/* Copyright (C) 1992-2020 Free Software Foundation, Inc. This file is part of the GNU C Library. Contributed by Ulrich Drepper, , August 1995. The GNU C Library is free software; you can redistribute it and/or modify it under the terms of the GNU Lesser General Public License as published by the Free Software Foundation; either version 2.1 of the License, or (at your option) any later version. The GNU C Library is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more details. You should have received a copy of the GNU Lesser General Public License along with the GNU C Library; if not, see . */ #ifndef _LINUX_I386_SYSDEP_H #define _LINUX_I386_SYSDEP_H 1 /* There is some commonality. */ #include #include /* Defines RTLD_PRIVATE_ERRNO and USE_DL_SYSINFO. */ #include #include /* For Linux we can use the system call table in the header file /usr/include/asm/unistd.h of the kernel. But these symbols do not follow the SYS_* syntax so we have to redefine the `SYS_ify' macro here. */ #undef SYS_ify #define SYS_ify(syscall_name) __NR_##syscall_name #ifndef I386_USE_SYSENTER # if defined USE_DL_SYSINFO \ && (IS_IN (libc) || IS_IN (libpthread)) # define I386_USE_SYSENTER 1 # else # define I386_USE_SYSENTER 0 # endif #endif /* Since GCC 5 and above can properly spill %ebx with PIC when needed, we can inline syscalls with 6 arguments if GCC 5 or above is used to compile glibc. Disable GCC 5 optimization when compiling for profiling or when -fno-omit-frame-pointer is used since asm ("ebp") can't be used to put the 6th argument in %ebp for syscall. */ #if __GNUC_PREREQ (5,0) && !defined PROF && CAN_USE_REGISTER_ASM_EBP # define OPTIMIZE_FOR_GCC_5 #endif #ifdef __ASSEMBLER__ /* Linux uses a negative return value to indicate syscall errors, unlike most Unices, which use the condition codes' carry flag. Since version 2.1 the return value of a system call might be negative even if the call succeeded. E.g., the `lseek' system call might return a large offset. Therefore we must not anymore test for < 0, but test for a real error by making sure the value in %eax is a real error number. Linus said he will make sure the no syscall returns a value in -1 .. -4095 as a valid result so we can savely test with -4095. */ /* We don't want the label for the error handle to be global when we define it here. */ #undef SYSCALL_ERROR_LABEL #define SYSCALL_ERROR_LABEL __syscall_error #undef PSEUDO #define PSEUDO(name, syscall_name, args) \ .text; \ ENTRY (name) \ DO_CALL (syscall_name, args); \ cmpl $-4095, %eax; \ jae SYSCALL_ERROR_LABEL #undef PSEUDO_END #define PSEUDO_END(name) \ SYSCALL_ERROR_HANDLER \ END (name) #undef PSEUDO_NOERRNO #define PSEUDO_NOERRNO(name, syscall_name, args) \ .text; \ ENTRY (name) \ DO_CALL (syscall_name, args) #undef PSEUDO_END_NOERRNO #define PSEUDO_END_NOERRNO(name) \ END (name) #define ret_NOERRNO ret /* The function has to return the error code. */ #undef PSEUDO_ERRVAL #define PSEUDO_ERRVAL(name, syscall_name, args) \ .text; \ ENTRY (name) \ DO_CALL (syscall_name, args); \ negl %eax #undef