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  • Nginx traffic is going to wrong upsteam when mixing named servers and default servers

    - by Morgan
    I have the below config file for nginx. The problem is all traffic is going to upstream clustera. How do I configure nginx to only send traffic for example.com to clustera and all the rest to clusterb? user www-data; worker_processes 1; error_log /var/log/nginx/error.log; pid /var/run/nginx.pid; events { worker_connections 1024; } http { include /etc/nginx/mime.types; log_format cache '\n*** $remote_addr [$time_local] ' '[$upstream_cache_status] $upstream_response_time ' '$host "$request" ($status) $body_bytes_sent ' '"$http_referer" "$http_user_agent" ' 'Cache-Control: $upstream_http_cache_control ' 'Expires: $upstream_http_expires ' ; access_log /var/log/nginx/access.log cache; sendfile on; keepalive_timeout 65; gzip on; gzip_vary on; gzip_comp_level 6; gzip_proxied any; gzip_disable "MSIE [1-6]\.(?!.*SV1)"; gzip_buffers 16 8k; include /etc/nginx/conf.d/*.conf; proxy_cache_key "$scheme$host$request_uri"; proxy_cache_path /var/cache/nginx levels=1:2 keys_zone=main:10m max_size=1g inactive=30m; upstream clustera { ip_hash; server a.example.com:80; } upstream clusterb { ip_hash; server b.example.com:80; } client_max_body_size 20m; client_body_buffer_size 128k; proxy_connect_timeout 300; proxy_send_timeout 300; proxy_read_timeout 300; # host for example.com should send traffic to clustera server { listen 80; server_name example.com; location ~*(png|jpeg|jpg|gif|ico|css|js)$ { proxy_pass http://clustera; proxy_set_header Host $host; proxy_set_header X-Real-IP $remote_addr; proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for; proxy_cache main; proxy_cache_valid 200 5m; proxy_cache_valid 302 1m; } location / { proxy_pass http://clustera; proxy_set_header Host $host; proxy_set_header X-Real-IP $remote_addr; proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for; } } # host for everyone else. traffic goes to clusterb server { listen 80; server_name _; if ( $http_user_agent ~* (spider|crawler|slurp) ) { return 503; } set $slow 0; if ( $http_user_agent ~* (bot) ) { set $slow 1; } if ( $slow ) { set $limit_rate 1k; } location ~*(png|jpeg|jpg|gif|ico|css|js)$ { proxy_pass http://clusterb; proxy_set_header Host $host; proxy_set_header X-Real-IP $remote_addr; proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for; proxy_cache main; proxy_cache_valid 200 5m; proxy_cache_valid 302 1m; } location /images { proxy_pass http://clisterb; proxy_set_header Host $host; proxy_set_header X-Real-IP $remote_addr; proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for; proxy_cache main; proxy_cache_valid 200 5m; proxy_cache_valid 302 1m; } location / { proxy_pass http://clusterb; proxy_set_header Host $host; proxy_set_header X-Real-IP $remote_addr; proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for; } } }

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  • Running 32 bit assembly code on a 64 bit Linux & 64 bit Processor : Explain the anomaly.

