
return copy_mem_out(&u.b[ea & 0xf], ea, size, regs);
}
#endif /* CONFIG_ALTIVEC */

Expand Down Expand Up @@ -725,7 +745,7 @@ static nokprobe_inline int do_vsx_load(struct instruction_op *op,
union vsx_reg buf;
int size = GETSIZE(op->type);

if (!address_ok(regs, ea, size) || copy_mem_in(mem, ea, size))
if (!address_ok(regs, ea, size) || copy_mem_in(mem, ea, size, regs))
return -EFAULT;

emulate_vsx_load(op, &buf, mem);
Expand Down Expand Up @@ -776,7 +796,7 @@ static nokprobe_inline int do_vsx_store(struct instruction_op *op,
}
preempt_enable();
emulate_vsx_store(op, &buf, mem);
return copy_mem_out(mem, ea, size);
return copy_mem_out(mem, ea, size, regs);
}
#endif /* CONFIG_VSX */

Expand All @@ -797,8 +817,10 @@ int emulate_dcbz(unsigned long ea, struct pt_regs *regs)
return -EFAULT;
for (i = 0; i < size; i += sizeof(long)) {
err = __put_user(0, (unsigned long __user *) (ea + i));
if (err)
if (err) {
regs->dar = ea;
return err;
}
}
return 0;
}
Expand Down Expand Up @@ -2640,8 +2662,10 @@ int emulate_step(struct pt_regs *regs, unsigned int instr)
err = emulate_dcbz(ea, regs);
break;
}
if (err)
if (err) {
regs->dar = ea;
return 0;
}
goto instr_done;

case LARX:
Expand All @@ -2668,12 +2692,16 @@ int emulate_step(struct pt_regs *regs, unsigned int instr)
break;
case 16:
err = do_lqarx(ea, &regs->gpr[op.reg]);
goto ldst_done;
break;
#endif
default:
return 0;
}
if (!err)
if (err) {
regs->dar = ea;
return 0;
}
if (size < 16)
regs->gpr[op.reg] = val;
goto ldst_done;

Expand Down Expand Up @@ -2711,6 +2739,8 @@ int emulate_step(struct pt_regs *regs, unsigned int instr)
regs->ccr = (regs->ccr & 0x0fffffff) |
(cr & 0xe0000000) |
((regs->xer >> 3) & 0x10000000);
else
regs->dar = ea;
goto ldst_done;

case LOAD:
Expand Down

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