10.0 BETA 3 with redports kernel panic

[Konstantin Belousov]

On Fri, Dec 20, 2013 at 07:45:55AM -0800, Sean Bruno wrote:
> With this change to pmap.c we blow up in keg_alloc_slab() now:
> 
> FreeBSD clang version 3.3 (tags/RELEASE_33/final 183502) 20130610
> kernel trap 12 with interrupts disabled
> 
> 
> Fatal trap 12: page fault while in kernel mode
> cpuid = 0; apic id = 00
> fault virtual address	= 0x8
> fault code		= supervisor write data, page not present
> instruction pointer	= 0x20:0xffffffff80b2602a
> stack pointer	        = 0x28:0xffffffff81a90a50
> frame pointer	        = 0x28:0xffffffff81a90ac0
> code segment		= base 0x0, limit 0xfffff, type 0x1b
> 			= DPL 0, pres 1, long 1, def32 0, gran 1
> processor eflags	= resume, IOPL = 0
> current process		= 0 ()
> [ thread pid 0 tid 0 ]
> Stopped at      keg_alloc_slab+0x13a:   movq    %r13,0x8(%rax)
> db> whe
> Tracing pid 0 tid 0 td 0xffffffff81527500
> keg_alloc_slab() at keg_alloc_slab+0x13a/frame 0xffffffff81a90ac0
> keg_fetch_slab() at keg_fetch_slab+0x152/frame 0xffffffff81a90b10
> zone_fetch_slab() at zone_fetch_slab+0x7e/frame 0xffffffff81a90b50
> zone_import() at zone_import+0x3c/frame 0xffffffff81a90b90
> uma_zalloc_arg() at uma_zalloc_arg+0x33e/frame 0xffffffff81a90c10
> malloc() at malloc+0x6a/frame 0xffffffff81a90c60
> init_dynamic_kenv() at init_dynamic_kenv+0x8d/frame 0xffffffff81a90c90
> mi_startup() at mi_startup+0x118/frame 0xffffffff81a90cb0
> btext() at btext+0x2c
> db> bt
> Tracing pid 0 tid 0 td 0xffffffff81527500
> keg_alloc_slab() at keg_alloc_slab+0x13a/frame 0xffffffff81a90ac0
> keg_fetch_slab() at keg_fetch_slab+0x152/frame 0xffffffff81a90b10
> zone_fetch_slab() at zone_fetch_slab+0x7e/frame 0xffffffff81a90b50
> zone_import() at zone_import+0x3c/frame 0xffffffff81a90b90
> uma_zalloc_arg() at uma_zalloc_arg+0x33e/frame 0xffffffff81a90c10
> malloc() at malloc+0x6a/frame 0xffffffff81a90c60
> init_dynamic_kenv() at init_dynamic_kenv+0x8d/frame 0xffffffff81a90c90
> mi_startup() at mi_startup+0x118/frame 0xffffffff81a90cb0
> btext() at btext+0x2c
> 

This could be related, indeed.

Lets limit the impact to the /dev/{,k}mem only.  Please try this.

diff --git a/sys/amd64/amd64/mem.c b/sys/amd64/amd64/mem.c
index abbbb21..2a9b7c1 100644
--- a/sys/amd64/amd64/mem.c
+++ b/sys/amd64/amd64/mem.c
@@ -98,7 +98,11 @@ memrw(struct cdev *dev, struct uio *uio, int flags)
 kmemphys:
 			o = v & PAGE_MASK;
 			c = min(uio->uio_resid, (u_int)(PAGE_SIZE - o));
-			error = uiomove((void *)PHYS_TO_DMAP(v), (int)c, uio);
+			v = PHYS_TO_DMAP(v);
+			if (v < DMAP_MIN_ADDRESS || v >= dmaplimit ||
+			    pmap_kextract(v) == 0)
+				return (EFAULT);
+			error = uiomove((void *)v, (int)c, uio);
 			continue;
 		}
 		else if (dev2unit(dev) == CDEV_MINOR_KMEM) {
diff --git a/sys/amd64/amd64/pmap.c b/sys/amd64/amd64/pmap.c
index 014020b..13404b0 100644
--- a/sys/amd64/amd64/pmap.c
+++ b/sys/amd64/amd64/pmap.c
@@ -321,7 +321,7 @@ SYSCTL_INT(_machdep, OID_AUTO, nkpt, CTLFLAG_RD, &nkpt, 0,
     "Number of kernel page table pages allocated on bootup");
 
 static int ndmpdp;
-static vm_paddr_t dmaplimit;
+vm_paddr_t dmaplimit;
 vm_offset_t kernel_vm_end = VM_MIN_KERNEL_ADDRESS;
 pt_entry_t pg_nx;
 
diff --git a/sys/amd64/include/pmap.h b/sys/amd64/include/pmap.h
index 3918282..e83e07e 100644
--- a/sys/amd64/include/pmap.h
+++ b/sys/amd64/include/pmap.h
@@ -369,6 +369,7 @@ extern vm_paddr_t phys_avail[];
 extern vm_paddr_t dump_avail[];
 extern vm_offset_t virtual_avail;
 extern vm_offset_t virtual_end;
+extern vm_paddr_t dmaplimit;
 
 #define	pmap_page_get_memattr(m)	((vm_memattr_t)(m)->md.pat_mode)
 #define	pmap_page_is_write_mapped(m)	(((m)->aflags & PGA_WRITEABLE) != 0)
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