1af170c50SDavid Howells #ifndef _ASM_X86_UCONTEXT_H 2af170c50SDavid Howells #define _ASM_X86_UCONTEXT_H 3af170c50SDavid Howells 4*6c25da5aSAndy Lutomirski /* 5*6c25da5aSAndy Lutomirski * Indicates the presence of extended state information in the memory 6*6c25da5aSAndy Lutomirski * layout pointed by the fpstate pointer in the ucontext's sigcontext 7*6c25da5aSAndy Lutomirski * struct (uc_mcontext). 8af170c50SDavid Howells */ 9*6c25da5aSAndy Lutomirski #define UC_FP_XSTATE 0x1 10*6c25da5aSAndy Lutomirski 11*6c25da5aSAndy Lutomirski #ifdef __x86_64__ 12*6c25da5aSAndy Lutomirski /* 13*6c25da5aSAndy Lutomirski * UC_SIGCONTEXT_SS will be set when delivering 64-bit or x32 signals on 14*6c25da5aSAndy Lutomirski * kernels that save SS in the sigcontext. All kernels that set 15*6c25da5aSAndy Lutomirski * UC_SIGCONTEXT_SS will correctly restore at least the low 32 bits of esp 16*6c25da5aSAndy Lutomirski * regardless of SS (i.e. they implement espfix). 17*6c25da5aSAndy Lutomirski * 18*6c25da5aSAndy Lutomirski * Kernels that set UC_SIGCONTEXT_SS will also set UC_STRICT_RESTORE_SS 19*6c25da5aSAndy Lutomirski * when delivering a signal that came from 64-bit code. 20*6c25da5aSAndy Lutomirski * 21*6c25da5aSAndy Lutomirski * Sigreturn restores SS as follows: 22*6c25da5aSAndy Lutomirski * 23*6c25da5aSAndy Lutomirski * if (saved SS is valid || UC_STRICT_RESTORE_SS is set || 24*6c25da5aSAndy Lutomirski * saved CS is not 64-bit) 25*6c25da5aSAndy Lutomirski * new SS = saved SS (will fail IRET and signal if invalid) 26*6c25da5aSAndy Lutomirski * else 27*6c25da5aSAndy Lutomirski * new SS = a flat 32-bit data segment 28*6c25da5aSAndy Lutomirski * 29*6c25da5aSAndy Lutomirski * This behavior serves three purposes: 30*6c25da5aSAndy Lutomirski * 31*6c25da5aSAndy Lutomirski * - Legacy programs that construct a 64-bit sigcontext from scratch 32*6c25da5aSAndy Lutomirski * with zero or garbage in the SS slot (e.g. old CRIU) and call 33*6c25da5aSAndy Lutomirski * sigreturn will still work. 34*6c25da5aSAndy Lutomirski * 35*6c25da5aSAndy Lutomirski * - Old DOSEMU versions sometimes catch a signal from a segmented 36*6c25da5aSAndy Lutomirski * context, delete the old SS segment (with modify_ldt), and change 37*6c25da5aSAndy Lutomirski * the saved CS to a 64-bit segment. These DOSEMU versions expect 38*6c25da5aSAndy Lutomirski * sigreturn to send them back to 64-bit mode without killing them, 39*6c25da5aSAndy Lutomirski * despite the fact that the SS selector when the signal was raised is 40*6c25da5aSAndy Lutomirski * no longer valid. UC_STRICT_RESTORE_SS will be clear, so the kernel 41*6c25da5aSAndy Lutomirski * will fix up SS for these DOSEMU versions. 42*6c25da5aSAndy Lutomirski * 43*6c25da5aSAndy Lutomirski * - Old and new programs that catch a signal and return without 44*6c25da5aSAndy Lutomirski * modifying the saved context will end up in exactly the state they 45*6c25da5aSAndy Lutomirski * started in, even if they were running in a segmented context when 46*6c25da5aSAndy Lutomirski * the signal was raised.. Old kernels would lose track of the 47*6c25da5aSAndy Lutomirski * previous SS value. 48*6c25da5aSAndy Lutomirski */ 49*6c25da5aSAndy Lutomirski #define UC_SIGCONTEXT_SS 0x2 50*6c25da5aSAndy Lutomirski #define UC_STRICT_RESTORE_SS 0x4 51*6c25da5aSAndy Lutomirski #endif 52af170c50SDavid Howells 53af170c50SDavid Howells #include <asm-generic/ucontext.h> 54af170c50SDavid Howells 55af170c50SDavid Howells #endif /* _ASM_X86_UCONTEXT_H */ 56