x86/asm/entry/64: Change the THREAD_INFO() definition to not depend on KERNEL_STACK_O...

This changes the THREAD_INFO() definition and all its callsites
so that they do not count stack position from
(top of stack - KERNEL_STACK_OFFSET), but from top of stack.

Semi-mysterious expressions THREAD_INFO(%rsp,RIP) - "why RIP??"
are now replaced by more logical THREAD_INFO(%rsp,SIZEOF_PTREGS)
- "calculate thread_info's address using information that
rsp is SIZEOF_PTREGS bytes below top of stack".

While at it, replace "(off)-THREAD_SIZE(reg)" with equivalent
"((off)-THREAD_SIZE)(reg)". The form without parentheses
falsely looks like we invoke THREAD_SIZE() macro.

Improve comment atop THREAD_INFO macro definition.

This patch does not change generated code (verified by objdump).

Signed-off-by: Denys Vlasenko <dvlasenk@redhat.com>
Acked-by: Borislav Petkov <bp@suse.de>
Acked-by: Andy Lutomirski <luto@kernel.org>
Cc: Alexei Starovoitov <ast@plumgrid.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Will Drewry <wad@chromium.org>
Link: http://lkml.kernel.org/r/1426785469-15125-1-git-send-email-dvlasenk@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

diff --git a/arch/x86/ia32/ia32entry.S b/arch/x86/ia32/ia32entry.S
index ad9efef..50190e1 100644 (file)
--- a/arch/x86/ia32/ia32entry.S
+++ b/arch/x86/ia32/ia32entry.S
@@ -127,7 +127,7 @@ ENTRY(ia32_sysenter_target)
        CFI_REL_OFFSET rsp,0
        pushfq_cfi
        /*CFI_REL_OFFSET rflags,0*/
-       movl    TI_sysenter_return+THREAD_INFO(%rsp,3*8-KERNEL_STACK_OFFSET),%r10d
+       movl    TI_sysenter_return+THREAD_INFO(%rsp,3*8),%r10d
        CFI_REGISTER rip,r10
        pushq_cfi $__USER32_CS
        /*CFI_REL_OFFSET cs,0*/
@@ -159,8 +159,8 @@ ENTRY(ia32_sysenter_target)
        jnz sysenter_fix_flags
 sysenter_flags_fixed:
 
-       orl     $TS_COMPAT,TI_status+THREAD_INFO(%rsp,RIP)
-       testl   $_TIF_WORK_SYSCALL_ENTRY,TI_flags+THREAD_INFO(%rsp,RIP)
+       orl     $TS_COMPAT,TI_status+THREAD_INFO(%rsp,SIZEOF_PTREGS)
+       testl   $_TIF_WORK_SYSCALL_ENTRY,TI_flags+THREAD_INFO(%rsp,SIZEOF_PTREGS)
        CFI_REMEMBER_STATE
        jnz  sysenter_tracesys
        cmpq    $(IA32_NR_syscalls-1),%rax
@@ -177,10 +177,10 @@ sysenter_dispatch:
        movq    %rax,RAX(%rsp)
        DISABLE_INTERRUPTS(CLBR_NONE)
        TRACE_IRQS_OFF
-       testl   $_TIF_ALLWORK_MASK,TI_flags+THREAD_INFO(%rsp,RIP)
+       testl   $_TIF_ALLWORK_MASK,TI_flags+THREAD_INFO(%rsp,SIZEOF_PTREGS)
        jnz     sysexit_audit
 sysexit_from_sys_call:
-       andl    $~TS_COMPAT,TI_status+THREAD_INFO(%rsp,RIP)
+       andl    $~TS_COMPAT,TI_status+THREAD_INFO(%rsp,SIZEOF_PTREGS)
        /* clear IF, that popfq doesn't enable interrupts early */
        andl    $~0x200,EFLAGS(%rsp)
        movl    RIP(%rsp),%edx          /* User %eip */
@@ -225,7 +225,7 @@ sysexit_from_sys_call:
        .endm
 
        .macro auditsys_exit exit
-       testl $(_TIF_ALLWORK_MASK & ~_TIF_SYSCALL_AUDIT),TI_flags+THREAD_INFO(%rsp,RIP)
+       testl $(_TIF_ALLWORK_MASK & ~_TIF_SYSCALL_AUDIT),TI_flags+THREAD_INFO(%rsp,SIZEOF_PTREGS)
        jnz ia32_ret_from_sys_call
        TRACE_IRQS_ON
        ENABLE_INTERRUPTS(CLBR_NONE)
@@ -240,7 +240,7 @@ sysexit_from_sys_call:
        movl $(_TIF_ALLWORK_MASK & ~_TIF_SYSCALL_AUDIT),%edi
        DISABLE_INTERRUPTS(CLBR_NONE)
        TRACE_IRQS_OFF
-       testl %edi,TI_flags+THREAD_INFO(%rsp,RIP)
+       testl %edi,TI_flags+THREAD_INFO(%rsp,SIZEOF_PTREGS)
        jz \exit
        CLEAR_RREGS
        jmp int_with_check
@@ -262,7 +262,7 @@ sysenter_fix_flags:
 
