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<p class="MsoNormal"><font size="3" face="Times New Roman"><span style="FONT-SIZE: 12pt" lang="EN">Hi.
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<p class="MsoNormal"><font size="3" face="Times New Roman"><span style="FONT-SIZE: 12pt" lang="EN">I am using linux 2.6.39 and MIPS core.
</span></font><font size="3" face="Times New Roman"><span style="FONT-SIZE: 12pt" lang="EN"><br>
</span></font></font><font color="#000000" size="2" face="Tahoma"><font size="3" face="Times New Roman"><span style="FONT-SIZE: 12pt" lang="EN">I am keen to find out how does linux restores a thread's stack pointer, program counter and return address.
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I have created a binary which spawns four threads. with a ps -eaL , then I kill one of the thread with kill -11 <thread_id>. In the kernel 'do_coredump' handler i can easily find out the stack pointer of the current crashed thread by reading the struct pt_regs->reg29.
My concern is to find out the stack pointers of rest of the 3 threads that did not crash. I did it this way:
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1. read the reg29 variable of struct thread_struct for each task (By traversing the list of task with list_for_each)
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2. Dump the values at address stored in reg29. <br>
3. Look out manually to locate the Stack pointer offset. Tried this by crashing all the threads and found that the stackpointer comes at a fixed offset and assumed that stack pointer to be correct and I went ahead.
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so you can say that my Stack pointer is stored at => reg29 + offset; <br>
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My question now is how to find this value of 'offset' dynamically. How does the kernel keeps a track of any thread's stack pointer while restoring the context. Since my observation was that the reg29 field of struct thread_struct at a glance seems to be a stack
pointer. but it is not. it is just an address where at some offset we can find our stack pointer stored.
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Thanks</span></font></font></p>
<p class="MsoNormal"><font color="#000000" size="2" face="Tahoma"><font size="3" face="times new roman"><span style="FONT-SIZE: 12pt" lang="EN">Smital Desai</span></font><font size="2" face="Arial"><span style="FONT-FAMILY: Arial; FONT-SIZE: 10pt"></span></font></p>
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