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authorAndy Lutomirski <luto@kernel.org>2015-10-05 17:48:11 -0700
committerIngo Molnar <mingo@kernel.org>2015-10-09 09:41:09 +0200
commita474e67c913d3ebaf02ba9d7835d5299d226c3ed (patch)
tree6b9ec92426db8a6e453c3748f34eda2f7cd070da /arch/x86/entry
parent710246df58041106b7de645f4b45770f8a59a269 (diff)
downloadlinux-a474e67c913d3ebaf02ba9d7835d5299d226c3ed.tar.bz2
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@kernel.org> Cc: Andy Lutomirski <luto@amacapital.net> Cc: Borislav Petkov <bp@alien8.de> Cc: Brian Gerst <brgerst@gmail.com> Cc: Denys Vlasenko <dvlasenk@redhat.com> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: linux-kernel@vger.kernel.org Link: http://lkml.kernel.org/r/b74615af58d785aa02d917213ec64e2022a2c796.1444091585.git.luto@kernel.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'arch/x86/entry')
-rw-r--r--arch/x86/entry/entry_64_compat.S90
-rw-r--r--arch/x86/entry/vdso/vdso32/system_call.S8
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 63ef9fa29002..8f109de51d03 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 */
- /* Unreachable. */
- ud2
+ /*
+ * User mode is traced as though IRQs are on, and SYSENTER
+ * turned them off.
+ */
+ TRACE_IRQS_OFF
+
+ 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