[PATCH 5/7] x86: kexec_file: lift CRASH_MAX_RANGES limit on crash_mem buffer
Dave Young
dyoung at redhat.com
Thu Mar 1 21:31:53 PST 2018
On 02/27/18 at 01:48pm, AKASHI Takahiro wrote:
> While CRASH_MAX_RANGES (== 16) seems to be good enough, fixed-number
> array is not a good idea in general.
>
> In this patch, size of crash_mem buffer is calculated as before and
> the buffer is now dynamically allocated. This change also allows removing
> crash_elf_data structure.
>
> Signed-off-by: AKASHI Takahiro <takahiro.akashi at linaro.org>
> Cc: Dave Young <dyoung at redhat.com>
> Cc: Vivek Goyal <vgoyal at redhat.com>
> Cc: Baoquan He <bhe at redhat.com>
> ---
> arch/x86/kernel/crash.c | 80 ++++++++++++++++++-------------------------------
> 1 file changed, 29 insertions(+), 51 deletions(-)
>
> diff --git a/arch/x86/kernel/crash.c b/arch/x86/kernel/crash.c
> index 913fd8021f8a..bfc37ad20d4a 100644
> --- a/arch/x86/kernel/crash.c
> +++ b/arch/x86/kernel/crash.c
> @@ -41,32 +41,14 @@
> /* Alignment required for elf header segment */
> #define ELF_CORE_HEADER_ALIGN 4096
>
> -/* This primarily represents number of split ranges due to exclusion */
> -#define CRASH_MAX_RANGES 16
> -
> struct crash_mem_range {
> u64 start, end;
> };
>
> struct crash_mem {
> - unsigned int nr_ranges;
> - struct crash_mem_range ranges[CRASH_MAX_RANGES];
> -};
> -
> -/* Misc data about ram ranges needed to prepare elf headers */
> -struct crash_elf_data {
> - struct kimage *image;
> - /*
> - * Total number of ram ranges we have after various adjustments for
> - * crash reserved region, etc.
> - */
> unsigned int max_nr_ranges;
> -
> - /* Pointer to elf header */
> - void *ehdr;
> - /* Pointer to next phdr */
> - void *bufp;
> - struct crash_mem mem;
> + unsigned int nr_ranges;
> + struct crash_mem_range ranges[0];
> };
>
> /* Used while preparing memory map entries for second kernel */
> @@ -217,26 +199,29 @@ static int get_nr_ram_ranges_callback(struct resource *res, void *arg)
> return 0;
> }
>
> -
> /* Gather all the required information to prepare elf headers for ram regions */
> -static void fill_up_crash_elf_data(struct crash_elf_data *ced,
> - struct kimage *image)
> +static struct crash_mem *fill_up_crash_elf_data(void)
> {
> unsigned int nr_ranges = 0;
> -
> - ced->image = image;
> + struct crash_mem *cmem;
>
> walk_system_ram_res(0, -1, &nr_ranges,
> get_nr_ram_ranges_callback);
I know it is probably not possible fail here, but for safe we can check
if nr_ranges == 0
>
> - ced->max_nr_ranges = nr_ranges;
> + /*
> + * Exclusion of crash region and/or crashk_low_res may cause
> + * another range split. So add extra two slots here.
> + */
> + nr_ranges += 2;
> + cmem = vmalloc(sizeof(struct crash_mem) +
> + sizeof(struct crash_mem_range) * nr_ranges);
> + if (!cmem)
> + return NULL;
vzalloc will be better.
