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Subject: [PATCH v2 10/12] ppc64/kexec_file: prepare elfcore header for
 crashing kernel
From:   Hari Bathini <hbathini@linux.ibm.com>
To:     Michael Ellerman <mpe@ellerman.id.au>,
        Andrew Morton <akpm@linux-foundation.org>
Cc:     Pingfan Liu <piliu@redhat.com>,
        Kexec-ml <kexec@lists.infradead.org>,
        Mimi Zohar <zohar@linux.ibm.com>,
        Petr Tesarik <ptesarik@suse.cz>,
        Mahesh J Salgaonkar <mahesh@linux.ibm.com>,
        Sourabh Jain <sourabhjain@linux.ibm.com>,
        lkml <linux-kernel@vger.kernel.org>,
        linuxppc-dev <linuxppc-dev@ozlabs.org>,
        Eric Biederman <ebiederm@xmission.com>,
        Thiago Jung Bauermann <bauerman@linux.ibm.com>,
        Dave Young <dyoung@redhat.com>, Vivek Goyal <vgoyal@redhat.com>
Date:   Fri, 03 Jul 2020 01:26:43 +0530
Message-ID: <159371979723.21555.9519023181134650934.stgit@hbathini.in.ibm.com>
In-Reply-To: <159371956443.21555.18251597651350106920.stgit@hbathini.in.ibm.com>
References: <159371956443.21555.18251597651350106920.stgit@hbathini.in.ibm.com>
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Prepare elf headers for the crashing kernel's core file using
crash_prepare_elf64_headers() and pass on this info to kdump
kernel by updating its command line with elfcorehdr parameter.
Also, add elfcorehdr location to reserve map to avoid it from
being stomped on while booting.

Signed-off-by: Hari Bathini <hbathini@linux.ibm.com>
---

Changes in v2:
* Tried merging adjacent memory ranges on hitting maximum ranges limit
  to reduce reallocations for memory ranges and also, minimize PT_LOAD
  segments for elfcore.
* Updated add_rtas_mem_range() & add_opal_mem_range() callsites based on
  the new prototype for these functions.


 arch/powerpc/include/asm/kexec.h  |    6 +
 arch/powerpc/kexec/elf_64.c       |   12 ++
 arch/powerpc/kexec/file_load.c    |   49 ++++++++++
 arch/powerpc/kexec/file_load_64.c |  181 +++++++++++++++++++++++++++++++++++++
 4 files changed, 248 insertions(+)

diff --git a/arch/powerpc/include/asm/kexec.h b/arch/powerpc/include/asm/kexec.h
index 037cf2b..8b0a6d6 100644
--- a/arch/powerpc/include/asm/kexec.h
+++ b/arch/powerpc/include/asm/kexec.h
@@ -112,12 +112,18 @@ struct kimage_arch {
 	unsigned long backup_start;
 	void *backup_buf;
 
+	unsigned long elfcorehdr_addr;
+	unsigned long elf_headers_sz;
+	void *elf_headers;
+
 #ifdef CONFIG_IMA_KEXEC
 	phys_addr_t ima_buffer_addr;
 	size_t ima_buffer_size;
 #endif
 };
 
+char *setup_kdump_cmdline(struct kimage *image, char *cmdline,
+			  unsigned long cmdline_len);
 int setup_purgatory(struct kimage *image, const void *slave_code,
 		    const void *fdt, unsigned long kernel_load_addr,
 		    unsigned long fdt_load_addr);
diff --git a/arch/powerpc/kexec/elf_64.c b/arch/powerpc/kexec/elf_64.c
index 4838b42..40a028c 100644
--- a/arch/powerpc/kexec/elf_64.c
+++ b/arch/powerpc/kexec/elf_64.c
@@ -36,6 +36,7 @@ static void *elf64_load(struct kimage *image, char *kernel_buf,
 	void *fdt;
 	const void *slave_code;
 	struct elfhdr ehdr;
+	char *modified_cmdline = NULL;
 	struct kexec_elf_info elf_info;
 	struct kexec_buf kbuf = { .image = image, .buf_min = 0,
 				  .buf_max = ppc64_rma_size };
@@ -74,6 +75,16 @@ static void *elf64_load(struct kimage *image, char *kernel_buf,
 			pr_err("Failed to load kdump kernel segments\n");
 			goto out;
 		}
+
+		/* Setup cmdline for kdump kernel case */
+		modified_cmdline = setup_kdump_cmdline(image, cmdline,
+						       cmdline_len);
+		if (!modified_cmdline) {
+			pr_err("Setting up cmdline for kdump kernel failed\n");
+			ret = -EINVAL;
+			goto out;
+		}
+		cmdline = modified_cmdline;
 	}
 
