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-rw-r--r--crash-driver.patch120
1 files changed, 120 insertions, 0 deletions
diff --git a/crash-driver.patch b/crash-driver.patch
index 3bfd8ee99..715ec54e8 100644
--- a/crash-driver.patch
+++ b/crash-driver.patch
@@ -600,3 +600,123 @@ index 085378a..0258bf8 100644
--
2.7.4
+From: Dave Anderson <anderson@redhat.com>
+Date: Fri, 18 Nov 2016 11:52:35 -0500
+Cc: onestero@redhat.com
+Subject: [PATCH v2] Restore live system crash analysis for ARM64
+
+This v2 version simplifies the copy out of the kimage_voffset value
+to user-space per Oleg's suggestion.
+
+Upstream status: N/A
+
+Test: v2 version tested successfully with a modified crash utility
+
+The following Linux 4.6 commit breaks support for live system
+crash analysis on ARM64:
+
+ commit a7f8de168ace487fa7b88cb154e413cf40e87fc6
+ Author: Ard Biesheuvel <ard.biesheuvel@linaro.org>
+ arm64: allow kernel Image to be loaded anywhere in physical memory
+
+The patchset drastically modified the kernel's virtual memory layout,
+where notably the static kernel text and data image was moved from the
+unity mapped region into the vmalloc region. Prior to Linux 4.6,
+the kernel's __virt_to_phys() function was this:
+
+ #define __virt_to_phys(x) (((phys_addr_t)(x) - PAGE_OFFSET + PHYS_OFFSET))
+
+When running on a live system, the crash utility could determine PAGE_OFFSET
+by looking at the virtual addresses compiled into the vmlinux file, and
+PHYS_OFFSET can be determined by looking at /proc/iomem.
+
+As of Linux 4.6, it is done differently:
+
+ #define __virt_to_phys(x) ({ \
+ phys_addr_t __x = (phys_addr_t)(x); \
+ __x & BIT(VA_BITS - 1) ? (__x & ~PAGE_OFFSET) + PHYS_OFFSET : \
+ (__x - kimage_voffset); })
+
+The PAGE_OFFSET/PHYS_OFFSET section of the conditional expression is for
+traditional unity-mapped virtual addresses, but kernel text and static
+data requires the new "kimage_voffset" variable. Unfortunately, the
+contents of the new "kimage_voffset" variable is not available or
+calculatable from a user-space perspective, even with root privileges.
+
+At least the ARM64 developers made its contents available to modules
+with an EXPORT_SYMBOL(kimage_voffset) declaration. Accordingly, with
+a modification to the /dev/crash driver to return its contents, the
+crash utility can run on a live system.
+
+The patch allows for architecture-specific DEV_CRASH_ARCH_DATA ioctls
+to be created, where this is the first instance of one.
+
+
+---
+ arch/arm64/include/asm/crash-driver.h | 16 ++++++++++++++++
+ drivers/char/crash.c | 13 ++++++++++++-
+ 2 files changed, 28 insertions(+), 1 deletion(-)
+
+diff --git a/arch/arm64/include/asm/crash-driver.h b/arch/arm64/include/asm/crash-driver.h
+index 43b26da..fe68e7c 100644
+--- a/arch/arm64/include/asm/crash-driver.h
++++ b/arch/arm64/include/asm/crash-driver.h
+@@ -3,4 +3,20 @@
+
+ #include <asm-generic/crash-driver.h>
+
++#define DEV_CRASH_ARCH_DATA _IOR('c', 1, long)
++
++static long
++crash_arch_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
++{
++ extern u64 kimage_voffset;
++
++ switch (cmd)
++ {
++ case DEV_CRASH_ARCH_DATA:
++ return put_user(kimage_voffset, (unsigned long __user *)arg);
++ default:
++ return -EINVAL;
++ }
++}
++
+ #endif /* _ARM64_CRASH_H */
+diff --git a/drivers/char/crash.c b/drivers/char/crash.c
+index 0258bf8..dfb767c 100644
+--- a/drivers/char/crash.c
++++ b/drivers/char/crash.c
+@@ -32,7 +32,7 @@
+ #include <asm/types.h>
+ #include <asm/crash-driver.h>
+
+-#define CRASH_VERSION "1.2"
++#define CRASH_VERSION "1.3"
+
+ /*
+ * These are the file operation functions that allow crash utility
+@@ -111,10 +111,21 @@ crash_release(struct inode *inode, struct file *filp)
+ return 0;
+ }
+
++static long
++crash_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
++{
++#ifdef DEV_CRASH_ARCH_DATA
++ return crash_arch_ioctl(file, cmd, arg);
++#else
++ return -EINVAL;
++#endif
++}
++
+ static struct file_operations crash_fops = {
+ .owner = THIS_MODULE,
+ .llseek = crash_llseek,
+ .read = crash_read,
++ .unlocked_ioctl = crash_ioctl,
+ .open = crash_open,
+ .release = crash_release,
+ };
+--
+1.8.3.1
+