[Crash-utility] [PATCH] xen: Add support for domU with Linux kernel 3.19 and newer
Honglei Wang
honglei.wang at oracle.com
Wed May 24 00:13:05 PDT 2017
crash patch c3413456599161cabc4e910a0ae91dfe5eec3c21 (xen: Add support for
dom0 with Linux kernel 3.19 and newer) from Daniel made crash utility
support xen dom0 vmcores after linux kernel commit
054954eb051f35e74b75a566a96fe756015352c8 (xen: switch to linear virtual
mapped sparse p2m list).
This patch can be deemed as a subsequent and make this utility support Xen
PV domU dumpfiles again.
Basically speaking, readmem() can't be used to read xen_p2m_addr associate
memory directly during m2p translation. It introduces infinite recursion.
Following call sequence shows the scenario, it comes from a section of
backtrace with only kvaddr, machine addr and mfn left as parameter:
module_init()
/* The first readmem() from module_init(). */
readmem(addr=0xffffffffa02fe4a0)
/* readmem() needs physical address, so calls kvtop(). */
kvtop(kvaddr=0xffffffffa02fe4a0)
x86_64_kvtop(kvaddr=ffffffffa02fe4a0)
/* Calculate physical address by traversing page tables. */
x86_64_kvtop_xen_wpt(kvaddr=0xffffffffa02fe4a0)
/*
* x86_64_kvtop_xen_wpt() is going to traverse the page table to
* get the physical address for 0xffffffffa02fe4a0. So, at first it
* is needed to translate the pgd from machine address to physical
* address. So invoke xen_m2p() here to do the translation. 0x58687f000
* is the pgd machine address in x86_64_kvtop_xen_wpt() and is needed
* to be translated to its physical address.
*/
xen_m2p(machine=0x58687f000)
__xen_m2p(machine=0x58687f000, mfn=0x58687f)
/*
* __xen_m2p() is going to search mfn 0x58687f in p2m VMA which starts
* at VMA 0xffffc900001cf000. It compares every mfn stored in it with
* 0x58687f. Once it's proved 0x58687f is one mfn in the p2m, its offset
* will be used to calculate the pfn.
*
* readmem() is invoked by __xen_m2p() to read the page from VMA
* 0xffffc900001cf000 here.
*/
readmem(addr=0xffffc900001cf000)
/*
* readmem() needs physical address of 0xffffc900001cf000 to make the
* reading done. So it invokes kvtop() to get the physical address.
*/
kvtop(kvaddr=0xffffc900001cf000)
x86_64_kvtop(kvaddr=0xffffc900001cf000)
/* It needs to calculate physical address by traversing page tables. */
x86_64_kvtop_xen_wpt(kvaddr=0xffffc900001cf000)
/*
* 0x581b7e000 is the machine address of pgd need to be translated here.
* The mfn is calculated in this way at x86_64_kvtop_xen_wpt():
*
* pml4 = ((ulong *)machdep->machspec->pml4) + pml4_index(kvaddr);
* pgd_paddr = (*pml4) & PHYSICAL_PAGE_MASK;
*
* The kvaddr 0xffffc900001cf000 here is quite different from the one
* above, so the machine address of pgd is not the same one. And this
* pgd is the one we use to access the VMA of p2m table.
*/
xen_m2p(machine=0x581b7e000)
__xen_m2p(machine=0x581b7e000, mfn=0x581b7e)
/*
* Looking for mfn 0x581b7e in the range of p2m page which starts at
* VMA 0xffffc900001f5000.
*/
readmem(addr=0xffffc900001f5000)
/* Need physical address of VMA 0xffffc900001f5000 as same reason above. */
kvtop(kvaddr=0xffffc900001f5000)
x86_64_kvtop(kvaddr=0xffffc900001f5000)
/* Need to traverse page tables to calculate physical address for it. */
x86_64_kvtop_xen_wpt(kvaddr=0xffffc900001f5000)
/*
* Unfortunately, machine address 0x581b7e000 have to be translated again.
* Endless loop starts from here.
*/
xen_m2p(machine=0x581b7e000)
__xen_m2p(machine=0x581b7e000, mfn=0x581b7e)
readmem(addr=0xffffc900001f5000)
Fortunately, PV domU p2m mapping is also stored at xd->xfd + xch_index_offset
and organized as struct xen_dumpcore_p2m. We have a chance to read the p2m
stuff directly from there, and then we avoid the loop above.
So, this patch implements a special reading function read_xc_p2m() to extract
the mfns from xd->xfd + xch_index_offset. This function does not need to read
mfns from p2m VMA like readmem() does, so, we avoid the endless loop introduced
by the address translation.
