From: Denys Vlasenko Date: Mon, 9 Mar 2015 18:39:23 +0000 (+0100) Subject: x86/asm/entry/64: Save user RSP in pt_regs->sp on SYSCALL64 fastpath X-Git-Tag: firefly_0821_release~176^2~2028^2~91 X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=263042e4630a85e856b4a8cd72f28dab33ef4741;p=firefly-linux-kernel-4.4.55.git x86/asm/entry/64: Save user RSP in pt_regs->sp on SYSCALL64 fastpath Prepare for the removal of 'usersp', by simplifying PER_CPU(old_rsp) usage: - use it only as temp storage - store the userspace stack pointer immediately in pt_regs->sp on syscall entry, instead of using it later, on syscall exit. - change C code to use pt_regs->sp only, instead of PER_CPU(old_rsp) and task->thread.usersp. FIXUP/RESTORE_TOP_OF_STACK are simplified as well. Signed-off-by: Denys Vlasenko Cc: Alexei Starovoitov Cc: Andy Lutomirski Cc: Borislav Petkov Cc: Frederic Weisbecker Cc: H. Peter Anvin Cc: Kees Cook Cc: Linus Torvalds Cc: Oleg Nesterov Cc: Steven Rostedt Cc: Will Drewry Link: http://lkml.kernel.org/r/1425926364-9526-4-git-send-email-dvlasenk@redhat.com Signed-off-by: Ingo Molnar --- diff --git a/arch/x86/include/asm/compat.h b/arch/x86/include/asm/compat.h index 59c6c401f79f..acdee09228b3 100644 --- a/arch/x86/include/asm/compat.h +++ b/arch/x86/include/asm/compat.h @@ -301,7 +301,7 @@ static inline void __user *arch_compat_alloc_user_space(long len) sp = task_pt_regs(current)->sp; } else { /* -128 for the x32 ABI redzone */ - sp = this_cpu_read(old_rsp) - 128; + sp = task_pt_regs(current)->sp - 128; } return (void __user *)round_down(sp - len, 16); diff --git a/arch/x86/include/asm/ptrace.h b/arch/x86/include/asm/ptrace.h index 4077d963a1a0..74bb2e0f3030 100644 --- a/arch/x86/include/asm/ptrace.h +++ b/arch/x86/include/asm/ptrace.h @@ -145,12 +145,8 @@ static inline bool user_64bit_mode(struct pt_regs *regs) #endif } -#define current_user_stack_pointer() this_cpu_read(old_rsp) -/* ia32 vs. x32 difference */ -#define compat_user_stack_pointer() \ - (test_thread_flag(TIF_IA32) \ - ? current_pt_regs()->sp \ - : this_cpu_read(old_rsp)) +#define current_user_stack_pointer() current_pt_regs()->sp +#define compat_user_stack_pointer() current_pt_regs()->sp #endif #ifdef CONFIG_X86_32 diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S index 703ced057199..d86788c3257b 100644 --- a/arch/x86/kernel/entry_64.S +++ b/arch/x86/kernel/entry_64.S @@ -128,8 +128,6 @@ ENDPROC(native_usergs_sysret64) * manipulation. */ .macro FIXUP_TOP_OF_STACK tmp offset=0 - movq PER_CPU_VAR(old_rsp),\tmp - movq \tmp,RSP+\offset(%rsp) movq $__USER_DS,SS+\offset(%rsp) movq $__USER_CS,CS+\offset(%rsp) movq RIP+\offset(%rsp),\tmp /* get rip */ @@ -139,8 +137,7 @@ ENDPROC(native_usergs_sysret64) .endm .macro RESTORE_TOP_OF_STACK tmp offset=0 - movq RSP+\offset(%rsp),\tmp - movq \tmp,PER_CPU_VAR(old_rsp) + /* nothing to do */ .endm /* @@ -222,9 +219,6 @@ ENDPROC(native_usergs_sysret64) * Interrupts are off on entry. * Only called from user space. * - * XXX if we had a free scratch register we could save the RSP into the stack frame - * and report it properly in ps. Unfortunately we haven't. - * * When user can change the frames always force IRET. That is because * it deals with uncanonical addresses better. SYSRET has trouble * with them due to bugs in both AMD and Intel CPUs. @@ -253,11 +247,13 @@ GLOBAL(system_call_after_swapgs) */ ENABLE_INTERRUPTS(CLBR_NONE) ALLOC_PT_GPREGS_ON_STACK 8 /* +8: space for orig_ax */ + movq %rcx,RIP(%rsp) + movq PER_CPU_VAR(old_rsp),%rcx + movq %r11,EFLAGS(%rsp) + movq %rcx,RSP(%rsp) + movq_cfi rax,ORIG_RAX SAVE_C_REGS_EXCEPT_RAX_RCX_R11 movq $-ENOSYS,RAX(%rsp) - movq_cfi rax,ORIG_RAX - movq %r11,EFLAGS(%rsp) - movq %rcx,RIP(%rsp) CFI_REL_OFFSET rip,RIP testl $_TIF_WORK_SYSCALL_ENTRY,TI_flags+THREAD_INFO(%rsp,RIP) jnz tracesys @@ -293,7 +289,7 @@ ret_from_sys_call: CFI_REGISTER rip,rcx movq EFLAGS(%rsp),%r11 /*CFI_REGISTER rflags,r11*/ - movq PER_CPU_VAR(old_rsp), %rsp + movq RSP(%rsp),%rsp /* * 64bit SYSRET restores rip from rcx, * rflags from r11 (but RF and VM bits are forced to 0), diff --git a/arch/x86/kernel/perf_regs.c b/arch/x86/kernel/perf_regs.c index 781861cc5ee8..02a8720414c0 100644 --- a/arch/x86/kernel/perf_regs.c +++ b/arch/x86/kernel/perf_regs.c @@ -177,7 +177,7 @@ void perf_get_regs_user(struct perf_regs *regs_user, * than just blindly copying user_regs. */ regs_user->abi = PERF_SAMPLE_REGS_ABI_64; - regs_user_copy->sp = this_cpu_read(old_rsp); + regs_user_copy->sp = user_regs->sp; regs_user_copy->cs = __USER_CS; regs_user_copy->ss = __USER_DS; regs_user_copy->cx = -1; /* usually contains garbage */ diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c index 1e393d27d701..e8c124a1f885 100644 --- a/arch/x86/kernel/process_64.c +++ b/arch/x86/kernel/process_64.c @@ -602,6 +602,5 @@ long sys_arch_prctl(int code, unsigned long addr) unsigned long KSTK_ESP(struct task_struct *task) { - return (test_tsk_thread_flag(task, TIF_IA32)) ? - (task_pt_regs(task)->sp) : ((task)->thread.usersp); + return task_pt_regs(task)->sp; }