Add patch from Dave Anderson to fix live system crash analysis on Aarch64
This commit is contained in:
Josh Boyer
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0617a9a8d0
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8afcc19c6a
@ -600,3 +600,123 @@ index 085378a..0258bf8 100644
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2.7.4
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2.7.4
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From: Dave Anderson <anderson@redhat.com>
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Date: Fri, 18 Nov 2016 11:52:35 -0500
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Cc: onestero@redhat.com
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Subject: [PATCH v2] Restore live system crash analysis for ARM64
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This v2 version simplifies the copy out of the kimage_voffset value
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to user-space per Oleg's suggestion.
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Upstream status: N/A
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Test: v2 version tested successfully with a modified crash utility
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The following Linux 4.6 commit breaks support for live system
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crash analysis on ARM64:
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commit a7f8de168ace487fa7b88cb154e413cf40e87fc6
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Author: Ard Biesheuvel <ard.biesheuvel@linaro.org>
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arm64: allow kernel Image to be loaded anywhere in physical memory
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The patchset drastically modified the kernel's virtual memory layout,
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where notably the static kernel text and data image was moved from the
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unity mapped region into the vmalloc region. Prior to Linux 4.6,
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the kernel's __virt_to_phys() function was this:
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#define __virt_to_phys(x) (((phys_addr_t)(x) - PAGE_OFFSET + PHYS_OFFSET))
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When running on a live system, the crash utility could determine PAGE_OFFSET
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by looking at the virtual addresses compiled into the vmlinux file, and
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PHYS_OFFSET can be determined by looking at /proc/iomem.
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As of Linux 4.6, it is done differently:
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#define __virt_to_phys(x) ({ \
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phys_addr_t __x = (phys_addr_t)(x); \
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__x & BIT(VA_BITS - 1) ? (__x & ~PAGE_OFFSET) + PHYS_OFFSET : \
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(__x - kimage_voffset); })
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The PAGE_OFFSET/PHYS_OFFSET section of the conditional expression is for
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traditional unity-mapped virtual addresses, but kernel text and static
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data requires the new "kimage_voffset" variable. Unfortunately, the
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contents of the new "kimage_voffset" variable is not available or
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calculatable from a user-space perspective, even with root privileges.
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At least the ARM64 developers made its contents available to modules
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with an EXPORT_SYMBOL(kimage_voffset) declaration. Accordingly, with
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a modification to the /dev/crash driver to return its contents, the
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crash utility can run on a live system.
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The patch allows for architecture-specific DEV_CRASH_ARCH_DATA ioctls
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to be created, where this is the first instance of one.
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---
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arch/arm64/include/asm/crash-driver.h | 16 ++++++++++++++++
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drivers/char/crash.c | 13 ++++++++++++-
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2 files changed, 28 insertions(+), 1 deletion(-)
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diff --git a/arch/arm64/include/asm/crash-driver.h b/arch/arm64/include/asm/crash-driver.h
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index 43b26da..fe68e7c 100644
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--- a/arch/arm64/include/asm/crash-driver.h
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+++ b/arch/arm64/include/asm/crash-driver.h
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@@ -3,4 +3,20 @@
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#include <asm-generic/crash-driver.h>
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+#define DEV_CRASH_ARCH_DATA _IOR('c', 1, long)
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+
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+static long
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+crash_arch_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
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+{
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+ extern u64 kimage_voffset;
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+
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+ switch (cmd)
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+ {
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+ case DEV_CRASH_ARCH_DATA:
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+ return put_user(kimage_voffset, (unsigned long __user *)arg);
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+ default:
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+ return -EINVAL;
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+ }
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+}
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+
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#endif /* _ARM64_CRASH_H */
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diff --git a/drivers/char/crash.c b/drivers/char/crash.c
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index 0258bf8..dfb767c 100644
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--- a/drivers/char/crash.c
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+++ b/drivers/char/crash.c
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@@ -32,7 +32,7 @@
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#include <asm/types.h>
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#include <asm/crash-driver.h>
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-#define CRASH_VERSION "1.2"
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+#define CRASH_VERSION "1.3"
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/*
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* These are the file operation functions that allow crash utility
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@@ -111,10 +111,21 @@ crash_release(struct inode *inode, struct file *filp)
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return 0;
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}
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+static long
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+crash_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
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+{
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+#ifdef DEV_CRASH_ARCH_DATA
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+ return crash_arch_ioctl(file, cmd, arg);
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+#else
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+ return -EINVAL;
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+#endif
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+}
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+
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static struct file_operations crash_fops = {
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.owner = THIS_MODULE,
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.llseek = crash_llseek,
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.read = crash_read,
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+ .unlocked_ioctl = crash_ioctl,
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.open = crash_open,
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.release = crash_release,
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};
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--
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1.8.3.1
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@ -2166,6 +2166,9 @@ fi
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#
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#
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#
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#
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%changelog
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%changelog
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* Tue Nov 22 2016 Josh Boyer <jwboyer@fedoraproject.org>
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- Add patch from Dave Anderson to fix live system crash analysis on Aarch64
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* Mon Nov 21 2016 Laura Abbott <labbott@redhat.com> - 4.9.0-0.rc6.git0.1
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* Mon Nov 21 2016 Laura Abbott <labbott@redhat.com> - 4.9.0-0.rc6.git0.1
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- Linux v4.9-rc6
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- Linux v4.9-rc6
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