[PATCH 5.15 012/139] parisc/unaligned: Fix fldd and fstd unaligned handlers on 32-bit kernel

Greg Kroah-Hartman
2022-02-28T17:54:10Z

From: Helge Deller <deller@gmx.de>

commit dd2288f4a020d693360e3e8d72f8b9d9c25f5ef6 upstream.

Usually the kernel provides fixup routines to emulate the fldd and fstd
floating-point instructions if they load or store 8-byte from/to a not
natuarally aligned memory location.

On a 32-bit kernel I noticed that those unaligned handlers didn't worked and
instead the application got a SEGV.
While checking the code I found two problems:

First, the OPCODE_FLDD_L and OPCODE_FSTD_L cases were ifdef'ed out by the
CONFIG_PA20 option, and as such those weren't built on a pure 32-bit kernel.
This is now fixed by moving the CONFIG_PA20 #ifdef to prevent the compilation
of OPCODE_LDD_L and OPCODE_FSTD_L only, and handling the fldd and fstd
instructions.

The second problem are two bugs in the 32-bit inline assembly code, where the
wrong registers where used. The calculation of the natural alignment used %2
(vall) instead of %3 (ior), and the first word was stored back to address %1
(valh) instead of %3 (ior).

Signed-off-by: Helge Deller <deller@gmx.de>
Cc: stable@vger.kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
arch/parisc/kernel/unaligned.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)

--- a/arch/parisc/kernel/unaligned.c
+++ b/arch/parisc/kernel/unaligned.c
@@ -397,7 +397,7 @@ static int emulate_std(struct pt_regs *r
__asm__ __volatile__ (
" mtsp %4, %%sr1\n"
" zdep %2, 29, 2, %%r19\n"
-" dep %%r0, 31, 2, %2\n"
+" dep %%r0, 31, 2, %3\n"
" mtsar %%r19\n"
" zvdepi -2, 32, %%r19\n"
"1: ldw 0(%%sr1,%3),%%r20\n"
@@ -409,7 +409,7 @@ static int emulate_std(struct pt_regs *r
" andcm %%r21, %%r19, %%r21\n"
" or %1, %%r20, %1\n"
" or %2, %%r21, %2\n"
-"3: stw %1,0(%%sr1,%1)\n"
+"3: stw %1,0(%%sr1,%3)\n"
"4: stw %%r1,4(%%sr1,%3)\n"
"5: stw %2,8(%%sr1,%3)\n"
" copy %%r0, %0\n"
@@ -596,7 +596,6 @@ void handle_unaligned(struct pt_regs *re
ret = ERR_NOTHANDLED; /* "undefined", but lets kill them. */
break;
}
-#ifdef CONFIG_PA20
switch (regs->iir & OPCODE2_MASK)
{
case OPCODE_FLDD_L:
@@ -607,14 +606,15 @@ void handle_unaligned(struct pt_regs *re
flop=1;
ret = emulate_std(regs, R2(regs->iir),1);
break;
+#ifdef CONFIG_PA20
case OPCODE_LDD_L:
ret = emulate_ldd(regs, R2(regs->iir),0);
break;
case OPCODE_STD_L:
ret = emulate_std(regs, R2(regs->iir),0);
break;
- }
#endif
+ }
switch (regs->iir & OPCODE3_MASK)
{