[tip: x86/entry] x86/entry: Convert double fault exception to IDTENTRY_DF

From: tip-bot2 for Thomas Gleixner
Date: Tue May 19 2020 - 16:02:53 EST

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The following commit has been merged into the x86/entry branch of tip:

Commit-ID: 095b7a3e7745e6fb7cf0a1c09967c4f43e76f8f4
Gitweb: https://git.kernel.org/tip/095b7a3e7745e6fb7cf0a1c09967c4f43e76f8f4
Author: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
AuthorDate: Tue, 25 Feb 2020 23:33:31 +01:00
Committer: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
CommitterDate: Tue, 19 May 2020 16:04:15 +02:00

x86/entry: Convert double fault exception to IDTENTRY_DF

Convert #DF to IDTENTRY_DF
- Implement the C entry point with DEFINE_IDTENTRY_DF
- Emit the ASM stub with DECLARE_IDTENTRY_DF on 64bit
- Remove the ASM idtentry in 64bit
- Adjust the 32bit shim code
- Fixup the XEN/PV code
- Remove the old prototypes

No functional change.

Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Reviewed-by: Alexandre Chartre <alexandre.chartre@xxxxxxxxxx>
Acked-by: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Acked-by: Andy Lutomirski <luto@xxxxxxxxxx>
Link: https://lkml.kernel.org/r/20200505135315.583415264@xxxxxxxxxxxxx

---
arch/x86/entry/entry_32.S | 4 ++--
arch/x86/entry/entry_64.S | 10 +---------
arch/x86/include/asm/idtentry.h | 3 +++
arch/x86/include/asm/traps.h | 5 -----
arch/x86/kernel/doublefault_32.c | 10 ++++------
arch/x86/kernel/idt.c | 4 ++--
arch/x86/kernel/traps.c | 17 ++++++++++++++---
arch/x86/xen/enlighten_pv.c | 4 ++--
arch/x86/xen/xen-asm_64.S | 2 +-
9 files changed, 29 insertions(+), 30 deletions(-)

diff --git a/arch/x86/entry/entry_32.S b/arch/x86/entry/entry_32.S
index 30c6ed3..28d13f0 100644
--- a/arch/x86/entry/entry_32.S
+++ b/arch/x86/entry/entry_32.S
@@ -1488,7 +1488,7 @@ ret_to_user:
jmp restore_all_switch_stack
SYM_CODE_END(handle_exception)

-SYM_CODE_START(double_fault)
+SYM_CODE_START(asm_exc_double_fault)
1:
/*
* This is a task gate handler, not an interrupt gate handler.
@@ -1526,7 +1526,7 @@ SYM_CODE_START(double_fault)
1:
hlt
jmp 1b
-SYM_CODE_END(double_fault)
+SYM_CODE_END(asm_exc_double_fault)

/*
* NMI is doubly nasty. It can happen on the first instruction of
diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
index d302839..d983a0d 100644
--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -680,15 +680,9 @@ SYM_CODE_START(\asmsym)
call paranoid_entry
UNWIND_HINT_REGS

- /* Read CR2 early */
- GET_CR2_INTO(%r12);
-
- TRACE_IRQS_OFF
-
movq %rsp, %rdi /* pt_regs pointer into first argument */
movq ORIG_RAX(%rsp), %rsi /* get error code into 2nd argument*/
movq $-1, ORIG_RAX(%rsp) /* no syscall to restart */
- movq %r12, %rdx /* Move CR2 into 3rd argument */
call \cfunc

jmp paranoid_exit
@@ -918,7 +912,7 @@ SYM_INNER_LABEL(native_irq_return_iret, SYM_L_GLOBAL)
/*
* This may fault. Non-paranoid faults on return to userspace are
* handled by fixup_bad_iret. These include #SS, #GP, and #NP.
- * Double-faults due to espfix64 are handled in do_double_fault.
+ * Double-faults due to espfix64 are handled in exc_double_fault.
* Other faults here are fatal.
*/
iretq
@@ -1073,8 +1067,6 @@ apicinterrupt IRQ_WORK_VECTOR irq_work_interrupt smp_irq_work_interrupt

idtentry X86_TRAP_PF page_fault do_page_fault has_error_code=1

-idtentry_df X86_TRAP_DF double_fault do_double_fault
-
#ifdef CONFIG_XEN_PV
idtentry 512 /* dummy */ hypervisor_callback xen_do_hypervisor_callback has_error_code=0
#endif
diff --git a/arch/x86/include/asm/idtentry.h b/arch/x86/include/asm/idtentry.h
index 9521f32..ce97478 100644
--- a/arch/x86/include/asm/idtentry.h
+++ b/arch/x86/include/asm/idtentry.h
@@ -368,4 +368,7 @@ DECLARE_IDTENTRY_XEN(X86_TRAP_NMI, nmi);
DECLARE_IDTENTRY_DEBUG(X86_TRAP_DB, exc_debug);
DECLARE_IDTENTRY_XEN(X86_TRAP_DB, debug);

