[PATCH] ARM/ARM64: don't enter kgdb when userspace executes a kgdb break instruction.
From: osandov@osandov.com (Omar Sandoval)
Date: 2014-07-30 07:12:50
Also in:
lkml
Subsystem:
arm port, arm64 port (aarch64 architecture), the rest · Maintainers:
Russell King, Catalin Marinas, Will Deacon, Linus Torvalds
The kgdb breakpoint hooks (kgdb_brk_fn and kgdb_compiled_brk_fn) should only be
entered when a kgdb break instruction is executed from the kernel. Otherwise,
if kgdb is enabled, a userspace program can cause the kernel to drop into the
debugger by executing either KGDB_BREAKINST or KGDB_COMPILED_BREAK on ARM, or
brk #KGDB_{DYN,COMPILED}_DGB_BRK_IMM on ARM64.
Signed-off-by: Omar Sandoval <osandov@osandov.com>
---
The following program reproduces the fixed problem on ARM:
.globl _start
_start:
udf #65006 @ KGDB_BREAKINST
And on ARM64:
.globl _start
_start:
brk #0x400 @ KGDB_DYN_DGB_BRK_IMM
arch/arm/kernel/kgdb.c | 4 ++++
arch/arm64/include/asm/debug-monitors.h | 4 +++-
arch/arm64/kernel/debug-monitors.c | 3 ++-
arch/arm64/kernel/kgdb.c | 4 ++++
4 files changed, 13 insertions(+), 2 deletions(-)
diff --git a/arch/arm/kernel/kgdb.c b/arch/arm/kernel/kgdb.c
index 778c2f7..a74b53c 100644
--- a/arch/arm/kernel/kgdb.c
+++ b/arch/arm/kernel/kgdb.c@@ -160,12 +160,16 @@ static int kgdb_compiled_brk_fn(struct pt_regs *regs, unsigned int instr) static struct undef_hook kgdb_brkpt_hook = { .instr_mask = 0xffffffff, .instr_val = KGDB_BREAKINST, + .cpsr_mask = MODE_MASK, + .cpsr_val = SVC_MODE, .fn = kgdb_brk_fn }; static struct undef_hook kgdb_compiled_brkpt_hook = { .instr_mask = 0xffffffff, .instr_val = KGDB_COMPILED_BREAK, + .cpsr_mask = MODE_MASK, + .cpsr_val = SVC_MODE, .fn = kgdb_compiled_brk_fn };
diff --git a/arch/arm64/include/asm/debug-monitors.h b/arch/arm64/include/asm/debug-monitors.h
index 6e9b5b3..e1d27ce 100644
--- a/arch/arm64/include/asm/debug-monitors.h
+++ b/arch/arm64/include/asm/debug-monitors.h@@ -105,8 +105,10 @@ void unregister_step_hook(struct step_hook *hook); struct break_hook { struct list_head node; - u32 esr_val; u32 esr_mask; + u32 esr_val; + u64 pstate_mask; + u64 pstate_val; int (*fn)(struct pt_regs *regs, unsigned int esr); };
diff --git a/arch/arm64/kernel/debug-monitors.c b/arch/arm64/kernel/debug-monitors.c
index a7fb874..594fac4 100644
--- a/arch/arm64/kernel/debug-monitors.c
+++ b/arch/arm64/kernel/debug-monitors.c@@ -303,7 +303,8 @@ static int call_break_hook(struct pt_regs *regs, unsigned int esr) read_lock(&break_hook_lock); list_for_each_entry(hook, &break_hook, node) - if ((esr & hook->esr_mask) == hook->esr_val) + if ((esr & hook->esr_mask) == hook->esr_val && + (regs->pstate & hook->pstate_mask) == hook->pstate_val) fn = hook->fn; read_unlock(&break_hook_lock);
diff --git a/arch/arm64/kernel/kgdb.c b/arch/arm64/kernel/kgdb.c
index 75c9cf1..80eb035 100644
--- a/arch/arm64/kernel/kgdb.c
+++ b/arch/arm64/kernel/kgdb.c@@ -236,12 +236,16 @@ static int kgdb_step_brk_fn(struct pt_regs *regs, unsigned int esr) static struct break_hook kgdb_brkpt_hook = { .esr_mask = 0xffffffff, .esr_val = DBG_ESR_VAL_BRK(KGDB_DYN_DGB_BRK_IMM), + .pstate_mask = PSR_MODE_MASK, + .pstate_val = PSR_MODE_EL1h, .fn = kgdb_brk_fn }; static struct break_hook kgdb_compiled_brkpt_hook = { .esr_mask = 0xffffffff, .esr_val = DBG_ESR_VAL_BRK(KDBG_COMPILED_DBG_BRK_IMM), + .pstate_mask = PSR_MODE_MASK, + .pstate_val = PSR_MODE_EL1h, .fn = kgdb_compiled_brk_fn };
--
2.0.3