jcs.org
qemu with hax to log dma reads & writes
jcs.org/2018/11/12/vfio
oslib-posix: add helpers for stack alloc and free
the allocated stack will be adjusted to the minimum supported stack size
by the OS and rounded up to be a multiple of the system pagesize.
Additionally an architecture dependent guard page is added to the stack
to catch stack overflows.
Signed-off-by: Peter Lieven <pl@kamp.de>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
authored by
Peter Lieven
and committed by
Kevin Wolf
8737d9e0
74e1ae7c
+69
+27
include/sysemu/os-posix.h
+27
include/sysemu/os-posix.h
···
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bool is_daemonized(void);
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/**
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* qemu_alloc_stack:
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* @sz: pointer to a size_t holding the requested usable stack size
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*
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* Allocate memory that can be used as a stack, for instance for
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* coroutines. If the memory cannot be allocated, this function
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* will abort (like g_malloc()). This function also inserts an
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* additional guard page to catch a potential stack overflow.
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* Note that the memory required for the guard page and alignment
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* and minimal stack size restrictions will increase the value of sz.
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*
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* The allocated stack must be freed with qemu_free_stack().
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*
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* Returns: pointer to (the lowest address of) the stack memory.
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*/
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void *qemu_alloc_stack(size_t *sz);
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/**
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* qemu_free_stack:
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* @stack: stack to free
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* @sz: size of stack in bytes
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*
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* Free a stack allocated via qemu_alloc_stack(). Note that sz must
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* be exactly the adjusted stack size returned by qemu_alloc_stack.
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*/
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void qemu_free_stack(void *stack, size_t sz);
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#endif
+42
util/oslib-posix.c
+42
util/oslib-posix.c
···
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}
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return pid;
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}
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void *qemu_alloc_stack(size_t *sz)
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{
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void *ptr, *guardpage;
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size_t pagesz = getpagesize();
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#ifdef _SC_THREAD_STACK_MIN
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/* avoid stacks smaller than _SC_THREAD_STACK_MIN */
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long min_stack_sz = sysconf(_SC_THREAD_STACK_MIN);
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*sz = MAX(MAX(min_stack_sz, 0), *sz);
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#endif
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/* adjust stack size to a multiple of the page size */
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*sz = ROUND_UP(*sz, pagesz);
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/* allocate one extra page for the guard page */
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*sz += pagesz;
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ptr = mmap(NULL, *sz, PROT_READ | PROT_WRITE,
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MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
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if (ptr == MAP_FAILED) {
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abort();
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}
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#if defined(HOST_IA64)
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/* separate register stack */
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guardpage = ptr + (((*sz - pagesz) / 2) & ~pagesz);
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#elif defined(HOST_HPPA)
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/* stack grows up */
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guardpage = ptr + *sz - pagesz;
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#else
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/* stack grows down */
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guardpage = ptr;
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#endif
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if (mprotect(guardpage, pagesz, PROT_NONE) != 0) {
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abort();
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}
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return ptr;
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}
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void qemu_free_stack(void *stack, size_t sz)
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{
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munmap(stack, sz);
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}