PSEUDO_END_ERRVAL #define PSEUDO_END_ERRVAL(name) \ END (name) #define ret_ERRVAL ret #define SYSCALL_ERROR_HANDLER /* Nothing here; code in sysdep.c is used. */ /* The original calling convention for system calls on Linux/i386 is to use int $0x80. */ #if I386_USE_SYSENTER # ifdef PIC # define ENTER_KERNEL call *%gs:SYSINFO_OFFSET # else # define ENTER_KERNEL call *_dl_sysinfo # endif #else # define ENTER_KERNEL int $0x80 #endif /* Linux takes system call arguments in registers: syscall number %eax call-clobbered arg 1 %ebx call-saved arg 2 %ecx call-clobbered arg 3 %edx call-clobbered arg 4 %esi call-saved arg 5 %edi call-saved arg 6 %ebp call-saved The stack layout upon entering the function is: 24(%esp) Arg# 6 20(%esp) Arg# 5 16(%esp) Arg# 4 12(%esp) Arg# 3 8(%esp) Arg# 2 4(%esp) Arg# 1 (%esp) Return address (Of course a function with say 3 arguments does not have entries for arguments 4, 5, and 6.) The following code tries hard to be optimal. A general assumption (which is true according to the data books I have) is that 2 * xchg is more expensive than pushl + movl + popl Beside this a neat trick is used. The calling conventions for Linux tell that among the registers used for parameters %ecx and %edx need not be saved. Beside this we may clobber this registers even when they are not used for parameter passing. As a result one can see below that we save the content of the %ebx register in the %edx register when we have less than 3 arguments (2 * movl is less expensive than pushl + popl). Second unlike for the other registers we don't save the content of %ecx and %edx when we have more than 1 and 2 registers resp. The code below might look a bit long but we have to take care for the pipelined processors (i586). Here the `pushl' and `popl' instructions are marked as NP (not pairable) but the exception is two consecutive of these instruction. This gives no penalty on other processors though. */ #undef DO_CALL #define DO_CALL(syscall_name, args) \ PUSHARGS_##args \ DOARGS_##args \ movl $SYS_ify (syscall_name), %eax; \ ENTER_KERNEL \ POPARGS_##args #define PUSHARGS_0 /* No arguments to push. */ #define DOARGS_0 /* No arguments to frob. */ #define POPARGS_0 /* No arguments to pop. */ #define _PUSHARGS_0 /* No arguments to push. */ #define _DOARGS_0(n) /* No arguments to frob. */ #define _POPARGS_0 /* No arguments to pop. */ #define PUSHARGS_1 movl %ebx, %edx; L(SAVEBX1): PUSHARGS_0 #define DOARGS_1 _DOARGS_1 (4) #define POPARGS_1 POPARGS_0; movl %edx, %ebx; L(RESTBX1): #define _PUSHARGS_1 pushl %ebx; cfi_adjust_cfa_offset (4); \ cfi_rel_offset (ebx, 0); L(PUSHBX1): _PUSHARGS_0 #define _DOARGS_1(n) movl n(%esp), %ebx; _DOARGS_0(n-4) #define _POPARGS_1 _POPARGS_0; popl %ebx; cfi_adjust_cfa_offset (-4); \ cfi_restore (ebx); L(POPBX1): #define PUSHARGS_2 PUSHARGS_1 #define DOARGS_2 _DOARGS_2 (8) #define POPARGS_2 POPARGS_1 #define _PUSHARGS_2 _PUSHARGS_1 #define _DOARGS_2(n) movl n(%esp), %ecx; _DOARGS_1 (n-4) #define _POPARGS_2 _POPARGS_1 #define PUSHARGS_3 _PUSHARGS_2 #define DOARGS_3 _DOARGS_3 (16) #define