[PATCH 5/7] x86: kexec_file: lift CRASH_MAX_RANGES limit on crash_mem buffer
AKASHI Takahiro
takahiro.akashi at linaro.org
Thu Mar 1 21:36:33 PST 2018
On Fri, Mar 02, 2018 at 01:31:53PM +0800, Dave Young wrote:
> 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
OK.
> >
> > - 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.
Sure.
-Takahiro AKASHI
> >
> > - /* 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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