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Message-Id: <d7ccd3ddb70380a7b0beb61d9b45083a9af66cf9.1441146105.git.luto@kernel.org> Date: Tue, 1 Sep 2015 15:41:21 -0700 From: Andy Lutomirski <luto@...nel.org> To: x86@...nel.org, linux-kernel@...r.kernel.org Cc: Brian Gerst <brgerst@...il.com>, Denys Vlasenko <dvlasenk@...hat.com>, Linus Torvalds <torvalds@...ux-foundation.org>, Borislav Petkov <bp@...en8.de>, Andy Lutomirski <luto@...nel.org> Subject: [RFC 21/30] x86/vdso/compat: Wire up SYSENTER and SYSCSALL for compat userspace What, you didn't realize that SYSENTER and SYSCALL were actually the same thing? :) Unlike the old code, this actually passes the ptrace_syscall_32 test on AMD systems. Signed-off-by: Andy Lutomirski <luto@...nel.org> --- arch/x86/entry/entry_64_compat.S | 90 +++++++++++++++++++------------- arch/x86/entry/vdso/vdso32/system_call.S | 8 +++ 2 files changed, 62 insertions(+), 36 deletions(-) diff --git a/arch/x86/entry/entry_64_compat.S b/arch/x86/entry/entry_64_compat.S index f384bb79b4fb..1c8ac2e64a1e 100644 --- a/arch/x86/entry/entry_64_compat.S +++ b/arch/x86/entry/entry_64_compat.S @@ -52,15 +52,18 @@ ENTRY(entry_SYSENTER_compat) SWAPGS_UNSAFE_STACK movq PER_CPU_VAR(cpu_current_top_of_stack), %rsp - /* Zero-extending 32-bit regs, do not remove */ - movl %ebp, %ebp + /* + * User tracing code (ptrace or signal handlers) might assume that + * the saved RAX contains a 32-bit number when we're invoking a 32-bit + * syscall. Just in case the high bits are nonzero, zero-extend + * the syscall number. (This could almost certainly be deleted + * with no ill effects.) + */ movl %eax, %eax - movl ASM_THREAD_INFO(TI_sysenter_return, %rsp, 0), %r10d - /* Construct struct pt_regs on stack */ pushq $__USER32_DS /* pt_regs->ss */ - pushq %rbp /* pt_regs->sp */ + pushq %rcx /* pt_regs->sp */ /* * Push flags. This is nasty. First, interrupts are currently @@ -70,17 +73,28 @@ ENTRY(entry_SYSENTER_compat) */ pushfq /* pt_regs->flags (except IF = 0) */ orl $X86_EFLAGS_IF, (%rsp) /* Fix saved flags */ + ASM_CLAC /* Clear AC after saving FLAGS */ pushq $__USER32_CS /* pt_regs->cs */ - pushq %r10 /* pt_regs->ip = thread_info->sysenter_return */ + xorq %r8,%r8 + pushq %r8 /* pt_regs->ip = 0 (placeholder) */ pushq %rax /* pt_regs->orig_ax */ pushq %rdi /* pt_regs->di */ pushq %rsi /* pt_regs->si */ pushq %rdx /* pt_regs->dx */ - pushq %rcx /* pt_regs->cx */ + pushq %rcx /* pt_regs->cx (will be overwritten) */ pushq $-ENOSYS /* pt_regs->ax */ + pushq %r8 /* pt_regs->r8 = 0 */ + pushq %r8 /* pt_regs->r9 = 0 */ + pushq %r8 /* pt_regs->r10 = 0 */ + pushq %r8 /* pt_regs->r11 = 0 */ + pushq %rbx /* pt_regs->rbx */ + pushq %rbp /* pt_regs->rbp */ + pushq %r8 /* pt_regs->r12 = 0 */ + pushq %r8 /* pt_regs->r13 = 0 */ + pushq %r8 /* pt_regs->r14 = 0 */ + pushq %r8 /* pt_regs->r15 = 0 */ cld - sub $(10*8), %rsp /* pt_regs->r8-11, bp, bx, r12-15 not saved */ /* * Sysenter doesn't filter flags, so we need to clear NT @@ -93,16 +107,15 @@ ENTRY(entry_SYSENTER_compat) jnz sysenter_fix_flags sysenter_flags_fixed: - /* Temporary: SYSENTER is disabled. */ -#ifdef