* [PATCH v2 0/3] Fix Thumb-2 undef handling for mixed-arch kernels
@ 2011-08-18 17:01 Dave Martin
2011-08-18 17:01 ` [PATCH v2 1/3] ARM: Make cpu_architecture into a global variable Dave Martin
` (3 more replies)
0 siblings, 4 replies; 9+ messages in thread
From: Dave Martin @ 2011-08-18 17:01 UTC (permalink / raw)
To: linux-arm-kernel
In kernels which support v6 and v7 platforms in a single binary
such as omap2plus_defconfig for example, undefined instruction
exceptions taken on Thumb instructions are not processed correctly,
because the kernel assumes at build-time that Thumb-2 won't be
supported in userspace.
This series implements a workaround, by allowing the __und_usr
handler to check the CPU architecture at runtime, in affected
kernels.
Changes since v1:
* Because cpu_architecture() is no longer trivial, it has been
moveed back out of line, into setup.c.
Changes since RFC:
* Renamed the global variable to __cpu_architecture and provided
cpu_architecture() as in inline function in <asm/system.h>.
This brings back the old API, but more efficiently.
* Dropped all the patches required to handle the reverted API
change.
* cpu_architecture is now declared __pure, which may lead to
slightly more efficient code in some cases.
* Added BUG_ON() to cpu_architecture() so that if
__cpu_architecture is not set early enough, it gets noticed.
Thanks to Tixy and Nicolas Pitre for their helpful feedback which
helped slim down this series.
Dave Martin (3):
ARM: Make cpu_architecture into a global variable
ARM: entry: Remove unnecessary masking when decoding Thumb-2
instructions
ARM: entry: Fix Thumb-2 undef handling for multi-CPU kernels
arch/arm/include/asm/system.h | 3 +-
arch/arm/kernel/entry-armv.S | 44 ++++++++++++++++++++++++++++++++++++----
arch/arm/kernel/setup.c | 20 +++++++++++++++++-
3 files changed, 60 insertions(+), 7 deletions(-)
--
1.7.4.1
^ permalink raw reply [flat|nested] 9+ messages in thread
* [PATCH v2 1/3] ARM: Make cpu_architecture into a global variable
2011-08-18 17:01 [PATCH v2 0/3] Fix Thumb-2 undef handling for mixed-arch kernels Dave Martin
@ 2011-08-18 17:01 ` Dave Martin
2011-08-18 17:01 ` [PATCH v2 2/3] ARM: entry: Remove unnecessary masking when decoding Thumb-2 instructions Dave Martin
` (2 subsequent siblings)
3 siblings, 0 replies; 9+ messages in thread
From: Dave Martin @ 2011-08-18 17:01 UTC (permalink / raw)
To: linux-arm-kernel
The CPU architecture really should not be changing at runtime, so
make it a global variable instead of a function.
The cpu_architecture() function declared in <asm/system.h> remains
the correct way to read this variable from C code.
Signed-off-by: Dave Martin <dave.martin@linaro.org>
---
arch/arm/include/asm/system.h | 3 ++-
arch/arm/kernel/setup.c | 20 +++++++++++++++++++-
2 files changed, 21 insertions(+), 2 deletions(-)
diff --git a/arch/arm/include/asm/system.h b/arch/arm/include/asm/system.h
index 832888d..4adf71b 100644
--- a/arch/arm/include/asm/system.h
+++ b/arch/arm/include/asm/system.h
@@ -57,6 +57,7 @@
#ifndef __ASSEMBLY__
+#include <linux/compiler.h>
#include <linux/linkage.h>
#include <linux/irqflags.h>
@@ -104,7 +105,7 @@ struct mm_struct;
extern void show_pte(struct mm_struct *mm, unsigned long addr);
extern void __show_regs(struct pt_regs *);
-extern int cpu_architecture(void);
+extern int __pure cpu_architecture(void);
extern void cpu_init(void);
void arm_machine_restart(char mode, const char *cmd);
diff --git a/arch/arm/kernel/setup.c b/arch/arm/kernel/setup.c
index 70bca64..1f11472 100644
--- a/arch/arm/kernel/setup.c
+++ b/arch/arm/kernel/setup.c
@@ -29,6 +29,8 @@
#include <linux/fs.h>
#include <linux/proc_fs.h>
#include <linux/memblock.h>
+#include <linux/bug.h>
+#include <linux/compiler.h>
#include <asm/unified.h>
#include <asm/cpu.h>
@@ -42,6 +44,7 @@
#include <asm/cacheflush.h>
#include <asm/cachetype.h>
#include <asm/tlbflush.h>
+#include <asm/system.h>
#include <asm/prom.h>
#include <asm/mach/arch.h>
@@ -115,6 +118,13 @@ struct outer_cache_fns outer_cache __read_mostly;
EXPORT_SYMBOL(outer_cache);
#endif
+/*
+ * Cached cpu_architecture() result for use by assembler code.
