diff options
Diffstat (limited to 'crash-driver.patch')
| -rw-r--r-- | crash-driver.patch | 120 |
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 + |