CONFIG_CONTEXT_TRACKING - call enter_from_user_mode -#endif - ENABLE_INTERRUPTS(CLBR_NONE) - movl $11, %edi - call do_exit + /* + * User mode is traced as though IRQs are on, and SYSENTER + * turned them off. + */ + TRACE_IRQS_OFF - /* Unreachable. */ - ud2 + movq %rsp, %rdi + call do_fast_syscall_32 + jmp .Lsyscall_32_done sysenter_fix_flags: pushq $X86_EFLAGS_FIXED @@ -135,26 +148,14 @@ ENDPROC(entry_SYSENTER_compat) * edi arg5 * esp user stack * 0(%esp) arg6 - * - * This is purely a fast path. For anything complicated we use the int 0x80 - * path below. We set up a complete hardware stack frame to share code - * with the int 0x80 path. */ ENTRY(entry_SYSCALL_compat) - /* - * Interrupts are off on entry. - * We do not frame this tiny irq-off block with TRACE_IRQS_OFF/ON, - * it is too small to ever cause noticeable irq latency. - */ + /* Interrupts are off on entry. */ SWAPGS_UNSAFE_STACK - /* Temporary: SYSCALL32 is disabled. */ - movl $-ENOSYS, %eax - USERGS_SYSRET32 - + /* Stash user ESP and switch to the kernel stack. */ movl %esp, %r8d movq PER_CPU_VAR(cpu_current_top_of_stack), %rsp - ENABLE_INTERRUPTS(CLBR_NONE) /* Zero-extending 32-bit regs, do not remove */ movl %eax, %eax @@ -169,13 +170,29 @@ ENTRY(entry_SYSCALL_compat) pushq %rdi /* pt_regs->di */ pushq %rsi /* pt_regs->si */ pushq %rdx /* pt_regs->dx */ - pushq %rbp /* pt_regs->cx */ - movl %ebp, %ecx + pushq %rcx /* pt_regs->cx (will be overwritten) */ pushq $-ENOSYS /* pt_regs->ax */ - sub $(10*8), %rsp /* pt_regs->r8-11, bp, bx, r12-15 not saved */ + xorq %r8,%r8 + pushq %r8 /* pt_regs->r8 = 0 */ + pushq %r8 /* pt_regs->r9 = 0 */ + pushq %r8 /* pt_regs->r10 = 0 */ + pushq %r8 /* pt_regs->r11 = 0 */ + pushq %rbx /* pt_regs->rbx */ + pushq %rbp /* pt_regs->rbp */ + pushq %r8 /* pt_regs->r12 = 0 */ + pushq %r8 /* pt_regs->r13 = 0 */ + pushq %r8 /* pt_regs->r14 = 0 */ + pushq %r8 /* pt_regs->r15 = 0 */ + + /* + * User mode is traced as though IRQs are on, and SYSENTER + * turned them off. + */ + TRACE_IRQS_OFF - /* Unreachable. */ - ud2 + movq %rsp, %rdi + call do_fast_syscall_32 + jmp .Lsyscall_32_done END(entry_SYSCALL_compat) /* @@ -243,6 +260,7 @@ ENTRY(entry_INT80_compat) movq %rsp, %rdi call do_int80_syscall_32 +.Lsyscall_32_done: /* Go back to user mode. */ TRACE_IRQS_ON diff --git a/arch/x86/entry/vdso/vdso32/system_call.S b/arch/x86/entry/vdso/vdso32/system_call.S index d591fe93e93a..00157cae71e0 100644 --- a/arch/x86/entry/vdso/vdso32/system_call.S +++ b/arch/x86/entry/vdso/vdso32/system_call.S @@ -3,6 +3,8 @@ */ #include <asm/dwarf2.h> +#include <asm/cpufeature.h> +#include <asm/alternative-asm.h> /* * First get the common code for the sigreturn entry points. @@ -28,6 +30,12 @@ __kernel_vsyscall: CFI_REL_OFFSET ecx, 0 movl %esp, %ecx +#ifdef CONFIG_X86_64 + /* If SYSENTER (Intel) or SYSCALL32 (AMD) is available, use it. */ + ALTERNATIVE_2 "", "sysenter", X86_FEATURE_SYSENTER32, \ + "syscall", X86_FEATURE_SYSCALL32 +#endif + /* Enter using int $0x80 */ movl (%esp), %ecx int $0x80 -- 2.4.3 -- 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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