The Netwide Assembler: NASM

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Chapter 6: Output Formats

NASM is a portable assembler, designed to be able to compile on any ANSI C-supporting platform and produce output to run on a variety of Intel x86 operating systems. For this reason, it has a large number of available output formats, selected using the -f option on the NASM command line. Each of these formats, along with its function t ; setup code comes last ; the resident part of the TSR goes here setup: ; now write the code that installs the TSR here absolute setup runtimevar1 resw 1 runtimevar2 resd 20 tsr_end:

This defines some variables `on top of' the setup code, so that after the setup has finished running, the space it took up can be re-used as data storage for the running TSR. The symbol `tsr_end' can be used to calculate the total size of the part of the TSR that needs to be made resident.

5.4 EXTERN: Importing Symbols from Other Modules

EXTERN is similar to the MASM directive EXTRN and the C keyword extern: it is used to declare a symbol which is not defined anywhere in the module being assembled, but is assumed to be defined in some other module and needs to be referred to by this one. Not every object-file format can support external variables: the bin format cannot.

The EXTERN directive takes as many arguments as you like. Each argument is the name of a symbol: 

          extern _printf 
          extern _sscanf,_fscanf

Some object-file formats provide extra features to the EXTERN directive. In all cases, the extra features are used by suffixing a colon to the symbol name followed by object-format specific text. For example, the obj format allows you to declare that the default segment base of an external should be the group dgroup by means of the directive 

          extern _variable:wrt dgroup

The primitive form of EXTERN differs from the user-level form only in that it can take only one argument at a time: the support for multiple arguments is implemented at the preprocessor level.

You can declare the same variable as EXTERN more than once: NASM will quietly ignore the second and later redeclarations. You can't declare a variable as EXTERN as well as something else, though.

5.5 GLOBAL: Exporting Symbols to Other Modules

GLOBAL is the other end of EXTERN: if one module declares a symbol as EXTERN and refers to it, then in order to prevent linker errors, some other module must actually define the symbol and declare it as GLOBAL. Some assemblers use the name PUBLIC for this purpose.

The GLOBAL directive applying to a symbol must appear before the definition of the symbol.

GLOBAL uses the same syntax as EXTERN, except that it must refer to symbols which are defined in the same module as the GLOBAL directive. For example: 

          global _main 
_main:    ; some code

GLOBAL, like EXTERN, allows object formats to define private extensions by means of a colon. The elf object format, for example, lets you specify whether global data items are functions or data: 

          global hashlookup:function, hashtable:data

Like EXTERN, the primitive form of GLOBAL differs from the user-level form only in that it can take only one argument at a time.

5.6 COMMON: Defining Common Data Areas

The COMMON directive is used to declare common variables. A common variable is much like a global variable declared in the uninitialised data section, so that 

          common intvar 4

is similar in function to 

          global intvar 
          section .bss 
intvar    resd 1

The difference is that if more than one module defines the same common variable, then at link time those variables will be merged, and references to intvar in all modules will point at the same piece of memory.

Like GLOBAL and EXTERN, COMMON supports object-format specific extensions. For example, the obj format allows common variables to be NEAR or FAR, and the elf format allows you to specify the alignment requirements of a common variable: 

          common commvar 4:near  ; works in OBJ 
          common intarray 100:4  ; works in ELF: 4 byte aligned

Once again, like EXTERN and GLOBAL, the primitive form of COMMON differs from the user-level form only in that it can take only one argument at a time.

5.7 CPU XXX: Defining CPU Dependencies

The CPU directive restricts assembly to those instructions which are available on the specified CPU.

Options are:

All options are case insensitive. All instructions will be selected only if they apply to the selected cpu or lower.

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The Netwide Assembler: NASM

Next Chapter | Previous Chapter | Contents | Index

Chapter 6: Output Formats

NASM is a portable assembler, designed to be able to compile on any ANSI C-supporting platform and produce output to run on a variety of Intel x86 operating systems. For this reason, it has a large number of available output formats, selected using the -f option on the NASM command line. Each of these formats, along with its function t ; setup code comes last ; the resident part of the TSR goes here setup: ; now write the code that installs the TSR here absolute setup runtimevar1 resw 1 runtimevar2 resd 20 tsr_end:

This defines some variables `on top of' the setup code, so that after the setup has finished running, the space it took up can be re-used as data storage for the running TSR. The symbol `tsr_end' can be used to calculate the total size of the part of the TSR that needs to be made resident.