+ * C code should use the cpu_architecture() function instead of accessing this
+ * variable directly.
+ */
+int __cpu_architecture __read_mostly = CPU_ARCH_UNKNOWN;
+
struct stack {
u32 irq[3];
u32 abt[3];
@@ -210,7 +220,7 @@ static const char *proc_arch[] = {
"?(17)",
};
-int cpu_architecture(void)
+static int __get_cpu_architecture(void)
{
int cpu_arch;
@@ -243,6 +253,13 @@ int cpu_architecture(void)
return cpu_arch;
}
+int __pure cpu_architecture(void)
+{
+ BUG_ON(__cpu_architecture == CPU_ARCH_UNKNOWN);
+
+ return __cpu_architecture;
+}
+
static int cpu_has_aliasing_icache(unsigned int arch)
{
int aliasing_icache;
@@ -413,6 +430,7 @@ static void __init setup_processor(void)
}
cpu_name = list->cpu_name;
+ __cpu_architecture = __get_cpu_architecture();
#ifdef MULTI_CPU
processor = *list->proc;
--
1.7.4.1
^ permalink raw reply related [flat|nested] 9+ messages in thread
* [PATCH v2 2/3] ARM: entry: Remove unnecessary masking when decoding Thumb-2 instructions
2011-08-18 17:01 [PATCH v2 0/3] Fix Thumb-2 undef handling for mixed-arch kernels Dave Martin
2011-08-18 17:01 ` [PATCH v2 1/3] ARM: Make cpu_architecture into a global variable Dave Martin
@ 2011-08-18 17:01 ` Dave Martin
2011-08-18 17:01 ` [PATCH v2 3/3] ARM: entry: Fix Thumb-2 undef handling for multi-CPU kernels Dave Martin
2011-08-18 22:29 ` [PATCH v2 0/3] Fix Thumb-2 undef handling for mixed-arch kernels Russell King - ARM Linux
3 siblings, 0 replies; 9+ messages in thread
From: Dave Martin @ 2011-08-18 17:01 UTC (permalink / raw)
To: linux-arm-kernel
When testing whether a Thumb-2 instruction is 32 bits long or not,
the masking done in order to test bits 11-15 of the first
instruction halfword won't affect the result of the comparison, so
remove it.
Signed-off-by: Dave Martin <dave.martin@linaro.org>
Reviewed-by: Jon Medhurst <tixy@yxit.co.uk>
Acked-by: Nicolas Pitre <nicolas.pitre@linaro.org>
---
arch/arm/kernel/entry-armv.S | 6 ++----
1 files changed, 2 insertions(+), 4 deletions(-)
diff --git a/arch/arm/kernel/entry-armv.S b/arch/arm/kernel/entry-armv.S
index a87cbf8..b7236d4 100644
--- a/arch/arm/kernel/entry-armv.S
+++ b/arch/arm/kernel/entry-armv.S
@@ -262,8 +262,7 @@ __und_svc:
ldr r0, [r4, #-4]
#else
ldrh r0, [r4, #-2] @ Thumb instruction at LR - 2
- and r9, r0, #0xf800
- cmp r9, #0xe800 @ 32-bit instruction if xx >= 0
+ cmp r0, #0xe800 @ 32-bit instruction if xx >= 0
ldrhhs r9, [r4] @ bottom 16 bits
orrhs r0, r9, r0, lsl #16
#endif
@@ -445,8 +444,7 @@ __und_usr:
ARM( ldrht r5, [r4], #2 )
THUMB( ldrht r5, [r4] )
THUMB( add r4, r4, #2 )
- and r0, r5, #0xf800 @ mask bits 111x x... .... ....
