From dfbdcda280eb762bae2184145cc0702932d41798 Mon Sep 17 00:00:00 2001
From: Ard Biesheuvel <ardb@kernel.org>
Date: Sat, 18 Sep 2021 10:44:34 +0200
Subject: gcc-plugins: arm-ssp: Prepare for THREAD_INFO_IN_TASK support
We will be enabling THREAD_INFO_IN_TASK support for ARM, which means
that we can no longer load the stack canary value by masking the stack
pointer and taking the copy that lives in thread_info. Instead, we will
be able to load it from the task_struct directly, by using the TPIDRURO
register which will hold the current task pointer when
THREAD_INFO_IN_TASK is in effect. This is much more straight-forward,
and allows us to declutter this code a bit while at it.
Note that this means that ARMv6 (non-v6K) SMP systems can no longer use
this feature, but those are quite rare to begin with, so this is a
reasonable trade off.
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Tested-by: Amit Daniel Kachhap <amit.kachhap@arm.com>
---
arch/arm/include/asm/thread_info.h | 3 ---
1 file changed, 3 deletions(-)
(limited to 'arch/arm/include/asm/thread_info.h')
diff --git a/arch/arm/include/asm/thread_info.h b/arch/arm/include/asm/thread_info.h
index 9a18da3e10cc..f0cacc733231 100644
--- a/arch/arm/include/asm/thread_info.h
+++ b/arch/arm/include/asm/thread_info.h
@@ -55,9 +55,6 @@ struct thread_info {
struct task_struct *task; /* main task structure */
__u32 cpu; /* cpu */
__u32 cpu_domain; /* cpu domain */
-#ifdef CONFIG_STACKPROTECTOR_PER_TASK
- unsigned long stack_canary;
-#endif
struct cpu_context_save cpu_context; /* cpu context */
__u32 abi_syscall; /* ABI type and syscall nr */
__u8 used_cp[16]; /* thread used copro */
--
cgit
From 50596b7559bf226bb35ad55855ee979453ec06a1 Mon Sep 17 00:00:00 2001
From: Ard Biesheuvel <ardb@kernel.org>
Date: Sat, 18 Sep 2021 10:44:37 +0200
Subject: ARM: smp: Store current pointer in TPIDRURO register if available
Now that the user space TLS register is assigned on every return to user
space, we can use it to keep the 'current' pointer while running in the
kernel. This removes the need to access it via thread_info, which is
located at the base of the stack, but will be moved out of there in a
subsequent patch.
Use the __builtin_thread_pointer() helper when available - this will
help GCC understand that reloading the value within the same function is
not necessary, even when using the per-task stack protector (which also
generates accesses via the TLS register). For example, the generated
code below loads TPIDRURO only once, and uses it to access both the
stack canary and the preempt_count fields.
<do_one_initcall>:
e92d 41f0 stmdb sp!, {r4, r5, r6, r7, r8, lr}
ee1d 4f70 mrc 15, 0, r4, cr13, cr0, {3}
4606 mov r6, r0
b094 sub sp, #80 ; 0x50
f8d4 34e8 ldr.w r3, [r4, #1256] ; 0x4e8 <- stack canary
9313 str r3, [sp, #76] ; 0x4c
f8d4 8004 ldr.w r8, [r4, #4] <- preempt count
Co-developed-by: Keith Packard <keithpac@amazon.com>
Signed-off-by: Keith Packard <keithpac@amazon.com>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Tested-by: Amit Daniel Kachhap <amit.kachhap@arm.com>
---
arch/arm/include/asm/thread_info.h | 2 ++
1 file changed, 2 insertions(+)
(limited to 'arch/arm/include/asm/thread_info.h')
diff --git a/arch/arm/include/asm/thread_info.h b/arch/arm/include/asm/thread_info.h
index f0cacc733231..76b6fbd5540c 100644
--- a/arch/arm/include/asm/thread_info.h
+++ b/arch/arm/include/asm/thread_info.h
@@ -29,6 +29,8 @@
struct task_struct;
+DECLARE_PER_CPU(struct task_struct *, __entry_task);
+
#include <asm/types.h>
struct cpu_context_save {
--
cgit
From 18ed1c01a7dd3d7c780b06a49124da237a4c1790 Mon Sep 17 00:00:00 2001
From: Ard Biesheuvel <ardb@kernel.org>
Date: Sat, 18 Sep 2021 10:44:38 +0200
Subject: ARM: smp: Enable THREAD_INFO_IN_TASK
Now that we no longer rely on thread_info living at the base of the task
stack to be able to access the 'current' pointer, we can wire up the
generic support for moving thread_info into the task struct itself.
