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Subject[patch 22/60] x86/entry: Clean up the SYSENTER_stack code
From: Andy Lutomirski <luto@kernel.org>

The existing code was a mess, mainly because C arrays are nasty. Turn
SYSENTER_stack into a struct, add a helper to find it, and do all the
obvious cleanups this enables.

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: Thomas Gleixner <tglx@linutronix.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/38ff640712c9b591b32de24a080daf13afaba234.1511497875.git.luto@kernel.org

---
arch/x86/entry/entry_32.S | 4 ++--
arch/x86/entry/entry_64.S | 2 +-
arch/x86/include/asm/fixmap.h | 5 +++++
arch/x86/include/asm/processor.h | 6 +++++-
arch/x86/kernel/asm-offsets.c | 6 ++----
arch/x86/kernel/cpu/common.c | 14 +++-----------
arch/x86/kernel/dumpstack.c | 7 +++----
7 files changed, 21 insertions(+), 23 deletions(-)

--- a/arch/x86/entry/entry_32.S
+++ b/arch/x86/entry/entry_32.S
@@ -942,7 +942,7 @@ ENTRY(debug)

/* Are we currently on the SYSENTER stack? */
movl PER_CPU_VAR(cpu_entry_area), %ecx
- addl $CPU_ENTRY_AREA_tss + CPU_TSS_SYSENTER_stack + SIZEOF_SYSENTER_stack, %ecx
+ addl $CPU_ENTRY_AREA_tss + TSS_STRUCT_SYSENTER_stack + SIZEOF_SYSENTER_stack, %ecx
subl %eax, %ecx /* ecx = (end of SYSENTER_stack) - esp */
cmpl $SIZEOF_SYSENTER_stack, %ecx
jb .Ldebug_from_sysenter_stack
@@ -986,7 +986,7 @@ ENTRY(nmi)

/* Are we currently on the SYSENTER stack? */
movl PER_CPU_VAR(cpu_entry_area), %ecx
- addl $CPU_ENTRY_AREA_tss + CPU_TSS_SYSENTER_stack + SIZEOF_SYSENTER_stack, %ecx
+ addl $CPU_ENTRY_AREA_tss + TSS_STRUCT_SYSENTER_stack + SIZEOF_SYSENTER_stack, %ecx
subl %eax, %ecx /* ecx = (end of SYSENTER_stack) - esp */
cmpl $SIZEOF_SYSENTER_stack, %ecx
jb .Lnmi_from_sysenter_stack
--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -158,7 +158,7 @@ END(native_usergs_sysret64)
_entry_trampoline - CPU_ENTRY_AREA_entry_trampoline(%rip)

/* The top word of the SYSENTER stack is hot and is usable as scratch space. */
-#define RSP_SCRATCH CPU_ENTRY_AREA_tss + CPU_TSS_SYSENTER_stack + \
+#define RSP_SCRATCH CPU_ENTRY_AREA_tss + TSS_STRUCT_SYSENTER_stack + \
SIZEOF_SYSENTER_stack - 8 + CPU_ENTRY_AREA

ENTRY(entry_SYSCALL_64_trampoline)
--- a/arch/x86/include/asm/fixmap.h
+++ b/arch/x86/include/asm/fixmap.h
@@ -239,5 +239,10 @@ static inline struct cpu_entry_area *get
return (struct cpu_entry_area *)__fix_to_virt(__get_cpu_entry_area_page_index(cpu, 0));
}

+static inline struct SYSENTER_stack *cpu_SYSENTER_stack(int cpu)
+{
+ return &get_cpu_entry_area(cpu)->tss.SYSENTER_stack;
+}
+
#endif /* !__ASSEMBLY__ */
#endif /* _ASM_X86_FIXMAP_H */
--- a/arch/x86/include/asm/processor.h
+++ b/arch/x86/include/asm/processor.h
@@ -337,12 +337,16 @@ struct x86_hw_tss {
#define IO_BITMAP_OFFSET (offsetof(struct tss_struct, io_bitmap) - offsetof(struct tss_struct, x86_tss))
#define INVALID_IO_BITMAP_OFFSET 0x8000

