Hi Rongwei,
On Tue, Sep 16, 2025 at 12:39 PM Rongwei Wang <[email protected]> wrote:
>
> From: Rongwei Wang <[email protected]>
>
> 'help -m' can show most of variables which
> relates to memory layout, e.g. userspace_top,
> page_offset, vmalloc_start_addr, etc. They
> aren't a visual way to show a memory layout
> for kernel space.
>
> This patch provides 'help -l' to show memory
> layout, usage likes:
>
> crash> help -l
> Gap Hole: 0xffffffffff7ff001 - 0xffffffffffffffff Size: 8.0 MB
> Fixmap Area: 0xffffffffff578000 - 0xffffffffff7ff000 Size: 2.5 MB
> Gap Hole: 0xffffffffff000001 - 0xffffffffff577fff Size: 5.5 MB
> Module Area: 0xffffffffa0000000 - 0xffffffffff000000 Size: 1.5 GB
> Gap Hole: 0xffffffff84826001 - 0xffffffff9fffffff Size: 439.9
> MB
> Kernel Image: 0xffffffff81000000 - 0xffffffff84826000 Size: 56.1 MB
> Gap Hole: 0xffffeb0000000000 - 0xffffffff80ffffff Size: 21.0 TB
> Vmemmap Area: 0xffffea0000000000 - 0xffffeaffffffffff Size: 1.0 TB
> Gap Hole: 0xffffe90000000000 - 0xffffe9ffffffffff Size: 1.0 TB
> Vmalloc Area: 0xffffc90000000000 - 0xffffe8ffffffffff Size: 32.0 TB
> Gap Hole: 0xffffc88000000000 - 0xffffc8ffffffffff Size: 512.0
> GB
> Linear Mapping: 0xffff888000000000 - 0xffffc87fffffffff Size: 64.0 TB
> Linear Gap: 0xffff800000000000 - 0xffff887fffffffff Size: 8.5 TB
> Gap Hole: 0x0000800000000000 - 0xffff7fffffffffff Size:
> 16776960.0 TB
> User Space: 0x0000000000000000 - 0x00007fffffffffff Size: 128.0
> TB
>
> Signed-off-by: Rongwei Wang <[email protected]>
> ---
> defs.h | 14 +++-
> help.c | 7 +-
> memory.c | 11 +++
> x86_64.c | 236 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
> 4 files changed, 266 insertions(+), 2 deletions(-)
>
> diff --git a/defs.h b/defs.h
> index 4fecb83..a3f00d5 100644
> --- a/defs.h
> +++ b/defs.h
> @@ -4100,12 +4100,23 @@ typedef signed int s32;
> #define __PHYSICAL_MASK_SHIFT_5LEVEL 52
> #define __PHYSICAL_MASK_SHIFT (machdep->machspec->physical_mask_shift)
> #define __PHYSICAL_MASK ((1UL << __PHYSICAL_MASK_SHIFT) - 1)
> -#define __VIRTUAL_MASK_SHIFT 48
> +#define __VIRTUAL_MASK_SHIFT 47
> #define __VIRTUAL_MASK ((1UL << __VIRTUAL_MASK_SHIFT) - 1)
> #define PAGE_SHIFT 12
> #define PAGE_SIZE (1UL << PAGE_SHIFT)
> #define PHYSICAL_PAGE_MASK (~(PAGE_SIZE-1) & __PHYSICAL_MASK )
>
> +
> +#define KASAN_SHADOW_OFFSET 0xdffffc0000000000
> +#define KASAN_SHADOW_SCALE_SHIFT 3
> +
> +#define KASAN_SHADOW_START (KASAN_SHADOW_OFFSET + \
> + ((-1UL << __VIRTUAL_MASK_SHIFT) >> \
> + KASAN_SHADOW_SCALE_SHIFT))
> +#define KASAN_SHADOW_END (KASAN_SHADOW_START + \
> + (1ULL << (__VIRTUAL_MASK_SHIFT - \
> + KASAN_SHADOW_SCALE_SHIFT)))
> +
> #define _PAGE_BIT_NX 63
> #define _PAGE_PRESENT 0x001
> #define _PAGE_RW 0x002
> @@ -5911,6 +5922,7 @@ int phys_to_page(physaddr_t, ulong *);
> int generic_get_kvaddr_ranges(struct vaddr_range *);
> int l1_cache_size(void);
> int dumpfile_memory(int);
> +void dump_memory_layout(void);
> #define DUMPFILE_MEM_USED (1)
> #define DUMPFILE_FREE_MEM (2)
> #define DUMPFILE_MEM_DUMP (3)
> diff --git a/help.c b/help.c
> index 5d61e0d..cd54744 100644
> --- a/help.c
> +++ b/help.c
> @@ -538,7 +538,7 @@ cmd_help(void)
> oflag = 0;
>
> while ((c = getopt(argcnt, args,