    - by claws
    Hello, I'm in an interesting problem.I forgot I'm using 64bit machine & OS and wrote a 32 bit assembly code. I don't know how to write 64 bit code. This is the x86 32-bit assembly code for Gnu Assembler (AT&T syntax) on Linux. //hello.S #include <asm/unistd.h> #include <syscall.h> #define STDOUT 1 .data hellostr: .ascii "hello wolrd\n"; helloend: .text .globl _start _start: movl $(SYS_write) , %eax //ssize_t write(int fd, const void *buf, size_t count); movl $(STDOUT) , %ebx movl $hellostr , %ecx movl $(helloend-hellostr) , %edx int $0x80 movl $(SYS_exit), %eax //void _exit(int status); xorl %ebx, %ebx int $0x80 ret Now, This code should run fine on a 32bit processor & 32 bit OS right? As we know 64 bit processors are backward compatible with 32 bit processors. So, that also wouldn't be a problem. The problem arises because of differences in system calls & call mechanism in 64-bit OS & 32-bit OS. I don't know why but they changed the system call numbers between 32-bit linux & 64-bit linux. asm/unistd_32.h defines: #define __NR_write 4 #define __NR_exit 1 asm/unistd_64.h defines: #define __NR_write 1 #define __NR_exit 60 Anyway using Macros instead of direct numbers is paid off. Its ensuring correct system call numbers. when I assemble & link & run the program. $cpp hello.S hello.s //pre-processor $as hello.s -o hello.o //assemble $ld hello.o // linker : converting relocatable to executable Its not printing helloworld. In gdb its showing: Program exited with code 01. I don't know how to debug in gdb. using tutorial I tried to debug it and execute instruction by instruction checking registers at each step. its always showing me "program exited with 01". It would be great if some on could show me how to debug this. (gdb) break _start Note: breakpoint -10 also set at pc 0x4000b0. Breakpoint 8 at 0x4000b0 (gdb) start Function "main" not defined. Make breakpoint pending on future shared library load? (y or [n]) y Temporary breakpoint 9 (main) pending. Starting program: /home/claws/helloworld Program exited with code 01. (gdb) info breakpoints Num Type Disp Enb Address What 8 breakpoint keep y 0x00000000004000b0 <_start> 9 breakpoint del y <PENDING> main I tried running strace. This is its output: execve("./helloworld", ["./helloworld"], [/* 39 vars */]) = 0 write(0, NULL, 12 <unfinished ... exit status 1> Explain the parameters of write(0, NULL, 12) system call in the output of strace? What exactly is happening? I want to know the reason why exactly its exiting with exitstatus=1? Can some one please show me how to debug this program using gdb? Why did they change the system call numbers? Kindly change this program appropriately so that it can run correctly on this machine. EDIT: After reading Paul R's answer. I checked my files claws@claws-desktop:~$ file ./hello.o ./hello.o: ELF 64-bit LSB relocatable, x86-64, version 1 (SYSV), not stripped claws@claws-desktop:~$ file ./hello ./hello: ELF 64-bit LSB executable, x86-64, version 1 (SYSV), statically linked, not stripped All of my questions still hold true. What exactly is happening in this case? Can someone please answer my questions and provide an x86-64 version of this code?

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  • Solaris X86 AESNI OpenSSL Engine

