On Sun, May 4, 2008 at 7:48 PM, Rene Herman <rene.herman@xxxxxxxxxxxx> wrote: > On 04-05-08 12:35, Anant Narayanan wrote: > > > > While implementing a binary format loader for a foreign executable format, > we have found the need to setup the user stack starting at (virtual) address > 0xE0000000 instead of the usual 0xC0000000. However a call to > setup_arg_pages() with that value returns -EINVAL. > > > > Is there any way to setup the stack such that it starts at 0xE0000000 and > > grows downwards? > > > > It depends. There's obviously no way that the user stack can reside in > kernelspace (well, sanely) so the question is, "is there any way to have > kernelspace limited to the last 512M instead of the last 1G as usual". > > I suppose this is on x86-32. If you're on machines with less than 384M of > memory the answer is, "sure, just increase PAGE_OFFSET" (look at the Kconfig > split selection to see how) while with more you'd need to suffer highmem. > Just FYI. A good writeup I found here: (include/asm-powerpc/page.h - formula may not be applicable to x86, but terminology should be identical): /* * KERNELBASE is the virtual address of the start of the kernel, it's often * the same as PAGE_OFFSET, but _might not be_. * * The kdump dump kernel is one example where KERNELBASE != PAGE_OFFSET. * * PAGE_OFFSET is the virtual address of the start of lowmem. * * PHYSICAL_START is the physical address of the start of the kernel. * * MEMORY_START is the physical address of the start of lowmem. * * KERNELBASE, PAGE_OFFSET, and PHYSICAL_START are all configurable on * ppc32 and based on how they are set we determine MEMORY_START. * * For the linear mapping the following equation should be true: * KERNELBASE - PAGE_OFFSET = PHYSICAL_START - MEMORY_START * * Also, KERNELBASE >= PAGE_OFFSET and PHYSICAL_START >= MEMORY_START * * There are two was to determine a physical address from a virtual one: * va = pa + PAGE_OFFSET - MEMORY_START * va = pa + KERNELBASE - PHYSICAL_START * * If you want to know something's offset from the start of the kernel you * should subtract KERNELBASE. * * If you want to test if something's a kernel address, use is_kernel_addr(). */ > If you're on general out-in-the-wild x86 the answer is "ofcourse not". See > first paragraph. > > Rene. > > > > -- > To unsubscribe from this list: send an email with > "unsubscribe kernelnewbies" to ecartis@xxxxxxxxxxxx > Please read the FAQ at http://kernelnewbies.org/FAQ > > -- Regards, Peter Teoh -- To unsubscribe from this list: send an email with "unsubscribe kernelnewbies" to ecartis@xxxxxxxxxxxx Please read the FAQ at http://kernelnewbies.org/FAQ
