[PATCH 4.4 61/73] MIPS: Fix pre-r6 emulation FPU initialisation

[PATCH 4.4 61/73] MIPS: Fix pre-r6 emulation FPU initialisation

[Greg Kroah-Hartman]

4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Paul Burton <paul.burton@imgtec.com>

commit 7e956304eb8a285304a78582e4537e72c6365f20 upstream.

In the mipsr2_decoder() function, used to emulate pre-MIPSr6
instructions that were removed in MIPSr6, the init_fpu() function is
called if a removed pre-MIPSr6 floating point instruction is the first
floating point instruction used by the task. However, init_fpu()
performs varous actions that rely upon not being migrated. For example
in the most basic case it sets the coprocessor 0 Status.CU1 bit to
enable the FPU & then loads FP register context into the FPU registers.
If the task were to migrate during this time, it may end up attempting
to load FP register context on a different CPU where it hasn't set the
CU1 bit, leading to errors such as:

    do_cpu invoked from kernel context![#2]:
    CPU: 2 PID: 7338 Comm: fp-prctl Tainted: G      D         4.7.0-00424-g49b0c82 #2
    task: 838e4000 ti: 88d38000 task.ti: 88d38000
    $ 0   : 00000000 00000001 ffffffff 88d3fef8
    $ 4   : 838e4000 88d38004 00000000 00000001
    $ 8   : 3400fc01 801f8020 808e9100 24000000
    $12   : dbffffff 807b69d8 807b0000 00000000
    $16   : 00000000 80786150 00400fc4 809c0398
    $20   : 809c0338 0040273c 88d3ff28 808e9d30
    $24   : 808e9d30 00400fb4
    $28   : 88d38000 88d3fe88 00000000 8011a2ac
    Hi    : 0040273c
    Lo    : 88d3ff28
    epc   : 80114178 _restore_fp+0x10/0xa0
    ra    : 8011a2ac mipsr2_decoder+0xd5c/0x1660
    Status: 1400fc03	KERNEL EXL IE
    Cause : 1080002c (ExcCode 0b)
    PrId  : 0001a920 (MIPS I6400)
    Modules linked in:
    Process fp-prctl (pid: 7338, threadinfo=88d38000, task=838e4000, tls=766527d0)
    Stack : 00000000 00000000 00000000 88d3fe98 00000000 00000000 809c0398 809c0338
    	  808e9100 00000000 88d3ff28 00400fc4 00400fc4 0040273c 7fb69e18 004a0000
    	  004a0000 004a0000 7664add0 8010de18 00000000 00000000 88d3fef8 88d3ff28
    	  808e9100 00000000 766527d0 8010e534 000c0000 85755000 8181d580 00000000
    	  00000000 00000000 004a0000 00000000 766527d0 7fb69e18 004a0000 80105c20
    	  ...
    Call Trace:
    [<80114178>] _restore_fp+0x10/0xa0
    [<8011a2ac>] mipsr2_decoder+0xd5c/0x1660
    [<8010de18>] do_ri+0x90/0x6b8
    [<80105c20>] ret_from_exception+0x0/0x10

Fix this by disabling preemption around the call to init_fpu(), ensuring
that it starts & completes on one CPU.

Signed-off-by: Paul Burton <paul.burton@imgtec.com>
Fixes: b0a668fb2038 ("MIPS: kernel: mips-r2-to-r6-emul: Add R2 emulator for MIPS R6")
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/14305/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 arch/mips/kernel/mips-r2-to-r6-emul.c |    2 ++
 1 file changed, 2 insertions(+)

--- a/arch/mips/kernel/mips-r2-to-r6-emul.c
+++ b/arch/mips/kernel/mips-r2-to-r6-emul.c
@@ -1164,7 +1164,9 @@ fpu_emul:
 		regs->regs[31] = r31;
 		regs->cp0_epc = epc;
 		if (!used_math()) {     /* First time FPU user.  */
+			preempt_disable();
 			err = init_fpu();
+			preempt_enable();
 			set_used_math();
 		}
 		lose_fpu(1);    /* Save FPU state for the emulator. */

[PATCH 4.4 63/73] MIPS: vDSO: Fix Malta EVA mapping to vDSO page structs

[Greg Kroah-Hartman]

4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: James Hogan <james.hogan@imgtec.com>

commit 554af0c396380baf416f54c439b99b495180b2f4 upstream.