    - by danx
    Solaris X86 AESNI OpenSSL Engine Cryptography is a major component of secure e-commerce. Since cryptography is compute intensive and adds a significant load to applications, such as SSL web servers (https), crypto performance is an important factor. Providing accelerated crypto hardware greatly helps these applications and will help lead to a wider adoption of cryptography, and lower cost, in e-commerce and other applications. The Intel Westmere microprocessor has six new instructions to acclerate AES encryption. They are called "AESNI" for "AES New Instructions". These are unprivileged instructions, so no "root", other elevated access, or context switch is required to execute these instructions. These instructions are used in a new built-in OpenSSL 1.0 engine available in Solaris 11, the aesni engine. Previous Work Previously, AESNI instructions were introduced into the Solaris x86 kernel and libraries. That is, the "aes" kernel module (used by IPsec and other kernel modules) and the Solaris pkcs11 library (for user applications). These are available in Solaris 10 10/09 (update 8) and above, and Solaris 11. The work here is to add the aesni engine to OpenSSL. X86 AESNI Instructions Intel's Xeon 5600 is one of the processors that support AESNI. This processor is used in the Sun Fire X4170 M2 As mentioned above, six new instructions acclerate AES encryption in processor silicon. The new instructions are: aesenc performs one round of AES encryption. One encryption round is composed of these steps: substitute bytes, shift rows, mix columns, and xor the round key. aesenclast performs the final encryption round, which is the same as above, except omitting the mix columns (which is only needed for the next encryption round). aesdec performs one round of AES decryption aesdeclast performs the final AES decryption round aeskeygenassist Helps expand the user-provided key into a "key schedule" of keys, one per round aesimc performs an "inverse mixed columns" operation to convert the encryption key schedule into a decryption key schedule pclmulqdq Not a AESNI instruction, but performs "carryless multiply" operations to acclerate AES GCM mode. Since the AESNI instructions are implemented in hardware, they take a constant number of cycles and are not vulnerable to side-channel timing attacks that attempt to discern some bits of data from the time taken to encrypt or decrypt the data. Solaris x86 and OpenSSL Software Optimizations Having X86 AESNI hardware crypto instructions is all well and good, but how do we access it? The software is available with Solaris 11 and is used automatically if you are running Solaris x86 on a AESNI-capable processor. AESNI is used internally in the kernel through kernel crypto modules and is available in user space through the PKCS#11 library. For OpenSSL on Solaris 11, AESNI crypto is available directly with a new built-in OpenSSL 1.0 engine, called the "aesni engine." This is in lieu of the extra overhead of going through the Solaris OpenSSL pkcs11 engine, which accesses Solaris crypto and digest operations. Instead, AESNI assembly is included directly in the new aesni engine. Instead of including the aesni engine in a separate library in /lib/openssl/engines/, the aesni engine is "built-in", meaning it is included directly in OpenSSL's libcrypto.so.1.0.0 library. This reduces overhead and the need to manually specify the aesni engine. Since the engine is built-in (that is, in libcrypto.so.1.0.0), the openssl -engine command line flag or API call is not needed to access the engine—the aesni engine is used automatically on AESNI hardware. Ciphers and Digests supported by OpenSSL aesni engine The Openssl aesni engine auto-detects if it's running on AESNI hardware and uses AESNI encryption instructions for these ciphers: AES-128-CBC, AES-192-CBC, AES-256-CBC, AES-128-CFB128, AES-192-CFB128, AES-256-CFB128, AES-128-CTR, AES-192-CTR, AES-256-CTR, AES-128-ECB, AES-192-ECB, AES-256-ECB, AES-128-OFB, AES-192-OFB, and AES-256-OFB. Implementation of the OpenSSL aesni engine The AESNI assembly language routines are not a part of the regular Openssl 1.0.0 release. AESNI is a part of the "HEAD" ("development" or "unstable") branch of OpenSSL, for future release. But AESNI is also available as a separate patch provided by Intel to the OpenSSL project for OpenSSL 1.0.0. A minimal amount of "glue" code in the aesni engine works between the OpenSSL libcrypto.so.1.0.0 library and the assembly functions. The aesni engine code is separate from the base OpenSSL code and requires patching only a few source files to use it. That means OpenSSL can be more easily updated to future versions without losing the performance from the built-in aesni engine. OpenSSL aesni engine Performance Here's some graphs of aesni engine performance I measured by running openssl speed -evp $algorithm where $algorithm is aes-128-cbc, aes-192-cbc, and aes-256-cbc. These are using the 64-bit version of openssl on the same AESNI hardware, a Sun Fire X4170 M2 with a Intel Xeon E5620 @2.40GHz, running Solaris 11 FCS. "Before" is openssl without the aesni engine and "after" is openssl with the aesni engine. The numbers are MBytes/second. OpenSSL aesni engine performance on Sun Fire X4170 M2 (Xeon E5620 @2.40GHz) (Higher is better; "before"=OpenSSL on AESNI without AESNI engine software, "after"=OpenSSL AESNI engine) As you can see the speedup is dramatic for all 3 key lengths and for data sizes from 16 bytes to 8 Kbytes—AESNI is about 7.5-8x faster over hand-coded amd64 assembly (without aesni instructions). Verifying the OpenSSL aesni engine is present The easiest way to determine if you are running the aesni engine is to type "openssl engine" on the command line. No configuration, API, or command line options are needed to use the OpenSSL aesni engine. If you are running on Intel AESNI hardware with Solaris 11 FCS, you'll see this output indicating you are using the aesni engine: intel-westmere $ openssl engine (aesni) Intel AES-NI engine (no-aesni) (dynamic) Dynamic engine loading support (pkcs11) PKCS #11 engine support If you are running on Intel without AESNI hardware you'll see this output indicating the hardware can't support the aesni engine: intel-nehalem $ openssl engine (aesni) Intel AES-NI engine (no-aesni) (dynamic) Dynamic engine loading support (pkcs11) PKCS #11 engine support For Solaris on SPARC or older Solaris OpenSSL software, you won't see any aesni engine line at all. Third-party OpenSSL software (built yourself or from outside Oracle) will not have the aesni engine either. Solaris 11 FCS comes with OpenSSL version 1.0.0e. The output of typing "openssl version" should be "OpenSSL 1.0.0e 6 Sep 2011". 64- and 32-bit OpenSSL OpenSSL comes in both 32- and 64-bit binaries. 64-bit executable is now the default, at /usr/bin/openssl, and OpenSSL 64-bit libraries at /lib/amd64/libcrypto.so.1.0.0 and libssl.so.1.0.0 The 32-bit executable is at /usr/bin/i86/openssl and the libraries are at /lib/libcrytpo.so.1.0.0 and libssl.so.1.0.0. Availability The OpenSSL AESNI engine is available in Solaris 11 x86 for both the 64- and 32-bit versions of OpenSSL. It is not available with Solaris 10. You must have a processor that supports AESNI instructions, otherwise OpenSSL will fallback to the older, slower AES implementation without AESNI. Processors that support AESNI include most Westmere and Sandy Bridge class processor architectures. Some low-end processors (such as for mobile/laptop platforms) do not support AESNI. The easiest way to determine if the processor supports AESNI is with the isainfo -v command—look for "amd64" and "aes" in the output: $ isainfo -v 64-bit amd64 applications pclmulqdq aes sse4.2 sse4.1 ssse3 popcnt tscp ahf cx16 sse3 sse2 sse fxsr mmx cmov amd_sysc cx8 tsc fpu Conclusion The Solaris 11 OpenSSL aesni engine provides easy access to powerful Intel AESNI hardware cryptography, in addition to Solaris userland PKCS#11 libraries and Solaris crypto kernel modules.