>
> - /* Exclusion of crash region could split memory ranges */
> - ced->max_nr_ranges++;
> + cmem->max_nr_ranges = nr_ranges;
> + cmem->nr_ranges = 0;
>
> - /* If crashk_low_res is not 0, another range split possible */
> - if (crashk_low_res.end)
> - ced->max_nr_ranges++;
> + return cmem;
> }
>
> static int exclude_mem_range(struct crash_mem *mem,
> @@ -293,10 +278,8 @@ static int exclude_mem_range(struct crash_mem *mem,
> return 0;
>
> /* Split happened */
> - if (i == CRASH_MAX_RANGES - 1) {
> - pr_err("Too many crash ranges after split\n");
> + if (i == mem->max_nr_ranges - 1)
> return -ENOMEM;
> - }
>
> /* Location where new range should go */
> j = i + 1;
> @@ -314,11 +297,10 @@ static int exclude_mem_range(struct crash_mem *mem,
>
> /*
> * Look for any unwanted ranges between mstart, mend and remove them. This
> - * might lead to split and split ranges are put in ced->mem.ranges[] array
> + * might lead to split and split ranges are put in cmem->ranges[] array
> */
> -static int elf_header_exclude_ranges(struct crash_elf_data *ced)
> +static int elf_header_exclude_ranges(struct crash_mem *cmem)
> {
> - struct crash_mem *cmem = &ced->mem;
> int ret = 0;
>
> /* Exclude crashkernel region */
> @@ -337,8 +319,7 @@ static int elf_header_exclude_ranges(struct crash_elf_data *ced)
>
> static int prepare_elf64_ram_headers_callback(struct resource *res, void *arg)
> {
> - struct crash_elf_data *ced = arg;
> - struct crash_mem *cmem = &ced->mem;
> + struct crash_mem *cmem = arg;
>
> cmem->ranges[cmem->nr_ranges].start = res->start;
> cmem->ranges[cmem->nr_ranges].end = res->end;
> @@ -347,7 +328,7 @@ static int prepare_elf64_ram_headers_callback(struct resource *res, void *arg)
> return 0;
> }
>
> -static int prepare_elf64_headers(struct crash_elf_data *ced, int kernel_map,
> +static int prepare_elf64_headers(struct crash_mem *cmem, int kernel_map,
> void **addr, unsigned long *sz)
> {
> Elf64_Ehdr *ehdr;
> @@ -356,12 +337,11 @@ static int prepare_elf64_headers(struct crash_elf_data *ced, int kernel_map,
> unsigned char *buf, *bufp;
> unsigned int cpu, i;
> unsigned long long notes_addr;
> - struct crash_mem *cmem = &ced->mem;
> unsigned long mstart, mend;
>
> /* extra phdr for vmcoreinfo elf note */
> nr_phdr = nr_cpus + 1;
> - nr_phdr += ced->max_nr_ranges;
> + nr_phdr += cmem->nr_ranges;
>
> /*
> * kexec-tools creates an extra PT_LOAD phdr for kernel text mapping
> @@ -455,29 +435,27 @@ static int prepare_elf64_headers(struct crash_elf_data *ced, int kernel_map,
> static int prepare_elf_headers(struct kimage *image, void **addr,
> unsigned long *sz)
> {
> - struct crash_elf_data *ced;
> + struct crash_mem *cmem;
> Elf64_Ehdr *ehdr;
> Elf64_Phdr *phdr;
> int ret, i;
>
> - ced = kzalloc(sizeof(*ced), GFP_KERNEL);
> - if (!ced)
> + cmem = fill_up_crash_elf_data();
> + if (!cmem)
> return -ENOMEM;
>
> - fill_up_crash_elf_data(ced, image);
> -
> - ret = walk_system_ram_res(0, -1, ced,
> + ret = walk_system_ram_res(0, -1, cmem,
> prepare_elf64_ram_headers_callback);
> if (ret)
> goto out;
>
> /* Exclude unwanted mem ranges */
> - ret = elf_header_exclude_ranges(ced);
> + ret = elf_header_exclude_ranges(cmem);
> if (ret)
> goto out;
>
> /* By default prepare 64bit headers */
> - ret = prepare_elf64_headers(ced,
> + ret = prepare_elf64_headers(cmem,
> (int)IS_ENABLED(CONFIG_X86_64), addr, sz);
> if (ret)
> goto out;
> @@ -496,7 +474,7 @@ static int prepare_elf_headers(struct kimage *image, void **addr,
> break;
> }
> out:
> - kfree(ced);
> + vfree(cmem);
> return ret;
> }
>
> --
> 2.16.2
>
Thanks
Dave
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