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glibc/sysdeps/unix/sysv/linux/i386/sysdep.h

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/* Copyright (C) 1992-2024 Free Software Foundation, Inc.
This file is part of the GNU C Library.
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
<https://www.gnu.org/licenses/>. */
#ifndef _LINUX_I386_SYSDEP_H
#define _LINUX_I386_SYSDEP_H 1
/* There is some commonality. */
#include <sysdeps/unix/sysv/linux/sysdep.h>
#include <sysdeps/unix/i386/sysdep.h>
/* Defines RTLD_PRIVATE_ERRNO and USE_DL_SYSINFO. */
#include <dl-sysdep.h>
#include <tls.h>
/* 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
#if !I386_USE_SYSENTER && IS_IN (libc) && !defined SHARED
/* Inside static libc, we have two versions. For compilation units
with !I386_USE_SYSENTER, the vDSO entry mechanism cannot be
used. */
# define I386_DO_SYSCALL_STRING "__libc_do_syscall_int80"
#else
# define I386_DO_SYSCALL_STRING "__libc_do_syscall"
#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 safely
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)));
/* 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;
};
# 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 HAVE_CLONE3_WRAPPER 1
# undef HAVE_INTERNAL_BRK_ADDR_SYMBOL
# define HAVE_INTERNAL_BRK_ADDR_SYMBOL 1
/* 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)
#define INTERNAL_SYSCALL_MAIN_NCS_0(name, args...) \
INTERNAL_SYSCALL_MAIN_NCS(name, 0, args)
#define INTERNAL_SYSCALL_MAIN_NCS_1(name, args...) \
INTERNAL_SYSCALL_MAIN_NCS(name, 1, args)
#define INTERNAL_SYSCALL_MAIN_NCS_2(name, args...) \
INTERNAL_SYSCALL_MAIN_NCS(name, 2, args)
#define INTERNAL_SYSCALL_MAIN_NCS_3(name, args...) \
INTERNAL_SYSCALL_MAIN_NCS(name, 3, args)
#define INTERNAL_SYSCALL_MAIN_NCS_4(name, args...) \
INTERNAL_SYSCALL_MAIN_NCS(name, 4, args)
#define INTERNAL_SYSCALL_MAIN_NCS_5(name, args...) \
INTERNAL_SYSCALL_MAIN_NCS(name, 5, args)
/* Each object using 6-argument inline syscalls must include a
definition of __libc_do_syscall. */
#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 " I386_DO_SYSCALL_STRING \
: "=a" (resultvar) \
: "i" (__NR_##name), "c" (arg2), "d" (arg3), "S" (arg4), "D" (&_xv) \
: "memory", "cc")
#define INTERNAL_SYSCALL_MAIN_NCS_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 " I386_DO_SYSCALL_STRING \
: "=a" (resultvar) \
: "a" (name), "c" (arg2), "d" (arg3), "S" (arg4), "D" (&_xv) \
: "memory", "cc")
#define INTERNAL_SYSCALL(name, nr, args...) \
({ \
register unsigned int resultvar; \
INTERNAL_SYSCALL_MAIN_##nr (name, args); \
(int) resultvar; })
#define INTERNAL_SYSCALL_NCS(name, nr, args...) \
({ \
register unsigned int resultvar; \
INTERNAL_SYSCALL_MAIN_NCS_##nr (name, args); \
(int) resultvar; })
#if I386_USE_SYSENTER
# 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_MAIN_NCS(name, nr, args...) \
LOADREGS_##nr(args) \
asm volatile ( \
"call *%%gs:%P2" \
: "=a" (resultvar) \
: "a" (name), "i" (offsetof (tcbhead_t, sysinfo)) \
ASMARGS_##nr(args) : "memory", "cc")
# else /* I386_USE_SYSENTER && !PIC */
# 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_MAIN_NCS(name, nr, args...) \
LOADREGS_##nr(args) \
asm volatile ( \
"call *_dl_sysinfo" \
: "=a" (resultvar) \
: "a" (name) ASMARGS_##nr(args) : "memory", "cc")
# endif /* I386_USE_SYSENTER && !PIC */
#else /* !I386_USE_SYSENTER */
# 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_MAIN_NCS(name, nr, args...) \
LOADREGS_##nr(args) \
asm volatile ( \
"int $0x80" \
: "=a" (resultvar) \
: "a" (name) ASMARGS_##nr(args) : "memory", "cc")
#endif /* !I386_USE_SYSENTER */
#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 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
#endif /* __ASSEMBLER__ */
/* 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 */
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