ARM: 9071/1: uprobes: Don't hook on thumb instructions

Since uprobes is not supported for thumb, check that the thumb bit is
not set when matching the uprobes instruction hooks.

The Arm UDF instructions used for uprobes triggering
(UPROBE_SWBP_ARM_INSN and UPROBE_SS_ARM_INSN) coincidentally share the
same encoding as a pair of unallocated 32-bit thumb instructions (not
UDF) when the condition code is 0b1111 (0xf). This in effect makes it
possible to trigger the uprobes functionality from thumb, and at that
using two unallocated instructions which are not permanently undefined.

Signed-off-by: Fredrik Strupe <fredrik@strupe.net>
Cc: stable@vger.kernel.org
Fixes: c7edc9e326d5 ("ARM: add uprobes support")
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>

diff --git a/arch/arm/probes/uprobes/core.c b/arch/arm/probes/uprobes/core.c
index c4b49b322e8a88238c1b4192ee112c22a7c00ec9..f5f790c6e5f896590b8394c7d6e0fa54c85d3879 100644 (file)
--- a/arch/arm/probes/uprobes/core.c
+++ b/arch/arm/probes/uprobes/core.c
@@ -204,7 +204,7 @@ unsigned long uprobe_get_swbp_addr(struct pt_regs *regs)
 static struct undef_hook uprobes_arm_break_hook = {
        .instr_mask     = 0x0fffffff,
        .instr_val      = (UPROBE_SWBP_ARM_INSN & 0x0fffffff),
-       .cpsr_mask      = MODE_MASK,
+       .cpsr_mask      = (PSR_T_BIT | MODE_MASK),
        .cpsr_val       = USR_MODE,
        .fn             = uprobe_trap_handler,
 };
@@ -212,7 +212,7 @@ static struct undef_hook uprobes_arm_break_hook = {
 static struct undef_hook uprobes_arm_ss_hook = {
        .instr_mask     = 0x0fffffff,
        .instr_val      = (UPROBE_SS_ARM_INSN & 0x0fffffff),
-       .cpsr_mask      = MODE_MASK,
+       .cpsr_mask      = (PSR_T_BIT | MODE_MASK),
        .cpsr_val       = USR_MODE,
        .fn             = uprobe_trap_handler,
 };