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  • Solaris X86 AESNI OpenSSL Engine

    - by danx
    Solaris X86 AESNI OpenSSL Engine Cryptography is a major component of secure e-commerce. Since cryptography is compute intensive and adds a significant load to applications, such as SSL web servers (https), crypto performance is an important factor. Providing accelerated crypto hardware greatly helps these applications and will help lead to a wider adoption of cryptography, and lower cost, in e-commerce and other applications. The Intel Westmere microprocessor has six new instructions to acclerate AES encryption. They are called "AESNI" for "AES New Instructions". These are unprivileged instructions, so no "root", other elevated access, or context switch is required to execute these instructions. These instructions are used in a new built-in OpenSSL 1.0 engine available in Solaris 11, the aesni engine. Previous Work Previously, AESNI instructions were introduced into the Solaris x86 kernel and libraries. That is, the "aes" kernel module (used by IPsec and other kernel modules) and the Solaris pkcs11 library (for user applications). These are available in Solaris 10 10/09 (update 8) and above, and Solaris 11. The work here is to add the aesni engine to OpenSSL. X86 AESNI Instructions Intel's Xeon 5600 is one of the processors that support AESNI. This processor is used in the Sun Fire X4170 M2 As mentioned above, six new instructions acclerate AES encryption in processor silicon. The new instructions are: aesenc performs one round of AES encryption. One encryption round is composed of these steps: substitute bytes, shift rows, mix columns, and xor the round key. aesenclast performs the final encryption round, which is the same as above, except omitting the mix columns (which is only needed for the next encryption round). aesdec performs one round of AES decryption aesdeclast performs the final AES decryption round aeskeygenassist Helps expand the user-provided key into a "key schedule" of keys, one per round aesimc performs an "inverse mixed columns" operation to convert the encryption key schedule into a decryption key schedule pclmulqdq Not a AESNI instruction, but performs "carryless multiply" operations to acclerate AES GCM mode. Since the AESNI instructions are implemented in hardware, they take a constant number of cycles and are not vulnerable to side-channel timing attacks that attempt to discern some bits of data from the time taken to encrypt or decrypt the data. Solaris x86 and OpenSSL Software Optimizations Having X86 AESNI hardware crypto instructions is all well and good, but how do we access it? The software is available with Solaris 11 and is used automatically if you are running Solaris x86 on a AESNI-capable processor. AESNI is used internally in the kernel through kernel crypto modules and is available in user space through the PKCS#11 library. For OpenSSL on Solaris 11, AESNI crypto is available directly with a new built-in OpenSSL 1.0 engine, called the "aesni engine." This is in lieu of the extra overhead of going through the Solaris OpenSSL pkcs11 engine, which accesses Solaris crypto and digest operations. Instead, AESNI assembly is included directly in the new aesni engine. Instead of including the aesni engine in a separate library in /lib/openssl/engines/, the aesni engine is "built-in", meaning it is included directly in OpenSSL's libcrypto.so.1.0.0 library. This reduces overhead and the need to manually specify the aesni engine. Since the engine is built-in (that is, in libcrypto.so.1.0.0), the openssl -engine command line flag or API call is not needed to access the engine—the aesni engine is used automatically on AESNI hardware. Ciphers and Digests supported by OpenSSL aesni engine The Openssl aesni engine auto-detects if it's running on AESNI hardware and uses AESNI encryption instructions for these ciphers: AES-128-CBC, AES-192-CBC, AES-256-CBC, AES-128-CFB128, AES-192-CFB128, AES-256-CFB128, AES-128-CTR, AES-192-CTR, AES-256-CTR, AES-128-ECB, AES-192-ECB, AES-256-ECB, AES-128-OFB, AES-192-OFB, and