linux-stable.git/arch/mips/lib/memset.S, branch linux-3.16.y

MIPS: memset: Fix CPU_DADDI_WORKAROUNDS `small_fixup' regression

2018-12-16T22:09:35+00:00

commit 148b9aba99e0bbadf361747d21456e1589015f74 upstream.

Fix a commit 8a8158c85e1e ("MIPS: memset.S: EVA & fault support for
small_memset") regression and remove assembly warnings:

arch/mips/lib/memset.S: Assembler messages:
arch/mips/lib/memset.S:243: Warning: Macro instruction expanded into multiple instructions in a branch delay slot

triggering with the CPU_DADDI_WORKAROUNDS option set and this code:

	PTR_SUBU	a2, t1, a0
	jr		ra
	 PTR_ADDIU	a2, 1

This is because with that option in place the DADDIU instruction, which
the PTR_ADDIU CPP macro expands to, becomes a GAS macro, which in turn
expands to an LI/DADDU (or actually ADDIU/DADDU) sequence:

 13c:	01a4302f 	dsubu	a2,t1,a0
 140:	03e00008 	jr	ra
 144:	24010001 	li	at,1
 148:	00c1302d 	daddu	a2,a2,at
	...

Correct this by switching off the `noreorder' assembly mode and letting
GAS schedule this jump's delay slot, as there is nothing special about
it that would require manual scheduling.  With this change in place
correct code is produced:

 13c:	01a4302f 	dsubu	a2,t1,a0
 140:	24010001 	li	at,1
 144:	03e00008 	jr	ra
 148:	00c1302d 	daddu	a2,a2,at
	...

Signed-off-by: Maciej W. Rozycki 
Signed-off-by: Paul Burton 
Fixes: 8a8158c85e1e ("MIPS: memset.S: EVA & fault support for small_memset")
Patchwork: https://patchwork.linux-mips.org/patch/20833/
Cc: Ralf Baechle 
[bwh: Backported to 3.16: adjust context]
Signed-off-by: Ben Hutchings

MIPS: memset.S: Fix clobber of v1 in last_fixup

2018-10-21T07:45:31+00:00

commit c96eebf07692e53bf4dd5987510d8b550e793598 upstream.

The label .Llast_fixup\@ is jumped to on page fault within the final
byte set loop of memset (on < MIPSR6 architectures). For some reason, in
this fault handler, the v1 register is randomly set to a2 & STORMASK.
This clobbers v1 for the calling function. This can be observed with the
following test code:

static int __init __attribute__((optimize("O0"))) test_clear_user(void)
{
  register int t asm("v1");
  char *test;
  int j, k;

  pr_info("\n\n\nTesting clear_user\n");
  test = vmalloc(PAGE_SIZE);

  for (j = 256; j < 512; j++) {
    t = 0xa5a5a5a5;
    if ((k = clear_user(test + PAGE_SIZE - 256, j)) != j - 256) {
        pr_err("clear_user (%px %d) returned %d\n", test + PAGE_SIZE - 256, j, k);
    }
    if (t != 0xa5a5a5a5) {
       pr_err("v1 was clobbered to 0x%x!\n", t);
    }
  }

  return 0;
}
late_initcall(test_clear_user);

Which demonstrates that v1 is indeed clobbered (MIPS64):

Testing clear_user
v1 was clobbered to 0x1!
v1 was clobbered to 0x2!
v1 was clobbered to 0x3!
v1 was clobbered to 0x4!
v1 was clobbered to 0x5!
v1 was clobbered to 0x6!
v1 was clobbered to 0x7!

Since the number of bytes that could not be set is already contained in
a2, the andi placing a value in v1 is not necessary and actively
harmful in clobbering v1.

Reported-by: James Hogan 
Signed-off-by: Matt Redfearn 
Cc: Ralf Baechle 
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/19109/
Signed-off-by: James Hogan 
Signed-off-by: Ben Hutchings

MIPS: memset.S: Fix return of __clear_user from Lpartial_fixup

2018-10-21T07:45:30+00:00

commit daf70d89f80c6e1772233da9e020114b1254e7e0 upstream.

The __clear_user function is defined to return the number of bytes that
could not be cleared. From the underlying memset / bzero implementation
this means setting register a2 to that number on return. Currently if a
page fault is triggered within the memset_partial block, the value
loaded into a2 on return is meaningless.