POPARGS_3 _POPARGS_3 #define _PUSHARGS_3 _PUSHARGS_2 #define _DOARGS_3(n) movl n(%esp), %edx; _DOARGS_2 (n-4) #define _POPARGS_3 _POPARGS_2 #define PUSHARGS_4 _PUSHARGS_4 #define DOARGS_4 _DOARGS_4 (24) #define POPARGS_4 _POPARGS_4 #define _PUSHARGS_4 pushl %esi; cfi_adjust_cfa_offset (4); \ cfi_rel_offset (esi, 0); L(PUSHSI1): _PUSHARGS_3 #define _DOARGS_4(n) movl n(%esp), %esi; _DOARGS_3 (n-4) #define _POPARGS_4 _POPARGS_3; popl %esi; cfi_adjust_cfa_offset (-4); \ cfi_restore (esi); L(POPSI1): #define PUSHARGS_5 _PUSHARGS_5 #define DOARGS_5 _DOARGS_5 (32) #define POPARGS_5 _POPARGS_5 #define _PUSHARGS_5 pushl %edi; cfi_adjust_cfa_offset (4); \ cfi_rel_offset (edi, 0); L(PUSHDI1): _PUSHARGS_4 #define _DOARGS_5(n) movl n(%esp), %edi; _DOARGS_4 (n-4) #define _POPARGS_5 _POPARGS_4; popl %edi; cfi_adjust_cfa_offset (-4); \ cfi_restore (edi); L(POPDI1): #define PUSHARGS_6 _PUSHARGS_6 #define DOARGS_6 _DOARGS_6 (40) #define POPARGS_6 _POPARGS_6 #define _PUSHARGS_6 pushl %ebp; cfi_adjust_cfa_offset (4); \ cfi_rel_offset (ebp, 0); L(PUSHBP1): _PUSHARGS_5 #define _DOARGS_6(n) movl n(%esp), %ebp; _DOARGS_5 (n-4) #define _POPARGS_6 _POPARGS_5; popl %ebp; cfi_adjust_cfa_offset (-4); \ cfi_restore (ebp); L(POPBP1): #else /* !__ASSEMBLER__ */ extern int __syscall_error (int) attribute_hidden __attribute__ ((__regparm__ (1))); #ifndef OPTIMIZE_FOR_GCC_5 /* We need some help from the assembler to generate optimal code. We define some macros here which later will be used. */ asm (".L__X'%ebx = 1\n\t" ".L__X'%ecx = 2\n\t" ".L__X'%edx = 2\n\t" ".L__X'%eax = 3\n\t" ".L__X'%esi = 3\n\t" ".L__X'%edi = 3\n\t" ".L__X'%ebp = 3\n\t" ".L__X'%esp = 3\n\t" ".macro bpushl name reg\n\t" ".if 1 - \\name\n\t" ".if 2 - \\name\n\t" "error\n\t" ".else\n\t" "xchgl \\reg, %ebx\n\t" ".endif\n\t" ".endif\n\t" ".endm\n\t" ".macro bpopl name reg\n\t" ".if 1 - \\name\n\t" ".if 2 - \\name\n\t" "error\n\t" ".else\n\t" "xchgl \\reg, %ebx\n\t" ".endif\n\t" ".endif\n\t" ".endm\n\t"); /* Six-argument syscalls use an out-of-line helper, because an inline asm using all registers apart from %esp cannot work reliably and the assembler does not support describing an asm that saves and restores %ebp itself as a separate stack frame. This structure stores the arguments not passed in registers; %edi is passed with a pointer to this structure. */ struct libc_do_syscall_args { int ebx, edi, ebp; }; #endif # define VDSO_NAME "LINUX_2.6" # define VDSO_HASH 61765110 /* List of system calls which are supported as vsyscalls. */ # define HAVE_CLOCK_GETTIME_VSYSCALL "__vdso_clock_gettime" # define HAVE_CLOCK_GETTIME64_VSYSCALL "__vdso_clock_gettime64" # define HAVE_GETTIMEOFDAY_VSYSCALL "__vdso_gettimeofday" # define HAVE_TIME_VSYSCALL "__vdso_time" # define HAVE_CLOCK_GETRES_VSYSCALL "__vdso_clock_getres" /* Define a macro which expands inline into the wrapper code for a system call. This use is for internal calls that do not need to handle errors normally. It will never touch errno. This returns just what the kernel gave back. The _NCS variant allows non-constant