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Message-ID: <20240831064141.3933745-1-liaochang1@huawei.com>
Date: Sat, 31 Aug 2024 06:41:41 +0000
From: Liao Chang <liaochang1@...wei.com>
To: <catalin.marinas@....com>, <will@...nel.org>, <mhiramat@...nel.org>,
<oleg@...hat.com>, <peterz@...radead.org>, <mark.rutland@....com>,
<liaochang1@...wei.com>, <maz@...nel.org>, <oliver.upton@...ux.dev>,
<ardb@...nel.org>, <anshuman.khandual@....com>, <ptosi@...gle.com>,
<mcgrof@...nel.org>, <rppt@...nel.org>, <kristina.martsenko@....com>
CC: <linux-arm-kernel@...ts.infradead.org>, <linux-kernel@...r.kernel.org>,
<linux-trace-kernel@...r.kernel.org>
Subject: [PATCH v2] arm64: Replace linked list with switch statement for breakpoint handlers
v2->v1:
Fix a bug of releasing spinlock in kgdb_arch_exit().
As suggested by Mark Rutland [0], this patch remove the linked list used
for breakpoint handlers and instroduces a switch statement based on the
immediate value.
To minimize the code duplication, a new enum break_hook_type is defined
to encapsulate all supported breakpoint types, used as indices in switch
statement. Macros iterate_break_hook() and __HOOK() generate a series of
switch statements for getting/setting handlers based on the immediate
value from ESR or the imm field of struct break_hook.
After that, All breakpint related immediate macros must now end with
_BRK_IMM, and breakpoint related mask macros must end with _BRK_MASK.
A new user field is added to struct break_hook to separate user and
kernel breakpint exceptions. This force the callers to be explicit about
the exception level that they come from [1]. Currently, only the uprobe
uses this field.
To prevent race condition during break_hook unregistration (primarily by
KGDB), a spinlock is defined in kgdb code. While there's still a
potential race where a CPU might be executing KGDB break_hook while
another CPU unregister it. this issue existed even before this
refactoring.
[0] https://lore.kernel.org/all/Zs3LnYkXL5sg2yBH@J2N7QTR9R3.cambridge.arm.com/
[1] https://lore.kernel.org/all/20190301132809.24653-7-will.deacon@arm.com/
Suggested-by: Mark Rutland <mark.rutland@....com>
Signed-off-by: Liao Chang <liaochang1@...wei.com>
---
arch/arm64/include/asm/brk-imm.h | 6 +-
arch/arm64/include/asm/debug-monitors.h | 7 +-
arch/arm64/include/asm/esr.h | 2 +-
arch/arm64/kernel/debug-monitors.c | 110 ++++++++++++++++++------
arch/arm64/kernel/kgdb.c | 6 ++
arch/arm64/kernel/probes/kprobes.c | 2 +-
arch/arm64/kernel/probes/uprobes.c | 3 +-
arch/arm64/kernel/traps.c | 4 +-
8 files changed, 100 insertions(+), 40 deletions(-)
diff --git a/arch/arm64/include/asm/brk-imm.h b/arch/arm64/include/asm/brk-imm.h
index beb42c62b6ac..a0c2ae4386ab 100644
--- a/arch/arm64/include/asm/brk-imm.h
+++ b/arch/arm64/include/asm/brk-imm.h
@@ -23,7 +23,7 @@
*/
#define KPROBES_BRK_IMM 0x004
#define UPROBES_BRK_IMM 0x005
-#define KPROBES_BRK_SS_IMM 0x006
+#define KPROBES_SS_BRK_IMM 0x006
#define KRETPROBES_BRK_IMM 0x007
#define FAULT_BRK_IMM 0x100
#define KGDB_DYN_DBG_BRK_IMM 0x400
@@ -36,7 +36,7 @@
#define CFI_BRK_IMM_TARGET GENMASK(4, 0)
#define CFI_BRK_IMM_TYPE GENMASK(9, 5)
-#define CFI_BRK_IMM_BASE 0x8000
-#define CFI_BRK_IMM_MASK (CFI_BRK_IMM_TARGET | CFI_BRK_IMM_TYPE)
+#define CFI_BRK_IMM 0x8000
+#define CFI_BRK_MASK (CFI_BRK_IMM_TARGET | CFI_BRK_IMM_TYPE)
#endif
diff --git a/arch/arm64/include/asm/debug-monitors.h b/arch/arm64/include/asm/debug-monitors.h
index 13d437bcbf58..8aedb7c01f69 100644
--- a/arch/arm64/include/asm/debug-monitors.h
+++ b/arch/arm64/include/asm/debug-monitors.h
@@ -41,7 +41,7 @@
/* kprobes BRK opcodes with ESR encoding */
#define BRK64_OPCODE_KPROBES (AARCH64_BREAK_MON | (KPROBES_BRK_IMM << 5))
-#define BRK64_OPCODE_KPROBES_SS (AARCH64_BREAK_MON | (KPROBES_BRK_SS_IMM << 5))
+#define BRK64_OPCODE_KPROBES_SS (AARCH64_BREAK_MON | (KPROBES_SS_BRK_IMM << 5))