The label .Lpartial_fixup\@ is jumped to on page fault. In order to work
out how many bytes failed to copy, the exception handler should find how
many bytes left in the partial block (andi a2, STORMASK), add that to
the partial block end address (a2), and subtract the faulting address to
get the remainder. Currently it incorrectly subtracts the partial block
start address (t1), which has additionally been clobbered to generate a
jump target in memset_partial. Fix this by adding the block end address
instead.

This issue was found with the following test code:
      int j, k;
      for (j = 0; j < 512; j++) {
        if ((k = clear_user(NULL, j)) != j) {
           pr_err("clear_user (NULL %d) returned %d\n", j, k);
        }
      }
Which now passes on Creator Ci40 (MIPS32) and Cavium Octeon II (MIPS64).

Suggested-by: James Hogan 
Signed-off-by: Matt Redfearn 
Cc: Ralf Baechle 
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/19108/
Signed-off-by: James Hogan 
Signed-off-by: Ben Hutchings

MIPS: memset.S: EVA & fault support for small_memset

2018-10-21T07:45:28+00:00

commit 8a8158c85e1e774a44fbe81106fa41138580dfd1 upstream.

The MIPS kernel memset / bzero implementation includes a small_memset
branch which is used when the region to be set is smaller than a long (4
bytes on 32bit, 8 bytes on 64bit). The current small_memset
implementation uses a simple store byte loop to write the destination.
There are 2 issues with this implementation:

1. When EVA mode is active, user and kernel address spaces may overlap.
Currently the use of the sb instruction means kernel mode addressing is
always used and an intended write to userspace may actually overwrite
some critical kernel data.

2. If the write triggers a page fault, for example by calling
__clear_user(NULL, 2), instead of gracefully handling the fault, an OOPS
is triggered.

Fix these issues by replacing the sb instruction with the EX() macro,
which will emit EVA compatible instuctions as required. Additionally
implement a fault fixup for small_memset which sets a2 to the number of
bytes that could not be cleared (as defined by __clear_user).

Reported-by: Chuanhua Lei 
Signed-off-by: Matt Redfearn 
Cc: Ralf Baechle 
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/18975/
Signed-off-by: James Hogan 
Signed-off-by: Ben Hutchings

MIPS: uaccess: Take EVA into account in [__]clear_user

2016-01-25T10:43:31+00:00

commit d6a428fb583738ad685c91a684748cdee7b2a05f upstream.

__clear_user() (and clear_user() which uses it), always access the user
mode address space, which results in EVA store instructions when EVA is
enabled even if the current user address limit is KERNEL_DS.

Fix this by adding a new symbol __bzero_kernel for the normal kernel
address space bzero in EVA mode, and call that from __clear_user() if
eva_kernel_access().

Signed-off-by: James Hogan 
Cc: Markos Chandras 
Cc: Paul Burton 
Cc: Leonid Yegoshin 
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/10844/
Signed-off-by: Ralf Baechle 
[james.hogan@imgtec.com: backport]
Signed-off-by: James Hogan 
Signed-off-by: Luis Henriques

MIPS: lib: memset: Add EVA support for the __bzero function.

2014-03-26T22:09:15+00:00

Build the __bzero function using the EVA load/store instructions
when operating in the EVA mode. This function is only used when
accessing user code so there is no need to build two distinct symbols
for user and kernel operations respectively.

Signed-off-by: Markos Chandras

MIPS: lib: memset: Use macro to build the __bzero symbol

2014-03-26T22:09:15+00:00

Build the __bzero symbol using a macor. In EVA mode we will
need to use similar code to do the userspace load operations so
it is better if we use a macro to avoid code duplications.

Signed-off-by: Markos Chandras

MIPS: lib: memset: Whitespace fixes

2014-03-26T22:09:14+00:00

Signed-off-by: Markos Chandras

MIPS: microMIPS: Optimise 'memset' core library function.

2013-05-09T15:55:19+00:00

Optimise 'memset' to use microMIPS instructions and/or optimisations
for binary size reduction. When the microMIPS ISA is not being used,
the library function compiles to the original binary code.

Signed-off-by: Steven J. Hill

MIPS: Whitespace cleanup.

2013-02-01T09:00:22+00:00

Having received another series of whitespace patches I decided to do this
once and for all rather than dealing with this kind of patches trickling
in forever.

Signed-off-by: Ralf Baechle