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Subject[patch 07/60] x86/dumpstack: Add get_stack_info() support for the SYSENTER stack
From: Andy Lutomirski <luto@kernel.org>

get_stack_info() doesn't currently know about the SYSENTER stack, so
unwinding will fail if we entered the kernel on the SYSENTER stack
and haven't fully switched off. Teach get_stack_info() about the
SYSENTER stack.

With future patches applied that run part of the entry code on the
SYSENTER stack and introduce an intentional BUG(), I would get:

PANIC: double fault, error_code: 0x0
...
RIP: 0010:do_error_trap+0x33/0x1c0
...
Call Trace:
Code: ...

With this patch, I get:

PANIC: double fault, error_code: 0x0
...
Call Trace:
<SYSENTER>
? async_page_fault+0x36/0x60
? invalid_op+0x22/0x40
? async_page_fault+0x36/0x60
? sync_regs+0x3c/0x40
? sync_regs+0x2e/0x40
? error_entry+0x6c/0xd0
? async_page_fault+0x36/0x60
</SYSENTER>
Code: ...

which is a lot more informative.

Signed-off-by: Andy Lutomirski <luto@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Borislav Petkov <bp@suse.de>
Cc: Rik van Riel <riel@redhat.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: https://lkml.kernel.org/r/c32ce8b363e27fa9b4a4773297d5b4b0f4b39e94.1511497875.git.luto@kernel.org

---
arch/x86/include/asm/stacktrace.h | 3 +++
arch/x86/kernel/dumpstack.c | 19 +++++++++++++++++++
arch/x86/kernel/dumpstack_32.c | 6 ++++++
arch/x86/kernel/dumpstack_64.c | 6 ++++++
4 files changed, 34 insertions(+)

--- a/arch/x86/include/asm/stacktrace.h
+++ b/arch/x86/include/asm/stacktrace.h
@@ -16,6 +16,7 @@ enum stack_type {
STACK_TYPE_TASK,
STACK_TYPE_IRQ,
STACK_TYPE_SOFTIRQ,
+ STACK_TYPE_SYSENTER,
STACK_TYPE_EXCEPTION,
STACK_TYPE_EXCEPTION_LAST = STACK_TYPE_EXCEPTION + N_EXCEPTION_STACKS-1,
};
@@ -28,6 +29,8 @@ struct stack_info {
bool in_task_stack(unsigned long *stack, struct task_struct *task,
struct stack_info *info);

+bool in_sysenter_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);

--- a/arch/x86/kernel/dumpstack.c
+++ b/arch/x86/kernel/dumpstack.c
@@ -43,6 +43,25 @@ bool in_task_stack(unsigned long *stack,
return true;
}

+bool in_sysenter_stack(unsigned long *stack, struct stack_info *info)
+{
+ struct tss_struct *tss = this_cpu_ptr(&cpu_tss);
+
+ /* Treat the canary as part of the stack for unwinding purposes. */
+ void *begin = &tss->SYSENTER_stack_canary;
+ void *end = (void *)&tss->SYSENTER_stack + sizeof(tss->SYSENTER_stack);
+
+ if ((void *)stack < begin || (void *)stack >= end)
+ return false;
+
+ info->type = STACK_TYPE_SYSENTER;
+ info->begin = begin;
+ info->end = end;
+ info->next_sp = NULL;
+
+ return true;
+}
+
static void printk_stack_address(unsigned long address, int reliable,
char *log_lvl)
{
--- a/arch/x86/kernel/dumpstack_32.c
+++ b/arch/x86/kernel/dumpstack_32.c
@@ -26,6 +26,9 @@ const char *stack_type_name(enum stack_t
if (type == STACK_TYPE_SOFTIRQ)
return "SOFTIRQ";

+ if (type == STACK_TYPE_SYSENTER)
+ return "SYSENTER";
+
return NULL;
}

@@ -93,6 +96,9 @@ int get_stack_info(unsigned long *stack,
if (task != current)
goto unknown;

+ if (in_sysenter_stack(stack, info))
+ goto recursion_check;
+
if (in_hardirq_stack(stack, info))
goto recursion_check;

--- a/arch/x86/kernel/dumpstack_64.c
+++ b/arch/x86/kernel/dumpstack_64.c
@@ -37,6 +37,9 @@ const char *stack_type_name(enum stack_t
if (type == STACK_TYPE_IRQ)
return "IRQ";

+ if (type == STACK_TYPE_SYSENTER)
+ return "SYSENTER";
+
if (type >= STACK_TYPE_EXCEPTION && type <= STACK_TYPE_EXCEPTION_LAST)
return exception_stack_names[type - STACK_TYPE_EXCEPTION];

@@ -115,6 +118,9 @@ int get_stack_info(unsigned long *stack,
if (in_irq_stack(stack, info))
goto recursion_check;

+ if (in_sysenter_stack(stack, info))
+ goto recursion_check;
+
goto unknown;

recursion_check:

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