5.4 EXTERN: Importing Symbols from Other Modules

EXTERN is similar to the MASM directive EXTRN and the C keyword extern: it is used to declare a symbol which is not defined anywhere in the module being assembled, but is assumed to be defined in some other module and needs to be referred to by this one. Not every object-file format can support external variables: the bin format cannot.

The EXTERN directive takes as many arguments as you like. Each argument is the name of a symbol: 

          extern _printf 
          extern _sscanf,_fscanf

Some object-file formats provide extra features to the EXTERN directive. In all cases, the extra features are used by suffixing a colon to the symbol name followed by object-format specific text. For example, the obj format allows you to declare that the default segment base of an external should be the group dgroup by means of the directive 

          extern _variable:wrt dgroup

The primitive form of EXTERN differs from the user-level form only in that it can take only one argument at a time: the support for multiple arguments is implemented at the preprocessor level.

You can declare the same variable as EXTERN more than once: NASM will quietly ignore the second and later redeclarations. You can't declare a variable as EXTERN as well as something else, though.

5.5 GLOBAL: Exporting Symbols to Other Modules

GLOBAL is the other end of EXTERN: if one module declares a symbol as EXTERN and refers to it, then in order to prevent linker errors, some other module must actually define the symbol and declare it as GLOBAL. Some assemblers use the name PUBLIC for this purpose.

The GLOBAL directive applying to a symbol must appear before the definition of the symbol.

GLOBAL uses the same syntax as EXTERN, except that it must refer to symbols which are defined in the same module as the GLOBAL directive. For example: 

          global _main 
_main:    ; some code

GLOBAL, like EXTERN, allows object formats to define private extensions by means of a colon. The elf object format, for example, lets you specify whether global data items are functions or data: 

          global hashlookup:function, hashtable:data

Like EXTERN, the primitive form of GLOBAL differs from the user-level form only in that it can take only one argument at a time.

5.6 COMMON: Defining Common Data Areas

The COMMON directive is used to declare common variables. A common variable is much like a global variable declared in the uninitialised data section, so that 

          common intvar 4

is similar in function to 

          global intvar 
          section .bss 
intvar    resd 1

The difference is that if more than one module defines the same common variable, then at link time those variables will be merged, and references to intvar in all modules will point at the same piece of memory.

Like GLOBAL and EXTERN, COMMON supports object-format specific extensions. For example, the obj format allows common variables to be NEAR or FAR, and the elf format allows you to specify the alignment requirements of a common variable: 

          common commvar 4:near  ; works in OBJ 
          common intarray 100:4  ; works in ELF: 4 byte aligned

Once again, like EXTERN and GLOBAL, the primitive form of COMMON differs from the user-level form only in that it can take only one argument at a time.

5.7 CPU XXX: Defining CPU Dependencies

The CPU directive restricts assembly to those instructions which are available on the specified CPU.

Options are:

All options are case insensitive. All instructions will be selected only if they apply to the selected cpu or lower.

Next Chapter | Previous Chapter | Contents | Index ./usr/share/doc/nasm/html/nasmdoc6.html0100644000000000000000000012644710165032410016702 0ustar rootrootNASM Manual

The Netwide Assembler: NASM

Next Chapter | Previous Chapter | Contents | Index

Chapter 6: Output Formats

NASM is a portable assembler, designed to be able to compile on any ANSI C-supporting platform and produce output to run on a variety of Intel x86 operating systems. For this reason, it has a large number of available output formats, selected using the -f option on the NASM command line. Each of these formats, along with its function t ; setup code comes last ; the resident part of the TSR goes here setup: ; now write the code that installs the TSR here absolute setup runtimevar1 resw 1 runtimevar2 resd 20 tsr_end:

This defines some variables `on top of' the setup code, so that after the setup has finished running, the space it took up can be re-used as data storage for the running TSR. The symbol `tsr_end' can be used to calculate the total size of the part of the TSR that needs to be made resident.

5.4 EXTERN: Importing Symbols from Other Modules

EXTERN is similar to the MASM directive EXTRN and the C keyword extern: it is used to declare a symbol which is not defined anywhere in the module being assembled, but is assumed to be defined in some other module and needs to be referred to by this one. Not every object-file format can support external variables: the bin format cannot.

