On 05/06/2014 02:38 AM, Wang Nan wrote:
> This patch fixs a problem introduced by commit e5d6a55 which make ARM
> kexec fails.
>
> Due to that commit, kernel is loaded at a dynamically offset: it computes
> extra_size using size of dtb, and load zImage at base + extra_size. When
> dtb size small (for example, 0x3000 bytes), kernel will be loaded at
> address like 0x60003000. For ARM zImage such address is incorrect.
>
> In kernel code arch/arm/boot/compressed/head.S, zImage builds a
> temporary page table at (pc & 0xf8000000) + TEXT_OFFSET - 0x4000. The
> related instructions sequence is:
>
> mov r4, pc
> and r4, r4, #0xf8000000
> add r4, r4, #TEXT_OFFSET @ (TEXT_OFFSET == 0x8000 on most platforms)
> call cache_on
> ...
> call __armv7_mmu_cache_on
> ...
> call __setup_mmu
> sub r3, r4, #16384 @ Page directory size
>
> r3 becomes page table pointer.
>
> When kernel is loaded at 0x60003000, page table is still built at
> 0x60004000, which destroys kernel.
>
> This patch make extra_size a fix value (0x8000) to avoid the failure.
>
> For the problem commit e5d6a55 tries solve, this patch uses
> locate_holes() to find a place can hold initrd and dtb.
>
> Change from v1:
> - Coding style enhancements.
>
> Signed-off-by: Wang Nan <wangnan0 at huawei.com>
> Cc: Daniel Mack <zonque at gmail.com>
Tested-by: Daniel Mack <zonque at gmail.com>
Many thanks again for the fix and the elaboration!
Daniel
> Cc: Sven Neumann <s.neumann at raumfeld.com>
> Cc: Simon Horman <horms at verge.net.au>
> ---
> kexec/arch/arm/kexec-zImage-arm.c | 37 +++++++++++++++++++++++++++++--------
> 1 file changed, 29 insertions(+), 8 deletions(-)
>
> diff --git a/kexec/arch/arm/kexec-zImage-arm.c b/kexec/arch/arm/kexec-zImage-arm.c
> index 4b5d3f4..bc99e79 100644
> --- a/kexec/arch/arm/kexec-zImage-arm.c
> +++ b/kexec/arch/arm/kexec-zImage-arm.c
> @@ -282,7 +282,7 @@ int zImage_arm_load(int argc, char **argv, const char *buf, off_t len,
> {
> unsigned long base;
> unsigned int atag_offset = 0x1000; /* 4k offset from memory start */
> - unsigned int extra_size = 0;
> + unsigned int extra_size = 0x8000; /* TEXT_OFFSET */
> const char *command_line;
> char *modified_cmdline = NULL;
> off_t command_line_len;
> @@ -356,16 +356,11 @@ int zImage_arm_load(int argc, char **argv, const char *buf, off_t len,
> if (command_line_len > COMMAND_LINE_SIZE)
> command_line_len = COMMAND_LINE_SIZE;
> }
> - if (ramdisk) {
> + if (ramdisk)
> ramdisk_buf = slurp_file(ramdisk, &initrd_size);
> - }
>
> - if (dtb_file) {
> + if (dtb_file)
> dtb_buf = slurp_file(dtb_file, &dtb_length);
> - extra_size = _ALIGN(dtb_length, getpagesize());
> - } else if (use_atags) {
> - extra_size = 0x8000; /* 32k should be plenty for ATAGs */
> - }
>
> /*
> * If we are loading a dump capture kernel, we need to update kernel
> @@ -460,6 +455,32 @@ int zImage_arm_load(int argc, char **argv, const char *buf, off_t len,
> create_flatten_tree(&dtb_buf, &dtb_length, command_line);
> }
>
> + /*
> + * Search in memory to make sure there is enough memory
> + * to hold initrd and dtb.
> + *
> + * Even if no initrd is used, this check is still
> + * required for dtb.
> + *
> + * Crash kernel use fixed address, no check is ok.
> + */
> + if ((info->kexec_flags & KEXEC_ON_CRASH) == 0) {
> + unsigned long page_size = getpagesize();
> + /*
> + * DTB size may be increase a little
> + * when setup initrd size. Add a full page
> + * for it is enough.
> + */
> + unsigned long hole_size = _ALIGN_UP(initrd_size, page_size) +
> + _ALIGN(dtb_length + page_size, page_size);
> + unsigned long initrd_base_new = locate_hole(info,
> + hole_size, page_size,
> + initrd_base, ULONG_MAX, INT_MAX);
> + if (base == ULONG_MAX)
> + return -1;
> + initrd_base = initrd_base_new;
> + }
> +
> if (ramdisk) {
> add_segment(info, ramdisk_buf, initrd_size,
> initrd_base, initrd_size);
>