> - "efNDdmM:ngcaBbHhkKsvVoptTzLOr")) != EOF) {
> + "efNDdmM:ngcaBbHhkKsvVoptTzLOrl")) != EOF) {
> switch(c)
> {
> case 'e':
> @@ -666,6 +666,7 @@ cmd_help(void)
> fprintf(fp, " -v - vm_table\n");
> fprintf(fp, " -V - vm_table (verbose)\n");
> fprintf(fp, " -z - help options\n");
> + fprintf(fp, " -l - show memory layout\n");
> return;
>
> case 'L':
> @@ -676,6 +677,10 @@ cmd_help(void)
> dump_registers();
> return;
>
> + case 'l':
> + dump_memory_layout();
> + return;
> +
> default:
> argerrs++;
> break;
> diff --git a/memory.c b/memory.c
> index 400d31a..55ed2f1 100644
> --- a/memory.c
> +++ b/memory.c
> @@ -17657,6 +17657,17 @@ dumpfile_memory(int cmd)
> return retval;
> }
>
> +#ifdef X86_64
> +extern void x86_64_dump_memory_layout(void);
> +#endif
> +
> +void dump_memory_layout(void)
> +{
> +#ifdef X86_64
> + x86_64_dump_memory_layout();
> +#endif
> +}
> +
> /*
> * Functions for sparse mem support
> */
> diff --git a/x86_64.c b/x86_64.c
> index d7da536..bfb53b4 100644
> --- a/x86_64.c
> +++ b/x86_64.c
> @@ -1151,6 +1151,242 @@ x86_64_dump_machdep_table(ulong arg)
> fprintf(fp, "excpetion_functions_orig\n");
> }
>
> +#define MAX_LAYOUT 32
> +struct mem_segment {
> + char name[64];
> + char desc[64];
> + unsigned long start;
> + unsigned long end;
> +};
> +
> +struct mem_layout {
> + int count;
> + struct mem_segment segs[MAX_LAYOUT];
> +};
> +
> +char* format_bytes(unsigned long bytes, char* buffer, int buffer_size)
> +{
> + const char* units[] = {"B", "KB", "MB", "GB", "TB"};
> + int i = 0;
> + double readable_size = (double)bytes;
Forget to mention, there is a function which is similar to this one
as: tools.c:pages_to_size(). Basically this function is trying to
convert num of pages to a total of bytes, then convert bytes into
B/KB/MB. Do you think these can be refactored, so format_bytes() and
tools.c:pages_to_size() can share some code of unit converting?
Thanks,
Tao Liu
> +
> + /* Handle the edge case of zero bytes */
> + if (bytes == 0) {
> + snprintf(buffer, buffer_size, "0 B");
> + return buffer;
> + }
> +
> + /* Handle negative values if necessary, though size is typically
> non-negative */
> + if (bytes < 0) {
> + snprintf(buffer, buffer_size, "Invalid size");
> + return buffer;
> + }
> +
> + while (readable_size >= 1024 && i < (sizeof(units) / sizeof(units[0])
> - 1)) {
> + readable_size /= 1024;
> + i++;
> + }
> +
> + memset(buffer, '\0', buffer_size);
> + snprintf(buffer, buffer_size, "%.1f %s", readable_size, units[i]);
> +
> + return buffer;
> +}
> +
> +int compare_segments(const void *a, const void *b)
> +{
> + const struct mem_segment *seg_a = (const struct mem_segment *)a;
> + const struct mem_segment *seg_b = (const struct mem_segment *)b;
> +
> + if (seg_a->start > seg_b->start) return -1;
> + if (seg_a->start < seg_b->start) return 1;
> + return 0;
> +}
> +
> +void print_layout(struct mem_layout *layout)
> +{
> + struct mem_segment *segs = layout->segs;
> + struct mem_segment seg;
> + int i;
> +
> + if (layout == NULL)
> + return;
> +
> + for (i=0; i<layout->count; i++) {
> + seg = segs[i];
> +
> + fprintf(fp, "%s:\t 0x%016lx - 0x%016lx\t Size: %s\n",
> seg.name, seg.start,
> + seg.end, seg.desc);
> + }
> +}
> +
