[PATCH v8 04/13] x86: kexec_file: factor out elf core header related functions

[AKASHI Takahiro]

exclude_mem_range() and prepare_elf64_headers() can be re-used on other
architectures, including arm64, as well. So let them factored out so as to
move them to generic side in the next patch.

fill_up_crash_elf_data() can potentially be commonalized for most
architectures who want to go through io resources (/proc/iomem) for a list
of "System RAM", but leave it private for now.

Signed-off-by: AKASHI Takahiro <takahiro.akashi@xxxxxxxxxx>
Cc: Dave Young <dyoung@xxxxxxxxxx>
Cc: Vivek Goyal <vgoyal@xxxxxxxxxx>
Cc: Baoquan He <bhe@xxxxxxxxxx>
---
 arch/x86/kernel/crash.c | 235 +++++++++++++++++++++---------------------------
 1 file changed, 103 insertions(+), 132 deletions(-)

diff --git a/arch/x86/kernel/crash.c b/arch/x86/kernel/crash.c
index 10e74d4778a1..5c19cfbf3b85 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 */
@@ -217,29 +199,32 @@ 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);
 
-	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;
 
-	/* 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,
+static int crash_exclude_mem_range(struct crash_mem *mem,
 		unsigned long long mstart, unsigned long long mend)
 {
 	int i, j;
@@ -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;
@@ -314,27 +297,20 @@ 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,
-		unsigned long long mstart, unsigned long long mend)
+static int elf_header_exclude_ranges(struct crash_mem *cmem)
 {
-	struct crash_mem *cmem = &ced->mem;
 	int ret = 0;
 
-	memset(cmem->ranges, 0, sizeof(cmem->ranges));
-
-	cmem->ranges[0].start = mstart;
-	cmem->ranges[0].end = mend;
-	cmem->nr_ranges = 1;
-
 	/* Exclude crashkernel region */
-	ret = exclude_mem_range(cmem, crashk_res.start, crashk_res.end);
+	ret = crash_exclude_mem_range(cmem, crashk_res.start, crashk_res.end);
 	if (ret)
 		return ret;
 
 	if (crashk_low_res.end) {
-		ret = exclude_mem_range(cmem, crashk_low_res.start, crashk_low_res.end);
+		ret = crash_exclude_mem_range(cmem, crashk_low_res.start,
+							crashk_low_res.end);
 		if (ret)
 			return ret;
 	}
@@ -344,70 +320,29 @@ 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;
-	Elf64_Ehdr *ehdr;
-	Elf64_Phdr *phdr;
-	unsigned long mstart, mend;
-	struct kimage *image = ced->image;
-	struct crash_mem *cmem;
-	int ret, i;
+	struct crash_mem *cmem = arg;
 
-	ehdr = ced->ehdr;
-
-	/* Exclude unwanted mem ranges */
-	ret = elf_header_exclude_ranges(ced, res->start, res->end);
-	if (ret)
-		return ret;
-
-	/* Go through all the ranges in ced->mem.ranges[] and prepare phdr */
-	cmem = &ced->mem;
-
-	for (i = 0; i < cmem->nr_ranges; i++) {
-		mstart = cmem->ranges[i].start;
-		mend = cmem->ranges[i].end;
-
-		phdr = ced->bufp;
-		ced->bufp += sizeof(Elf64_Phdr);
-
-		phdr->p_type = PT_LOAD;
-		phdr->p_flags = PF_R|PF_W|PF_X;
-		phdr->p_offset  = mstart;
-
-		/*
-		 * If a range matches backup region, adjust offset to backup
-		 * segment.
-		 */
-		if (mstart == image->arch.backup_src_start &&
-		    (mend - mstart + 1) == image->arch.backup_src_sz)
-			phdr->p_offset = image->arch.backup_load_addr;
-
-		phdr->p_paddr = mstart;
-		phdr->p_vaddr = (unsigned long long) __va(mstart);
-		phdr->p_filesz = phdr->p_memsz = mend - mstart + 1;
-		phdr->p_align = 0;
-		ehdr->e_phnum++;
-		pr_debug("Crash PT_LOAD elf header. phdr=%p vaddr=0x%llx, paddr=0x%llx, sz=0x%llx e_phnum=%d p_offset=0x%llx\n",
-			phdr, phdr->p_vaddr, phdr->p_paddr, phdr->p_filesz,
-			ehdr->e_phnum, phdr->p_offset);
-	}
+	cmem->ranges[cmem->nr_ranges].start = res->start;
+	cmem->ranges[cmem->nr_ranges].end = res->end;
+	cmem->nr_ranges++;
 
-	return ret;
+	return 0;
 }
 
-static int prepare_elf64_headers(struct crash_elf_data *ced,
-		void **addr, unsigned long *sz)
+static int crash_prepare_elf64_headers(struct crash_mem *cmem, int kernel_map,
+					void **addr, unsigned long *sz)
 {
 	Elf64_Ehdr *ehdr;
 	Elf64_Phdr *phdr;
 	unsigned long nr_cpus = num_possible_cpus(), nr_phdr, elf_sz;
-	unsigned char *buf, *bufp;
-	unsigned int cpu;
+	unsigned char *buf;
+	unsigned int cpu, i;
 	unsigned long long notes_addr;
-	int ret;
+	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
@@ -425,9 +360,8 @@ static int prepare_elf64_headers(struct crash_elf_data *ced,
 	if (!buf)
 		return -ENOMEM;
 
