<html><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /></head><body style='font-size: 10pt'>
<div style="color: #000000; font-family: Cantarell; font-size: 15px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;">Hi,</div>
<div style="color: #000000; font-family: Cantarell; font-size: 15px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;"> </div>
<div style="color: #000000; font-family: Cantarell; font-size: 15px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;">I <strong>compile main.s</strong> and it generates <strong>main.o</strong>. With objdump I can see:</div>
<div style="color: #000000; font-family: Cantarell; font-size: 15px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;"> </div>
<div style="color: #000000; font-family: Cantarell; font-size: 15px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;">0000000000000000 <_start>:</div>
<div style="color: #000000; font-family: Cantarell; font-size: 15px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;"> 0:<span class="Apple-tab-span" style="white-space: pre;"> </span>b8 01 00 00 00 <span class="Apple-tab-span" style="white-space: pre;"> </span>mov $0x1,%eax</div>
<div style="color: #000000; font-family: Cantarell; font-size: 15px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;"> 5:<span class="Apple-tab-span" style="white-space: pre;"> </span>bb 00 00 00 00 <span class="Apple-tab-span" style="white-space: pre;"> </span>mov $0x0,%ebx</div>
<div style="color: #000000; font-family: Cantarell; font-size: 15px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;"> a:<span class="Apple-tab-span" style="white-space: pre;"> </span>cd 80 <span class="Apple-tab-span" style="white-space: pre;"> </span> int $0x80</div>
<div style="color: #000000; font-family: Cantarell; font-size: 15px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;"> </div>
<div style="color: #000000; font-family: Cantarell; font-size: 15px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;">After<strong> link main.o</strong> it generates <strong>main</strong>. With objdump I now can see:</div>
<div style="color: #000000; font-family: Cantarell; font-size: 15px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;"> </div>
<div style="color: #000000; font-family: Cantarell; font-size: 15px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;">0000000000400078 <_start>:</div>
<div style="color: #000000; font-family: Cantarell; font-size: 15px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;"> 400078:<span class="Apple-tab-span" style="white-space: pre;"> </span>b8 01 00 00 00 <span class="Apple-tab-span" style="white-space: pre;"> </span>mov $0x1,%eax</div>
<div style="color: #000000; font-family: Cantarell; font-size: 15px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;"> 40007d:<span class="Apple-tab-span" style="white-space: pre;"> </span>bb 00 00 00 00 <span class="Apple-tab-span" style="white-space: pre;"> </span>mov $0x0,%ebx</div>
<div style="color: #000000; font-family: Cantarell; font-size: 15px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;"> 400082:<span class="Apple-tab-span" style="white-space: pre;"> </span>cd 80 <span class="Apple-tab-span" style="white-space: pre;"> </span> int $0x80</div>
<div style="color: #000000; font-family: Cantarell; font-size: 15px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;"> </div>
<div style="color: #000000; font-family: Cantarell; font-size: 15px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;">So, linker generates virtual address, doesn't it? But why it starts at 400078 and not in other any location? Is there any logic here? A virtual address can start at 0?</div>
<div style="color: #000000; font-family: Cantarell; font-size: 15px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;"> </div>
<div style="color: #000000; font-family: Cantarell; font-size: 15px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;">Regards.</div>
<p>El 29.09.2016 09:25, arshad hussain escribió:</p>
<blockquote type="cite" style="padding: 0 0.4em; border-left: #1010ff 2px solid; margin: 0"><!-- html ignored --><!-- head ignored --><!-- meta ignored -->
<div class="pre" style="margin: 0; padding: 0; font-family: monospace"><br />
<blockquote type="cite" style="padding: 0 0.4em; border-left: #1010ff 2px solid; margin: 0">On 28-Sep-2016, at 10:36 am, Madhu K <<a href="mailto:madhu.sk89@gmail.com">madhu.sk89@gmail.com</a>> wrote:<br /><br /> Hi All,</blockquote>
<br /> The support comes right through from the architecture. <br /><br /> Linear address: Also virtual address. This is Address CPU can address. This is 0 - 4GB under 32bit architecture.<br /> Physical address: This are actual memory installed in your system. Linear address have to be converted to <br /> physical address eventually. MMU translate linear address with the help of paging to physical address.<br /><br /><br />
<blockquote type="cite" style="padding: 0 0.4em; border-left: #1010ff 2px solid; margin: 0"><br /> This is to understand the Virtual address space.Basically who generates the virtual addresses CPU or GNU compiler?</blockquote>
<br /> A program image generated by compiler & linker uses Virtual Address . During execution of the program CPU + MMU <br /> translates or maps each virtual address to physical address.<br /><br /> Net-net this is architecture dependent and would highly recommend reading Intel's Architecture Manual for your reference.<br /><br />
<blockquote type="cite" style="padding: 0 0.4em; border-left: #1010ff 2px solid; margin: 0"><br /> Thanks<br /> Madhu<br /> _______________________________________________<br /> Kernelnewbies mailing list<br /><a href="mailto:Kernelnewbies@kernelnewbies.org">Kernelnewbies@kernelnewbies.org</a><br /><a href="https://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies">https://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies</a></blockquote>
<br /><br /> _______________________________________________<br /> Kernelnewbies mailing list<br /><a href="mailto:Kernelnewbies@kernelnewbies.org">Kernelnewbies@kernelnewbies.org</a><br /><a href="https://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies">https://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies</a></div>
</blockquote>
<p><br /></p>
</body></html>