From 9b55613f42e8d40d5c9ccb8970bde6af4764b2ab Mon Sep 17 00:00:00 2001
From: Russell King <rmk+kernel@arm.linux.org.uk>
Date: Fri, 11 Sep 2015 16:44:02 +0100
Subject: ARM: fix Thumb2 signal handling when ARMv6 is enabled
When a kernel is built covering ARMv6 to ARMv7, we omit to clear the
IT state when entering a signal handler. This can cause the first
few instructions to be conditionally executed depending on the parent
context.
In any case, the original test for >= ARMv7 is broken - ARMv6 can have
Thumb-2 support as well, and an ARMv6T2 specific build would omit this
code too.
Relax the test back to ARMv6 or greater. This results in us always
clearing the IT state bits in the PSR, even on CPUs where these bits
are reserved. However, they're reserved for the IT state, so this
should cause no harm.
Cc: <stable@vger.kernel.org>
Fixes: d71e1352e240 ("Clear the IT state when invoking a Thumb-2 signal handler")
Acked-by: Tony Lindgren <tony@atomide.com>
Tested-by: H. Nikolaus Schaller <hns@goldelico.com>
Tested-by: Grazvydas Ignotas <notasas@gmail.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
---
arch/arm/kernel/signal.c | 15 ++++++++++-----
1 file changed, 10 insertions(+), 5 deletions(-)
(limited to 'arch/arm/kernel')
diff --git a/arch/arm/kernel/signal.c b/arch/arm/kernel/signal.c
index 423663e23791..586eef26203d 100644
--- a/arch/arm/kernel/signal.c
+++ b/arch/arm/kernel/signal.c
@@ -343,12 +343,17 @@ setup_return(struct pt_regs *regs, struct ksignal *ksig,
*/
thumb = handler & 1;
-#if __LINUX_ARM_ARCH__ >= 7
+#if __LINUX_ARM_ARCH__ >= 6
/*
- * Clear the If-Then Thumb-2 execution state
- * ARM spec requires this to be all 000s in ARM mode
- * Snapdragon S4/Krait misbehaves on a Thumb=>ARM
- * signal transition without this.
+ * Clear the If-Then Thumb-2 execution state. ARM spec
+ * requires this to be all 000s in ARM mode. Snapdragon
+ * S4/Krait misbehaves on a Thumb=>ARM signal transition
+ * without this.
+ *
+ * We must do this whenever we are running on a Thumb-2
+ * capable CPU, which includes ARMv6T2. However, we elect
+ * to do this whenever we're on an ARMv6 or later CPU for
+ * simplicity.
*/
cpsr &= ~PSR_IT_MASK;
#endif
--
cgit v1.2.3
From 12fc7306e6ffae4e86680892f2286063d7d6eae7 Mon Sep 17 00:00:00 2001
From: Russell King <rmk+kernel@arm.linux.org.uk>
Date: Wed, 16 Sep 2015 11:08:49 +0100
Subject: ARM: get rid of needless #if in signal handling code
Remove the #if statement which caused trouble for kernels that support
both ARMv6 and ARMv7. Older architectures do not implement these bits,
so it should be safe to always clear them.
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
---
arch/arm/kernel/signal.c | 6 ++----
1 file changed, 2 insertions(+), 4 deletions(-)
(limited to 'arch/arm/kernel')
diff --git a/arch/arm/kernel/signal.c b/arch/arm/kernel/signal.c
index 586eef26203d..29e5dc70bb41 100644
--- a/arch/arm/kernel/signal.c
+++ b/arch/arm/kernel/signal.c
@@ -343,7 +343,6 @@ setup_return(struct pt_regs *regs, struct ksignal *ksig,
*/
thumb = handler & 1;
-#if __LINUX_ARM_ARCH__ >= 6
/*
* Clear the If-Then Thumb-2 execution state. ARM spec
* requires this to be all 000s in ARM mode. Snapdragon
@@ -352,11 +351,10 @@ setup_return(struct pt_regs *regs, struct ksignal *ksig,
*
* We must do this whenever we are running on a Thumb-2
* capable CPU, which includes ARMv6T2. However, we elect
- * to do this whenever we're on an ARMv6 or later CPU for
- * simplicity.
+ * to always do this to simplify the code; this field is
+ * marked UNK/SBZP for older architectures.
*/
cpsr &= ~PSR_IT_MASK;
-#endif
if (thumb) {
cpsr |= PSR_T_BIT;
--
cgit v1.2.3
From 7ae85dc7687c7e7119053d83d02c560ea217b772 Mon Sep 17 00:00:00 2001
From: Doug Anderson <armlinux@m.disordat.com>
Date: Wed, 26 Aug 2015 18:26:49 +0100
Subject: ARM: 8425/1: kgdb: Don't try to stop the machine when setting
breakpoints
In (23a4e40 arm: kgdb: Handle read-only text / modules) we moved to
using patch_text() to set breakpoints so that we could handle the case
when we had CONFIG_DEBUG_RODATA. That patch used patch_text().