The EXTERN directive takes as many arguments as you like. Each argument is the name of a symbol: 

          extern _printf 
          extern _sscanf,_fscanf

Some object-file formats provide extra features to the EXTERN directive. In all cases, the extra features are used by suffixing a colon to the symbol name followed by object-format specific text. For example, the obj format allows you to declare that the default segment base of an external should be the group dgroup by means of the directive 

          extern _variable:wrt dgroup

The primitive form of EXTERN differs from the user-level form only in that it can take only one argument at a time: the support for multiple arguments is implemented at the preprocessor level.

You can declare the same variable as EXTERN more than once: NASM will quietly ignore the second and later redeclarations. You can't declare a variable as EXTERN as well as something else, though.

5.5 GLOBAL: Exporting Symbols to Other Modules

GLOBAL is the other end of EXTERN: if one module declares a symbol as EXTERN and refers to it, then in order to prevent linker errors, some other module must actually define the symbol and declare it as GLOBAL. Some assemblers use the name PUBLIC for this purpose.

The GLOBAL directive applying to a symbol must appear before the definition of the symbol.

GLOBAL uses the same syntax as EXTERN, except that it must refer to symbols which are defined in the same module as the GLOBAL directive. For example: 

          global _main 
_main:    ; some code

GLOBAL, like EXTERN, allows object formats to define private extensions by means of a colon. The elf object format, for example, lets you specify whether global data items are functions or data: 

          global hashlookup:function, hashtable:data

Like EXTERN, the primitive form of GLOBAL differs from the user-level form only in that it can take only one argument at a time.

5.6 COMMON: Defining Common Data Areas

The COMMON directive is used to declare common variables. A common variable is much like a global variable declared in the uninitialised data section, so that 

          common intvar 4

is similar in function to 

          global intvar 
          section .bss 
intvar    resd 1

The difference is that if more than one module defines the same common variable, then at link time those variables will be merged, and references to intvar in all modules will point at the same piece of memory.

Like GLOBAL and EXTERN, COMMON supports object-format specific extensions. For example, the obj format allows common variables to be NEAR or FAR, and the elf format allows you to specify the alignment requirements of a common variable: 

          common commvar 4:near  ; works in OBJ 
          common intarray 100:4  ; works in ELF: 4 byte aligned

Once again, like EXTERN and GLOBAL, the primitive form of COMMON differs from the user-level form only in that it can take only one argument at a time.

5.7 CPU XXX: Defining CPU Dependencies

The CPU directive restricts assembly to those instructions which are available on the specified CPU.

Options are:

All options are case insensitive. All instructions will be selected only if they apply to the selected cpu or lower.

Next Chapter | Previous Chapter | Contents | Index ./usr/share/doc/nasm/html/nasmdoc6.html0100644000000000000000000012644710165032410016702 0ustar rootrootNASM Manual

The Netwide Assembler: NASM

Next Chapter | Previous Chapter | Contents | Index

Chapter 6: Output Formats

NASM is a portable assembler, designed to be able to compile on any ANSI C-supporting platform and produce output to run on a variety of Intel x86 operating systems. For this reason, it has a large number of available output formats, selected using the -f option on the NASM command line. Each of these formats, along with its function t ; setup code comes last ; the resident part of the TSR goes here setup: ; now write the code that installs the TSR here absolute setup runtimevar1 resw 1 runtimevar2 resd 20 tsr_end:

This defines some variables `on top of' the setup code, so that after the setup has finished running, the space it took up can be re-used as data storage for the running TSR. The symbol `tsr_end' can be used to calculate the total size of the part of the TSR that needs to be made resident.

5.4 EXTERN: Importing Symbols from Other Modules

EXTERN is similar to the MASM directive EXTRN and the C keyword extern: it is used to declare a symbol which is not defined anywhere in the module being assembled, but is assumed to be defined in some other module and needs to be referred to by this one. Not every object-file format can support external variables: the bin format cannot.

