[patch-RFC 23/26] Prepare x86_64 for TIF_SYSCALL_TRACE async flag set in entry.S
When the flag is inactive upon syscall entry and concurrently activated before exit, we seem to reach a state where the top of stack is incorrect upon return to user space. Fix this by fixing the top of stack and jumping to int_ret_from_sys_call if we detect that thread flags has been modified. We make sure that the thread flag read is coherent between our new test and the ALLWORK_MASK test by first saving it in a register used for both comparisons. Signed-off-by: Mathieu Desnoyers <[EMAIL PROTECTED]> CC: Andi Kleen <[EMAIL PROTECTED]> CC: Thomas Gleixner <[EMAIL PROTECTED]> CC: Ingo Molnar <[EMAIL PROTECTED]> CC: H. Peter Anvin <[EMAIL PROTECTED]> --- arch/x86/kernel/entry_64.S | 12 1 file changed, 12 insertions(+) Index: linux-2.6-lttng/arch/x86/kernel/entry_64.S === --- linux-2.6-lttng.orig/arch/x86/kernel/entry_64.S 2007-11-13 09:25:25.0 -0500 +++ linux-2.6-lttng/arch/x86/kernel/entry_64.S 2007-11-13 09:49:48.0 -0500 @@ -268,6 +268,8 @@ sysret_check: /* Handle reschedules */ /* edx: work, edi: workmask */ sysret_careful: + testl $(_TIF_SYSCALL_TRACE|_TIF_SYSCALL_AUDIT|_TIF_SECCOMP),%edx + jnz ret_from_sys_call_trace bt $TIF_NEED_RESCHED,%edx jnc sysret_signal TRACE_IRQS_ON @@ -279,6 +281,16 @@ sysret_careful: CFI_ADJUST_CFA_OFFSET -8 jmp sysret_check +ret_from_sys_call_trace: + TRACE_IRQS_ON + sti + SAVE_REST + FIXUP_TOP_OF_STACK %rdi + movq %rsp,%rdi + LOAD_ARGS ARGOFFSET /* reload args from stack in case ptrace changed it */ + RESTORE_REST + jmp int_ret_from_sys_call + /* Handle a signal */ sysret_signal: TRACE_IRQS_ON -- Mathieu Desnoyers Computer Engineering Ph.D. Student, Ecole Polytechnique de Montreal OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F BA06 3F25 A8FE 3BAE 9A68 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
[patch-RFC 23/26] Prepare x86_64 for TIF_SYSCALL_TRACE async flag set in entry.S
When the flag is inactive upon syscall entry and concurrently activated before exit, we seem to reach a state where the top of stack is incorrect upon return to user space. Fix this by fixing the top of stack and jumping to int_ret_from_sys_call if we detect that thread flags has been modified. We make sure that the thread flag read is coherent between our new test and the ALLWORK_MASK test by first saving it in a register used for both comparisons. Signed-off-by: Mathieu Desnoyers [EMAIL PROTECTED] CC: Andi Kleen [EMAIL PROTECTED] CC: Thomas Gleixner [EMAIL PROTECTED] CC: Ingo Molnar [EMAIL PROTECTED] CC: H. Peter Anvin [EMAIL PROTECTED] --- arch/x86/kernel/entry_64.S | 12 1 file changed, 12 insertions(+) Index: linux-2.6-lttng/arch/x86/kernel/entry_64.S === --- linux-2.6-lttng.orig/arch/x86/kernel/entry_64.S 2007-11-13 09:25:25.0 -0500 +++ linux-2.6-lttng/arch/x86/kernel/entry_64.S 2007-11-13 09:49:48.0 -0500 @@ -268,6 +268,8 @@ sysret_check: /* Handle reschedules */ /* edx: work, edi: workmask */ sysret_careful: + testl $(_TIF_SYSCALL_TRACE|_TIF_SYSCALL_AUDIT|_TIF_SECCOMP),%edx + jnz ret_from_sys_call_trace bt $TIF_NEED_RESCHED,%edx jnc sysret_signal TRACE_IRQS_ON @@ -279,6 +281,16 @@ sysret_careful: CFI_ADJUST_CFA_OFFSET -8 jmp sysret_check +ret_from_sys_call_trace: + TRACE_IRQS_ON + sti + SAVE_REST + FIXUP_TOP_OF_STACK %rdi + movq %rsp,%rdi + LOAD_ARGS ARGOFFSET /* reload args from stack in case ptrace changed it */ + RESTORE_REST + jmp int_ret_from_sys_call + /* Handle a signal */ sysret_signal: TRACE_IRQS_ON -- Mathieu Desnoyers Computer Engineering Ph.D. Student, Ecole Polytechnique de Montreal OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F BA06 3F25 A8FE 3BAE 9A68 -- To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