- cmp r0, #0xe800 @ 32bit instruction if xx != 0
+ cmp r5, #0xe800 @ 32bit instruction if xx != 0
blo __und_usr_unknown
3: ldrht r0, [r4]
add r2, r2, #2 @ r2 is PC + 2, make it PC + 4
--
1.7.4.1
^ permalink raw reply related [flat|nested] 9+ messages in thread
* [PATCH v2 3/3] ARM: entry: Fix Thumb-2 undef handling for multi-CPU kernels
2011-08-18 17:01 [PATCH v2 0/3] Fix Thumb-2 undef handling for mixed-arch kernels Dave Martin
2011-08-18 17:01 ` [PATCH v2 1/3] ARM: Make cpu_architecture into a global variable Dave Martin
2011-08-18 17:01 ` [PATCH v2 2/3] ARM: entry: Remove unnecessary masking when decoding Thumb-2 instructions Dave Martin
@ 2011-08-18 17:01 ` Dave Martin
2011-08-18 22:29 ` [PATCH v2 0/3] Fix Thumb-2 undef handling for mixed-arch kernels Russell King - ARM Linux
3 siblings, 0 replies; 9+ messages in thread
From: Dave Martin @ 2011-08-18 17:01 UTC (permalink / raw)
To: linux-arm-kernel
When v6 and >=v7 boards are supported in the same kernel, the
__und_usr code currently makes a build-time assumption that Thumb-2
instructions occurring in userspace don't need to be supported.
Strictly speaking this is incorrect.
This patch fixes the above case by doing a run-time check on the
CPU architecture in these cases. This only affects kernels which
support v6 and >=v7 CPUs together: plain v6 and plain v7 kernels
are unaffected.
Signed-off-by: Dave Martin <dave.martin@linaro.org>
Reviewed-by: Jon Medhurst <tixy@yxit.co.uk>
---
arch/arm/kernel/entry-armv.S | 38 +++++++++++++++++++++++++++++++++++++-
1 files changed, 37 insertions(+), 1 deletions(-)
diff --git a/arch/arm/kernel/entry-armv.S b/arch/arm/kernel/entry-armv.S
index b7236d4..9ad50c4 100644
--- a/arch/arm/kernel/entry-armv.S
+++ b/arch/arm/kernel/entry-armv.S
@@ -24,6 +24,7 @@
#include <asm/unwind.h>
#include <asm/unistd.h>
#include <asm/tls.h>
+#include <asm/system.h>
#include "entry-header.S"
#include <asm/entry-macro-multi.S>
@@ -439,7 +440,27 @@ __und_usr:
#endif
beq call_fpe
@ Thumb instruction
-#if __LINUX_ARM_ARCH__ >= 7
+#if CONFIG_ARM_THUMB && __LINUX_ARM_ARCH__ >= 6 && CONFIG_CPU_V7
+/*
+ * Thumb-2 instruction handling. Note that because pre-v6 and >= v6 platforms
+ * can never be supported in a single kernel, this code is not applicable at
+ * all when __LINUX_ARM_ARCH__ < 6. This allows simplifying assumptions to be
+ * made about .arch directives.
