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syscall.2: Some fixes to Eugene Syromyatnikov's patch 

Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
This commit is contained in:
Michael Kerrisk 2018-10-14 16:48:54 +02:00
parent 2ad7b4c46c
commit 5b7630723c
1 changed files with 24 additions and 22 deletions
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46
man2/syscall.2
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@ -240,42 +240,44 @@ and so on up to
.IR "trap #0x17"
for 7-argument system calls.
.IP [5]
The x32 ABI shares syscall table with x86-64 ABI, however, there are some
The x32 ABI shares syscall table with x86-64 ABI, but there are some
nuances:
.RS
.IP \(bu 3
In order to signalise that a system call is called under the x32 ABI, additional
.I __X32_SYSCALL_BIT
In order to indicate that a system call is called under the x32 ABI,
an additional bit,
.BR __X32_SYSCALL_BIT ,
is bitwise-ORed with the system call number.
The ABI used by a process affects some things, signal handling or syscall
restarting, for example.
The ABI used by a process affects some process behaviors,
including signal handling or system call restarting.
.IP \(bu
Since x32 has different sizes for
.I long
and pointer types, layouts of some (but not all;
.B struct timeval
.I struct timeval
or
.B struct rlimit
are 64-bit, for example) structures are different, and, in order to handle this,
additional syscalls are added to the syscall table, starting from number 512
.I struct rlimit
are 64-bit, for example) structures are different.
In order to handle this,
additional system calls are added to the system call table,
starting from number 512
(without the
.IR __X32_SYSCALL_BIT );
for example,
.BR __X32_SYSCALL_BIT ).
For example,
.B __NR_readv
is defined to 19 for x86-64 ABI and to
is defined as 19 for the x86-64 ABI and as
.IR __X32_SYSCALL_BIT " | " \fB515\fP
for x32 ABI.
Most of there additional system calls are actually identical to the syscalls
used for providing i386 compat; there are some notable exceptions, however,
such as
for the x32 ABI.
Most of these additional system calls are actually identical
to the system calls used for providing i386 compat.
There are some notable exceptions, however, such as
.BR preadv2 (2),
that uses
.B struct iovec
entities with 4-byte pointers and sizes ("compat_iovec" in kernel's terms), but
passes 8-byte
which uses
.I struct iovec
entities with 4-byte pointers and sizes ("compat_iovec" in kernel terms),
but passes an 8-byte
.I pos
argument in a single register and not two, as it is implemented in every other
ABI.
argument in a single register and not two, as is done in every other ABI.
.RE
.if t \{\
.in