AES-256-OFB. Implementation of the OpenSSL aesni engine The AESNI assembly language routines are not a part of the regular Openssl 1.0.0 release. AESNI is a part of the "HEAD" ("development" or "unstable") branch of OpenSSL, for future release. But AESNI is also available as a separate patch provided by Intel to the OpenSSL project for OpenSSL 1.0.0. A minimal amount of "glue" code in the aesni engine works between the OpenSSL libcrypto.so.1.0.0 library and the assembly functions. The aesni engine code is separate from the base OpenSSL code and requires patching only a few source files to use it. That means OpenSSL can be more easily updated to future versions without losing the performance from the built-in aesni engine. OpenSSL aesni engine Performance Here's some graphs of aesni engine performance I measured by running openssl speed -evp $algorithm where $algorithm is aes-128-cbc, aes-192-cbc, and aes-256-cbc. These are using the 64-bit version of openssl on the same AESNI hardware, a Sun Fire X4170 M2 with a Intel Xeon E5620 @2.40GHz, running Solaris 11 FCS. "Before" is openssl without the aesni engine and "after" is openssl with the aesni engine. The numbers are MBytes/second. OpenSSL aesni engine performance on Sun Fire X4170 M2 (Xeon E5620 @2.40GHz) (Higher is better; "before"=OpenSSL on AESNI without AESNI engine software, "after"=OpenSSL AESNI engine) As you can see the speedup is dramatic for all 3 key lengths and for data sizes from 16 bytes to 8 Kbytes—AESNI is about 7.5-8x faster over hand-coded amd64 assembly (without aesni instructions). Verifying the OpenSSL aesni engine is present The easiest way to determine if you are running the aesni engine is to type "openssl engine" on the command line. No configuration, API, or command line options are needed to use the OpenSSL aesni engine. If you are running on Intel AESNI hardware with Solaris 11 FCS, you'll see this output indicating you are using the aesni engine: intel-westmere $ openssl engine (aesni) Intel AES-NI engine (no-aesni) (dynamic) Dynamic engine loading support (pkcs11) PKCS #11 engine support If you are running on Intel without AESNI hardware you'll see this output indicating the hardware can't support the aesni engine: intel-nehalem $ openssl engine (aesni) Intel AES-NI engine (no-aesni) (dynamic) Dynamic engine loading support (pkcs11) PKCS #11 engine support For Solaris on SPARC or older Solaris OpenSSL software, you won't see any aesni engine line at all. Third-party OpenSSL software (built yourself or from outside Oracle) will not have the aesni engine either. Solaris 11 FCS comes with OpenSSL version 1.0.0e. The output of typing "openssl version" should be "OpenSSL 1.0.0e 6 Sep 2011". 64- and 32-bit OpenSSL OpenSSL comes in both 32- and 64-bit binaries. 64-bit executable is now the default, at /usr/bin/openssl, and OpenSSL 64-bit libraries at /lib/amd64/libcrypto.so.1.0.0 and libssl.so.1.0.0 The 32-bit executable is at /usr/bin/i86/openssl and the libraries are at /lib/libcrytpo.so.1.0.0 and libssl.so.1.0.0. Availability The OpenSSL AESNI engine is available in Solaris 11 x86 for both the 64- and 32-bit versions of OpenSSL. It is not available with Solaris 10. You must have a processor that supports AESNI instructions, otherwise OpenSSL will fallback to the older, slower AES implementation without AESNI. Processors that support AESNI include most Westmere and Sandy Bridge class processor architectures. Some low-end processors (such as for mobile/laptop platforms) do not support AESNI. The easiest way to determine if the processor supports AESNI is with the isainfo -v command—look for "amd64" and "aes" in the output: $ isainfo -v 64-bit amd64 applications pclmulqdq aes sse4.2 sse4.1 ssse3 popcnt tscp ahf cx16 sse3 sse2 sse fxsr mmx cmov amd_sysc cx8 tsc fpu Conclusion The Solaris 11 OpenSSL aesni engine provides easy access to powerful Intel AESNI hardware cryptography, in addition to Solaris userland PKCS#11 libraries and Solaris crypto kernel modules.