+ */
+#if __LINUX_ARM_ARCH__ < 7
+/* If the target CPU may not be Thumb-2-capable, a run-time check is needed: */
+#define NEED_CPU_ARCHITECTURE
+ ldr r5, .LCcpu_architecture
+ ldr r5, [r5]
+ cmp r5, #CPU_ARCH_ARMv7
+ blo __und_usr_unknown
+/*
+ * The following code won't get run unless the running CPU really is v7, so
+ * coding round the lack of ldrht on older arches is pointless. Temporarily
+ * override the assembler target arch with the minimum required instead:
+ */
+ .arch armv6t2
+#endif
2:
ARM( ldrht r5, [r4], #2 )
THUMB( ldrht r5, [r4] )
@@ -449,7 +470,16 @@ __und_usr:
3: ldrht r0, [r4]
add r2, r2, #2 @ r2 is PC + 2, make it PC + 4
orr r0, r0, r5, lsl #16
+
+#if __LINUX_ARM_ARCH__ < 7
+/* If the target arch was overridden, change it back: */
+#ifdef CONFIG_CPU_32v6K
+ .arch armv6k
#else
+ .arch armv6
+#endif
+#endif /* __LINUX_ARM_ARCH__ < 7 */
+#else /* !(CONFIG_ARM_THUMB && __LINUX_ARM_ARCH__ >= 6 && CONFIG_CPU_V7) */
b __und_usr_unknown
#endif
UNWIND(.fnend )
@@ -576,6 +606,12 @@ call_fpe:
movw_pc lr @ CP#14 (Debug)
movw_pc lr @ CP#15 (Control)
+#ifdef NEED_CPU_ARCHITECTURE
+ .align 2
+.LCcpu_architecture:
+ .word __cpu_architecture
+#endif
+
#ifdef CONFIG_NEON
.align 6
--
1.7.4.1
^ permalink raw reply related [flat|nested] 9+ messages in thread
* [PATCH v2 0/3] Fix Thumb-2 undef handling for mixed-arch kernels
2011-08-18 17:01 [PATCH v2 0/3] Fix Thumb-2 undef handling for mixed-arch kernels Dave Martin
` (2 preceding siblings ...)
2011-08-18 17:01 ` [PATCH v2 3/3] ARM: entry: Fix Thumb-2 undef handling for multi-CPU kernels Dave Martin
@ 2011-08-18 22:29 ` Russell King - ARM Linux
2011-08-19 8:44 ` Tixy
2011-08-19 9:00 ` Dave Martin
3 siblings, 2 replies; 9+ messages in thread
From: Russell King - ARM Linux @ 2011-08-18 22:29 UTC (permalink / raw)
To: linux-arm-kernel
On Thu, Aug 18, 2011 at 06:01:51PM +0100, Dave Martin wrote:
> In kernels which support v6 and v7 platforms in a single binary
> such as omap2plus_defconfig for example, undefined instruction
> exceptions taken on Thumb instructions are not processed correctly,
> because the kernel assumes at build-time that Thumb-2 won't be
> supported in userspace.
Unless there's any further comments from anyone, I think this is now
ready. Thanks.
^ permalink raw reply [flat|nested] 9+ messages in thread
* [PATCH v2 0/3] Fix Thumb-2 undef handling for mixed-arch kernels
2011-08-18 22:29 ` [PATCH v2 0/3] Fix Thumb-2 undef handling for mixed-arch kernels Russell King - ARM Linux
@ 2011-08-19 8:44 ` Tixy
2011-08-19 9:10 ` Dave Martin
2011-08-19 9:00 ` Dave Martin
1 sibling, 1 reply; 9+ messages in thread
From: Tixy @ 2011-08-19 8:44 UTC (permalink / raw)
To: linux-arm-kernel
On Thu, 2011-08-18 at 23:29 +0100, Russell King - ARM Linux wrote:
> On Thu, Aug 18, 2011 at 06:01:51PM +0100, Dave Martin wrote:
> > In kernels which support v6 and v7 platforms in a single binary
> > such as omap2plus_defconfig for example, undefined instruction
> > exceptions taken on Thumb instructions are not processed correctly,
> > because the kernel assumes at build-time that Thumb-2 won't be
> > supported in userspace.
>
> Unless there's any further comments from anyone, I think this is now
> ready. Thanks.
I've no further comments.
^ permalink raw reply [flat|nested] 9+ messages in thread
* [PATCH v2 0/3] Fix Thumb-2 undef handling for mixed-arch kernels
2011-08-18 22:29 ` [PATCH v2 0/3] Fix Thumb-2 undef handling for mixed-arch kernels Russell King - ARM Linux
2011-08-19 8:44 ` Tixy
@ 2011-08-19 9:00 ` Dave Martin
1 sibling, 0 replies; 9+ messages in thread
From: Dave Martin @ 2011-08-19 9:00 UTC (permalink / raw)
To: linux-arm-kernel
On Thu, Aug 18, 2011 at 11:29:06PM +0100, Russell King - ARM Linux wrote:
> On Thu, Aug 18, 2011 at 06:01:51PM +0100, Dave Martin wrote:
> > In kernels which support v6 and v7 platforms in a single binary
> > such as omap2plus_defconfig for example, undefined instruction
> > exceptions taken on Thumb instructions are not processed correctly,
> > because the kernel assumes at build-time that Thumb-2 won't be
> > supported in userspace.
