@ -73,12 +82,14 @@ Recently, Intel has introduced an essentially identical version of AMD64 called
When an AMD64\-supporting processor is executing in 64\-bit mode, a number of additional extensions are available, including extra general purpose registers, extra SSE2 registers, and RIP\-relative addressing\&.
.PP
Yasm extends the base NASM syntax to support AMD64 as follows\&. To enable assembly of instructions for the 64\-bit mode of AMD64 processors, use the directive
\fBBITS 64\fR\&. As with NASM\'s BITS directive, this does not change the format of the output object file to 64 bits; it only changes the assembler mode to assume that the instructions being assembled will be run in 64\-bit mode\&. To specify an AMD64 object file, use
\fBBITS 64\fR\&. As with NASM\*(Aqs BITS directive, this does not change the format of the output object file to 64 bits; it only changes the assembler mode to assume that the instructions being assembled will be run in 64\-bit mode\&. To specify an AMD64 object file, use
\fB\-m amd64\fR
on the Yasm command line, or explicitly target a 64\-bit object format such as
\fB\-f win64\fR
or
\fB\-f elf64\fR\&.
\fB\-f elfx32\fR
can be used to select 32\-bit ELF object format for AMD64 processors\&.
Usually the size of a memory reference can be deduced by which registers you\'re moving\-\-for example, "mov [rax],ecx" is a 32\-bit move, because ecx is 32 bits\&. YASM currently gives the non\-obvious "invalid combination of opcode and operands" error if it can\'t figure out how much memory you\'re moving\&. The fix in this case is to add a memory size specifier: qword, dword, word, or byte\&.
Usually the size of a memory reference can be deduced by which registers you\*(Aqre moving\-\-for example, "mov [rax],ecx" is a 32\-bit move, because ecx is 32 bits\&. YASM currently gives the non\-obvious "invalid combination of opcode and operands" error if it can\*(Aqt figure out how much memory you\*(Aqre moving\&. The fix in this case is to add a memory size specifier: qword, dword, word, or byte\&.
.PP
Here\'s a 64\-bit memory move, which sets 8 bytes starting at rax:
Here\*(Aqs a 64\-bit memory move, which sets 8 bytes starting at rax:
.sp
.ifn\{\
.RS4
@ -776,7 +787,7 @@ mov qword [rax], 1
.RE
.\}
.PP
Here\'s a 32\-bit memory move, which sets 4 bytes:
Here\*(Aqs a 32\-bit memory move, which sets 4 bytes:
.sp
.ifn\{\
.RS4
@ -788,7 +799,7 @@ mov dword [rax], 1
.RE
.\}
.PP
Here\'s a 16\-bit memory move, which sets 2 bytes:
Here\*(Aqs a 16\-bit memory move, which sets 2 bytes:
.sp
.ifn\{\
.RS4
@ -800,7 +811,7 @@ mov word [rax], 1
.RE
.\}
.PP
Here\'s an 8\-bit memory move, which sets 1 byte:
Here\*(Aqs an 8\-bit memory move, which sets 1 byte:
The standard Yasm distribution includes a number of modules for different object formats (Yasm\'s primary output)\&.
The standard Yasm distribution includes a number of modules for different object formats (Yasm\*(Aqs primary output)\&.
.PP
The object format is selected on the
\fByasm\fR(1)
@ -46,14 +55,16 @@ The
\(lqdbg\(rq
object format is not a
\(lqreal\(rq
object format; the output file it creates simply describes the sequence of calls made to it by Yasm and the final object and symbol table information in a human\-readable text format (that in a normal object format would get processed into that object format\'s particular binary representation)\&. This object format is not intended for real use, but rather for debugging Yasm\'s internals\&.
object format; the output file it creates simply describes the sequence of calls made to it by Yasm and the final object and symbol table information in a human\-readable text format (that in a normal object format would get processed into that object format\*(Aqs particular binary representation)\&. This object format is not intended for real use, but rather for debugging Yasm\*(Aqs internals\&.
.SH"ELF"
.PP
The ELF object format really comes in two flavors:
The ELF object format really comes in three flavors:
\(lqelf32\(rq
(for 32\-bit targets) and
(for 32\-bit targets),
\(lqelf64\(rq
(for 64\-bit targets)\&. ELF is a standard object format in common use on modern Unix and compatible systems (e\&.g\&. Linux, FreeBSD)\&. ELF has complex support for relocatable and shared objects\&.
(for 64\-bit targets and
\(lqelfx32\(rq
(for x32 targets)\&. ELF is a standard object format in common use on modern Unix and compatible systems (e\&.g\&. Linux, FreeBSD)\&. ELF has complex support for relocatable and shared objects\&.
.SH"MACHO"
.PP
The Mach\-O object format really comes in two flavors:
@ -74,7 +85,7 @@ The Win64 object format produces object files compatible with Microsoft compiler
Windows platform\&. This format is very similar to the win32 object format, but produces 64\-bit objects\&.
.SH"XDF"
.PP
The XDF object format is essentially a simplified version of COFF\&. It\'s a multi\-section relocatable format that supports 64\-bit physical and virtual addresses\&.
The XDF object format is essentially a simplified version of COFF\&. It\*(Aqs a multi\-section relocatable format that supports 64\-bit physical and virtual addresses\&.
Peter Johnson
13 years ago