> +#define __round_mask(x, y) ((__typeof__(x))((y)-1))
> +#define round_up(x, y) ((((x)-1) | __round_mask(x, y))+1)
> +#define round_down(x, y) ((x) & ~__round_mask(x, y))
> +
> +/*
> + * memory layout:
> + *
> + * Gap Area: 0xffffffffff7ff001 - 0xffffffffffffffff Size:
> 8.0 MB
> + * Fixmap Area: 0xffffffffff578000 - 0xffffffffff7ff000 Size:
> 2.5 MB
> + * Gap Area: 0xffffffffff000001 - 0xffffffffff577fff Size:
> 5.5 MB
> + * Module Area: 0xffffffffa0000000 - 0xffffffffff000000 Size:
> 1.5 GB
> + * Gap Area: 0xffffffff84826001 - 0xffffffff9fffffff Size:
> 439.9 MB
> + * Kernel Image: 0xffffffff81000000 - 0xffffffff84826000 Size:
> 56.1 MB
> + * Gap Area: 0xffffeb0000000000 - 0xffffffff80ffffff Size:
> 21.0 TB
> + * Vmemmap Area: 0xffffea0000000000 - 0xffffeaffffffffff Size:
> 1.0 TB
> + * Gap Area: 0xffffe90000000000 - 0xffffe9ffffffffff Size:
> 1.0 TB
> + * Vmalloc Area: 0xffffc90000000000 - 0xffffe8ffffffffff Size:
> 32.0 TB
> + * Gap Area: 0xffffc88000000000 - 0xffffc8ffffffffff Size:
> 512.0 GB
> + * Linear Mapping: 0xffff888000000000 - 0xffffc87fffffffff Size:
> 64.0 TB
> + * Linear Gap: 0xffff800000000000 - 0xffff887fffffffff Size:
> 8.5 TB
> + * Gap Area: 0x0000800000000000 - 0xffff7fffffffffff
> Size:16776960.0 TB
> + * User Space: 0x0000000000000000 - 0x00007fffffffffff Size:
> 128.0 TB
> + *
> + * kernel space:
> + * _end, _text
> + * vmemmap_end: ms->vmemmap_end
> + * vmemmap_vaddr: ms->vmemmap_vaddr
> + * vmalloc_end: ms->vmalloc_end
> + * vmalloc_start_addr: ms->vmalloc_start_addr
> + * page_offset_base: ms->page_offset
> + *
> + * user space:
> + * userspace_top: ms->userspace_top
> + *
> + */
> +void x86_64_dump_memory_layout(void)
> +{
> + struct mem_layout *layout = NULL;
> + ulong text_start, text_end;
> + struct machine_specific *ms = machdep->machspec;
> + int i, next_idx;
> + char size_buf[20];
> + long value = 0;
> +
> + layout = malloc(sizeof(struct mem_layout));
> + if (layout == NULL || layout->count == 0) {
> + printf("Layout is empty, nothing to print.\n");
> + return;
> + }
> +
> + /* Create a temporary copy to sort for printing, preserving the
> original order. */
> + struct mem_segment *segments = layout->segs;
> + if(!segments) {
> + perror("Failed to allocate memory for sorting");
> + return;
> + }
> +
> + if (!symbol_exists("_text"))
> + return;
> + else
> + text_start = symbol_value("_text");
> +
> + if (!symbol_exists("_end"))
> + return;
> + else
> + text_end = symbol_value("_end");
> +
> + snprintf(segments[0].name, 64, "Kernel Image");
> + snprintf(segments[0].desc, 64, "%s",
> + format_bytes(text_end - text_start + 1, size_buf, 20));
> + segments[0].start = text_start;
> + segments[0].end = text_end;
> +
> + snprintf(segments[1].name, 64, "Vmemmap Area");
> + snprintf(segments[1].desc, 64, "%s",
> + format_bytes(ms->vmemmap_end - ms->vmemmap_vaddr + 1,
> size_buf, 20));
> + segments[1].start = (ulong)ms->vmemmap_vaddr;
> + segments[1].end = (ulong)ms->vmemmap_end;
> +
> + snprintf(segments[2].name, 64, "Module Area");
> + snprintf(segments[2].desc, 64, "%s",
> + format_bytes(ms->modules_end - ms->modules_vaddr + 1,
> size_buf, 20));
> + segments[2].start = (ulong)ms->modules_vaddr;
> + segments[2].end = (ulong)ms->modules_end;