>
> Unless there's any further comments from anyone, I think this is now
> ready. Thanks.
OK, I'll send it to the patch system if nobody comes back with anything.
Cheers
---Dave
^ permalink raw reply [flat|nested] 9+ messages in thread
* [PATCH v2 0/3] Fix Thumb-2 undef handling for mixed-arch kernels
2011-08-19 8:44 ` Tixy
@ 2011-08-19 9:10 ` Dave Martin
2011-08-19 9:22 ` Tixy
0 siblings, 1 reply; 9+ messages in thread
From: Dave Martin @ 2011-08-19 9:10 UTC (permalink / raw)
To: linux-arm-kernel
On Fri, Aug 19, 2011 at 09:44:28AM +0100, Tixy wrote:
> On Thu, 2011-08-18 at 23:29 +0100, Russell King - ARM Linux wrote:
> > On Thu, Aug 18, 2011 at 06:01:51PM +0100, Dave Martin wrote:
> > > In kernels which support v6 and v7 platforms in a single binary
> > > such as omap2plus_defconfig for example, undefined instruction
> > > exceptions taken on Thumb instructions are not processed correctly,
> > > because the kernel assumes at build-time that Thumb-2 won't be
> > > supported in userspace.
> >
> > Unless there's any further comments from anyone, I think this is now
> > ready. Thanks.
>
> I've no further comments.
Are you happy for me to transfer your reviewed-by to the new version of
patch 1? I removed the tags beacuse it's changed, though perhaps
unnecessarily -- the changes are fairly minor compared with the last
version.
Cheers
---Dave
^ permalink raw reply [flat|nested] 9+ messages in thread
* [PATCH v2 0/3] Fix Thumb-2 undef handling for mixed-arch kernels
2011-08-19 9:10 ` Dave Martin
@ 2011-08-19 9:22 ` Tixy
0 siblings, 0 replies; 9+ messages in thread
From: Tixy @ 2011-08-19 9:22 UTC (permalink / raw)
To: linux-arm-kernel
On Fri, 2011-08-19 at 10:10 +0100, Dave Martin wrote:
> On Fri, Aug 19, 2011 at 09:44:28AM +0100, Tixy wrote:
> > On Thu, 2011-08-18 at 23:29 +0100, Russell King - ARM Linux wrote:
> > > On Thu, Aug 18, 2011 at 06:01:51PM +0100, Dave Martin wrote:
> > > > In kernels which support v6 and v7 platforms in a single binary
> > > > such as omap2plus_defconfig for example, undefined instruction
> > > > exceptions taken on Thumb instructions are not processed correctly,
> > > > because the kernel assumes at build-time that Thumb-2 won't be
> > > > supported in userspace.
> > >
> > > Unless there's any further comments from anyone, I think this is now
> > > ready. Thanks.
> >
> > I've no further comments.
>
> Are you happy for me to transfer your reviewed-by to the new version of
> patch 1?
Yes, I compared the new patch to the old one.
^ permalink raw reply [flat|nested] 9+ messages in thread
end of thread, other threads:[~2011-08-19 9:22 UTC | newest]
Thread overview: 9+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2011-08-18 17:01 [PATCH v2 0/3] Fix Thumb-2 undef handling for mixed-arch kernels Dave Martin
2011-08-18 17:01 ` [PATCH v2 1/3] ARM: Make cpu_architecture into a global variable Dave Martin
2011-08-18 17:01 ` [PATCH v2 2/3] ARM: entry: Remove unnecessary masking when decoding Thumb-2 instructions Dave Martin
2011-08-18 17:01 ` [PATCH v2 3/3] ARM: entry: Fix Thumb-2 undef handling for multi-CPU kernels Dave Martin
2011-08-18 22:29 ` [PATCH v2 0/3] Fix Thumb-2 undef handling for mixed-arch kernels Russell King - ARM Linux
2011-08-19 8:44 ` Tixy
2011-08-19 9:10 ` Dave Martin
2011-08-19 9:22 ` Tixy
2011-08-19 9:00 ` Dave Martin
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