Signed-off-by: Honglei Wang <honglei.wang at oracle.com>
Reviewed-by: Daniel Kiper <daniel.kiper at oracle.com>
---
kernel.c | 151 +++++++++++++++++++++++++++++++++++++++++++++++++++++++------
xendump.c | 2 +-
xendump.h | 2 +
3 files changed, 140 insertions(+), 15 deletions(-)
diff --git a/kernel.c b/kernel.c
index 395736c..7a5ce64 100644
--- a/kernel.c
+++ b/kernel.c
@@ -22,6 +22,7 @@
#include <libgen.h>
#include <ctype.h>
#include <stdbool.h>
+#include "xendump.h"
static void do_module_cmd(ulong, char *, ulong, char *, char *);
static void show_module_taint(void);
@@ -67,6 +68,9 @@ static ulong __xen_m2p(ulonglong, ulong);
static ulong __xen_pvops_m2p_l2(ulonglong, ulong);
static ulong __xen_pvops_m2p_l3(ulonglong, ulong);
static ulong __xen_pvops_m2p_hyper(ulonglong, ulong);
+static ulong __xen_pvops_m2p_domU(ulonglong, ulong);
+static int read_xc_p2m(ulonglong addr, void *buffer, long size);
+static void read_p2m(ulong cache_index, int memtype, void *buffer);
static int search_mapping_page(ulong, ulong *, ulong *, ulong *);
static void read_in_kernel_config_err(int, char *);
static void BUG_bytes_init(void);
@@ -181,10 +185,7 @@ kernel_init()
&kt->pvops_xen.p2m_mid_missing);
get_symbol_data("p2m_missing", sizeof(ulong),
&kt->pvops_xen.p2m_missing);
- } else if (symbol_exists("xen_p2m_addr")) {
- if (!XEN_CORE_DUMPFILE())
- error(FATAL, "p2m array in new format is unreadable.");
- } else {
+ } else if (!symbol_exists("xen_p2m_addr")) {
kt->pvops_xen.p2m_top_entries = get_array_length("p2m_top", NULL, 0);
kt->pvops_xen.p2m_top = symbol_value("p2m_top");
kt->pvops_xen.p2m_missing = symbol_value("p2m_missing");
@@ -9305,13 +9306,7 @@ __xen_m2p(ulonglong machine, ulong mfn)
if (memtype == PHYSADDR)
pc->curcmd_flags |= XEN_MACHINE_ADDR;
- if (!readmem(kt->p2m_mapping_cache[c].mapping, memtype,
- mp, PAGESIZE(), "phys_to_machine_mapping page (cached)",
- RETURN_ON_ERROR))
- error(FATAL, "cannot access "
- "phys_to_machine_mapping page\n");
- else
- kt->last_mapping_read = kt->p2m_mapping_cache[c].mapping;
+ read_p2m(c, memtype, mp);
if (memtype == PHYSADDR)
pc->curcmd_flags &= ~XEN_MACHINE_ADDR;
@@ -9349,9 +9344,12 @@ __xen_m2p(ulonglong machine, ulong mfn)
*/
if (symbol_exists("p2m_mid_missing"))
pfn = __xen_pvops_m2p_l3(machine, mfn);
- else if (symbol_exists("xen_p2m_addr"))
- pfn = __xen_pvops_m2p_hyper(machine, mfn);
- else
+ else if (symbol_exists("xen_p2m_addr")) {
+ if (XEN_CORE_DUMPFILE())
+ pfn = __xen_pvops_m2p_hyper(machine, mfn);
+ else
+ pfn = __xen_pvops_m2p_domU(machine, mfn);
+ } else
pfn = __xen_pvops_m2p_l2(machine, mfn);
if (pfn != XEN_MFN_NOT_FOUND)
@@ -9559,6 +9557,131 @@ __xen_pvops_m2p_hyper(ulonglong machine, ulong mfn)
return XEN_MFN_NOT_FOUND;
}
+static void read_p2m(ulong cache_index, int memtype, void *buffer)
+{
+ /*
+ * Use special read function for PV domain p2m reading.
+ * See the comments of read_xc_p2m().
+ */
+ if (symbol_exists("xen_p2m_addr") && !XEN_CORE_DUMPFILE()) {
+ if (!read_xc_p2m(kt->p2m_mapping_cache[cache_index].mapping,
+ buffer, PAGESIZE()))
+ error(FATAL, "cannot access phys_to_machine_mapping page\n");
+ } else if (!readmem(kt->p2m_mapping_cache[cache_index].mapping, memtype,
+ buffer, PAGESIZE(), "phys_to_machine_mapping page (cached)",
+ RETURN_ON_ERROR))
+ error(FATAL, "cannot access phys_to_machine_mapping page\n");
+
+ kt->last_mapping_read = kt->p2m_mapping_cache[cache_index].mapping;
+}
+
+/*
+ * PV domain p2m mapping info is stored in xd->xfd at xch_index_offset. It
+ * is organized as struct xen_dumpcore_p2m and the pfns are progressively
+ * increased by 1 from 0.
+ *
+ * This is a special p2m reading function for xen PV domain vmcores after
+ * kernel commit 054954eb051f35e74b75a566a96fe756015352c8 (xen: switch
+ * to linear virtual mapped sparse p2m list). It is invoked for reading
+ * p2m associate stuff by read_p2m().