/* uprobes BRK opcodes with ESR encoding */
#define BRK64_OPCODE_UPROBES (AARCH64_BREAK_MON | (UPROBES_BRK_IMM << 5))
@@ -74,15 +74,12 @@ void register_kernel_step_hook(struct step_hook *hook);
void unregister_kernel_step_hook(struct step_hook *hook);
struct break_hook {
- struct list_head node;
int (*fn)(struct pt_regs *regs, unsigned long esr);
u16 imm;
u16 mask; /* These bits are ignored when comparing with imm */
+ int user; /* Breakpoint exception from userspace */
};
-void register_user_break_hook(struct break_hook *hook);
-void unregister_user_break_hook(struct break_hook *hook);
-
void register_kernel_break_hook(struct break_hook *hook);
void unregister_kernel_break_hook(struct break_hook *hook);
diff --git a/arch/arm64/include/asm/esr.h b/arch/arm64/include/asm/esr.h
index 56c148890daf..0fc2710a7154 100644
--- a/arch/arm64/include/asm/esr.h
+++ b/arch/arm64/include/asm/esr.h
@@ -403,7 +403,7 @@ static inline bool esr_is_data_abort(unsigned long esr)
static inline bool esr_is_cfi_brk(unsigned long esr)
{
return ESR_ELx_EC(esr) == ESR_ELx_EC_BRK64 &&
- (esr_brk_comment(esr) & ~CFI_BRK_IMM_MASK) == CFI_BRK_IMM_BASE;
+ (esr_brk_comment(esr) & ~CFI_BRK_MASK) == CFI_BRK_IMM;
}
static inline bool esr_fsc_is_translation_fault(unsigned long esr)
diff --git a/arch/arm64/kernel/debug-monitors.c b/arch/arm64/kernel/debug-monitors.c
index 024a7b245056..0b92a58682e2 100644
--- a/arch/arm64/kernel/debug-monitors.c
+++ b/arch/arm64/kernel/debug-monitors.c
@@ -276,47 +276,103 @@ static int single_step_handler(unsigned long unused, unsigned long esr,
}
NOKPROBE_SYMBOL(single_step_handler);
-static LIST_HEAD(user_break_hook);
-static LIST_HEAD(kernel_break_hook);
-
-void register_user_break_hook(struct break_hook *hook)
-{
- register_debug_hook(&hook->node, &user_break_hook);
-}
-
-void unregister_user_break_hook(struct break_hook *hook)
-{
- unregister_debug_hook(&hook->node);
-}
+enum break_hook_type {
+ KPROBES = 0,
+ UPROBES,
+ KPROBES_SS,
+ KRETPROBES,
+ FAULT,
+ KGDB_DYN_DBG,
+ KGDB_COMPILED_DBG,
+ BUG,
+ KASAN,
+ UBSAN,
+ CFI,
+ NR_BRK,
+};
+
+static struct break_hook *break_hooks[NR_BRK];
+
+#define iterate_break_hook(imm) ({ \
+ switch (imm) { \
+ __HOOK(KPROBES) \
+ __HOOK(UPROBES) \
+ __HOOK(KPROBES_SS) \
+ __HOOK(KRETPROBES) \
+ __HOOK(FAULT) \
+ __HOOK(KGDB_DYN_DBG) \
+ __HOOK(KGDB_COMPILED_DBG) \
+ __HOOK(BUG) \
+ __HOOK(KASAN) \
+ __HOOK(UBSAN) \
+ __HOOK(CFI) \
+ default : \
+ break; \
+ } \
+})
+
+#undef __HOOK
+#define __HOOK(nr) \
+ case nr ## _BRK_IMM: \
+ { return break_hooks[nr]; }
+
+static struct break_hook *find_break_hook(unsigned long imm)
+{
+ iterate_break_hook(imm);
+ return NULL;
+}
+
+#undef __HOOK
+#define __HOOK(nr) \
+ case nr ## _BRK_IMM: \
+ { break_hooks[nr] = hook; break; }
void register_kernel_break_hook(struct break_hook *hook)
{
- register_debug_hook(&hook->node, &kernel_break_hook);
+ iterate_break_hook(hook->imm);
}
+#undef __HOOK
+#define __HOOK(nr) \
+ case nr ## _BRK_IMM: \
+ { break_hooks[nr] = NULL; break; }
+
void unregister_kernel_break_hook(struct break_hook *hook)
{
- unregister_debug_hook(&hook->node);
+ iterate_break_hook(hook->imm);
}
+#undef __HOOK
+#define __HOOK(nr) \
+ do { \
+ if (!hook) \
+ hook = find_break_hook(imm & ~(nr ## _BRK_MASK)); \
+ } while (0)
+
static int call_break_hook(struct pt_regs *regs, unsigned long esr)
{
- struct break_hook *hook;
- struct list_head *list;
- int (*fn)(struct pt_regs *regs, unsigned long esr) = NULL;
+ unsigned long imm = esr_brk_comment(esr);
+ struct break_hook *hook = NULL;
- list = user_mode(regs) ? &user_break_hook : &kernel_break_hook;
+ hook = find_break_hook(imm);
+ if (likely(hook))
+ goto call_hook;
- /*
- * Since brk exception disables interrupt, this function is
- * entirely not preemptible, and we can use rcu list safely here.