The page structures associated with the vDSO pages in the kernel image
are calculated using virt_to_page(), which uses __pa() under the hood to
find the pfn associated with the virtual address. The vDSO data pointers
however point to kernel symbols, so __pa_symbol() should really be used
instead.

Since there is no equivalent to virt_to_page() which uses __pa_symbol(),
fix init_vdso_image() to work directly with pfns, calculated with
__phys_to_pfn(__pa_symbol(...)).

This issue broke the Malta Enhanced Virtual Addressing (EVA)
configuration which has a non-default implementation of __pa_symbol().
This is because it uses a physical alias so that the kernel executes
from KSeg0 (VA 0x80000000 -> PA 0x00000000), while RAM is provided to
the kernel in the KUSeg range (VA 0x00000000 -> PA 0x80000000) which
uses the same underlying RAM.

Since there are no page structures associated with the low physical
address region, some arbitrary kernel memory would be interpreted as a
page structure for the vDSO pages and badness ensues.

Fixes: ebb5e78cc634 ("MIPS: Initial implementation of a VDSO")
Signed-off-by: James Hogan <james.hogan@imgtec.com>
Cc: Leonid Yegoshin <leonid.yegoshin@imgtec.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/14229/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 arch/mips/kernel/vdso.c |    8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

--- a/arch/mips/kernel/vdso.c
+++ b/arch/mips/kernel/vdso.c
@@ -39,16 +39,16 @@ static struct vm_special_mapping vdso_vv
 static void __init init_vdso_image(struct mips_vdso_image *image)
 {
 	unsigned long num_pages, i;
+	unsigned long data_pfn;
 
 	BUG_ON(!PAGE_ALIGNED(image->data));
 	BUG_ON(!PAGE_ALIGNED(image->size));
 
 	num_pages = image->size / PAGE_SIZE;
 
-	for (i = 0; i < num_pages; i++) {
-		image->mapping.pages[i] =
-			virt_to_page(image->data + (i * PAGE_SIZE));
-	}
+	data_pfn = __phys_to_pfn(__pa_symbol(image->data));
+	for (i = 0; i < num_pages; i++)
+		image->mapping.pages[i] = pfn_to_page(data_pfn + i);
 }
 
 static int __init init_vdso(void)

[PATCH 4.4 64/73] MIPS: Remove compact branch policy Kconfig entries

[Greg Kroah-Hartman]

4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Paul Burton <paul.burton@imgtec.com>

commit b03c1e3b8eed9026733c473071d1f528358a0e50 upstream.

Commit c1a0e9bc885d ("MIPS: Allow compact branch policy to be changed")
added Kconfig entries allowing for the compact branch policy used by the
compiler for MIPSr6 kernels to be specified. This can be useful for
debugging, particularly in systems where compact branches have recently
been introduced.

Unfortunately mainline gcc 5.x supports MIPSr6 but not the
-mcompact-branches compiler flag, leading to MIPSr6 kernels failing to
build with gcc 5.x with errors such as:

  mipsel-linux-gnu-gcc: error: unrecognized command line option '-mcompact-branches=optimal'
  make[2]: *** [kernel/bounds.s] Error 1

Fixing this by hiding the Kconfig entry behind another seems to be more
hassle than it's worth, as MIPSr6 & compact branches have been around
for a while now and if policy does need to be set for debug it can be
done easily enough with KCFLAGS. Therefore remove the compact branch
policy Kconfig entries & their handling in the Makefile.

This reverts commit c1a0e9bc885d ("MIPS: Allow compact branch policy to
be changed").

