diff options
authorFredrik Strupe <>2020-05-18 19:41:11 +0100
committerRussell King <>2020-05-19 11:41:54 +0100
commit3866f217aaa81bf7165c7f27362eee5d7919c496 (patch)
parent513149cba8f2b2cadf1e0ecc13d008cb78a455c8 (diff)
ARM: 8977/1: ptrace: Fix mask for thumb breakpoint hookfixes
call_undef_hook() in traps.c applies the same instr_mask for both 16-bit and 32-bit thumb instructions. If instr_mask then is only 16 bits wide (0xffff as opposed to 0xffffffff), the first half-word of 32-bit thumb instructions will be masked out. This makes the function match 32-bit thumb instructions where the second half-word is equal to instr_val, regardless of the first half-word. The result in this case is that all undefined 32-bit thumb instructions with the second half-word equal to 0xde01 (udf #1) work as breakpoints and will raise a SIGTRAP instead of a SIGILL, instead of just the one intended 16-bit instruction. An example of such an instruction is 0xeaa0de01, which is unallocated according to Arm ARM and should raise a SIGILL, but instead raises a SIGTRAP. This patch fixes the issue by setting all the bits in instr_mask, which will still match the intended 16-bit thumb instruction (where the upper half is always 0), but not any 32-bit thumb instructions. Cc: Oleg Nesterov <> Signed-off-by: Fredrik Strupe <> Signed-off-by: Russell King <>
1 files changed, 2 insertions, 2 deletions
diff --git a/arch/arm/kernel/ptrace.c b/arch/arm/kernel/ptrace.c
index b606cded90cd..4cc6a7eff635 100644
--- a/arch/arm/kernel/ptrace.c
+++ b/arch/arm/kernel/ptrace.c
@@ -219,8 +219,8 @@ static struct undef_hook arm_break_hook = {
static struct undef_hook thumb_break_hook = {
- .instr_mask = 0xffff,
- .instr_val = 0xde01,
+ .instr_mask = 0xffffffff,
+ .instr_val = 0x0000de01,
.cpsr_mask = PSR_T_BIT,
.cpsr_val = PSR_T_BIT,
.fn = break_trap,