The EXTERN directive takes as many arguments as you like. Each argument is the name of a symbol: 

          extern _printf 
          extern _sscanf,_fscanf

Some object-file formats provide extra features to the EXTERN directive. In all cases, the extra features are used by suffixing a colon to the symbol name followed by object-format specific text. For example, the obj format allows you to declare that the default segment base of an external should be the group dgroup by means of the directive 

          extern _variable:wrt dgroup

The primitive form of EXTERN differs from the user-level form only in that it can take only one argument at a time: the support for multiple arguments is implemented at the preprocessor level.

You can declare the same variable as EXTERN more than once: NASM will quietly ignore the second and later redeclarations. You can't declare a variable as EXTERN as well as something else, though.

5.5 GLOBAL: Exporting Symbols to Other Modules

GLOBAL is the other end of EXTERN: if one module declares a symbol as EXTERN and refers to it, then in order to prevent linker errors, some other module must actually define the symbol and declare it as GLOBAL. Some assemblers use the name PUBLIC for this purpose.

The GLOBAL directive applying to a symbol must appear before the definition of the symbol.

GLOBAL uses the same syntax as EXTERN, except that it must refer to symbols which are defined in the same module as the GLOBAL directive. For example: 

          global _main 
_main:    ; some code

GLOBAL, like EXTERN, allows object formats to define private extensions by means of a colon. The elf object format, for example, lets you specify whether global data items are functions or data: 

          global hashlookup:function, hashtable:data

Like EXTERN, the primitive form of GLOBAL differs from the user-level form only in that it can take only one argument at a time.

5.6 COMMON: Defining Common Data Areas

The COMMON directive is used to declare common variables. A common variable is much like a global variable declared in the uninitialised data section, so that 

          common intvar 4

is similar in function to 

          global intvar 
          section .bss 
intvar    resd 1

The difference is that if more than one module defines the same common variable, then at link time those variables will be merged, and references to intvar in all modules will point at the same piece of memory.

Like GLOBAL and EXTERN, COMMON supports object-format specific extensions. For example, the obj format allows common variables to be NEAR or FAR, and the elf format allows you to specify the alignment requirements of a common variable: 

          common commvar 4:near  ; works in OBJ 
          common intarray 100:4  ; works in ELF: 4 byte aligned

Once again, like EXTERN and GLOBAL, the primitive form of COMMON differs from the user-level form only in that it can take only one argument at a time.

5.7 CPU XXX: Defining CPU Dependencies

The CPU directive restricts assembly to those instructions which are available on the specified CPU.

Options are:

All options are case insensitive. All instructions will be selected only if they apply to the selected cpu or lower.

Next Chapter | Previous Chapter | Contents | Index ./usr/share/doc/nasm/html/nasmdoc6.html0100644000000000000000000012644710165032410016702 0ustar rootrootNASM Manual

The Netwide Assembler: NASM

Next Chapter | Previous Chapter | Contents | Index

Chapter 6: Output Formats

NASM is a portable assembler, designed to be able to compile on any ANSI C-supporting platform and produce output to run on a variety of Intel x86 operating systems. For this reason, it has a large number of available output formats, selected using the -f option on the NASM command line. Each of these formats, along with its function t ; setup code comes last ; the resident part of the TSR goes here setup: ; now write the code that installs the TSR here absolute setup runtimevar1 resw 1 runtimevar2 resd 20 tsr_end:

This defines some variables `on top of' the setup code, so that after the setup has finished running, the space it took up can be re-used as data storage for the running TSR. The symbol `tsr_end' can be used to calculate the total size of the part of the TSR that needs to be made resident.

5.4 EXTERN: Importing Symbols from Other Modules

EXTERN is similar to the MASM directive EXTRN and the C keyword extern: it is used to declare a symbol which is not defined anywhere in the module being assembled, but is assumed to be defined in some other module and needs to be referred to by this one. Not every object-file format can support external variables: the bin format cannot.

The EXTERN directive takes as many arguments as you like. Each argument is the name of a symbol: 

          extern _printf 
          extern _sscanf,_fscanf

Some object-file formats provide extra features to the EXTERN directive. In all cases, the extra features are used by suffixing a colon to the symbol name followed by object-format specific text. For example, the obj format allows you to declare that the default segment base of an external should be the group dgroup by means of the directive 

          extern _variable:wrt dgroup

The primitive form of EXTERN differs from the user-level form only in that it can take only one argument at a time: the support for multiple arguments is implemented at the preprocessor level.

