Date: Fri, 28 Oct 2016 20:14:35 +0000 From: "LeMay, Michael" <michael.lemay@...el.com> To: "musl@...ts.openwall.com" <musl@...ts.openwall.com> Subject: [RFC PATCH v2 2/2] avoid invoking vDSO when separate stack segment is enabled The Linux vDSO code may be incompatible with programs that use a separate stack segment. This patch prevents the vDSO from being invoked when that feature is enabled. Signed-off-by: Michael LeMay <michael.lemay@...el.com> --- arch/i386/syscall_arch.h | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/arch/i386/syscall_arch.h b/arch/i386/syscall_arch.h index 4c9d874..4d7c3c2 100644 --- a/arch/i386/syscall_arch.h +++ b/arch/i386/syscall_arch.h @@ -52,8 +52,17 @@ static inline long __syscall6(long n, long a1, long a2, long a3, long a4, long a return __ret; } +#if !SEP_STACK_SEG +/* The vDSO may not be compiled with support for a separate stack segment. + * Avoid invoking the vDSO when this feature is enabled, since it may try to + * access the stack using memory operands with base registers other than EBP or + * ESP without also using a stack segment override prefix. A special compiler + * pass needs to be used to add such prefixes, and it is unlikely that a pass + * of that sort was applied when the vDSO was compiled. + */ #define VDSO_USEFUL #define VDSO_CGT_SYM "__vdso_clock_gettime" #define VDSO_CGT_VER "LINUX_2.6" +#endif #define SYSCALL_USE_SOCKETCALL -- 2.7.4
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