+struct SYSENTER_stack {
+ unsigned long words[64];
+};
+
struct tss_struct {
/*
* Space for the temporary SYSENTER stack, used for SYSENTER
* and the entry trampoline as well.
*/
- unsigned long SYSENTER_stack[64];
+ struct SYSENTER_stack SYSENTER_stack;

/*
* The fixed hardware portion. This must not cross a page boundary
--- a/arch/x86/kernel/asm-offsets.c
+++ b/arch/x86/kernel/asm-offsets.c
@@ -94,10 +94,8 @@ void common(void) {
BLANK();
DEFINE(PTREGS_SIZE, sizeof(struct pt_regs));

- /* Offset from cpu_tss to SYSENTER_stack */
- OFFSET(CPU_TSS_SYSENTER_stack, tss_struct, SYSENTER_stack);
- /* Size of SYSENTER_stack */
- DEFINE(SIZEOF_SYSENTER_stack, sizeof(((struct tss_struct *)0)->SYSENTER_stack));
+ OFFSET(TSS_STRUCT_SYSENTER_stack, tss_struct, SYSENTER_stack);
+ DEFINE(SIZEOF_SYSENTER_stack, sizeof(struct SYSENTER_stack));

/* Layout info for cpu_entry_area */
OFFSET(CPU_ENTRY_AREA_tss, cpu_entry_area, tss);
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -1339,12 +1339,7 @@ void enable_sep_cpu(void)

tss->x86_tss.ss1 = __KERNEL_CS;
wrmsr(MSR_IA32_SYSENTER_CS, tss->x86_tss.ss1, 0);
-
- wrmsr(MSR_IA32_SYSENTER_ESP,
- (unsigned long)&get_cpu_entry_area(cpu)->tss +
- offsetofend(struct tss_struct, SYSENTER_stack),
- 0);
-
+ wrmsr(MSR_IA32_SYSENTER_ESP, (unsigned long)(cpu_SYSENTER_stack(cpu) + 1), 0);
wrmsr(MSR_IA32_SYSENTER_EIP, (unsigned long)entry_SYSENTER_32, 0);

put_cpu();
@@ -1461,9 +1456,7 @@ void syscall_init(void)
* AMD doesn't allow SYSENTER in long mode (either 32- or 64-bit).
*/
wrmsrl_safe(MSR_IA32_SYSENTER_CS, (u64)__KERNEL_CS);
- wrmsrl_safe(MSR_IA32_SYSENTER_ESP,
- (unsigned long)&get_cpu_entry_area(cpu)->tss +
- offsetofend(struct tss_struct, SYSENTER_stack));
+ wrmsrl_safe(MSR_IA32_SYSENTER_ESP, (unsigned long)(cpu_SYSENTER_stack(cpu) + 1));
wrmsrl_safe(MSR_IA32_SYSENTER_EIP, (u64)entry_SYSENTER_compat);
#else
wrmsrl(MSR_CSTAR, (unsigned long)ignore_sysret);
@@ -1678,8 +1671,7 @@ void cpu_init(void)
*/
set_tss_desc(cpu, &get_cpu_entry_area(cpu)->tss.x86_tss);
load_TR_desc();
- load_sp0((unsigned long)&get_cpu_entry_area(cpu)->tss +
- offsetofend(struct tss_struct, SYSENTER_stack));
+ load_sp0((unsigned long)(cpu_SYSENTER_stack(cpu) + 1));

load_mm_ldt(&init_mm);

--- a/arch/x86/kernel/dumpstack.c
+++ b/arch/x86/kernel/dumpstack.c
@@ -45,11 +45,10 @@ bool in_task_stack(unsigned long *stack,

bool in_sysenter_stack(unsigned long *stack, struct stack_info *info)
{
- int cpu = smp_processor_id();
- struct tss_struct *tss = &get_cpu_entry_area(cpu)->tss;
+ struct SYSENTER_stack *ss = cpu_SYSENTER_stack(smp_processor_id());

- void *begin = &tss->SYSENTER_stack;
- void *end = (void *)&tss->SYSENTER_stack + sizeof(tss->SYSENTER_stack);
+ void *begin = ss;
+ void *end = ss + 1;

if ((void *)stack < begin || (void *)stack >= end)
return false;

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