Signed-off-by: Paul Burton <paul.burton@imgtec.com>
Reported-by: kbuild test robot <fengguang.wu@intel.com>
Fixes: c1a0e9bc885d ("MIPS: Allow compact branch policy to be changed")
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/14241/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 arch/mips/Kconfig.debug |   36 ------------------------------------
 arch/mips/Makefile      |    4 ----
 2 files changed, 40 deletions(-)

--- a/arch/mips/Kconfig.debug
+++ b/arch/mips/Kconfig.debug
@@ -113,42 +113,6 @@ config SPINLOCK_TEST
 	help
 	  Add several files to the debugfs to test spinlock speed.
 
-if CPU_MIPSR6
-
-choice
-	prompt "Compact branch policy"
-	default MIPS_COMPACT_BRANCHES_OPTIMAL
-
-config MIPS_COMPACT_BRANCHES_NEVER
-	bool "Never (force delay slot branches)"
-	help
-	  Pass the -mcompact-branches=never flag to the compiler in order to
-	  force it to always emit branches with delay slots, and make no use
-	  of the compact branch instructions introduced by MIPSr6. This is
-	  useful if you suspect there may be an issue with compact branches in
-	  either the compiler or the CPU.
-
-config MIPS_COMPACT_BRANCHES_OPTIMAL
-	bool "Optimal (use where beneficial)"
-	help
-	  Pass the -mcompact-branches=optimal flag to the compiler in order for
-	  it to make use of compact branch instructions where it deems them
-	  beneficial, and use branches with delay slots elsewhere. This is the
-	  default compiler behaviour, and should be used unless you have a
-	  reason to choose otherwise.
-
-config MIPS_COMPACT_BRANCHES_ALWAYS
-	bool "Always (force compact branches)"
-	help
-	  Pass the -mcompact-branches=always flag to the compiler in order to
-	  force it to always emit compact branches, making no use of branch
-	  instructions with delay slots. This can result in more compact code
-	  which may be beneficial in some scenarios.
-
-endchoice
-
-endif # CPU_MIPSR6
-
 config SCACHE_DEBUGFS
 	bool "L2 cache debugfs entries"
 	depends on DEBUG_FS
--- a/arch/mips/Makefile
+++ b/arch/mips/Makefile
@@ -204,10 +204,6 @@ toolchain-msa				:= $(call cc-option-yn,
 cflags-$(toolchain-msa)			+= -DTOOLCHAIN_SUPPORTS_MSA
 endif
 
-cflags-$(CONFIG_MIPS_COMPACT_BRANCHES_NEVER)	+= -mcompact-branches=never
-cflags-$(CONFIG_MIPS_COMPACT_BRANCHES_OPTIMAL)	+= -mcompact-branches=optimal
-cflags-$(CONFIG_MIPS_COMPACT_BRANCHES_ALWAYS)	+= -mcompact-branches=always
-
 #
 # Firmware support
 #

[PATCH 4.4 65/73] MIPS: Avoid a BUG warning during prctl(PR_SET_FP_MODE, ...)

[Greg Kroah-Hartman]

4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Marcin Nowakowski <marcin.nowakowski@imgtec.com>

commit b244614a60ab7ce54c12a9cbe15cfbf8d79d0967 upstream.

cpu_has_fpu macro uses smp_processor_id() and is currently executed
with preemption enabled, that triggers the warning at runtime.

It is assumed throughout the kernel that if any CPU has an FPU, then all
CPUs would have an FPU as well, so it is safe to perform the check with
preemption enabled - change the code to use raw_ variant of the check to
avoid the warning.