Note that this requires us to update the cpu field in thread_info
explicitly, now that the core code no longer does so. Ideally, we would
switch the percpu code to access the cpu field in task_struct instead,
but this unleashes #include circular dependency hell.
Co-developed-by: Keith Packard <keithpac@amazon.com>
Signed-off-by: Keith Packard <keithpac@amazon.com>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Tested-by: Amit Daniel Kachhap <amit.kachhap@arm.com>
---
arch/arm/include/asm/thread_info.h | 10 +++++++++-
1 file changed, 9 insertions(+), 1 deletion(-)
(limited to 'arch/arm/include/asm/thread_info.h')
diff --git a/arch/arm/include/asm/thread_info.h b/arch/arm/include/asm/thread_info.h
index 76b6fbd5540c..787511396f3f 100644
--- a/arch/arm/include/asm/thread_info.h
+++ b/arch/arm/include/asm/thread_info.h
@@ -54,7 +54,9 @@ struct cpu_context_save {
struct thread_info {
unsigned long flags; /* low level flags */
int preempt_count; /* 0 => preemptable, <0 => bug */
+#ifndef CONFIG_THREAD_INFO_IN_TASK
struct task_struct *task; /* main task structure */
+#endif
__u32 cpu; /* cpu */
__u32 cpu_domain; /* cpu domain */
struct cpu_context_save cpu_context; /* cpu context */
@@ -70,11 +72,16 @@ struct thread_info {
#define INIT_THREAD_INFO(tsk) \
{ \
- .task = &tsk, \
+ INIT_THREAD_INFO_TASK(tsk) \
.flags = 0, \
.preempt_count = INIT_PREEMPT_COUNT, \
}
+#ifdef CONFIG_THREAD_INFO_IN_TASK
+#define INIT_THREAD_INFO_TASK(tsk)
+#else
+#define INIT_THREAD_INFO_TASK(tsk) .task = &(tsk),
+
/*
* how to get the thread information struct from C
*/
@@ -85,6 +92,7 @@ static inline struct thread_info *current_thread_info(void)
return (struct thread_info *)
(current_stack_pointer & ~(THREAD_SIZE - 1));
}
+#endif
#define thread_saved_pc(tsk) \
((unsigned long)(task_thread_info(tsk)->cpu_context.pc))
--
cgit
From fa191b711c32ba107cf8d3474cd860407b7e997a Mon Sep 17 00:00:00 2001
From: Ard Biesheuvel <ardb@kernel.org>
Date: Fri, 29 Oct 2021 17:45:32 +0100
Subject: ARM: 9150/1: Fix PID_IN_CONTEXTIDR regression when
THREAD_INFO_IN_TASK=y
The code that implements the rarely used PID_IN_CONTEXTIDR feature
dereferences the 'task' field of struct thread_info directly, and this
is no longer possible when THREAD_INFO_IN_TASK=y, as the 'task' field is
omitted from the struct definition in that case. Instead, we should just
cast the thread_info pointer to a task_struct pointer, given that the
former is now the first member of the latter.
So use a helper that abstracts this, and provide implementations for
both cases.
Reported by: Arnd Bergmann <arnd@arndb.de>
Fixes: 18ed1c01a7dd ("ARM: smp: Enable THREAD_INFO_IN_TASK")
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
---
arch/arm/include/asm/thread_info.h | 11 +++++++++++
1 file changed, 11 insertions(+)
(limited to 'arch/arm/include/asm/thread_info.h')
diff --git a/arch/arm/include/asm/thread_info.h b/arch/arm/include/asm/thread_info.h
index 787511396f3f..164e15f26485 100644
--- a/arch/arm/include/asm/thread_info.h
+++ b/arch/arm/include/asm/thread_info.h
@@ -79,9 +79,20 @@ struct thread_info {
#ifdef CONFIG_THREAD_INFO_IN_TASK
#define INIT_THREAD_INFO_TASK(tsk)
+
+static inline struct task_struct *thread_task(struct thread_info* ti)
+{
+ return (struct task_struct *)ti;
+}
+
#else
#define INIT_THREAD_INFO_TASK(tsk) .task = &(tsk),
+static inline struct task_struct *thread_task(struct thread_info* ti)
+{
+ return ti->task;
+}
+
/*
* how to get the thread information struct from C
*/
--
cgit