Philippe Gerum wrote:
Alessandro Pittaluga wrote:
Hi,
When trying to access with gdb to variables allocated on a shared heap,
the following message is returned:
(gdb) print mypointer
$5 = (MYTYPE *) 0xb7dc4020
(gdb) print *mypointer
Cannot access memory at address 0xb7dc4020
All the applications (kernel and userland) are accessing correctly to
the heap-allocated memory.
Is this the expected behaviour or there's something wrong in my
installation?
Your installation is correct, GDB and Xenomai are too; unfortunately,
the following explanation is still accurate, i.e. a restriction in the
ptrace support:
http://sourceware.redhat.com/ml/gdb/2004-01/msg00152.html
Since you can call routines inside your program from the GDB cli, the
best solution at hand would be to implement the suggestion found in this
post: e.g.
void print_heap (void)
{
... output the heap contents...
}
and,
(gdb) call print_heap()
You could even pass arguments to print_heap() for customizing your output.
A possible option to work around that would be to stop having heaps
marked as I/O regions though, but the kernel-provided remapping helper
we use currently forces this property. I'll look at this when time allows.
Well, actually, I find this issue annoying enough from the user POV to
require an immediate fix. Could you please try the attached patch
(applies against 2.1.0 and trunk/), and let me know of the outcome? TIA,
--
Philippe.
Index: include/asm-generic/wrappers.h
===================================================================
--- include/asm-generic/wrappers.h (revision 793)
+++ include/asm-generic/wrappers.h (working copy)
@@ -46,8 +46,12 @@
#define module_param_named(name,var,type,mode) module_param(var,type,mode)
/* VM */
-#define wrap_remap_page_range(vma,from,to,size,prot) ({ \
+#define wrap_remap_vm_page(vma,from,to) ({ \
vma->vm_flags |= VM_RESERVED; \
+ remap_page_range(from,virt_to_phys((void *)to),PAGE_SIZE,PAGE_SHARED); \
+})
+#define wrap_remap_io_page_range(vma,from,to,size,prot) ({ \
+ vma->vm_flags |= VM_RESERVED; \
remap_page_range(from,to,size,prot); \
})
#define wrap_switch_mm(prev,next,task) \
@@ -144,12 +148,29 @@
/* VM */
#if LINUX_VERSION_CODE >= KERNEL_VERSION(2,6,10)
-#define wrap_remap_page_range(vma,from,to,size,prot) \
+#if LINUX_VERSION_CODE >= KERNEL_VERSION(2,6,15)
+#define wrap_remap_vm_page(vma,from,to) ({ \
+ vma->vm_flags |= VM_RESERVED; \
+ vm_insert_page(vma,from,vmalloc_to_page((void *)to)); \
+})
+#else /* LINUX_VERSION_CODE < KERNEL_VERSION(2,6,15) */
+/* Actually, this is a best-effort, and has the unwanted side-effet of
+ * setting the VM_IO flag on the vma, which prevents GDB inspection of
+ * the mmapped memory. Anyway, this legacy would only hit setups using
+ * oldish 2.6 kernel revisions. */
+#define wrap_remap_vm_page(vma,from,to) \
+ remap_pfn_range(vma,from,(to) >> PAGE_SHIFT,PAGE_SHIFT,PAGE_SHARED)
+#endif /* LINUX_VERSION_CODE >= KERNEL_VERSION(2,6,15) */
+#define wrap_remap_io_page_range(vma,from,to,size,prot) \
/* Sets VM_RESERVED | VM_IO | VM_PFNMAP on the vma. */ \
remap_pfn_range(vma,from,(to) >> PAGE_SHIFT,size,prot)
#else /* LINUX_VERSION_CODE < KERNEL_VERSION(2,6,10) */
-#define wrap_remap_page_range(vma,from,to,size,prot) do { \
+#define wrap_remap_vm_page(vma,from,to) ({ \
vma->vm_flags |= VM_RESERVED; \
+ remap_page_range(from,virt_to_phys((void *)to),PAGE_SIZE,PAGE_SHARED); \
+})
+#define wrap_remap_io_page_range(vma,from,to,size,prot) do { \
+ vma->vm_flags |= VM_RESERVED; \
remap_page_range(vma,from,to,size,prot); \
} while (0)
#endif /* LINUX_VERSION_CODE >= KERNEL_VERSION(2,6,10) */
