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x86/kdump: Remove the backup region handling
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When the crashkernel kernel command line option is specified, the low
1M memory will always be reserved now. Therefore, it's not necessary to
create a backup region anymore and also no need to copy the contents of
the first 640k to it.

Remove all the code related to handling that backup region.

 [ bp: Massage commit message. ]

Signed-off-by: Lianbo Jiang <lijiang@redhat.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: bhe@redhat.com
Cc: Dave Young <dyoung@redhat.com>
Cc: d.hatayama@fujitsu.com
Cc: dhowells@redhat.com
Cc: ebiederm@xmission.com
Cc: horms@verge.net.au
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jürgen Gross <jgross@suse.com>
Cc: kexec@lists.infradead.org
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Cc: vgoyal@redhat.com
Cc: x86-ml <x86@kernel.org>
Link: https://lkml.kernel.org/r/20191108090027.11082-3-lijiang@redhat.com
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@lian-bo @suryasaimadhu
lian-bo authored and suryasaimadhu committed Nov 14, 2019
1 parent 6f599d8 commit 7c321eb
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Showing 5 changed files with 11 additions and 162 deletions.
10 changes: 0 additions & 10 deletions arch/x86/include/asm/kexec.h
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Original file line number Diff line number Diff line change
Expand Up @@ -66,10 +66,6 @@ struct kimage;
# define KEXEC_ARCH KEXEC_ARCH_X86_64
#endif

/* Memory to backup during crash kdump */
#define KEXEC_BACKUP_SRC_START (0UL)
#define KEXEC_BACKUP_SRC_END (640 * 1024UL - 1) /* 640K */

/*
* This function is responsible for capturing register states if coming
* via panic otherwise just fix up the ss and sp if coming via kernel
Expand Down Expand Up @@ -154,12 +150,6 @@ struct kimage_arch {
pud_t *pud;
pmd_t *pmd;
pte_t *pte;
/* Details of backup region */
unsigned long backup_src_start;
unsigned long backup_src_sz;

/* Physical address of backup segment */
unsigned long backup_load_addr;

/* Core ELF header buffer */
void *elf_headers;
Expand Down
10 changes: 0 additions & 10 deletions arch/x86/include/asm/purgatory.h
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Original file line number Diff line number Diff line change
Expand Up @@ -6,16 +6,6 @@
#include <linux/purgatory.h>

extern void purgatory(void);
/*
* These forward declarations serve two purposes:
*
* 1) Make sparse happy when checking arch/purgatory
* 2) Document that these are required to be global so the symbol
* lookup in kexec works
*/
extern unsigned long purgatory_backup_dest;
extern unsigned long purgatory_backup_src;
extern unsigned long purgatory_backup_sz;
#endif /* __ASSEMBLY__ */

#endif /* _ASM_PURGATORY_H */
87 changes: 11 additions & 76 deletions arch/x86/kernel/crash.c
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Original file line number Diff line number Diff line change
Expand Up @@ -188,8 +188,6 @@ void native_machine_crash_shutdown(struct pt_regs *regs)

#ifdef CONFIG_KEXEC_FILE

static unsigned long crash_zero_bytes;

static int get_nr_ram_ranges_callback(struct resource *res, void *arg)
{
unsigned int *nr_ranges = arg;
Expand Down Expand Up @@ -232,6 +230,11 @@ static int elf_header_exclude_ranges(struct crash_mem *cmem)
{
int ret = 0;

/* Exclude the low 1M because it is always reserved */
ret = crash_exclude_mem_range(cmem, 0, 1<<20);
if (ret)
return ret;

/* Exclude crashkernel region */
ret = crash_exclude_mem_range(cmem, crashk_res.start, crashk_res.end);
if (ret)
Expand Down Expand Up @@ -261,9 +264,7 @@ static int prepare_elf_headers(struct kimage *image, void **addr,
unsigned long *sz)
{
struct crash_mem *cmem;
Elf64_Ehdr *ehdr;
Elf64_Phdr *phdr;
int ret, i;
int ret;

cmem = fill_up_crash_elf_data();
if (!cmem)
Expand All @@ -282,22 +283,7 @@ static int prepare_elf_headers(struct kimage *image, void **addr,
/* By default prepare 64bit headers */
ret = crash_prepare_elf64_headers(cmem,
IS_ENABLED(CONFIG_X86_64), addr, sz);
if (ret)
goto out;

/*
* If a range matches backup region, adjust offset to backup
* segment.
*/
ehdr = (Elf64_Ehdr *)*addr;
phdr = (Elf64_Phdr *)(ehdr + 1);
for (i = 0; i < ehdr->e_phnum; phdr++, i++)
if (phdr->p_type == PT_LOAD &&
phdr->p_paddr == image->arch.backup_src_start &&
phdr->p_memsz == image->arch.backup_src_sz) {
phdr->p_offset = image->arch.backup_load_addr;
break;
}
out:
vfree(cmem);
return ret;
Expand Down Expand Up @@ -336,19 +322,11 @@ static int memmap_exclude_ranges(struct kimage *image, struct crash_mem *cmem,
unsigned long long mend)
{
unsigned long start, end;
int ret = 0;

cmem->ranges[0].start = mstart;
cmem->ranges[0].end = mend;
cmem->nr_ranges = 1;

/* Exclude Backup region */
start = image->arch.backup_load_addr;
end = start + image->arch.backup_src_sz - 1;
ret = crash_exclude_mem_range(cmem, start, end);
if (ret)
return ret;

/* Exclude elf header region */
start = image->arch.elf_load_addr;
end = start + image->arch.elf_headers_sz - 1;
Expand All @@ -371,11 +349,11 @@ int crash_setup_memmap_entries(struct kimage *image, struct boot_params *params)
memset(&cmd, 0, sizeof(struct crash_memmap_data));
cmd.params = params;