-	bufp = buf;
-	ehdr = (Elf64_Ehdr *)bufp;
-	bufp += sizeof(Elf64_Ehdr);
+	ehdr = (Elf64_Ehdr *)buf;
+	phdr = (Elf64_Phdr *)(ehdr + 1);
 	memcpy(ehdr->e_ident, ELFMAG, SELFMAG);
 	ehdr->e_ident[EI_CLASS] = ELFCLASS64;
 	ehdr->e_ident[EI_DATA] = ELFDATA2LSB;
@@ -443,42 +377,51 @@ static int prepare_elf64_headers(struct crash_elf_data *ced,
 
 	/* Prepare one phdr of type PT_NOTE for each present cpu */
 	for_each_present_cpu(cpu) {
-		phdr = (Elf64_Phdr *)bufp;
-		bufp += sizeof(Elf64_Phdr);
 		phdr->p_type = PT_NOTE;
 		notes_addr = per_cpu_ptr_to_phys(per_cpu_ptr(crash_notes, cpu));
 		phdr->p_offset = phdr->p_paddr = notes_addr;
 		phdr->p_filesz = phdr->p_memsz = sizeof(note_buf_t);
 		(ehdr->e_phnum)++;
+		phdr++;
 	}
 
 	/* Prepare one PT_NOTE header for vmcoreinfo */
-	phdr = (Elf64_Phdr *)bufp;
-	bufp += sizeof(Elf64_Phdr);
 	phdr->p_type = PT_NOTE;
 	phdr->p_offset = phdr->p_paddr = paddr_vmcoreinfo_note();
 	phdr->p_filesz = phdr->p_memsz = VMCOREINFO_NOTE_SIZE;
 	(ehdr->e_phnum)++;
+	phdr++;
 
-#ifdef CONFIG_X86_64
 	/* Prepare PT_LOAD type program header for kernel text region */
-	phdr = (Elf64_Phdr *)bufp;
-	bufp += sizeof(Elf64_Phdr);
-	phdr->p_type = PT_LOAD;
-	phdr->p_flags = PF_R|PF_W|PF_X;
-	phdr->p_vaddr = (Elf64_Addr)_text;
-	phdr->p_filesz = phdr->p_memsz = _end - _text;
-	phdr->p_offset = phdr->p_paddr = __pa_symbol(_text);
-	(ehdr->e_phnum)++;
-#endif
+	if (kernel_map) {
+		phdr->p_type = PT_LOAD;
+		phdr->p_flags = PF_R|PF_W|PF_X;
+		phdr->p_vaddr = (Elf64_Addr)_text;
+		phdr->p_filesz = phdr->p_memsz = _end - _text;
+		phdr->p_offset = phdr->p_paddr = __pa_symbol(_text);
+		ehdr->e_phnum++;
+		phdr++;
+	}
 
-	/* Prepare PT_LOAD headers for system ram chunks. */
-	ced->ehdr = ehdr;
-	ced->bufp = bufp;
-	ret = walk_system_ram_res(0, -1, ced,
-			prepare_elf64_ram_headers_callback);
-	if (ret < 0)
-		return ret;
+	/* Go through all the ranges in cmem->ranges[] and prepare phdr */
+	for (i = 0; i < cmem->nr_ranges; i++) {
+		mstart = cmem->ranges[i].start;
+		mend = cmem->ranges[i].end;
+
+		phdr->p_type = PT_LOAD;
+		phdr->p_flags = PF_R|PF_W|PF_X;
+		phdr->p_offset  = mstart;
+
+		phdr->p_paddr = mstart;
+		phdr->p_vaddr = (unsigned long long) __va(mstart);
+		phdr->p_filesz = phdr->p_memsz = mend - mstart + 1;
+		phdr->p_align = 0;
+		ehdr->e_phnum++;
+		phdr++;
+		pr_debug("Crash PT_LOAD elf header. phdr=%p vaddr=0x%llx, paddr=0x%llx, sz=0x%llx e_phnum=%d p_offset=0x%llx\n",
+			phdr, phdr->p_vaddr, phdr->p_paddr, phdr->p_filesz,
+			ehdr->e_phnum, phdr->p_offset);
+	}
 
 	*addr = buf;
 	*sz = elf_sz;
@@ -489,18 +432,46 @@ static int prepare_elf64_headers(struct crash_elf_data *ced,
 static int prepare_elf_headers(struct kimage *image, void **addr,
 					unsigned long *sz)
 {
-	struct crash_elf_data *ced;
-	int ret;
+	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, cmem,
+				prepare_elf64_ram_headers_callback);
+	if (ret)
+		goto out;
+
+	/* Exclude unwanted mem ranges */
+	ret = elf_header_exclude_ranges(cmem);
+	if (ret)
+		goto out;
 
 	/* By default prepare 64bit headers */
-	ret =  prepare_elf64_headers(ced, addr, sz);
-	kfree(ced);
+	ret =  crash_prepare_elf64_headers(cmem,
+				(int)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;
 }
 
@@ -546,14 +517,14 @@ static int memmap_exclude_ranges(struct kimage *image, struct crash_mem *cmem,
 	/* Exclude Backup region */
 	start = image->arch.backup_load_addr;
 	end = start + image->arch.backup_src_sz - 1;
-	ret = exclude_mem_range(cmem, start, end);
+	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;
-	return exclude_mem_range(cmem, start, end);
+	return crash_exclude_mem_range(cmem, start, end);
 }
 
 /* Prepare memory map for crash dump kernel */
-- 
2.16.2