+/* #DF */
+DECLARE_IDTENTRY_DF(X86_TRAP_DF, exc_double_fault);
+
#endif
diff --git a/arch/x86/include/asm/traps.h b/arch/x86/include/asm/traps.h
index 9bd602d..f5a2e43 100644
--- a/arch/x86/include/asm/traps.h
+++ b/arch/x86/include/asm/traps.h
@@ -11,18 +11,13 @@

#define dotraplinkage __visible

-#ifdef CONFIG_X86_64
-asmlinkage void double_fault(void);
-#endif
asmlinkage void page_fault(void);
asmlinkage void async_page_fault(void);

#if defined(CONFIG_X86_64) && defined(CONFIG_XEN_PV)
-asmlinkage void xen_double_fault(void);
asmlinkage void xen_page_fault(void);
#endif

-dotraplinkage void do_double_fault(struct pt_regs *regs, long error_code, unsigned long cr2);
dotraplinkage void do_page_fault(struct pt_regs *regs, unsigned long error_code, unsigned long address);

#ifdef CONFIG_X86_64
diff --git a/arch/x86/kernel/doublefault_32.c b/arch/x86/kernel/doublefault_32.c
index 3793646..25692bd 100644
--- a/arch/x86/kernel/doublefault_32.c
+++ b/arch/x86/kernel/doublefault_32.c
@@ -11,7 +11,6 @@
#include <asm/desc.h>
#include <asm/traps.h>

-extern void double_fault(void);
#define ptr_ok(x) ((x) > PAGE_OFFSET && (x) < PAGE_OFFSET + MAXMEM)

#define TSS(x) this_cpu_read(cpu_tss_rw.x86_tss.x)
@@ -22,7 +21,7 @@ static void set_df_gdt_entry(unsigned int cpu);
* Called by double_fault with CR0.TS and EFLAGS.NT cleared. The CPU thinks
* we're running the doublefault task. Cannot return.
*/
-asmlinkage notrace void __noreturn doublefault_shim(void)
+asmlinkage noinstr void __noreturn doublefault_shim(void)
{
unsigned long cr2;
struct pt_regs regs;
@@ -41,7 +40,7 @@ asmlinkage notrace void __noreturn doublefault_shim(void)
* Fill in pt_regs. A downside of doing this in C is that the unwinder
* won't see it (no ENCODE_FRAME_POINTER), so a nested stack dump
* won't successfully unwind to the source of the double fault.
- * The main dump from do_double_fault() is fine, though, since it
+ * The main dump from exc_double_fault() is fine, though, since it
* uses these regs directly.
*
* If anyone ever cares, this could be moved to asm.
@@ -71,7 +70,7 @@ asmlinkage notrace void __noreturn doublefault_shim(void)
regs.cx = TSS(cx);
regs.bx = TSS(bx);

- do_double_fault(&regs, 0, cr2);
+ exc_double_fault(&regs, 0, cr2);

/*
* x86_32 does not save the original CR3 anywhere on a task switch.
@@ -85,7 +84,6 @@ asmlinkage notrace void __noreturn doublefault_shim(void)
*/
panic("cannot return from double fault\n");
}
-NOKPROBE_SYMBOL(doublefault_shim);

DEFINE_PER_CPU_PAGE_ALIGNED(struct doublefault_stack, doublefault_stack) = {
.tss = {
@@ -96,7 +94,7 @@ DEFINE_PER_CPU_PAGE_ALIGNED(struct doublefault_stack, doublefault_stack) = {
.ldt = 0,
.io_bitmap_base = IO_BITMAP_OFFSET_INVALID,

- .ip = (unsigned long) double_fault,
+ .ip = (unsigned long) asm_exc_double_fault,
.flags = X86_EFLAGS_FIXED,
.es = __USER_DS,
.cs = __KERNEL_CS,
diff --git a/arch/x86/kernel/idt.c b/arch/x86/kernel/idt.c
index ddf3f3d..ec55479 100644
--- a/arch/x86/kernel/idt.c
+++ b/arch/x86/kernel/idt.c
@@ -91,7 +91,7 @@ static const __initconst struct idt_data def_idts[] = {
#ifdef CONFIG_X86_32
TSKG(X86_TRAP_DF, GDT_ENTRY_DOUBLEFAULT_TSS),
#else
- INTG(X86_TRAP_DF, double_fault),
+ INTG(X86_TRAP_DF, asm_exc_double_fault),
#endif
INTG(X86_TRAP_DB, asm_exc_debug),

