x86: kexec_file: lift CRASH_MAX_RANGES limit on crash_mem buffer

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.

Link: http://lkml.kernel.org/r/20180306102303.9063-6-takahiro.akashi@linaro.org
Signed-off-by: AKASHI Takahiro <takahiro.akashi@linaro.org>
Acked-by: Dave Young <dyoung@redhat.com>
Tested-by: Dave Young <dyoung@redhat.com>
Cc: Vivek Goyal <vgoyal@redhat.com>
Cc: Baoquan He <bhe@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/arch/x86/kernel/crash.c b/arch/x86/kernel/crash.c
index d10ba3114c487365e59e90a9b26191b69d6e1ad9..8175c0c205e6e63a148b103964da74953d489cc1 100644 (file)
--- 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 */
@@ -218,26 +200,31 @@ 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);
+       if (!nr_ranges)
+               return NULL;
 
-       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 = vzalloc(sizeof(struct crash_mem) +
+                       sizeof(struct crash_mem_range) * nr_ranges);
+       if (!cmem)
+               return NULL;
 
-       /* 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,
@@ -294,10 +281,8 @@ 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;
@@ -315,11 +300,10 @@ 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 */
@@ -338,8 +322,7 @@ 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;
@@ -348,7 +331,7 @@ static int prepare_elf64_ram_headers_callback(struct resource *res, void *arg)
        return 0;
 }
 
-static int prepare_elf64_headers(struct crash_elf_data *ced, bool kernel_map,
+static int prepare_elf64_headers(struct crash_mem *cmem, bool kernel_map,
                void **addr, unsigned long *sz)
 {
        Elf64_Ehdr *ehdr;
@@ -357,12 +340,11 @@ static int prepare_elf64_headers(struct crash_elf_data *ced, bool 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
@@ -456,29 +438,27 @@ static int prepare_elf64_headers(struct crash_elf_data *ced, bool 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, IS_ENABLED(CONFIG_X86_64), addr, sz);
+       ret =  prepare_elf64_headers(cmem, IS_ENABLED(CONFIG_X86_64), addr, sz);
        if (ret)
                goto out;
 
@@ -496,7 +476,7 @@ static int prepare_elf_headers(struct kimage *image, void **addr,
                        break;
                }
 out:
-       kfree(ced);
+       vfree(cmem);
        return ret;
 }