ARM: 7735/2: Preserve the user r/w register TPIDRURW on context switch and fork
Since commit 6a1c53124aa1 the user writeable TLS register was zeroed to
prevent it from being used as a covert channel between two tasks.
There are more and more applications coming to Windows RT,
Wine could support them, but mostly they expect to have
the thread environment block (TEB) in TPIDRURW.
This patch preserves that register per thread instead of clearing it.
Unlike the TPIDRURO, which is already switched, the TPIDRURW
can be updated from userspace so needs careful treatment in the case that we
modify TPIDRURW and call fork(). To avoid this we must always read
TPIDRURW in copy_thread.
Signed-off-by: André Hentschel <nerv@dawncrow.de>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Jonathan Austin <jonathan.austin@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
diff --git a/arch/arm/kernel/entry-armv.S b/arch/arm/kernel/entry-armv.S
index 582b405..a39cfc2a1 100644
--- a/arch/arm/kernel/entry-armv.S
+++ b/arch/arm/kernel/entry-armv.S
@@ -685,15 +685,16 @@
UNWIND(.fnstart )
UNWIND(.cantunwind )
add ip, r1, #TI_CPU_SAVE
- ldr r3, [r2, #TI_TP_VALUE]
ARM( stmia ip!, {r4 - sl, fp, sp, lr} ) @ Store most regs on stack
THUMB( stmia ip!, {r4 - sl, fp} ) @ Store most regs on stack
THUMB( str sp, [ip], #4 )
THUMB( str lr, [ip], #4 )
+ ldr r4, [r2, #TI_TP_VALUE]
+ ldr r5, [r2, #TI_TP_VALUE + 4]
#ifdef CONFIG_CPU_USE_DOMAINS
ldr r6, [r2, #TI_CPU_DOMAIN]
#endif
- set_tls r3, r4, r5
+ switch_tls r1, r4, r5, r3, r7
#if defined(CONFIG_CC_STACKPROTECTOR) && !defined(CONFIG_SMP)
ldr r7, [r2, #TI_TASK]
ldr r8, =__stack_chk_guard
diff --git a/arch/arm/kernel/process.c b/arch/arm/kernel/process.c
index f219703..0870641 100644
--- a/arch/arm/kernel/process.c
+++ b/arch/arm/kernel/process.c
@@ -39,6 +39,7 @@
#include <asm/thread_notify.h>
#include <asm/stacktrace.h>
#include <asm/mach/time.h>
+#include <asm/tls.h>
#ifdef CONFIG_CC_STACKPROTECTOR
#include <linux/stackprotector.h>
@@ -343,7 +344,8 @@
clear_ptrace_hw_breakpoint(p);
if (clone_flags & CLONE_SETTLS)
- thread->tp_value = childregs->ARM_r3;
+ thread->tp_value[0] = childregs->ARM_r3;
+ thread->tp_value[1] = get_tpuser();
thread_notify(THREAD_NOTIFY_COPY, thread);
diff --git a/arch/arm/kernel/ptrace.c b/arch/arm/kernel/ptrace.c
index 03deeff..2bc1514 100644
--- a/arch/arm/kernel/ptrace.c
+++ b/arch/arm/kernel/ptrace.c
@@ -849,7 +849,7 @@
#endif
case PTRACE_GET_THREAD_AREA:
- ret = put_user(task_thread_info(child)->tp_value,
+ ret = put_user(task_thread_info(child)->tp_value[0],
datap);
break;
diff --git a/arch/arm/kernel/traps.c b/arch/arm/kernel/traps.c
index 18b32e8..517bfd4 100644
--- a/arch/arm/kernel/traps.c
+++ b/arch/arm/kernel/traps.c
@@ -581,7 +581,7 @@
return regs->ARM_r0;
case NR(set_tls):
- thread->tp_value = regs->ARM_r0;
+ thread->tp_value[0] = regs->ARM_r0;
if (tls_emu)
return 0;
if (has_tls_reg) {
@@ -699,7 +699,7 @@
int reg = (instr >> 12) & 15;
if (reg == 15)
return 1;
- regs->uregs[reg] = current_thread_info()->tp_value;
+ regs->uregs[reg] = current_thread_info()->tp_value[0];
regs->ARM_pc += 4;
return 0;
}