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  • Explanation of the disassembly of the simplest program (x86)

    - by noname
    The following code int _main() {return 0;} Compiled using the command: gcc -s -nostdlib -nostartfiles 01-simple.c -o01-simple.exe gcc version 4.4.1 (TDM-1 mingw32) OllyDbg produced this output: http://imgur.com/g81vK.png Can you explain what happens here? Analysis so far: // these two seems to be an idiom: PUSH EBP // places EBP on stack MOV EBP, ESP // overwrites EBP with ESP MOV EAX, 0 // EAX = 0 LEAVE // == mov esp, ebp // pop ebp // according to // http://en.wikipedia.org/wiki/X86_instruction_listings What is the meaning of all this?

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  • Oracle VM Administration: Oracle VM Server for x86 - new Training

    - by Antoinette O'Sullivan
     Oracle VM Administration: Oracle VM Server for x86 - new course just released. This 3 day hands-on course teaches students how to build a virtualization platform using the Oracle VM Manager and Oracle VM Server for x86. Students learn how deploy and manage highly configurable, inter-connected virtual machines. The course teaches students how to install and configure Oracle VM Server for x86 as well as details of network and storage configuration, pool and repository creation, and virtual machine management. You can follow this class that brings you great hands-on experience either in-class or from your own desk.

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  • Operand size conflict in x86 Assembly??

    - by Mark V.
    I'm a novice programmer who is attempting assembly for the first time. Sorry in advance if this is an incredibly lame question. I have a character stored in the EAX register, but I need to move it to my DL register. When I try: mov dl, eax I get an error C2443: operand size conflict. I know that the eax register is 32 bit while the dl is 8 bit... am I on to something?? How do I go about solving this.

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  • Drawing a stack frame for x86 assembly

    - by drozzy
    So, I am kind of confused about drawing a stack frame for my assembly code. I have a feeling I started out wrong. Here is what I got so far, but as you can see I am confused at step 5, because I think my initial layout is wrong. Can you tell me where I went wrong?

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  • ASM x86 relative JMP

    - by benlaug
    Hi, I'm doing some ASM code in a C code with the asm function. My environment is DVL with gcc version 3. Hi need to make a JMP to a relative address like %eip+0x1f. How can I do this ? Thanks

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  • Using an array in embedded x86 assembly??

    - by Mark V.
    Hey all I have a method (C++) that returns a character and takes an array of characters as its parameters. I'm messing with assembly for the first time and just trying to return the first character of the array in the dl register. Here's what I have so far: char returnFirstChar(char arrayOfLetters[]) { char max; __asm { push eax push ebx push ecx push edx mov dl, 0 mov eax, arrayOfLetters[0] xor edx, edx mov dl, al mov max, dl pop edx pop ecx pop ebx pop eax } return max; } For some reason this method returns a ? Any idea whats going on? Thanks

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  • x86 assembler question

    - by b-gen-jack-o-neill
    Hi, I have 2 simple, but maybe tricky questions. Let´s say I have assembler instruction: MOV EAX,[ebx+6*7] - what I am curious is, does this instruction really actually translates into opcode as it stands,so computation of code in brackets is encoded into opcode, or is this just pseudo intruction for compiler, not CPU, so that compiler before computes the value in brackets using add mul and so, store outcome in some reg and than uses MOV EAX,reg with computed value? Just to be clear, I know the output will be the same. I am interested in execution. Second is about LEA instruction. I know what it does, but I am more interested wheather its real instruction, so compiles does not further change it, just make it into opcode as it stands, or just pseudo code for compiler to, again, first compute adress and than store it.

