Attachment 72754 Details for Bug 156580

[patch] Correct 2.6 fix

signal-iret (text/plain), 2.45 KB, created by Andreas Kleen on 2006-03-14 12:24:51 UTC

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Creator: Andreas Kleen

Created: 2006-03-14 12:24:51 UTC

Size: 2.45 KB

patch

obsolete

>Fix up handling of non canonical user RIPs 
>
>EM64T CPUs have somewhat weird error reporting for non canonical RIPs in SYSRET.
>We can't handle any exceptions there because the exception handler would
>end up running on the user stack which is unsafe. To avoid problems
>any code that might end up with a user touched pt_regs should return
>using int_ret_from_syscall. int_ret_from_syscall ends up using IRET,
>which allows safe exceptions.
>
>Signed-off-by: Andi Kleen <ak@suse.de>
>
>---
> arch/x86_64/kernel/entry.S |   29 +++++++++++------------------
> 1 files changed, 11 insertions(+), 18 deletions(-)
>
>Index: linux/arch/x86_64/kernel/entry.S
>===================================================================
>--- linux.orig/arch/x86_64/kernel/entry.S
>+++ linux/arch/x86_64/kernel/entry.S
>@@ -178,6 +178,12 @@ rff_trace:
>  * Interrupts are off on entry.
>  * Only called from user space.
>  *
>+ * EM64T CPUs have somewhat weird error reporting for non canonical RIPs in SYSRET. 
>+ * We can't handle any exceptions there because the exception handler would
>+ * end up running on the user stack which is unsafe. To avoid problems 
>+ * any code that might end up with a user touched pt_regs should return
>+ * using int_ret_from_syscall.
>+ *
>  * 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.
>  */ 			 		
>@@ -254,7 +260,9 @@ sysret_signal:
> 	xorl %esi,%esi # oldset -> arg2
> 	call ptregscall_common
> 1:	movl $_TIF_NEED_RESCHED,%edi
>-	jmp sysret_check
>+	/* Stack frame might have been changed. The IRET path does
>+	   some additional checks to handle this */
>+	jmp int_with_check
> 	
> badsys:
> 	movq $-ENOSYS,RAX-ARGOFFSET(%rsp)
>@@ -280,7 +288,8 @@ tracesys:			 
> 	call syscall_trace_leave
> 	RESTORE_TOP_OF_STACK %rbx
> 	RESTORE_REST
>-	jmp ret_from_sys_call
>+	/* Stack frame might have been changed. Use the more careful IRET path */
>+	jmp int_ret_from_sys_call
> 	CFI_ENDPROC
> 		
> /* 
>@@ -408,25 +417,9 @@ ENTRY(stub_execve)
> 	CFI_ADJUST_CFA_OFFSET -8
> 	CFI_REGISTER rip, r11
> 	SAVE_REST
>-	movq %r11, %r15
>-	CFI_REGISTER rip, r15
> 	FIXUP_TOP_OF_STACK %r11
> 	call sys_execve
>-	GET_THREAD_INFO(%rcx)
>-	bt $TIF_IA32,threadinfo_flags(%rcx)
>-	CFI_REMEMBER_STATE
>-	jc exec_32bit
> 	RESTORE_TOP_OF_STACK %r11
>-	movq %r15, %r11
>-	CFI_REGISTER rip, r11
>-	RESTORE_REST
>-	pushq %r11
>-	CFI_ADJUST_CFA_OFFSET 8
>-	CFI_REL_OFFSET rip, 0
>-	ret
>-
>-exec_32bit:
>-	CFI_RESTORE_STATE
> 	movq %rax,RAX(%rsp)
> 	RESTORE_REST
> 	jmp int_ret_from_sys_call

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Attachments on bug 156580: 72752 | 72753 | 72754 | 75839 | 75840