[PATCH v6 47/76] x86/dumpstack/64: Add noinstr version of get_stack_info()

Joerg Roedel
2020-08-24T09:07:42Z

From: Joerg Roedel <jroedel@suse.de>

The get_stack_info functionality is needed in the entry code for the #VC
exception handler. Provide a version of it in the .text.noinstr
section which can be called safely from there.

Signed-off-by: Joerg Roedel <jroedel@suse.de>
Link: https://lore.kernel.org/r/20200724160336.5435-47-joro@8bytes.org
---
arch/x86/include/asm/stacktrace.h | 2 ++
arch/x86/kernel/dumpstack.c | 7 +++---
arch/x86/kernel/dumpstack_64.c | 39 ++++++++++++++++++-------------
arch/x86/mm/cpu_entry_area.c | 3 ++-
4 files changed, 31 insertions(+), 20 deletions(-)

diff --git a/arch/x86/include/asm/stacktrace.h b/arch/x86/include/asm/stacktrace.h
index 5ae5a68e469d..49600643faba 100644
--- a/arch/x86/include/asm/stacktrace.h
+++ b/arch/x86/include/asm/stacktrace.h
@@ -35,6 +35,8 @@ bool in_entry_stack(unsigned long *stack, struct stack_info *info);

int get_stack_info(unsigned long *stack, struct task_struct *task,
struct stack_info *info, unsigned long *visit_mask);
+bool get_stack_info_noinstr(unsigned long *stack, struct task_struct *task,
+ struct stack_info *info);

const char *stack_type_name(enum stack_type type);

diff --git a/arch/x86/kernel/dumpstack.c b/arch/x86/kernel/dumpstack.c
index 48ce44576947..74147f7b3d82 100644
--- a/arch/x86/kernel/dumpstack.c
+++ b/arch/x86/kernel/dumpstack.c
@@ -29,8 +29,8 @@ static int die_counter;

static struct pt_regs exec_summary_regs;

-bool in_task_stack(unsigned long *stack, struct task_struct *task,
- struct stack_info *info)
+bool noinstr in_task_stack(unsigned long *stack, struct task_struct *task,
+ struct stack_info *info)
{
unsigned long *begin = task_stack_page(task);
unsigned long *end = task_stack_page(task) + THREAD_SIZE;
@@ -46,7 +46,8 @@ bool in_task_stack(unsigned long *stack, struct task_struct *task,
return true;
}

-bool in_entry_stack(unsigned long *stack, struct stack_info *info)
+/* Called from get_stack_info_noinstr - so must be noinstr too */
+bool noinstr in_entry_stack(unsigned long *stack, struct stack_info *info)
{
struct entry_stack *ss = cpu_entry_stack(smp_processor_id());

diff --git a/arch/x86/kernel/dumpstack_64.c b/arch/x86/kernel/dumpstack_64.c
index c49cf594714b..5a85730eb0ca 100644
--- a/arch/x86/kernel/dumpstack_64.c
+++ b/arch/x86/kernel/dumpstack_64.c
@@ -85,7 +85,7 @@ struct estack_pages estack_pages[CEA_ESTACK_PAGES] ____cacheline_aligned = {
EPAGERANGE(VC2),
};

-static bool in_exception_stack(unsigned long *stack, struct stack_info *info)
+static bool __always_inline in_exception_stack(unsigned long *stack, struct stack_info *info)
{
unsigned long begin, end, stk = (unsigned long)stack;
const struct estack_pages *ep;
@@ -126,7 +126,7 @@ static bool in_exception_stack(unsigned long *stack, struct stack_info *info)
return true;
}

-static bool in_irq_stack(unsigned long *stack, struct stack_info *info)
+static bool __always_inline in_irq_stack(unsigned long *stack, struct stack_info *info)
{
unsigned long *end = (unsigned long *)this_cpu_read(hardirq_stack_ptr);
unsigned long *begin = end - (IRQ_STACK_SIZE / sizeof(long));
@@ -151,32 +151,38 @@ static bool in_irq_stack(unsigned long *stack, struct stack_info *info)
return true;
}

-int get_stack_info(unsigned long *stack, struct task_struct *task,
- struct stack_info *info, unsigned long *visit_mask)
+bool noinstr get_stack_info_noinstr(unsigned long *stack, struct task_struct *task,
+ struct stack_info *info)
{
- if (!stack)
- goto unknown;
-
- task = task ? : current;
-
if (in_task_stack(stack, task, info))
- goto recursion_check;
+ return true;

if (task != current)
- goto unknown;
+ return false;

if (in_exception_stack(stack, info))
- goto recursion_check;
+ return true;

if (in_irq_stack(stack, info))
- goto recursion_check;
+ return true;

if (in_entry_stack(stack, info))
- goto recursion_check;
+ return true;

- goto unknown;
+ return false;
+}
+
+int get_stack_info(unsigned long *stack, struct task_struct *task,
+ struct stack_info *info, unsigned long *visit_mask)
+{
+ task = task ? : current;
+
+ if (!stack)
+ goto unknown;
+
+ if (!get_stack_info_noinstr(stack, task, info))
+ goto unknown;

-recursion_check:
/*
* Make sure we don't iterate through any given stack more than once.
* If it comes up a second time then there's something wrong going on:
@@ -196,4 +202,5 @@ int get_stack_info(unsigned long *stack, struct task_struct *task,
unknown:
info->type = STACK_TYPE_UNKNOWN;
return -EINVAL;
+
}
diff --git a/arch/x86/mm/cpu_entry_area.c b/arch/x86/mm/cpu_entry_area.c
index 770b613790b3..f5e1e60c9095 100644
--- a/arch/x86/mm/cpu_entry_area.c
+++ b/arch/x86/mm/cpu_entry_area.c
@@ -21,7 +21,8 @@ DEFINE_PER_CPU(struct cea_exception_stacks*, cea_exception_stacks);
DECLARE_PER_CPU_PAGE_ALIGNED(struct doublefault_stack, doublefault_stack);
#endif

-struct cpu_entry_area *get_cpu_entry_area(int cpu)
+/* Is called from entry code, so must be noinstr */
+noinstr struct cpu_entry_area *get_cpu_entry_area(int cpu)
{
unsigned long va = CPU_ENTRY_AREA_PER_CPU + cpu * CPU_ENTRY_AREA_SIZE;
BUILD_BUG_ON(sizeof(struct cpu_entry_area) % PAGE_SIZE != 0);
--
2.28.0