 	if (initrd != NULL) {
@@ -130,6 +141,7 @@ static void *elf64_load(struct kimage *image, char *kernel_buf,
 		pr_err("Error setting up the purgatory.\n");
 
 out:
+	kfree(modified_cmdline);
 	kexec_free_elf_info(&elf_info);
 
 	/* Make kimage_file_post_load_cleanup free the fdt buffer for us. */
diff --git a/arch/powerpc/kexec/file_load.c b/arch/powerpc/kexec/file_load.c
index 99a2c4d..2e74992 100644
--- a/arch/powerpc/kexec/file_load.c
+++ b/arch/powerpc/kexec/file_load.c
@@ -17,11 +17,46 @@
 #include <linux/slab.h>
 #include <linux/kexec.h>
 #include <linux/libfdt.h>
+#include <asm/setup.h>
 #include <asm/ima.h>
 
 #define SLAVE_CODE_SIZE		256	/* First 0x100 bytes */
 
 /**
+ * setup_kdump_cmdline - Prepend "elfcorehdr=<addr> " to command line
+ *                       of kdump kernel for exporting the core.
+ * @image:               Kexec image
+ * @cmdline:             Command line parameters to update.
+ * @cmdline_len:         Length of the cmdline parameters.
+ *
+ * kdump segment must be setup before calling this function.
+ *
+ * Returns new cmdline buffer for kdump kernel on success, NULL otherwise.
+ */
+char *setup_kdump_cmdline(struct kimage *image, char *cmdline,
+			  unsigned long cmdline_len)
+{
+	int elfcorehdr_strlen;
+	char *cmdline_ptr;
+
+	cmdline_ptr = kzalloc(COMMAND_LINE_SIZE, GFP_KERNEL);
+	if (!cmdline_ptr)
+		return NULL;
+
+	elfcorehdr_strlen = sprintf(cmdline_ptr, "elfcorehdr=0x%lx ",
+				    image->arch.elfcorehdr_addr);
+
+	if (elfcorehdr_strlen + cmdline_len > COMMAND_LINE_SIZE) {
+		pr_err("Appending elfcorehdr=<addr> exceeds cmdline size\n");
+		kfree(cmdline_ptr);
+		return NULL;
+	}
+
+	memcpy(cmdline_ptr + elfcorehdr_strlen, cmdline, cmdline_len);
+	return cmdline_ptr;
+}
+
+/**
  * setup_purgatory - initialize the purgatory's global variables
  * @image:		kexec image.
  * @slave_code:		Slave code for the purgatory.
@@ -215,6 +250,20 @@ int setup_new_fdt(const struct kimage *image, void *fdt,
 		}
 	}
 
+	if (image->type == KEXEC_TYPE_CRASH) {
+		/*
+		 * Avoid elfcorehdr from being stomped on in kdump kernel by
+		 * setting up memory reserve map.
+		 */
+		ret = fdt_add_mem_rsv(fdt, image->arch.elfcorehdr_addr,
+				      image->arch.elf_headers_sz);
+		if (ret) {
+			pr_err("Error reserving elfcorehdr memory: %s\n",
+			       fdt_strerror(ret));
+			goto err;
+		}
+	}
+
 	ret = setup_ima_buffer(image, fdt, chosen_node);
 	if (ret) {
 		pr_err("Error setting up the new device tree.\n");
diff --git a/arch/powerpc/kexec/file_load_64.c b/arch/powerpc/kexec/file_load_64.c
index f91530e..6f895fa 100644
--- a/arch/powerpc/kexec/file_load_64.c
+++ b/arch/powerpc/kexec/file_load_64.c
@@ -122,6 +122,77 @@ static int get_usable_memory_ranges(struct crash_mem **mem_ranges)
 }
 
