Re: [PATCH v4 08/10] arm64: kexec_file: set up for crash dump adding elf core header

From: Julien Thierry
Date: Thu Oct 05 2017 - 10:16:03 EST



On 02/10/17 07:14, AKASHI Takahiro wrote:
load_crashdump_segments() creates and loads a memory segment of elf core
header for crash dump.

"linux,usable-memory-range" and "linux,elfcorehdr" will add to the 2nd
kernel's device-tree blob. The logic of this cod is also from kexec-tools.

Signed-off-by: AKASHI Takahiro <takahiro.akashi@xxxxxxxxxx>
Cc: Catalin Marinas <catalin.marinas@xxxxxxx>
Cc: Will Deacon <will.deacon@xxxxxxx>
---
arch/arm64/include/asm/kexec.h | 5 ++
arch/arm64/kernel/machine_kexec_file.c | 149 +++++++++++++++++++++++++++++++++
kernel/kexec_file.c | 2 +-
3 files changed, 155 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/include/asm/kexec.h b/arch/arm64/include/asm/kexec.h
index 2fadd3cbf3af..edb702e64a8a 100644
--- a/arch/arm64/include/asm/kexec.h
+++ b/arch/arm64/include/asm/kexec.h
@@ -98,6 +98,10 @@ static inline void crash_post_resume(void) {}
struct kimage_arch {
void *dtb_buf;
+ /* Core ELF header buffer */
+ void *elf_headers;
+ unsigned long elf_headers_sz;
+ unsigned long elf_load_addr;
};
struct kimage;
@@ -113,6 +117,7 @@ extern int load_other_segments(struct kimage *image,
unsigned long kernel_load_addr,
char *initrd, unsigned long initrd_len,
char *cmdline, unsigned long cmdline_len);
+extern int load_crashdump_segments(struct kimage *image);
#endif
#endif /* __ASSEMBLY__ */
diff --git a/arch/arm64/kernel/machine_kexec_file.c b/arch/arm64/kernel/machine_kexec_file.c
index 8a09d89f6266..1d30b4773af5 100644
--- a/arch/arm64/kernel/machine_kexec_file.c
+++ b/arch/arm64/kernel/machine_kexec_file.c
@@ -32,6 +32,10 @@ int arch_kimage_file_post_load_cleanup(struct kimage *image)
vfree(image->arch.dtb_buf);
image->arch.dtb_buf = NULL;
+ vfree(image->arch.elf_headers);
+ image->arch.elf_headers = NULL;
+ image->arch.elf_headers_sz = 0;
+
return _kexec_kernel_post_load_cleanup(image);
}
@@ -48,6 +52,77 @@ int arch_kexec_walk_mem(struct kexec_buf *kbuf, int (*func)(u64, u64, void *))
return walk_system_ram_res(0, ULONG_MAX, kbuf, func);
}
+static int __init arch_kexec_file_init(void)
+{
+ /* Those values are used later on loading the kernel */
+ __dt_root_addr_cells = dt_root_addr_cells;
+ __dt_root_size_cells = dt_root_size_cells;
+
+ return 0;
+}
+late_initcall(arch_kexec_file_init);
+
+#define FDT_ALIGN(x, a) (((x) + (a) - 1) & ~((a) - 1))
+#define FDT_TAGALIGN(x) (FDT_ALIGN((x), FDT_TAGSIZE))
+
+static int fdt_prop_len(const char *prop_name, int len)
+{
+ return (strlen(prop_name) + 1) +
+ sizeof(struct fdt_property) +
+ FDT_TAGALIGN(len);
+}
+
+static bool cells_size_fitted(unsigned long base, unsigned long size)
+{
+ /* if *_cells >= 2, cells can hold 64-bit values anyway */
+ if ((__dt_root_addr_cells == 1) && (base >= (1ULL << 32)))
+ return false;
+
+ if ((__dt_root_size_cells == 1) && (size >= (1ULL << 32)))
+ return false;
+
+ return true;
+}
+
+static void fill_property(void *buf, u64 val64, int cells)
+{
+ u32 val32;
+ int i;
+
+ if (cells == 1) {
+ val32 = cpu_to_fdt32((u32)val64);
+ memcpy(buf, &val32, sizeof(val32));
+ } else {
+ for (i = 0; i < (cells * sizeof(u32) - sizeof(u64)); i++)
+ *(char *)buf++ = 0;
+

Should we use memset for this?

+ val64 = cpu_to_fdt64(val64);
+ memcpy(buf, &val64, sizeof(val64));
+ }
+}
+
+static int fdt_setprop_range(void *fdt, int nodeoffset, const char *name,
+ unsigned long addr, unsigned long size)
+{
+ u64 range[2];

Could we just add some BUG/WARN when either __dt_root_addr_cells or __dt_root_size_cells is greater than 2?

Both to make sure we have sane values and because it will be easier to debug than overwriting things on the stack.