 sysenter_tracesys:
 #ifdef CONFIG_AUDITSYSCALL
-       testl   $(_TIF_WORK_SYSCALL_ENTRY & ~_TIF_SYSCALL_AUDIT),TI_flags+THREAD_INFO(%rsp,RIP)
+       testl   $(_TIF_WORK_SYSCALL_ENTRY & ~_TIF_SYSCALL_AUDIT),TI_flags+THREAD_INFO(%rsp,SIZEOF_PTREGS)
        jz      sysenter_auditsys
 #endif
        SAVE_EXTRA_REGS
@@ -346,8 +346,8 @@ ENTRY(ia32_cstar_target)
 1:     movl    (%r8),%r9d
        _ASM_EXTABLE(1b,ia32_badarg)
        ASM_CLAC
-       orl     $TS_COMPAT,TI_status+THREAD_INFO(%rsp,RIP)
-       testl   $_TIF_WORK_SYSCALL_ENTRY,TI_flags+THREAD_INFO(%rsp,RIP)
+       orl     $TS_COMPAT,TI_status+THREAD_INFO(%rsp,SIZEOF_PTREGS)
+       testl   $_TIF_WORK_SYSCALL_ENTRY,TI_flags+THREAD_INFO(%rsp,SIZEOF_PTREGS)
        CFI_REMEMBER_STATE
        jnz   cstar_tracesys
        cmpq $IA32_NR_syscalls-1,%rax
@@ -364,10 +364,10 @@ cstar_dispatch:
        movq %rax,RAX(%rsp)
        DISABLE_INTERRUPTS(CLBR_NONE)
        TRACE_IRQS_OFF
-       testl $_TIF_ALLWORK_MASK,TI_flags+THREAD_INFO(%rsp,RIP)
+       testl $_TIF_ALLWORK_MASK,TI_flags+THREAD_INFO(%rsp,SIZEOF_PTREGS)
        jnz sysretl_audit
 sysretl_from_sys_call:
-       andl $~TS_COMPAT,TI_status+THREAD_INFO(%rsp,RIP)
+       andl $~TS_COMPAT,TI_status+THREAD_INFO(%rsp,SIZEOF_PTREGS)
        RESTORE_RSI_RDI_RDX
        movl RIP(%rsp),%ecx
        CFI_REGISTER rip,rcx
@@ -402,7 +402,7 @@ sysretl_audit:
 
 cstar_tracesys:
 #ifdef CONFIG_AUDITSYSCALL
-       testl $(_TIF_WORK_SYSCALL_ENTRY & ~_TIF_SYSCALL_AUDIT),TI_flags+THREAD_INFO(%rsp,RIP)
+       testl $(_TIF_WORK_SYSCALL_ENTRY & ~_TIF_SYSCALL_AUDIT),TI_flags+THREAD_INFO(%rsp,SIZEOF_PTREGS)
        jz cstar_auditsys
 #endif
        xchgl %r9d,%ebp
@@ -469,8 +469,8 @@ ENTRY(ia32_syscall)
           this could be a problem. */
        ALLOC_PT_GPREGS_ON_STACK
        SAVE_C_REGS_EXCEPT_R891011
-       orl $TS_COMPAT,TI_status+THREAD_INFO(%rsp,RIP)
-       testl $_TIF_WORK_SYSCALL_ENTRY,TI_flags+THREAD_INFO(%rsp,RIP)
+       orl $TS_COMPAT,TI_status+THREAD_INFO(%rsp,SIZEOF_PTREGS)
+       testl $_TIF_WORK_SYSCALL_ENTRY,TI_flags+THREAD_INFO(%rsp,SIZEOF_PTREGS)
        jnz ia32_tracesys
        cmpq $(IA32_NR_syscalls-1),%rax
        ja ia32_badsys

diff --git a/arch/x86/include/asm/thread_info.h b/arch/x86/include/asm/thread_info.h
index 0abf7ab..ae9c2f1 100644 (file)
--- a/arch/x86/include/asm/thread_info.h
+++ b/arch/x86/include/asm/thread_info.h
@@ -207,10 +207,12 @@ static inline unsigned long current_stack_pointer(void)
        _ASM_SUB $(THREAD_SIZE-KERNEL_STACK_OFFSET),reg ;
 
 /*
- * Same if PER_CPU_VAR(kernel_stack) is, perhaps with some offset, already in
- * a certain register (to be used in assembler memory operands).
+ * ASM operand which evaluates to thread_info address
+ * if it is known that "reg" is exactly "off" bytes below stack top.
+ * Example (fetch thread_info->fieldname):
+ *  mov TI_fieldname+THREAD_INFO(reg, off),%eax
  */
-#define THREAD_INFO(reg, off) KERNEL_STACK_OFFSET+(off)-THREAD_SIZE(reg)
+#define THREAD_INFO(reg, off) ((off)-THREAD_SIZE)(reg)
 
 #endif
 

diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S
index 9184392..8076df9 100644 (file)
--- a/arch/x86/kernel/entry_64.S
+++ b/arch/x86/kernel/entry_64.S
@@ -258,7 +258,7 @@ GLOBAL(system_call_after_swapgs)
        SAVE_C_REGS_EXCEPT_RAX_RCX_R11
        movq    $-ENOSYS,RAX(%rsp)
        CFI_REL_OFFSET rip,RIP
-       testl $_TIF_WORK_SYSCALL_ENTRY,TI_flags+THREAD_INFO(%rsp,RIP)
+       testl $_TIF_WORK_SYSCALL_ENTRY,TI_flags+THREAD_INFO(%rsp,SIZEOF_PTREGS)
        jnz tracesys
 system_call_fastpath:
 #if __SYSCALL_MASK == ~0
@@ -276,7 +276,7 @@ system_call_fastpath:
  * Has incompletely filled pt_regs, iret frame is also incomplete.
  */
 ret_from_sys_call:
-       testl $_TIF_ALLWORK_MASK,TI_flags+THREAD_INFO(%rsp,RIP)
+       testl $_TIF_ALLWORK_MASK,TI_flags+THREAD_INFO(%rsp,SIZEOF_PTREGS)
        jnz int_ret_from_sys_call_fixup /* Go the the slow path */
 
        LOCKDEP_SYS_EXIT