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glibc/sysdeps/unix/sysv/linux/i386/sysdep.h
Florian Weimer a78e6a10d0 i386: Remove broken CAN_USE_REGISTER_ASM_EBP (bug 28771) 
The configure check for CAN_USE_REGISTER_ASM_EBP tried to compile a
simple function that uses %ebp as an inline assembly operand.  If
compilation failed, CAN_USE_REGISTER_ASM_EBP was set 0, which
eventually had these consequences:

(1) %ebx was avoided as an inline assembly operand, with an
    assembler macro hack to avoid unnecessary register moves.
(2) %ebp was avoided as an inline assembly operand, using an
    out-of-line syscall function for 6-argument system calls.

(1) is no longer needed for any GCC version that is supported for
building glibc.  %ebx can be used directly as a register operand.
Therefore, this commit removes the %ebx avoidance completely.  This
avoids the assembler macro hack, which turns out to be incompatible
with the current Systemtap probe macros (which switch to .altmacro
unconditionally).

(2) is still needed in many build configurations.  The existing
configure check cannot really capture that because the simple function
succeeds to compile, while the full glibc build still fails.
Therefore, this commit removes the check, the CAN_USE_REGISTER_ASM_EBP
macro, and uses the out-of-line syscall function for 6-argument system
calls unconditionally.

Reviewed-by: H.J. Lu <hjl.tools@gmail.com>
2022-01-13 14:59:44 +01:00

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/* Copyright (C) 1992-2022 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
#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)));
/* 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 __libc_do_syscall" \
: "=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 __libc_do_syscall" \
: "=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__ */
/* 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 */
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