+ */
+static int read_xc_p2m(ulonglong addr, void *buffer, long size)
+{
+ ulong i, new_p2m_buf_size;
+ off_t offset;
+ struct xen_dumpcore_p2m *new_p2m_buf;
+ static struct xen_dumpcore_p2m *p2m_buf;
+ static ulong p2m_buf_size = 0;
+
+ if (size <= 0) {
+ if ((CRASHDEBUG(1) && !STREQ(pc->curcmd, "search")) ||
+ CRASHDEBUG(2))
+ error(INFO, "invalid size request: %ld\n", size);
+ return FALSE;
+ }
+
+ /*
+ * We extract xen_dumpcore_p2m.gmfn and copy them into the
+ * buffer. So, we need temporary p2m_buf whose size is
+ * (size * (sizeof(struct xen_dumpcore_p2m) / sizeof(ulong)))
+ * to put xen_dumpcore_p2m structures read from xd->xfd.
+ */
+ new_p2m_buf_size = size * (sizeof(struct xen_dumpcore_p2m) / sizeof(ulong));
+
+ if (p2m_buf_size != new_p2m_buf_size) {
+ p2m_buf_size = new_p2m_buf_size;
+
+ new_p2m_buf = realloc(p2m_buf, p2m_buf_size);
+ if (new_p2m_buf == NULL) {
+ free(p2m_buf);
+ error(FATAL, "cannot realloc p2m buffer\n");
+ }
+ p2m_buf = new_p2m_buf;
+ }
+
+ offset = addr * (sizeof(struct xen_dumpcore_p2m) / sizeof(ulong));
+ offset += xd->xc_core.header.xch_index_offset;
+
+ if (lseek(xd->xfd, offset, SEEK_SET) == -1)
+ error(FATAL,
+ "cannot lseek to xch_index_offset offset 0x%lx\n", offset);
+ if (read(xd->xfd, (void*)p2m_buf, p2m_buf_size) != p2m_buf_size)
+ error(FATAL,
+ "cannot read from xch_index_offset offset 0x%lx\n", offset);
+
+ for (i = 0; i < size / sizeof(ulong); i++)
+ *((ulong *)buffer + i) = p2m_buf[i].gmfn;
+
+ return TRUE;
+}
+
+static ulong
+__xen_pvops_m2p_domU(ulonglong machine, ulong mfn)
+{
+ ulong c, end, i, mapping, p, pfn, start;
+
+ /*
+ * xch_nr_pages is the number of pages of p2m mapping. It is composed
+ * of struct xen_dumpcore_p2m. The stuff we want to copy into the mapping
+ * page is mfn whose type is unsigned long.
+ * So actual number of p2m pages should be:
+ *
+ * xch_nr_pages / (sizeof(struct xen_dumpcore_p2m) / sizeof(ulong))
+ */
+ for (p = 0;
+ p < xd->xc_core.header.xch_nr_pages /
+ (sizeof(struct xen_dumpcore_p2m) / sizeof(ulong));
+ ++p) {
+
+ mapping = p * PAGESIZE();
+
+ if (mapping != kt->last_mapping_read) {
+ if (!read_xc_p2m(mapping, (void *)kt->m2p_page, PAGESIZE()))
+ error(FATAL, "cannot read the last mapping page\n");
+ kt->last_mapping_read = mapping;
+ }
+ kt->p2m_pages_searched++;
+
+ if (search_mapping_page(mfn, &i, &start, &end)) {
+ pfn = p * XEN_PFNS_PER_PAGE + i;
+ c = kt->p2m_cache_index;
+ if (CRASHDEBUG (1))
+ console("mfn: %lx (%llx) i: %ld pfn: %lx (%llx)\n",
+ mfn, machine, i, pfn, XEN_PFN_TO_PSEUDO(pfn));
+
+ kt->p2m_mapping_cache[c].start = start;
+ kt->p2m_mapping_cache[c].end = end;
+ kt->p2m_mapping_cache[c].mapping = mapping;
+ kt->p2m_mapping_cache[c].pfn = p * XEN_PFNS_PER_PAGE;
+ kt->p2m_cache_index = (c+1) % P2M_MAPPING_CACHE;
+
+ return pfn;
+ }
+ }
+
+ return XEN_MFN_NOT_FOUND;
+}
+
/*
* Search for an mfn in the current mapping page, and if found,
* determine the range of contiguous mfns that it's contained
diff --git a/xendump.c b/xendump.c
index 8170b22..4bd59b5 100644
--- a/xendump.c
+++ b/xendump.c
@@ -19,7 +19,7 @@
#include "xendump.h"
static struct xendump_data xendump_data = { 0 };
-static struct xendump_data *xd = &xendump_data;
+struct xendump_data *xd = &xendump_data;
static int xc_save_verify(char *);
static int xc_core_verify(char *, char *);
diff --git a/xendump.h b/xendump.h
index 08d41b4..b7bae65 100644
--- a/xendump.h
+++ b/xendump.h
@@ -192,3 +192,5 @@ struct xen_dumpcore_p2m {
uint64_t pfn;
uint64_t gmfn;
};
+
+extern struct xendump_data *xd;
--
1.7.1
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