Signed-off-by: Marcin Nowakowski <marcin.nowakowski@imgtec.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/14125/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 arch/mips/kernel/process.c |    8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

--- a/arch/mips/kernel/process.c
+++ b/arch/mips/kernel/process.c
@@ -593,14 +593,14 @@ int mips_set_process_fp_mode(struct task
 		return -EOPNOTSUPP;
 
 	/* Avoid inadvertently triggering emulation */
-	if ((value & PR_FP_MODE_FR) && cpu_has_fpu &&
-	    !(current_cpu_data.fpu_id & MIPS_FPIR_F64))
+	if ((value & PR_FP_MODE_FR) && raw_cpu_has_fpu &&
+	    !(raw_current_cpu_data.fpu_id & MIPS_FPIR_F64))
 		return -EOPNOTSUPP;
-	if ((value & PR_FP_MODE_FRE) && cpu_has_fpu && !cpu_has_fre)
+	if ((value & PR_FP_MODE_FRE) && raw_cpu_has_fpu && !cpu_has_fre)
 		return -EOPNOTSUPP;
 
 	/* FR = 0 not supported in MIPS R6 */
-	if (!(value & PR_FP_MODE_FR) && cpu_has_fpu && cpu_has_mips_r6)
+	if (!(value & PR_FP_MODE_FR) && raw_cpu_has_fpu && cpu_has_mips_r6)
 		return -EOPNOTSUPP;
 
 	/* Proceed with the mode switch */

[PATCH 4.4 66/73] MIPS: Add a missing ".set pop" in an early commit

[Greg Kroah-Hartman]

4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Huacai Chen <chenhc@lemote.com>

commit 3cbc6fc9c99f1709203711f125bc3b79487aba06 upstream.

Commit 842dfc11ea9a21 ("MIPS: Fix build with binutils 2.24.51+") missing
a ".set pop" in macro fpu_restore_16even, so add it.

Signed-off-by: Huacai Chen <chenhc@lemote.com>
Acked-by: Manuel Lauss <manuel.lauss@gmail.com>
Cc: Steven J . Hill <Steven.Hill@caviumnetworks.com>
Cc: Fuxin Zhang <zhangfx@lemote.com>
Cc: Zhangjin Wu <wuzhangjin@gmail.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/14210/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 arch/mips/include/asm/asmmacro.h |    1 +
 1 file changed, 1 insertion(+)

--- a/arch/mips/include/asm/asmmacro.h
+++ b/arch/mips/include/asm/asmmacro.h
@@ -135,6 +135,7 @@
 	ldc1	$f28, THREAD_FPR28(\thread)
 	ldc1	$f30, THREAD_FPR30(\thread)
 	ctc1	\tmp, fcr31
+	.set	pop
 	.endm
 
 	.macro	fpu_restore_16odd thread

[PATCH 4.4 67/73] MIPS: paravirt: Fix undefined reference to smp_bootstrap

[Greg Kroah-Hartman]

4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Matt Redfearn <matt.redfearn@imgtec.com>

commit 951c39cd3bc0aedf67fbd8fb4b9380287e6205d1 upstream.

If the paravirt machine is compiles without CONFIG_SMP, the following
linker error occurs

arch/mips/kernel/head.o: In function `kernel_entry':
(.ref.text+0x10): undefined reference to `smp_bootstrap'

due to the kernel entry macro always including SMP startup code.
Wrap this code in CONFIG_SMP to fix the error.

Signed-off-by: Matt Redfearn <matt.redfearn@imgtec.com>
Cc: linux-mips@linux-mips.org
Cc: linux-kernel@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/14212/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 arch/mips/include/asm/mach-paravirt/kernel-entry-init.h |    2 ++
 1 file changed, 2 insertions(+)

--- a/arch/mips/include/asm/mach-paravirt/kernel-entry-init.h
+++ b/arch/mips/include/asm/mach-paravirt/kernel-entry-init.h
@@ -11,11 +11,13 @@
 #define CP0_EBASE $15, 1
 
 	.macro  kernel_entry_setup
+#ifdef CONFIG_SMP
 	mfc0	t0, CP0_EBASE
 	andi	t0, t0, 0x3ff		# CPUNum
 	beqz	t0, 1f
 	# CPUs other than zero goto smp_bootstrap
 	j	smp_bootstrap
+#endif /* CONFIG_SMP */
 
 1:
 	.endm