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  • x86 Assembly Question about outputting

    - by jdea
    My code looks like this _declspec(naked) void f(unsigned int input,unsigned int *output) { __asm{ push dword ptr[esp+4] call factorial pop ecx mov [output], eax //copy result ret } } __declspec(naked) unsigned int factorial(unsigned int n) { __asm{ push esi mov esi, dword ptr [esp+8] cmp esi, 1 jg RECURSE mov eax, 1 jmp END RECURSE: dec esi push esi call factorial pop esi inc esi mul esi END: pop esi ret } } Its a factorial function and I'm trying to output the answer after it recursively calculates the number that was passed in But what I get returned as an output is the same large number I keep getting Not sure about what is wrong with my output, by I also see this error CXX0030: Error: expression cannot be evaluated Thanks!

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  • an x86 question

    - by wide
    i'm working for my exam. i didn't resolved this question. does anyone help me? assume that there are two block, BLOCK1 AND BLOCK2. every block has 50 bytes. write a program to add BLOCK1 with BLOCK2 , and store result to BLOCK2 using LODS, STOS and LOOP etc. assembly commands?

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  • x86 assembly question

    - by kevin
    This is my assembly program which is just a function to swap *x *y. So first argument from main is address of x which is in 8(%ebp) and second one is address of y is in 12(%ebp). The program does swap x and y. I need 7 lines for doing this. can you make it 6 lines and there is a condition you can use only %eax, %ecx, and %edx 3 registers. I think about it so much, but I can't make it 6 lines. There must be a way, isn't it? This might be not a big deal, but if there is a way to get it in 6lines I want to know. movl 8(%ebp), %eax movl (%eax), %ecx movl 12(%ebp), %edx movl (%edx), %eax movl %ecx, (%edx) movl 8(%ebp), %ecx movl %eax, (%ecx)

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  • Change an array's value in x86 assembly (embedded in C++)

    - by VV
    I am messing around with assembly for the first time, and can't seem to change the index values of an array. Here's the method I am working on int ascending_sort( char arrayOfLetters[], int arraySize ) { char temp; __asm { //??? } } And these are what I tried mov temp, 'X' mov al, temp mov arrayOfLetters[0], al And this gave me an error C2415: improper operand type so I tried mov temp, 'X' mov al, temp mov BYTE PTR arrayOfLetters[0], al This complied, but it didn't change the array...

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  • Call/Ret in x86 assembly embedded in C++

    - by SP658
    This is probably trivial, but for some reason I can't it to work. Its supposed to be a simple function that changes the last byte of a dword to 'AA' (10101010), but nothing happens when I call the function. It just returns my original dword __declspec(naked) long function(unsigned long inputDWord, unsigned long *outputDWord) { _asm{ mov ebx, dword ptr[esp+4] push ebx call SET_AA pop ebx mov eax, dword ptr[esp+8] mov dword ptr[eax], ebx } } __declspec(naked) unsigned long SET_AA( unsigned long inputDWord ) { __asm{ mov eax, [esp+4] mov al, 0xAA ret } }

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  • How to make a C program that can run x86 hex codes

    - by Iowa15
    I have an array of hex codes that translate into assembly instructions and I want to create program in C that can execute these. unsigned char rawData[5356] = { 0x4C, 0x01, 0x0A, 0x00, 0x00, 0x00, 0x00, 0x00, 0x64, 0x0C, 0x00, 0x00, 0x3D, 0x00, 0x00, 0x00, 0x00, 0x00, 0x04, 0x01, 0x2E, 0x74, 0x65, 0x78, 0x74, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0xB4, 0x05, 0x00, 0x00, 0xA4, 0x01, 0x00, 0x00, 0x68, 0x08, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x61, 0x00, 0x00, 0x00, 0x20, 0x00, 0x30, 0x60, 0x2E, 0x64, 0x61, 0x74, 0x61, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x40, 0x00, 0x30, 0xC0, 0x2E, 0x62, 0x73, 0x73, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x04, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x80, 0x00, 0x30, 0xC0, 0x2F, 0x34, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x14, 0x00, 0x00, 0x00, 0x58, 0x07, 0x00, 0x00, 0x32, 0x0C, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01, 0x00, 0x00, 0x00, 0x20, 0x10, 0x30, 0x60, 0x2F, 0x33, 0x32, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x14, 0x00, 0x00, 0x00, 0x6C, 0x07, 0x00, 0x00,...and so on