+ void *prop;
+ size_t buf_size;
+ int result;
+
+ prop = range;
+ buf_size = (__dt_root_addr_cells + __dt_root_size_cells) * sizeof(u32);
+
+ fill_property(prop, addr, __dt_root_addr_cells);
+ prop += __dt_root_addr_cells * sizeof(u32);
+
+ fill_property(prop, size, __dt_root_size_cells);
+ prop += __dt_root_size_cells * sizeof(u32);

This is not needed (or at least we aren't doing anything with it).

Apart from that, patch seems fine.

Cheers,

+
+ result = fdt_setprop(fdt, nodeoffset, name, range, buf_size);
+
+ return result;
+}
+
int setup_dtb(struct kimage *image,
unsigned long initrd_load_addr, unsigned long initrd_len,
char *cmdline, unsigned long cmdline_len,
@@ -60,10 +135,26 @@ int setup_dtb(struct kimage *image,
int range_len;
int ret;
+ /* check ranges against root's #address-cells and #size-cells */
+ if (image->type == KEXEC_TYPE_CRASH &&
+ (!cells_size_fitted(image->arch.elf_load_addr,
+ image->arch.elf_headers_sz) ||
+ !cells_size_fitted(crashk_res.start,
+ crashk_res.end - crashk_res.start + 1))) {
+ pr_err("Crash memory region doesn't fit into DT's root cell sizes.\n");
+ ret = -EINVAL;
+ goto out_err;
+ }
+
/* duplicate dt blob */
buf_size = fdt_totalsize(initial_boot_params);
range_len = (__dt_root_addr_cells + __dt_root_size_cells) * sizeof(u32);
+ if (image->type == KEXEC_TYPE_CRASH)
+ buf_size += fdt_prop_len("linux,elfcorehdr", range_len)
+ + fdt_prop_len("linux,usable-memory-range",
+ range_len);
+
if (initrd_load_addr)
buf_size += fdt_prop_len("initrd-start", sizeof(u64))
+ fdt_prop_len("initrd-end", sizeof(u64));
@@ -85,6 +176,23 @@ int setup_dtb(struct kimage *image,
if (nodeoffset < 0)
goto out_err;
+ if (image->type == KEXEC_TYPE_CRASH) {
+ /* add linux,elfcorehdr */
+ ret = fdt_setprop_range(buf, nodeoffset, "linux,elfcorehdr",
+ image->arch.elf_load_addr,
+ image->arch.elf_headers_sz);
+ if (ret)
+ goto out_err;
+
+ /* add linux,usable-memory-range */
+ ret = fdt_setprop_range(buf, nodeoffset,
+ "linux,usable-memory-range",
+ crashk_res.start,
+ crashk_res.end - crashk_res.start + 1);
+ if (ret)
+ goto out_err;
+ }
+
/* add bootargs */
if (cmdline) {
ret = fdt_setprop(buf, nodeoffset, "bootargs",
@@ -211,3 +319,44 @@ int load_other_segments(struct kimage *image, unsigned long kernel_load_addr,
image->arch.dtb_buf = NULL;
return ret;
}
+
+int load_crashdump_segments(struct kimage *image)
+{
+ void *elf_addr;
+ unsigned long elf_sz;
+ struct kexec_buf kbuf;
+ int ret;
+
+ if (image->type != KEXEC_TYPE_CRASH)
+ return 0;
+
+ /* Prepare elf headers and add a segment */
+ ret = prepare_elf_headers(image, &elf_addr, &elf_sz);
+ if (ret) {
+ pr_err("Preparing elf core header failed\n");
+ return ret;
+ }
+
+ kbuf.image = image;
+ kbuf.buffer = elf_addr;
+ kbuf.bufsz = elf_sz;
+ kbuf.memsz = elf_sz;
+ kbuf.buf_align = PAGE_SIZE;
+ kbuf.buf_min = crashk_res.start;
+ kbuf.buf_max = crashk_res.end + 1;
+ kbuf.top_down = 1;
+
+ ret = kexec_add_buffer(&kbuf);
+ if (ret) {
+ vfree(elf_addr);
+ return ret;
+ }
+ image->arch.elf_headers = elf_addr;
+ image->arch.elf_headers_sz = elf_sz;
+ image->arch.elf_load_addr = kbuf.mem;
+
+ pr_debug("Loaded elf core header at 0x%lx bufsz=0x%lx memsz=0x%lx\n",
+ image->arch.elf_load_addr, elf_sz, elf_sz);
+
+ return ret;
+}
diff --git a/kernel/kexec_file.c b/kernel/kexec_file.c
index 8a7f029c5995..82a98f284cf5 100644
--- a/kernel/kexec_file.c
+++ b/kernel/kexec_file.c
@@ -1340,7 +1340,7 @@ static int prepare_elf64_headers(struct crash_elf_data *ced,
phdr->p_filesz = phdr->p_memsz = VMCOREINFO_NOTE_SIZE;
(ehdr->e_phnum)++;
-#ifdef CONFIG_X86_64
+#if defined(CONFIG_X86_64) || defined(CONFIG_ARM64)
/* Prepare PT_LOAD type program header for kernel text region */
phdr = (Elf64_Phdr *)bufp;
bufp += sizeof(Elf64_Phdr);


--
Julien Thierry