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authorAndi Kleen2006-03-12 23:52:59 +0100
committerLinus Torvalds2006-03-12 22:56:29 -0800
commitc33d4568aca9028a22857f94f5e0850012b6444b (patch)
tree7a33d918e4d35b0444820595cb2aaaae1f1f5bfa
parent31fe4d331729e9687db84521c3ceb8e43390efcf (diff)
[PATCH] x86-64: 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. Cc: Ernie Petrides <petrides@redhat.com> Signed-off-by: Andi Kleen <ak@suse.de> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
-rw-r--r--arch/x86_64/kernel/entry.S29
1 files changed, 11 insertions, 18 deletions
diff --git a/arch/x86_64/kernel/entry.S b/arch/x86_64/kernel/entry.S
index 7c10e9009d61..22cb6ee074b9 100644
--- a/arch/x86_64/kernel/entry.S
+++ b/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