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ARM: save and reset the address limit when entering an exception

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When we enter an exception, the current address limit should not apply
to the exception context: if the exception context wishes to access
kernel space via the user accessors (eg, perf code), it must explicitly
request such access.

Acked-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
This commit is contained in:
Russell King 2016-05-13 11:40:20 +01:00
parent dd665be0e2
commit e6978e4bf1
5 changed files with 20 additions and 6 deletions
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2
arch/arm/include/asm/ptrace.h
View file

@ -22,7 +22,7 @@ struct pt_regs {
struct svc_pt_regs {
struct pt_regs regs;
u32 dacr;
u32 unused;
u32 addr_limit;
};
#define to_svc_pt_regs(r) container_of(r, struct svc_pt_regs, regs)

1
arch/arm/kernel/asm-offsets.c
View file

@ -109,6 +109,7 @@ int main(void)
DEFINE(S_OLD_R0, offsetof(struct pt_regs, ARM_ORIG_r0));
DEFINE(PT_REGS_SIZE, sizeof(struct pt_regs));
DEFINE(SVC_DACR, offsetof(struct svc_pt_regs, dacr));
DEFINE(SVC_ADDR_LIMIT, offsetof(struct svc_pt_regs, addr_limit));
DEFINE(SVC_REGS_SIZE, sizeof(struct svc_pt_regs));
BLANK();
#ifdef CONFIG_CACHE_L2X0

7
arch/arm/kernel/entry-armv.S
View file

@ -185,6 +185,12 @@ ENDPROC(__und_invalid)
@
stmia r7, {r2 - r6}
get_thread_info tsk
ldr r0, [tsk, #TI_ADDR_LIMIT]
mov r1, #TASK_SIZE
str r1, [tsk, #TI_ADDR_LIMIT]
str r0, [sp, #SVC_ADDR_LIMIT]
uaccess_save r0
.if \uaccess
uaccess_disable r0
@ -213,7 +219,6 @@ __irq_svc:
irq_handler
#ifdef CONFIG_PREEMPT
get_thread_info tsk
ldr r8, [tsk, #TI_PREEMPT] @ get preempt count
ldr r0, [tsk, #TI_FLAGS] @ get flags
teq r8, #0 @ if preempt count != 0

4
arch/arm/kernel/entry-header.S
View file

@ -215,7 +215,9 @@
blne trace_hardirqs_off
#endif
.endif
ldr r1, [sp, #SVC_ADDR_LIMIT]
uaccess_restore
str r1, [tsk, #TI_ADDR_LIMIT]
#ifndef CONFIG_THUMB2_KERNEL
@ ARM mode SVC restore
@ -259,7 +261,9 @@
@ on the stack remains correct).
@
.macro svc_exit_via_fiq
ldr r1, [sp, #SVC_ADDR_LIMIT]
uaccess_restore
str r1, [tsk, #TI_ADDR_LIMIT]
#ifndef CONFIG_THUMB2_KERNEL
@ ARM mode restore
mov r0, sp

12
arch/arm/kernel/process.c
View file

@ -96,19 +96,23 @@ void __show_regs(struct pt_regs *regs)
unsigned long flags;
char buf[64];
#ifndef CONFIG_CPU_V7M
unsigned int domain;
unsigned int domain, fs;
#ifdef CONFIG_CPU_SW_DOMAIN_PAN
/*
* Get the domain register for the parent context. In user
* mode, we don't save the DACR, so lets use what it should
* be. For other modes, we place it after the pt_regs struct.
*/
if (user_mode(regs))
if (user_mode(regs)) {
domain = DACR_UACCESS_ENABLE;
else
fs = get_fs();
} else {
domain = to_svc_pt_regs(regs)->dacr;
fs = to_svc_pt_regs(regs)->addr_limit;
}
#else
domain = get_domain();
fs = get_fs();
#endif
#endif
@ -144,7 +148,7 @@ void __show_regs(struct pt_regs *regs)
if ((domain & domain_mask(DOMAIN_USER)) ==
domain_val(DOMAIN_USER, DOMAIN_NOACCESS))
segment = "none";
else if (get_fs() == get_ds())
else if (fs == get_ds())
segment = "kernel";
else
segment = "user";