 /**
+ * get_crash_memory_ranges - Get crash memory ranges. This list includes
+ *                           first/crashing kernel's memory regions that
+ *                           would be exported via an elfcore.
+ * @mem_ranges:              Range list to add the memory ranges to.
+ *
+ * Returns 0 on success, negative errno on error.
+ */
+static int get_crash_memory_ranges(struct crash_mem **mem_ranges)
+{
+	struct memblock_region *reg;
+	struct crash_mem *tmem;
+	int ret;
+
+	for_each_memblock(memory, reg) {
+		u64 base, size;
+
+		base = (u64)reg->base;
+		size = (u64)reg->size;
+
+		/* Skip backup memory region, which needs a separate entry */
+		if (base == BACKUP_SRC_START) {
+			if (size > BACKUP_SRC_SIZE) {
+				base = BACKUP_SRC_END + 1;
+				size -= BACKUP_SRC_SIZE;
+			} else
+				continue;
+		}
+
+		ret = add_mem_range(mem_ranges, base, size);
+		if (ret)
+			goto out;
+
+		/* Try merging adjacent ranges before reallocation attempt */
+		if ((*mem_ranges)->nr_ranges == (*mem_ranges)->max_nr_ranges)
+			sort_memory_ranges(*mem_ranges, true);
+	}
+
+	/* Reallocate memory ranges if there is no space to split ranges */
+	tmem = *mem_ranges;
+	if (tmem && (tmem->nr_ranges == tmem->max_nr_ranges)) {
+		tmem = realloc_mem_ranges(mem_ranges);
+		if (!tmem)
+			goto out;
+	}
+
+	/* Exclude crashkernel region */
+	ret = crash_exclude_mem_range(tmem, crashk_res.start, crashk_res.end);
+	if (ret)
+		goto out;
+
+	ret = add_rtas_mem_range(mem_ranges);
+	if (ret)
+		goto out;
+
+	ret = add_opal_mem_range(mem_ranges);
+	if (ret)
+		goto out;
+
+	/* create a separate program header for the backup region */
+	ret = add_mem_range(mem_ranges, BACKUP_SRC_START, BACKUP_SRC_SIZE);
+	if (ret)
+		goto out;
+
+	sort_memory_ranges(*mem_ranges, false);
+out:
+	if (ret)
+		pr_err("Failed to setup crash memory ranges\n");
+	return ret;
+}
+
+/**
  * __locate_mem_hole_top_down - Looks top down for a large enough memory hole
  *                              in the memory regions between buf_min & buf_max
  *                              for the buffer. If found, sets kbuf->mem.
@@ -898,6 +969,103 @@ static int load_backup_segment(struct kimage *image, struct kexec_buf *kbuf)
 }
 
