From 8afcc19c6a79fde4ee4bff362f44cff1249150a9 Mon Sep 17 00:00:00 2001 From: Josh Boyer Date: Nov 22 2016 13:35:07 +0000 Subject: Add patch from Dave Anderson to fix live system crash analysis on Aarch64 --- diff --git a/crash-driver.patch b/crash-driver.patch index 3bfd8ee..715ec54 100644 --- a/crash-driver.patch +++ b/crash-driver.patch @@ -600,3 +600,123 @@ index 085378a..0258bf8 100644 -- 2.7.4 +From: Dave Anderson +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 + 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 + ++#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 + #include + +-#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 + diff --git a/kernel.spec b/kernel.spec index 996e950..42a9d08 100644 --- a/kernel.spec +++ b/kernel.spec @@ -2166,6 +2166,9 @@ fi # # %changelog +* Tue Nov 22 2016 Josh Boyer +- Add patch from Dave Anderson to fix live system crash analysis on Aarch64 + * Mon Nov 21 2016 Laura Abbott - 4.9.0-0.rc6.git0.1 - Linux v4.9-rc6