> +
> + snprintf(segments[3].name, 64, "Vmalloc Area");
> + snprintf(segments[3].desc, 64, "%s",
> + format_bytes(ms->vmalloc_end - ms->vmalloc_start_addr + 1,
> size_buf, 20));
> + segments[3].start = (ulong)ms->vmalloc_start_addr;
> + segments[3].end = (ulong)ms->vmalloc_end;
> +
> + snprintf(segments[4].name, 64, "Linear Mapping");
> + segments[4].start = (ulong)ms->page_offset;
> + segments[4].end = (ulong)ms->page_offset + (1UL <<
> machdep->max_physmem_bits) - 1;
> + snprintf(segments[4].desc, 64, "%s",
> + format_bytes(1UL << machdep->max_physmem_bits, size_buf,
> 20));
> +
> + snprintf(segments[5].name, 64, "User Space");
> + snprintf(segments[5].desc, 64, "%s",
> + format_bytes((ulong)ms->userspace_top, size_buf, 20));
> + segments[5].start = 0UL;
> + segments[5].end = (ulong)ms->userspace_top - 1;
> +
> + snprintf(segments[6].name, 64, "Linear Gap");
> + segments[6].start = -1UL - (1UL << __VIRTUAL_MASK_SHIFT) + 1;
> + segments[6].end = (ulong)ms->page_offset - 1;
> + snprintf(segments[6].desc, 64, "%s",
> + format_bytes(segments[6].end - segments[6].start + 1,
> size_buf, 20));
> +
> + layout->count = 7;
> + if (kernel_symbol_exists("kasan_init")) {
> + snprintf(segments[7].name, 64, "KASAN");
> + segments[7].start = KASAN_SHADOW_START;
> + segments[7].end = KASAN_SHADOW_END;
> + snprintf(segments[7].desc, 64, "%s",
> + format_bytes(segments[7].end - segments[7].start +
> 1, size_buf, 20));
> + layout->count++;
> + }
> +
> + if (enumerator_value("__end_of_permanent_fixed_addresses", &value)) {
> + unsigned fixaddr_size = 0;
> + int idx = layout->count;
> +
> + fixaddr_size = value << PAGE_SHIFT;
> +
> + snprintf(segments[7].name, 64, "Fixmap Area");
> + segments[idx].end = round_up(VSYSCALL_START + PAGE_SIZE, 1 <<
> PMD_SHIFT) - PAGE_SIZE;
> + segments[idx].start = segments[idx].end - fixaddr_size;
> +
> + snprintf(segments[idx].desc, 64, "%s",
> + format_bytes(segments[idx].end - segments[idx].start
> + 1, size_buf, 20));
> + layout->count++;
> + }
> +
> + /* Sort segments from highest address to lowest. */
> + qsort(segments, layout->count, sizeof(struct mem_segment),
> compare_segments);
> +
> + next_idx = layout->count;
> + /* Insert gap area */
> + for (i=0; i<layout->count; i++) {
> + unsigned long prev_start;
> + unsigned long end = segments[i].end;
> +
> + if (i == 0)
> + prev_start = -1UL;
> + else
> + prev_start = segments[i-1].start;
> +
> + if (prev_start == (end + 1))
> + continue;
> +
> + snprintf(segments[next_idx].name, 64, "Gap Hole");
> + segments[next_idx].start = end + 1;
> + segments[next_idx].end = (i == 0) ? prev_start : prev_start -
> 1;
> + snprintf(segments[next_idx].desc, 64, "%s",
> + format_bytes(segments[next_idx].end -
> segments[next_idx].start + 1, size_buf, 20));
> +
> + next_idx++;
> + }
> +
> + layout->count = next_idx;
> + qsort(segments, layout->count, sizeof(struct mem_segment),
> compare_segments);
> +
> + print_layout(layout);
> + free(layout);
> +}
> +
> /*
> * Gather the cpu_pda array info, updating any smp-related items that
> * were possibly bypassed or improperly initialized in kernel_init().
> --
> 2.43.5
>
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