- */
- list_for_each_entry_rcu(hook, list, node) {
- if ((esr_brk_comment(esr) & ~hook->mask) == hook->imm)
- fn = hook->fn;
- }
+#ifdef CONFIG_KASAN_SW_TAGS
+ __HOOK(KASAN);
+#endif
+#ifdef CONFIG_UBSAN_TRAP
+ __HOOK(UBSAN);
+#endif
+#ifdef CONFIG_CFI_CLANG
+ __HOOK(CFI);
+#endif
+
+call_hook:
+ if (hook && (user_mode(regs) == hook->user))
+ return hook->fn(regs, esr);
- return fn ? fn(regs, esr) : DBG_HOOK_ERROR;
+ return DBG_HOOK_ERROR;
}
NOKPROBE_SYMBOL(call_break_hook);
diff --git a/arch/arm64/kernel/kgdb.c b/arch/arm64/kernel/kgdb.c
index 4e1f983df3d1..e491a5704e61 100644
--- a/arch/arm64/kernel/kgdb.c
+++ b/arch/arm64/kernel/kgdb.c
@@ -304,6 +304,8 @@ static struct notifier_block kgdb_notifier = {
.priority = -INT_MAX,
};
+static DEFINE_SPINLOCK(kgdb_hook_lock);
+
/*
* kgdb_arch_init - Perform any architecture specific initialization.
* This function will handle the initialization of any architecture
@@ -316,9 +318,11 @@ int kgdb_arch_init(void)
if (ret != 0)
return ret;
+ spin_lock(&kgdb_hook_lock);
register_kernel_break_hook(&kgdb_brkpt_hook);
register_kernel_break_hook(&kgdb_compiled_brkpt_hook);
register_kernel_step_hook(&kgdb_step_hook);
+ spin_unlock(&kgdb_hook_lock);
return 0;
}
@@ -329,9 +333,11 @@ int kgdb_arch_init(void)
*/
void kgdb_arch_exit(void)
{
+ spin_lock(&kgdb_hook_lock);
unregister_kernel_break_hook(&kgdb_brkpt_hook);
unregister_kernel_break_hook(&kgdb_compiled_brkpt_hook);
unregister_kernel_step_hook(&kgdb_step_hook);
+ spin_unlock(&kgdb_hook_lock);
unregister_die_notifier(&kgdb_notifier);
}
diff --git a/arch/arm64/kernel/probes/kprobes.c b/arch/arm64/kernel/probes/kprobes.c
index 4268678d0e86..b0e28d48bb19 100644
--- a/arch/arm64/kernel/probes/kprobes.c
+++ b/arch/arm64/kernel/probes/kprobes.c
@@ -360,7 +360,7 @@ kprobe_breakpoint_ss_handler(struct pt_regs *regs, unsigned long esr)
}
static struct break_hook kprobes_break_ss_hook = {
- .imm = KPROBES_BRK_SS_IMM,
+ .imm = KPROBES_SS_BRK_IMM,
.fn = kprobe_breakpoint_ss_handler,
};
diff --git a/arch/arm64/kernel/probes/uprobes.c b/arch/arm64/kernel/probes/uprobes.c
index d49aef2657cd..24130161c62d 100644
--- a/arch/arm64/kernel/probes/uprobes.c
+++ b/arch/arm64/kernel/probes/uprobes.c
@@ -190,6 +190,7 @@ static int uprobe_single_step_handler(struct pt_regs *regs,
static struct break_hook uprobes_break_hook = {
.imm = UPROBES_BRK_IMM,
.fn = uprobe_breakpoint_handler,
+ .user = 1,
};
/* uprobe single step handler hook */
@@ -199,7 +200,7 @@ static struct step_hook uprobes_step_hook = {
static int __init arch_init_uprobes(void)
{
- register_user_break_hook(&uprobes_break_hook);
+ register_kernel_break_hook(&uprobes_break_hook);
register_user_step_hook(&uprobes_step_hook);
return 0;
diff --git a/arch/arm64/kernel/traps.c b/arch/arm64/kernel/traps.c
index 9e22683aa921..6aefb0ba41ec 100644
--- a/arch/arm64/kernel/traps.c
+++ b/arch/arm64/kernel/traps.c
@@ -1025,8 +1025,8 @@ static int cfi_handler(struct pt_regs *regs, unsigned long esr)
static struct break_hook cfi_break_hook = {
.fn = cfi_handler,
- .imm = CFI_BRK_IMM_BASE,
- .mask = CFI_BRK_IMM_MASK,
+ .imm = CFI_BRK_IMM,
+ .mask = CFI_BRK_MASK,
};
#endif /* CONFIG_CFI_CLANG */
--
2.34.1
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