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  • x86 and Memory Addressing

    - by IM
    I've been reading up on memory models in an assembly book I picked up and I have a question or two. Let's say that the address bus has 32 lines, the data bus has 32 lines and the CPU is 32-bit (for simplicity). Now if the CPU makes a read request and sends the 32bit address, but only needs 8 bits, all 32 bits come back anyway? Also, the addresses in memory are still addressed per byte correct? So fetching one byte would bring back 0000 0001 to address 0000 0004? Thanks in advance

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  • x86 Assembly - printf doesn't print without "\n"

    - by Bitani
    So I'm confused. I'm going through the book "Programming from the Ground Up" and am working with using libraries. printf is working just fine so long as I include a "\n" in the string, but without it it will print absolutely nothing. Any idea why this happens? Code: .section .data my_str: .ascii "Jimmy Joe is %d years old!\n\0" my_num: .long 76 .section .text .globl _start _start: pushl my_num pushl $my_str call printf movl $1, %eax movl $0, %ebx int $0x80 Also, when I use -m elf_i386 for 32-bit mode and -dynamic-linker /lib/ld-linux.so.2 -lc to link, I get the warning ld: skipping incompatible /usr/lib64/libc.so when searching for -lc If that makes any difference, or if anybody has any suggestions as to how to have it load the 32-bit library directly. Thanks!

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  • just x86 assembly question~~!!

    - by kevin
    this is my assembly program which is just a function to swap *x *y. so first argument from main is address of x which is in 8(%ebp) and second one is address of y is in 12(%ebp). the program does swap x and y. I need 7 lines for doing this. can you make it 6 lines and there is a condition you can use only %eax,%ecx, and %edx 3 registers. I think about it so much.. but.. I can't make it 6 lines...there must be a way.. isn't it? this might be not a big deal.. but if there is a way to get it in 6lines. I want to know.. if you know the way~ help me~ plz~ thank you and have a good and nice day~ movl 8(%ebp), %eax movl (%eax), %ecx movl 12(%ebp), %edx movl (%edx), %eax movl %ecx, (%edx) movl 8(%ebp), %ecx movl %eax, (%ecx)

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  • x86 linux - how to create custom malloc with address hint

    - by nandu
    Hi, I want to create a custom malloc which allocates memory blocks within a given address range. I am writing a pthreads application in which threads are bound to unique cores on a many-core machine. The memory controllers are statically mapped, so that certain range of addresses on main memory are electrically closer to a core. I want to minimize the latency of communication between cores and main memory by allocating thread memory on these "closer" regions. Any ideas would be most appreciated. Thank you! Nandu

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  • Open x86 'SOFTWARE' registry key on an x64 machine in C#

    - by Lance May
    I am trying to read the 32-bit HKLM\SOFTWARE registry key from a 64-bit (C#) application. This, of course, keeps redirecting my view to HKLM\SOFTWARE\Wow6432Node. According to what I've found this is doable, but I can't seem to find a .NET example anywhere. I just need to read; not write. Anyone ran across this before?

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  • reading keyboard input without "consuming" it in x86 assembly

    - by Bob
    Ok so here the deal: I have an assignment regarding DOS and interrupts: I need to write a sort of key-logger function that can be called from C code. what it means is a c program would call an assembly function called startlog that would indicate to start logging the keys pressed until a function called endlog is called. the logging should work like this: write the ascii value of any key pressed without disturbing the C code between startlog and endlog, meaning that if the C code also needs to read the input (let's say by scanf, it would work ok). I managed to write the logger by changing the interrupt vector 9th entry (interrupt for keyboard press) to a function I wrote that writes the values to a file, and it works fine. however the C code does not get the input. Basically what i did is read the key pressed using int 21h, however after reading the ascii value it is "consumed" so I need a way to either simulate the key press again or read the value without "consuming" it so next time a key is read it reads the same key. (I described the code in english because it is long and clumsy assembly code)

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