 /**
+ * update_backup_region_phdr - Update backup region's offset for the core to
+ *                             export the region appropriately.
+ * @image:                     Kexec image.
+ * @ehdr:                      ELF core header.
+ *
+ * Assumes an exclusive program header is setup for the backup region
+ * in the ELF headers
+ *
+ * Returns nothing.
+ */
+static void update_backup_region_phdr(struct kimage *image, Elf64_Ehdr *ehdr)
+{
+	Elf64_Phdr *phdr;
+	unsigned int i;
+
+	phdr = (Elf64_Phdr *)(ehdr + 1);
+	for (i = 0; i < ehdr->e_phnum; i++) {
+		if (phdr->p_paddr == BACKUP_SRC_START) {
+			phdr->p_offset = image->arch.backup_start;
+			pr_debug("Backup region offset updated to 0x%lx\n",
+				 image->arch.backup_start);
+			return;
+		}
+	}
+}
+
+/**
+ * prepare_elf_headers - Prepare headers for the elfcore to be exported as
+ *                       /proc/vmcore by the kdump kernel.
+ * @image:               Kexec image.
+ * @cmem:                Crash memory ranges to be exported via elfcore.
+ * @addr:                Vmalloc'd memory allocated by crash_prepare_elf64_headers
+ *                       to prepare the elf headers.
+ * @sz:                  Size of the vmalloc'd memory allocated.
+ *
+ * Returns 0 on success, negative errno on error.
+ */
+static int prepare_elf_headers(struct kimage *image, struct crash_mem *cmem,
+			       void **addr, unsigned long *sz)
+{
+	int ret;
+
+	ret = crash_prepare_elf64_headers(cmem, false, addr, sz);
+
+	/* Fix the offset for backup region in the ELF header */
+	if (!ret)
+		update_backup_region_phdr(image, *addr);
+
+	return ret;
+}
+
+/**
+ * load_elfcorehdr_segment - Setup crash memory ranges and initialize elfcorehdr
+ *                           segment needed to load kdump kernel.
+ * @image:                   Kexec image.
+ * @kbuf:                    Buffer contents and memory parameters.
+ *
+ * Returns 0 on success, negative errno on error.
+ */
+static int load_elfcorehdr_segment(struct kimage *image, struct kexec_buf *kbuf)
+{
+	struct crash_mem *cmem = NULL;
+	unsigned long headers_sz;
+	void *headers = NULL;
+	int ret;
+
+	ret = get_crash_memory_ranges(&cmem);
+	if (ret)
+		goto out;
+
+	/* Setup elfcorehdr segment */
+	ret = prepare_elf_headers(image, cmem, &headers, &headers_sz);
+	if (ret) {
+		pr_err("Failed to prepare elf headers for the core\n");
+		goto out;
+	}
+
+	kbuf->buffer = headers;
+	kbuf->mem = KEXEC_BUF_MEM_UNKNOWN;
+	kbuf->bufsz = kbuf->memsz = headers_sz;
+	kbuf->top_down = false;
+
+	ret = kexec_add_buffer(kbuf);
+	if (ret) {
+		vfree(headers);
+		goto out;
+	}
+
+	image->arch.elfcorehdr_addr = kbuf->mem;
+	image->arch.elf_headers_sz = headers_sz;
+	image->arch.elf_headers = headers;
+out:
+	kfree(cmem);
+	return ret;
+}
+
+/**
  * load_crashdump_segments_ppc64 - Initialize the additional segements needed
  *                                 to load kdump kernel.
  * @image:                         Kexec image.
@@ -918,6 +1086,15 @@ int load_crashdump_segments_ppc64(struct kimage *image,
 	}
 	pr_debug("Loaded the backup region at 0x%lx\n", kbuf->mem);
 
+	/* Load elfcorehdr segment - to export crashing kernel's vmcore */
+	ret = load_elfcorehdr_segment(image, kbuf);
+	if (ret) {
+		pr_err("Failed to load elfcorehdr segment\n");
+		return ret;
+	}
+	pr_debug("Loaded elf core header at 0x%lx, bufsz=0x%lx memsz=0x%lx\n",
+		 image->arch.elfcorehdr_addr, kbuf->bufsz, kbuf->memsz);
+
 	return 0;
 }
 
@@ -1281,5 +1458,9 @@ int arch_kimage_file_post_load_cleanup(struct kimage *image)
 	vfree(image->arch.backup_buf);
 	image->arch.backup_buf = NULL;
 
+	vfree(image->arch.elf_headers);
+	image->arch.elf_headers = NULL;
+	image->arch.elf_headers_sz = 0;
+
 	return kexec_image_post_load_cleanup_default(image);
 }