/* Add first 640K segment */
ei.addr = image->arch.backup_src_start;
ei.size = image->arch.backup_src_sz;
ei.type = E820_TYPE_RAM;
add_e820_entry(params, &ei);
/* Add the low 1M */
cmd.type = E820_TYPE_RAM;
flags = IORESOURCE_SYSTEM_RAM | IORESOURCE_BUSY;
walk_iomem_res_desc(IORES_DESC_NONE, flags, 0, (1<<20)-1, &cmd,
memmap_entry_callback);

/* Add ACPI tables */
cmd.type = E820_TYPE_ACPI;
Expand Down Expand Up @@ -424,55 +402,12 @@ int crash_setup_memmap_entries(struct kimage *image, struct boot_params *params)
return ret;
}

static int determine_backup_region(struct resource *res, void *arg)
{
struct kimage *image = arg;

image->arch.backup_src_start = res->start;
image->arch.backup_src_sz = resource_size(res);

/* Expecting only one range for backup region */
return 1;
}

int crash_load_segments(struct kimage *image)
{
int ret;
struct kexec_buf kbuf = { .image = image, .buf_min = 0,
.buf_max = ULONG_MAX, .top_down = false };

/*
* Determine and load a segment for backup area. First 640K RAM
* region is backup source
*/

ret = walk_system_ram_res(KEXEC_BACKUP_SRC_START, KEXEC_BACKUP_SRC_END,
image, determine_backup_region);

/* Zero or postive return values are ok */
if (ret < 0)
return ret;

/* Add backup segment. */
if (image->arch.backup_src_sz) {
kbuf.buffer = &crash_zero_bytes;
kbuf.bufsz = sizeof(crash_zero_bytes);
kbuf.memsz = image->arch.backup_src_sz;
kbuf.buf_align = PAGE_SIZE;
/*
* Ideally there is no source for backup segment. This is
* copied in purgatory after crash. Just add a zero filled
* segment for now to make sure checksum logic works fine.
*/
ret = kexec_add_buffer(&kbuf);
if (ret)
return ret;
image->arch.backup_load_addr = kbuf.mem;
pr_debug("Loaded backup region at 0x%lx backup_start=0x%lx memsz=0x%lx\n",
image->arch.backup_load_addr,
image->arch.backup_src_start, kbuf.memsz);
}

/* Prepare elf headers and add a segment */
ret = prepare_elf_headers(image, &kbuf.buffer, &kbuf.bufsz);
if (ret)
Expand Down
47 changes: 0 additions & 47 deletions arch/x86/kernel/machine_kexec_64.c
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Original file line number Diff line number Diff line change
Expand Up @@ -298,48 +298,6 @@ static void load_segments(void)
);
}

#ifdef CONFIG_KEXEC_FILE
/* Update purgatory as needed after various image segments have been prepared */
static int arch_update_purgatory(struct kimage *image)
{
int ret = 0;

if (!image->file_mode)
return 0;

/* Setup copying of backup region */
if (image->type == KEXEC_TYPE_CRASH) {
ret = kexec_purgatory_get_set_symbol(image,
"purgatory_backup_dest",
&image->arch.backup_load_addr,
sizeof(image->arch.backup_load_addr), 0);
if (ret)
return ret;

ret = kexec_purgatory_get_set_symbol(image,
"purgatory_backup_src",
&image->arch.backup_src_start,
sizeof(image->arch.backup_src_start), 0);
if (ret)
return ret;

ret = kexec_purgatory_get_set_symbol(image,
"purgatory_backup_sz",
&image->arch.backup_src_sz,
sizeof(image->arch.backup_src_sz), 0);
if (ret)
return ret;
}

return ret;
}
#else /* !CONFIG_KEXEC_FILE */
static inline int arch_update_purgatory(struct kimage *image)
{
return 0;
}
#endif /* CONFIG_KEXEC_FILE */

int machine_kexec_prepare(struct kimage *image)
{
unsigned long start_pgtable;
Expand All @@ -353,11 +311,6 @@ int machine_kexec_prepare(struct kimage *image)
if (result)
return result;

/* update purgatory as needed */
result = arch_update_purgatory(image);
if (result)
return result;

return 0;
}

Expand Down
19 changes: 0 additions & 19 deletions arch/x86/purgatory/purgatory.c
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Original file line number Diff line number Diff line change
Expand Up @@ -14,28 +14,10 @@

#include "../boot/string.h"

unsigned long purgatory_backup_dest __section(.kexec-purgatory);
unsigned long purgatory_backup_src __section(.kexec-purgatory);
unsigned long purgatory_backup_sz __section(.kexec-purgatory);

u8 purgatory_sha256_digest[SHA256_DIGEST_SIZE] __section(.kexec-purgatory);

struct kexec_sha_region purgatory_sha_regions[KEXEC_SEGMENT_MAX] __section(.kexec-purgatory);

/*
* On x86, second kernel requries first 640K of memory to boot. Copy
* first 640K to a backup region in reserved memory range so that second
* kernel can use first 640K.
*/
static int copy_backup_region(void)
{
if (purgatory_backup_dest) {
memcpy((void *)purgatory_backup_dest,
(void *)purgatory_backup_src, purgatory_backup_sz);
}
return 0;
}

static int verify_sha256_digest(void)
{
struct kexec_sha_region *ptr, *end;
Expand Down Expand Up @@ -66,7 +48,6 @@ void purgatory(void)
for (;;)
;
}
copy_backup_region();
}

/*
Expand Down

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