You can declare the same variable as EXTERN more than once: NASM will quietly ignore the second and later redeclarations. You can't declare a variable as EXTERN as well as something else, though.

5.5 GLOBAL: Exporting Symbols to Other Modules

GLOBAL is the other end of EXTERN: if one module declares a symbol as EXTERN and refers to it, then in order to prevent linker errors, some other module must actually define the symbol and declare it as GLOBAL. Some assemblers use the name PUBLIC for this purpose.

The GLOBAL directive applying to a symbol must appear before the definition of the symbol.

GLOBAL uses the same syntax as EXTERN, except that it must refer to symbols which are defined in the same module as the GLOBAL directive. For example: 

          global _main 
_main:    ; some code

GLOBAL, like EXTERN, allows object formats to define private extensions by means of a colon. The elf object format, for example, lets you specify whether global data items are functions or data: 

          global hashlookup:function, hashtable:data

Like EXTERN, the primitive form of GLOBAL differs from the user-level form only in that it can take only one argument at a time.

5.6 COMMON: Defining Common Data Areas

The COMMON directive is used to declare common variables. A common variable is much like a global variable declared in the uninitialised data section, so that 

          common intvar 4

is similar in function to 

          global intvar 
          section .bss 
intvar    resd 1

The difference is that if more than one module defines the same common variable, then at link time those variables will be merged, and references to intvar in all modules will point at the same piece of memory.

Like GLOBAL and EXTERN, COMMON supports object-format specific extensions. For example, the obj format allows common variables to be NEAR or FAR, and the elf format allows you to specify the alignment requirements of a common variable: 

          common commvar 4:near  ; works in OBJ 
          common intarray 100:4  ; works in ELF: 4 byte aligned

Once again, like EXTERN and GLOBAL, the primitive form of COMMON differs from the user-level form only in that it can take only one argument at a time.

5.7 CPU XXX: Defining CPU Dependencies

The CPU directive restricts assembly to those instructions which are available on the specified CPU.

Options are:

All options are case insensitive. All instructions will be selected only if they apply to the selected cpu or lower.

Next Chapter | Previous Chapter | Contents | Index ./usr/share/doc/nasm/html/nasmdoc6.html0100644000000000000000000012644710165032410016702 0ustar rootrootNASM Manual

The Netwide Assembler: NASM

Next Chapter | Previous Chapter | Contents | Index

Chapter 6: Output Formats

NASM is a portable assembler, designed to be able to compile on any ANSI C-supporting platform and produce output to run on a variety of Intel x86 operating systems. For this reason, it has a large number of available output formats, selected using the -f option on the NASM command line. Each of these formats, along with its function t ; setup code comes last ; the resident part of the TSR goes here setup: ; now write the code that installs the TSR here absolute setup runtimevar1 resw 1 runtimevar2 resd 20 tsr_end:

This defines some variables `on top of' the setup code, so that after the setup has finished running, the space it took up can be re-used as data storage for the running TSR. The symbol `tsr_end' can be used to calculate the total size of the part of the TSR that needs to be made resident.

5.4 EXTERN: Importing Symbols from Other Modules

EXTERN is similar to the MASM directive EXTRN and the C keyword extern: it is used to declare a symbol which is not defined anywhere in the module being assembled, but is assumed to be defined in some other module and needs to be referred to by this one. Not every object-file format can support external variables: the bin format cannot.

The EXTERN directive takes as many arguments as you like. Each argument is the name of a symbol: 

          extern _printf 
          extern _sscanf,_fscanf

Some object-file formats provide extra features to the EXTERN directive. In all cases, the extra features are used by suffixing a colon to the symbol name followed by object-format specific text. For example, the obj format allows you to declare that the default segment base of an external should be the group dgroup by means of the directive 

          extern _variable:wrt dgroup

The primitive form of EXTERN differs from the user-level form only in that it can take only one argument at a time: the support for multiple arguments is implemented at the preprocessor level.

You can declare the same variable as EXTERN more than once: NASM will quietly ignore the second and later redeclarations. You can't declare a variable as EXTERN as well as something else, though.

5.5 GLOBAL: Exporting Symbols to Other Modules

GLOBAL is the other end of EXTERN: if one module declares a symbol as EXTERN and refers to it, then in order to prevent linker errors, some other module must actually define the symbol and declare it as GLOBAL<