Index: include/asm-generic/system.h
===================================================================
--- include/asm-generic/system.h (revision 793)
+++ include/asm-generic/system.h (working copy)
@@ -346,15 +346,22 @@
#endif /* CONFIG_SMP */
-static inline int xnarch_remap_page_range(struct vm_area_struct *vma,
- unsigned long uvaddr,
- unsigned long paddr,
- unsigned long size,
- pgprot_t prot)
+static inline int xnarch_remap_vm_page(struct vm_area_struct *vma,
+ unsigned long from,
+ unsigned long to)
{
- return wrap_remap_page_range(vma,uvaddr,paddr,size,prot);
+ return wrap_remap_vm_page(vma,from,to);
}
+static inline int xnarch_remap_io_page_range(struct vm_area_struct *vma,
+ unsigned long from,
+ unsigned long to,
+ unsigned long size,
+ pgprot_t prot)
+{
+ return wrap_remap_io_page_range(vma,from,to,size,prot);
+}
+
#ifdef XENO_POD_MODULE
#ifdef CONFIG_SMP
Index: ksrc/skins/rtdm/drvlib.c
===================================================================
--- ksrc/skins/rtdm/drvlib.c (revision 793)
+++ ksrc/skins/rtdm/drvlib.c (working copy)
@@ -1390,9 +1390,9 @@
vma->vm_ops = mmap_data->vm_ops;
vma->vm_private_data = mmap_data->vm_private_data;
- return xnarch_remap_page_range(vma, vma->vm_start,
- virt_to_phys(mmap_data->src_addr),
- vma->vm_end - vma->vm_start, PAGE_SHARED);
+ return xnarch_remap_io_page_range(vma, vma->vm_start,
+ virt_to_phys(mmap_data->src_addr),
+ vma->vm_end - vma->vm_start, PAGE_SHARED);
}
static struct file_operations rtdm_mmap_fops = {
Index: ksrc/nucleus/heap.c
===================================================================
--- ksrc/nucleus/heap.c (revision 793)
+++ ksrc/nucleus/heap.c (working copy)
@@ -920,6 +920,10 @@
return kva;
}
+#else /* !CONFIG_MMU */
+
+#define __va_to_kva(va) (va)
+
#endif /* CONFIG_MMU */
static int xnheap_mmap (struct file *file,
@@ -952,23 +956,14 @@
vaddr = (unsigned long)heap->archdep.heapbase;
- /* MMU-less vmalloc() is a wrapper to kmalloc(), so it always
- provides contiguous memory, and we always ask for kmalloc-based
- heaps in such context. */
-
-#ifdef CONFIG_MMU
if (!heap->archdep.kmflags)
{
unsigned long maddr = vma->vm_start;
while (size > 0)
{
- if (xnarch_remap_page_range(vma,
- maddr,
- __pa(__va_to_kva(vaddr)),
- PAGE_SIZE,
- PAGE_SHARED))
- return -ENXIO;
+ if (xnarch_remap_vm_page(vma,maddr,vaddr))
+ return -EAGAIN;
maddr += PAGE_SIZE;
vaddr += PAGE_SIZE;
@@ -976,13 +971,12 @@
}
}
else
-#endif /* CONFIG_MMU */
- if (xnarch_remap_page_range(vma,
- vma->vm_start,
- virt_to_phys((void *)vaddr),
- size,
- PAGE_SHARED))
- return -ENXIO;
+ if (xnarch_remap_io_page_range(vma,
+ vma->vm_start,
+ virt_to_phys((void *)vaddr),
+ size,
+ PAGE_SHARED))
+ return -EAGAIN;
atomic_inc(&heap->archdep.numaps);
@@ -1047,7 +1041,6 @@
/* Size must be page-aligned. */
-#ifdef CONFIG_MMU
if (!kmflags)
{
ptr = vmalloc(size);
@@ -1061,7 +1054,6 @@
SetPageReserved(virt_to_page(__va_to_kva(vaddr)));
}
else /* Otherwise, we have been asked for some vmalloc() space. */
-#endif /* CONFIG_MMU */
{
ptr = kmalloc(size,kmflags);
@@ -1086,7 +1078,6 @@
vabase = (unsigned long)ptr;
-#ifdef CONFIG_MMU
if (!kmflags)
{
for (vaddr = vabase; vaddr < vabase + size; vaddr += PAGE_SIZE)
@@ -1095,7 +1086,6 @@
vfree(ptr);
}
else
-#endif /* CONFIG_MMU */
{
for (vaddr = vabase; vaddr < vabase + size; vaddr += PAGE_SIZE)
ClearPageReserved(virt_to_page(vaddr));
@@ -1112,9 +1102,6 @@
spl_t s;
int err;
-#ifndef CONFIG_MMU
- memflags = memflags ?: GFP_USER;
-#endif /* CONFIG_MMU */
heapsize = PAGE_ALIGN(heapsize);
heapbase = __alloc_and_reserve_heap(heapsize,memflags);
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