@@ -187,7 +187,7 @@ gate_desc debug_idt_table[IDT_ENTRIES] __page_aligned_bss;
static const __initconst struct idt_data ist_idts[] = {
ISTG(X86_TRAP_DB, asm_exc_debug, IST_INDEX_DB),
ISTG(X86_TRAP_NMI, asm_exc_nmi, IST_INDEX_NMI),
- ISTG(X86_TRAP_DF, double_fault, IST_INDEX_DF),
+ ISTG(X86_TRAP_DF, asm_exc_double_fault, IST_INDEX_DF),
#ifdef CONFIG_X86_MCE
ISTG(X86_TRAP_MC, asm_exc_machine_check, IST_INDEX_MCE),
#endif
diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
index 41bb0cb..35298c1 100644
--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -319,12 +319,19 @@ __visible void __noreturn handle_stack_overflow(const char *message,
* from the TSS. Returning is, in principle, okay, but changes to regs will
* be lost. If, for some reason, we need to return to a context with modified
* regs, the shim code could be adjusted to synchronize the registers.
+ *
+ * The 32bit #DF shim provides CR2 already as an argument. On 64bit it needs
+ * to be read before doing anything else.
*/
-dotraplinkage void do_double_fault(struct pt_regs *regs, long error_code, unsigned long cr2)
+DEFINE_IDTENTRY_DF(exc_double_fault)
{
static const char str[] = "double fault";
struct task_struct *tsk = current;

+#ifdef CONFIG_X86_64
+ unsigned long address = read_cr2();
+#endif
+
#ifdef CONFIG_X86_ESPFIX64
extern unsigned char native_irq_return_iret[];

@@ -381,6 +388,7 @@ dotraplinkage void do_double_fault(struct pt_regs *regs, long error_code, unsign
#endif

nmi_enter();
+ instrumentation_begin();
notify_die(DIE_TRAP, str, regs, error_code, X86_TRAP_DF, SIGSEGV);

tsk->thread.error_code = error_code;
@@ -424,13 +432,16 @@ dotraplinkage void do_double_fault(struct pt_regs *regs, long error_code, unsign
* stack even if the actual trigger for the double fault was
* something else.
*/
- if ((unsigned long)task_stack_page(tsk) - 1 - cr2 < PAGE_SIZE)
- handle_stack_overflow("kernel stack overflow (double-fault)", regs, cr2);
+ if ((unsigned long)task_stack_page(tsk) - 1 - address < PAGE_SIZE) {
+ handle_stack_overflow("kernel stack overflow (double-fault)",
+ regs, address);
+ }
#endif

pr_emerg("PANIC: double fault, error_code: 0x%lx\n", error_code);
die("double fault", regs, error_code);
panic("Machine halted.");
+ instrumentation_end();
}

DEFINE_IDTENTRY(exc_bounds)
diff --git a/arch/x86/xen/enlighten_pv.c b/arch/x86/xen/enlighten_pv.c
index 535dde1..851ea41 100644
--- a/arch/x86/xen/enlighten_pv.c
+++ b/arch/x86/xen/enlighten_pv.c
@@ -617,7 +617,7 @@ struct trap_array_entry {

static struct trap_array_entry trap_array[] = {
TRAP_ENTRY_REDIR(exc_debug, exc_xendebug, true ),
- { double_fault, xen_double_fault, true },
+ TRAP_ENTRY(exc_double_fault, true ),
#ifdef CONFIG_X86_MCE
TRAP_ENTRY(exc_machine_check, true ),
#endif
@@ -652,7 +652,7 @@ static bool __ref get_trap_addr(void **addr, unsigned int ist)
* Replace trap handler addresses by Xen specific ones.
* Check for known traps using IST and whitelist them.
* The debugger ones are the only ones we care about.
- * Xen will handle faults like double_fault, * so we should never see
+ * Xen will handle faults like double_fault, so we should never see
* them. Warn if there's an unexpected IST-using fault handler.
*/
for (nr = 0; nr < ARRAY_SIZE(trap_array); nr++) {
diff --git a/arch/x86/xen/xen-asm_64.S b/arch/x86/xen/xen-asm_64.S
index 9999ea3..e46d863 100644
--- a/arch/x86/xen/xen-asm_64.S
+++ b/arch/x86/xen/xen-asm_64.S
@@ -37,7 +37,7 @@ xen_pv_trap asm_exc_overflow
xen_pv_trap asm_exc_bounds
xen_pv_trap asm_exc_invalid_op
xen_pv_trap asm_exc_device_not_available
-xen_pv_trap double_fault
+xen_pv_trap asm_exc_double_fault
xen_pv_trap asm_exc_coproc_segment_overrun
xen_pv_trap asm_exc_invalid_tss
xen_pv_trap asm_exc_segment_not_present

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Previous message: tip-bot2 for Thomas Gleixner: "[tip: x86/entry] x86/entry: Convert Debug exception to IDTENTRY_DB"
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