Unfortunately, patch_text() assumes that we're not in atomic context
when it runs since it needs to grab a mutex and also wait for other
CPUs to stop (which it does with a completion).
This would result in a stack crawl if you had
CONFIG_DEBUG_ATOMIC_SLEEP and tried to set a breakpoint in kgdb. The
crawl looked something like:
BUG: scheduling while atomic: swapper/0/0/0x00010007
CPU: 0 PID: 0 Comm: swapper/0 Not tainted 4.2.0-rc7-00133-geb63b34 #1073
Hardware name: Rockchip (Device Tree)
(unwind_backtrace) from [<c00133d4>] (show_stack+0x20/0x24)
(show_stack) from [<c05400e8>] (dump_stack+0x84/0xb8)
(dump_stack) from [<c004913c>] (__schedule_bug+0x54/0x6c)
(__schedule_bug) from [<c054065c>] (__schedule+0x80/0x668)
(__schedule) from [<c0540cfc>] (schedule+0xb8/0xd4)
(schedule) from [<c0543a3c>] (schedule_timeout+0x2c/0x234)
(schedule_timeout) from [<c05417c0>] (wait_for_common+0xf4/0x188)
(wait_for_common) from [<c0541874>] (wait_for_completion+0x20/0x24)
(wait_for_completion) from [<c00a0104>] (__stop_cpus+0x58/0x70)
(__stop_cpus) from [<c00a0580>] (stop_cpus+0x3c/0x54)
(stop_cpus) from [<c00a06c4>] (__stop_machine+0xcc/0xe8)
(__stop_machine) from [<c00a0714>] (stop_machine+0x34/0x44)
(stop_machine) from [<c00173e8>] (patch_text+0x28/0x34)
(patch_text) from [<c001733c>] (kgdb_arch_set_breakpoint+0x40/0x4c)
(kgdb_arch_set_breakpoint) from [<c00a0d68>] (kgdb_validate_break_address+0x2c/0x60)
(kgdb_validate_break_address) from [<c00a0e90>] (dbg_set_sw_break+0x1c/0xdc)
(dbg_set_sw_break) from [<c00a2e88>] (gdb_serial_stub+0x9c4/0xba4)
(gdb_serial_stub) from [<c00a11cc>] (kgdb_cpu_enter+0x1f8/0x60c)
(kgdb_cpu_enter) from [<c00a18cc>] (kgdb_handle_exception+0x19c/0x1d0)
(kgdb_handle_exception) from [<c0016f7c>] (kgdb_compiled_brk_fn+0x30/0x3c)
(kgdb_compiled_brk_fn) from [<c00091a4>] (do_undefinstr+0x1a4/0x20c)
(do_undefinstr) from [<c001400c>] (__und_svc_finish+0x0/0x34)
It turns out that when we're in kgdb all the CPUs are stopped anyway
so there's no reason we should be calling patch_text(). We can
instead directly call __patch_text() which assumes that CPUs have
already been stopped.
Fixes: 23a4e4050ba9 ("arm: kgdb: Handle read-only text / modules")
Reported-by: Aapo Vienamo <avienamo@nvidia.com>
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Reviewed-by: Stephen Boyd <sboyd@codeaurora.org>
Acked-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
---
arch/arm/kernel/kgdb.c | 8 +++++---
1 file changed, 5 insertions(+), 3 deletions(-)
(limited to 'arch/arm/kernel')
diff --git a/arch/arm/kernel/kgdb.c b/arch/arm/kernel/kgdb.c
index a6ad93c9bce3..fd9eefce0a7b 100644
--- a/arch/arm/kernel/kgdb.c
+++ b/arch/arm/kernel/kgdb.c
@@ -259,15 +259,17 @@ int kgdb_arch_set_breakpoint(struct kgdb_bkpt *bpt)
if (err)
return err;
- patch_text((void *)bpt->bpt_addr,
- *(unsigned int *)arch_kgdb_ops.gdb_bpt_instr);
+ /* Machine is already stopped, so we can use __patch_text() directly */
+ __patch_text((void *)bpt->bpt_addr,
+ *(unsigned int *)arch_kgdb_ops.gdb_bpt_instr);
return err;
}
int kgdb_arch_remove_breakpoint(struct kgdb_bkpt *bpt)
{
- patch_text((void *)bpt->bpt_addr, *(unsigned int *)bpt->saved_instr);
+ /* Machine is already stopped, so we can use __patch_text() directly */
+ __patch_text((void *)bpt->bpt_addr, *(unsigned int *)bpt->saved_instr);
return 0;
}
--
cgit v1.2.3