syscall numbers but it is not possible to use more than four parameters. */ #undef INTERNAL_SYSCALL #define INTERNAL_SYSCALL_MAIN_0(name, args...) \ INTERNAL_SYSCALL_MAIN_INLINE(name, 0, args) #define INTERNAL_SYSCALL_MAIN_1(name, args...) \ INTERNAL_SYSCALL_MAIN_INLINE(name, 1, args) #define INTERNAL_SYSCALL_MAIN_2(name, args...) \ INTERNAL_SYSCALL_MAIN_INLINE(name, 2, args) #define INTERNAL_SYSCALL_MAIN_3(name, args...) \ INTERNAL_SYSCALL_MAIN_INLINE(name, 3, args) #define INTERNAL_SYSCALL_MAIN_4(name, args...) \ INTERNAL_SYSCALL_MAIN_INLINE(name, 4, args) #define INTERNAL_SYSCALL_MAIN_5(name, args...) \ INTERNAL_SYSCALL_MAIN_INLINE(name, 5, args) /* Each object using 6-argument inline syscalls must include a definition of __libc_do_syscall. */ #ifdef OPTIMIZE_FOR_GCC_5 # define INTERNAL_SYSCALL_MAIN_6(name, args...) \ INTERNAL_SYSCALL_MAIN_INLINE(name, 6, args) #else /* GCC 5 */ # define INTERNAL_SYSCALL_MAIN_6(name, arg1, arg2, arg3, \ arg4, arg5, arg6) \ struct libc_do_syscall_args _xv = \ { \ (int) (arg1), \ (int) (arg5), \ (int) (arg6) \ }; \ asm volatile ( \ "movl %1, %%eax\n\t" \ "call __libc_do_syscall" \ : "=a" (resultvar) \ : "i" (__NR_##name), "c" (arg2), "d" (arg3), "S" (arg4), "D" (&_xv) \ : "memory", "cc") #endif /* GCC 5 */ #define INTERNAL_SYSCALL(name, nr, args...) \ ({ \ register unsigned int resultvar; \ INTERNAL_SYSCALL_MAIN_##nr (name, args); \ (int) resultvar; }) #if I386_USE_SYSENTER # ifdef OPTIMIZE_FOR_GCC_5 # ifdef PIC # define INTERNAL_SYSCALL_MAIN_INLINE(name, nr, args...) \ LOADREGS_##nr(args) \ asm volatile ( \ "call *%%gs:%P2" \ : "=a" (resultvar) \ : "a" (__NR_##name), "i" (offsetof (tcbhead_t, sysinfo)) \ ASMARGS_##nr(args) : "memory", "cc") # define INTERNAL_SYSCALL_NCS(name, nr, args...) \ ({ \ register unsigned int resultvar; \ LOADREGS_##nr(args) \ asm volatile ( \ "call *%%gs:%P2" \ : "=a" (resultvar) \ : "a" (name), "i" (offsetof (tcbhead_t, sysinfo)) \ ASMARGS_##nr(args) : "memory", "cc"); \ (int) resultvar; }) # else # define INTERNAL_SYSCALL_MAIN_INLINE(name, nr, args...) \ LOADREGS_##nr(args) \ asm volatile ( \ "call *_dl_sysinfo" \ : "=a" (resultvar) \ : "a" (__NR_##name) ASMARGS_##nr(args) : "memory", "cc") # define INTERNAL_SYSCALL_NCS(name, nr, args...) \ ({ \ register unsigned int resultvar; \ LOADREGS_##nr(args) \ asm volatile ( \ "call *_dl_sysinfo" \ : "=a" (resultvar) \ : "a" (name) ASMARGS_##nr(args) : "memory", "cc"); \ (int) resultvar; }) # endif # else /* GCC 5 */ # ifdef PIC # define INTERNAL_SYSCALL_MAIN_INLINE(name, nr, args...) \ EXTRAVAR_##nr \ asm volatile ( \ LOADARGS_##nr \ "movl %1, %%eax\n\t" \ "call *%%gs:%P2\n\t" \ RESTOREARGS_##nr \ : "=a" (resultvar) \ : "i" (__NR_##name), "i" (offsetof (tcbhead_t, sysinfo)) \ ASMFMT_##nr(args) : "memory", "cc") # define INTERNAL_SYSCALL_NCS(name, nr, args...) \ ({ \ register unsigned int resultvar; \ EXTRAVAR_##nr \ asm volatile ( \ LOADARGS_##nr \ "call *%%gs:%P2\n\t" \ RESTOREARGS_##nr \ : "=a" (resultvar) \ : "0" (name), "i" (offsetof (tcbhead_t, sysinfo)) \ ASMFMT_##nr(args) : "memory", "cc"); \ (int) resultvar; }) # else # define INTERNAL_SYSCALL_MAIN_INLINE(name, nr, args...) \ EXTRAVAR_##nr \ asm volatile ( \ LOADARGS_##nr \ "movl %1, %%eax\n\t" \ "call *_dl_sysinfo\n\t" \ RESTOREARGS_##nr \ : "=a" (resultvar) \ : "i" (__NR_##name) ASMFMT_##nr(args) : "memory", "cc") # define INTERNAL_SYSCALL_NCS(name, nr, args...) \ ({ \ register unsigned int resultvar; \ EXTRAVAR_##nr \ asm volatile ( \ LOADARGS_##nr \ "call *_dl_sysinfo\n\t" \ RESTOREARGS_##nr \ : "=a" (resultvar) \ : "0" (name) ASMFMT_##nr(args) : "memory", "cc"); \ (int) resultvar; }) # endif # endif /* GCC 5 */ #else # ifdef OPTIMIZE_FOR_GCC_5 # define INTERNAL_SYSCALL_MAIN_INLINE(name, nr, args...) \ LOADREGS_##nr(args) \ asm volatile ( \ "int $0x80" \ : "=a" (resultvar) \ : "a" (__NR_##name) ASMARGS_##nr(args) : "memory", "cc") # define INTERNAL_SYSCALL_NCS(name, nr, args...) \ ({ \ register unsigned int resultvar; \ LOADREGS_##nr(args) \ asm volatile ( \ "int $0x80" \ : "=a" (resultvar) \ : "a" (name) ASMARGS_##nr(args) : "memory", "cc"); \ (int) resultvar; }) # else /* GCC 5 */ # define INTERNAL_SYSCALL_MAIN_INLINE(name, nr, args...) \ EXTRAVAR_##nr \ asm volatile ( \ LOADARGS_##nr \ "movl %1, %%eax\n\t" \ "int $0x80\n\t" \ RESTOREARGS_##nr \ : "=a" (resultvar) \ : "i" (__NR_##name) ASMFMT_##nr(args) : "memory", "cc") # define INTERNAL_SYSCALL_NCS(name, nr, args...) \ ({ \ register unsigned int resultvar; \ EXTRAVAR_##nr \ asm volatile ( \ LOADARGS_##nr \ "int $0x80\n\t" \ RESTOREARGS_##nr \ : "=a" (resultvar) \ : "0" (name) ASMFMT_##nr(args) : "memory", "cc"); \ (int) resultvar; }) # endif /* GCC 5 */ #endif #define LOADARGS_0 #ifdef __PIC__ # if I386_USE_SYSENTER && defined PIC # define LOADARGS_1 \ "bpushl .L__X'%k3, %k3\n\t" # define LOADARGS_5 \ "movl %%ebx, %4\n\t" \ "movl %3, %%ebx\n\t" # else # define LOADARGS_1 \ "bpushl .L__X'%k2, %k2\n\t" # define LOADARGS_5 \ "movl %%ebx, %3\n\t" \ "movl %2, %%ebx\n\t" # endif # define LOADARGS_2 LOADARGS_1 # define LOADARGS_3 \ "xchgl %%ebx, %%edi\n\t" # define LOADARGS_4 LOADARGS_3 #else # define LOADARGS_1 # define LOADARGS_2 # define LOADARGS_3 # define LOADARGS_4 # define LOADARGS_5 #endif #define RESTOREARGS_0 #ifdef __PIC__ # if I386_USE_SYSENTER && defined PIC # define RESTOREARGS_1 \ "bpopl .L__X'%k3, %k3\n\t" # define RESTOREARGS_5 \ "movl %4, %%ebx" # else # define RESTOREARGS_1 \ "bpopl .L__X'%k2, %k2\n\t" # define RESTOREARGS_5 \ "movl %3, %%ebx" # endif # define RESTOREARGS_2 RESTOREARGS_1 # define RESTOREARGS_3 \ "xchgl %%edi, %%ebx\n\t" # define RESTOREARGS_4 RESTOREARGS_3 #else # define RESTOREARGS_1 # define RESTOREARGS_2 # define RESTOREARGS_3 # define RESTOREARGS_4 # define RESTOREARGS_5 #endif #ifdef OPTIMIZE_FOR_GCC_5 # define LOADREGS_0() # define ASMARGS_0() # define LOADREGS_1(arg1) \ LOADREGS_0 () # define ASMARGS_1(arg1) \ ASMARGS_0 (), "b" ((unsigned int) (arg1)) # define LOADREGS_2(arg1, arg2) \ LOADREGS_1 (arg1) # define ASMARGS_2(arg1, arg2) \ ASMARGS_1 (arg1), "c" ((unsigned int) (arg2)) # define LOADREGS_3(arg1, arg2, arg3) \ LOADREGS_2 (arg1, arg2) # define ASMARGS_3(arg1, arg2, arg3) \ ASMARGS_2 (arg1, arg2), "d" ((unsigned int) (arg3)) # define LOADREGS_4(arg1, arg2, arg3, arg4) \ LOADREGS_3 (arg1, arg2, arg3) # define ASMARGS_4(arg1, arg2, arg3, arg4) \ ASMARGS_3 (arg1, arg2, arg3), "S" ((unsigned int) (arg4)) # define LOADREGS_5(arg1, arg2, arg3, arg4, arg5) \ LOADREGS_4 (arg1, arg2, arg3, arg4) # define ASMARGS_5(arg1, arg2, arg3, arg4, arg5) \ ASMARGS_4 (arg1, arg2, arg3, arg4), "D" ((unsigned int) (arg5)) # define LOADREGS_6(arg1, arg2, arg3, arg4, arg5, arg6) \ register unsigned int _a6 asm ("ebp") = (unsigned int) (arg6); \ LOADREGS_5 (arg1, arg2, arg3, arg4, arg5) # define ASMARGS_6(arg1, arg2, arg3, arg4, arg5, arg6) \ ASMARGS_5 (arg1, arg2, arg3, arg4, arg5), "r" (_a6) #endif /* GCC 5 */ #define ASMFMT_0() #ifdef __PIC__ # define ASMFMT_1(arg1) \ , "cd" (arg1) # define ASMFMT_2(arg1, arg2) \ , "d" (arg1), "c" (arg2) # define ASMFMT_3(arg1, arg2, arg3) \ , "D" (arg1), "c" (arg2), "d" (arg3) # define ASMFMT_4(arg1, arg2, arg3, arg4) \ , "D" (arg1), "c" (arg2), "d" (arg3), "S" (arg4) # define ASMFMT_5(arg1, arg2, arg3, arg4, arg5) \ , "0" (arg1), "m" (_xv), "c" (arg2), "d" (arg3), "S" (arg4), "D" (arg5) #else # define ASMFMT_1(arg1) \ , "b" (arg1) # define ASMFMT_2(arg1, arg2) \ , "b" (arg1), "c" (arg2) # define ASMFMT_3(arg1, arg2, arg3) \ , "b" (arg1), "c" (arg2), "d" (arg3) # define ASMFMT_4(arg1, arg2, arg3, arg4) \ , "b" (arg1), "c" (arg2), "d" (arg3), "S" (arg4) # define ASMFMT_5(arg1, arg2, arg3, arg4, arg5) \ , "b" (arg1), "c" (arg2), "d" (arg3), "S" (arg4), "D" (arg5) #endif #define EXTRAVAR_0 #define EXTRAVAR_1 #define EXTRAVAR_2 #define EXTRAVAR_3 #define EXTRAVAR_4 #ifdef __PIC__ # define EXTRAVAR_5 int _xv; #else # define EXTRAVAR_5 #endif /* Consistency check for position-independent code. */ #if defined __PIC__ && !defined OPTIMIZE_FOR_GCC_5 # define check_consistency() \ ({ int __res; \ __asm__ __volatile__ \ (LOAD_PIC_REG_STR (cx) ";" \ "subl %%ebx, %%ecx;" \ "je 1f;" \ "ud2;" \ "1:\n" \ : "=c" (__res)); \ __res; }) #endif #endif /* __ASSEMBLER__ */ /* Pointer mangling support. */ #if IS_IN (rtld) /* We cannot use the thread descriptor because in ld.so we use setjmp earlier than the descriptor is initialized. Using a global variable is too complicated here since we have no PC-relative addressing mode. */ #else # ifdef __ASSEMBLER__ # define PTR_MANGLE(reg) xorl %gs:POINTER_GUARD, reg; \ roll $9, reg # define PTR_DEMANGLE(reg) rorl $9, reg; \ xorl %gs:POINTER_GUARD, reg # else # define PTR_MANGLE(var) asm ("xorl %%gs:%c2, %0\n" \ "roll $9, %0" \ : "=r" (var) \ : "0" (var), \ "i" (offsetof (tcbhead_t, \ pointer_guard))) # define PTR_DEMANGLE(var) asm ("rorl $9, %0\n" \ "xorl %%gs:%c2, %0" \ : "=r" (var) \ : "0" (var), \ "i" (offsetof (tcbhead_t, \ pointer_guard))) # endif #endif /* Each shadow stack slot takes 4 bytes. Assuming that each stack frame takes 128 bytes, this is used to compute shadow stack size from stack size. */ #define STACK_SIZE_TO_SHADOW_STACK_SIZE_SHIFT 5 #endif /* linux/i386/sysdep.h */