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authorRussell King <rmk+kernel@arm.linux.org.uk>2015-08-20 10:32:02 +0100
committerRussell King <rmk+kernel@arm.linux.org.uk>2015-08-26 20:27:02 +0100
commit2190fed67ba6f3e8129513929f2395843645e928 (patch)
tree45a4db5061c12e2926f7a1c89d56c7bbf47f0e61 /arch/arm/kernel/entry-armv.S
parentaa06e5c1f9c2b466712be904cc5b56a813e24cfd (diff)
downloadlinux-linaro-stable-2190fed67ba6f3e8129513929f2395843645e928.tar.gz
ARM: entry: provide uaccess assembly macro hooks
Provide hooks into the kernel entry and exit paths to permit control of userspace visibility to the kernel. The intended use is: - on entry to kernel from user, uaccess_disable will be called to disable userspace visibility - on exit from kernel to user, uaccess_enable will be called to enable userspace visibility - on entry from a kernel exception, uaccess_save_and_disable will be called to save the current userspace visibility setting, and disable access - on exit from a kernel exception, uaccess_restore will be called to restore the userspace visibility as it was before the exception occurred. These hooks allows us to keep userspace visibility disabled for the vast majority of the kernel, except for localised regions where we want to explicitly access userspace. Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Diffstat (limited to 'arch/arm/kernel/entry-armv.S')
-rw-r--r--arch/arm/kernel/entry-armv.S30
1 files changed, 22 insertions, 8 deletions
diff --git a/arch/arm/kernel/entry-armv.S b/arch/arm/kernel/entry-armv.S
index d19adcf6c580..61f00a3f3047 100644
--- a/arch/arm/kernel/entry-armv.S
+++ b/arch/arm/kernel/entry-armv.S
@@ -149,10 +149,10 @@ ENDPROC(__und_invalid)
#define SPFIX(code...)
#endif
- .macro svc_entry, stack_hole=0, trace=1
+ .macro svc_entry, stack_hole=0, trace=1, uaccess=1
UNWIND(.fnstart )
UNWIND(.save {r0 - pc} )
- sub sp, sp, #(S_FRAME_SIZE + \stack_hole - 4)
+ sub sp, sp, #(S_FRAME_SIZE + 8 + \stack_hole - 4)
#ifdef CONFIG_THUMB2_KERNEL
SPFIX( str r0, [sp] ) @ temporarily saved
SPFIX( mov r0, sp )
@@ -167,7 +167,7 @@ ENDPROC(__und_invalid)
ldmia r0, {r3 - r5}
add r7, sp, #S_SP - 4 @ here for interlock avoidance
mov r6, #-1 @ "" "" "" ""
- add r2, sp, #(S_FRAME_SIZE + \stack_hole - 4)
+ add r2, sp, #(S_FRAME_SIZE + 8 + \stack_hole - 4)
SPFIX( addeq r2, r2, #4 )
str r3, [sp, #-4]! @ save the "real" r0 copied
@ from the exception stack
@@ -185,6 +185,11 @@ ENDPROC(__und_invalid)
@
stmia r7, {r2 - r6}
+ uaccess_save r0
+ .if \uaccess
+ uaccess_disable r0
+ .endif
+
.if \trace
#ifdef CONFIG_TRACE_IRQFLAGS
bl trace_hardirqs_off
@@ -194,7 +199,7 @@ ENDPROC(__und_invalid)
.align 5
__dabt_svc:
- svc_entry
+ svc_entry uaccess=0
mov r2, sp
dabt_helper
THUMB( ldr r5, [sp, #S_PSR] ) @ potentially updated CPSR
@@ -368,7 +373,7 @@ ENDPROC(__fiq_abt)
#error "sizeof(struct pt_regs) must be a multiple of 8"
#endif
- .macro usr_entry, trace=1
+ .macro usr_entry, trace=1, uaccess=1
UNWIND(.fnstart )
UNWIND(.cantunwind ) @ don't unwind the user space
sub sp, sp, #S_FRAME_SIZE
@@ -400,6 +405,10 @@ ENDPROC(__fiq_abt)
ARM( stmdb r0, {sp, lr}^ )
THUMB( store_user_sp_lr r0, r1, S_SP - S_PC )
+ .if \uaccess
+ uaccess_disable ip
+ .endif
+
@ Enable the alignment trap while in kernel mode
ATRAP( teq r8, r7)
ATRAP( mcrne p15, 0, r8, c1, c0, 0)
@@ -435,7 +444,7 @@ ENDPROC(__fiq_abt)
.align 5
__dabt_usr:
- usr_entry
+ usr_entry uaccess=0
kuser_cmpxchg_check
mov r2, sp
dabt_helper
@@ -458,7 +467,7 @@ ENDPROC(__irq_usr)
.align 5
__und_usr:
- usr_entry
+ usr_entry uaccess=0
mov r2, r4
mov r3, r5
@@ -484,6 +493,8 @@ __und_usr:
1: ldrt r0, [r4]
ARM_BE8(rev r0, r0) @ little endian instruction
+ uaccess_disable ip
+
@ r0 = 32-bit ARM instruction which caused the exception
@ r2 = PC value for the following instruction (:= regs->ARM_pc)
@ r4 = PC value for the faulting instruction
@@ -518,9 +529,10 @@ __und_usr_thumb:
2: ldrht r5, [r4]
ARM_BE8(rev16 r5, r5) @ little endian instruction
cmp r5, #0xe800 @ 32bit instruction if xx != 0
- blo __und_usr_fault_16 @ 16bit undefined instruction
+ blo __und_usr_fault_16_pan @ 16bit undefined instruction
3: ldrht r0, [r2]
ARM_BE8(rev16 r0, r0) @ little endian instruction
+ uaccess_disable ip
add r2, r2, #2 @ r2 is PC + 2, make it PC + 4
str r2, [sp, #S_PC] @ it's a 2x16bit instr, update
orr r0, r0, r5, lsl #16
@@ -715,6 +727,8 @@ ENDPROC(no_fp)
__und_usr_fault_32:
mov r1, #4
b 1f
+__und_usr_fault_16_pan:
+ uaccess_disable ip
__und_usr_fault_16:
mov r1, #2
1: mov r0, sp