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Date: Thu, 19 Mar 2015 18:17:45 +0100 From: Denys Vlasenko <dvlasenk@...hat.com> To: Andy Lutomirski <luto@...capital.net> Cc: Denys Vlasenko <dvlasenk@...hat.com>, Linus Torvalds <torvalds@...ux-foundation.org>, Steven Rostedt <rostedt@...dmis.org>, Ingo Molnar <mingo@...nel.org>, Borislav Petkov <bp@...en8.de>, "H. Peter Anvin" <hpa@...or.com>, Oleg Nesterov <oleg@...hat.com>, Frederic Weisbecker <fweisbec@...il.com>, Alexei Starovoitov <ast@...mgrid.com>, Will Drewry <wad@...omium.org>, Kees Cook <keescook@...omium.org>, x86@...nel.org, linux-kernel@...r.kernel.org Subject: [PATCH 1/5] x86: change THREAD_INFO definition to not depend on KERNEL_STACK_OFFSET This changes 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@...hat.com> CC: Linus Torvalds <torvalds@...ux-foundation.org> CC: Steven Rostedt <rostedt@...dmis.org> CC: Ingo Molnar <mingo@...nel.org> CC: Borislav Petkov <bp@...en8.de> CC: "H. Peter Anvin" <hpa@...or.com> CC: Andy Lutomirski <luto@...capital.net> CC: Oleg Nesterov <oleg@...hat.com> CC: Frederic Weisbecker <fweisbec@...il.com> CC: Alexei Starovoitov <ast@...mgrid.com> CC: Will Drewry <wad@...omium.org> CC: Kees Cook <keescook@...omium.org> CC: x86@...nel.org CC: linux-kernel@...r.kernel.org --- Changes since last version: * split this change into a separate patch * on Borislav's request, improve comment atop THREAD_INFO definition. arch/x86/ia32/ia32entry.S | 30 +++++++++++++++--------------- arch/x86/include/asm/thread_info.h | 8 +++++--- arch/x86/kernel/entry_64.S | 4 ++-- 3 files changed, 22 insertions(+), 20 deletions(-) diff --git a/arch/x86/ia32/ia32entry.S b/arch/x86/ia32/ia32entry.S index ad9efef..50190e1 100644 --- 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 ba115eb..0519945 100644 --- 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 0c91256..d785a7d 100644 --- 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 -- 1.8.1.4 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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