[PATCH v3 05/21] vmcore: allocate buffer for ELF headers on page-sizealignment

[HATAYAMA Daisuke]

Allocate buffer for ELF headers on page-size aligned boudary to
satisfy mmap() requirement. For this, __get_free_pages() is used
instead of kmalloc().

Also, later patch will decrease actually used buffer size for ELF
headers, so it's necessary to keep original buffer size and actually
used buffer size separately. elfcorebuf_sz_orig keeps the original one
and elfcorebuf_sz the actually used one.

Reviewed-by: Zhang Yanfei <zhangyanfei@xxxxxxxxxxxxxx>
Signed-off-by: HATAYAMA Daisuke <d.hatayama@xxxxxxxxxxxxxx>
---

 fs/proc/vmcore.c |   30 +++++++++++++++++++++---------
 1 files changed, 21 insertions(+), 9 deletions(-)

diff --git a/fs/proc/vmcore.c b/fs/proc/vmcore.c
index 7d2dc4c..17e2501 100644
--- a/fs/proc/vmcore.c
+++ b/fs/proc/vmcore.c
@@ -31,6 +31,7 @@ static LIST_HEAD(vmcore_list);
 /* Stores the pointer to the buffer containing kernel elf core headers. */
 static char *elfcorebuf;
 static size_t elfcorebuf_sz;
+static size_t elfcorebuf_sz_orig;
 
 /* Total size of vmcore file. */
 static u64 vmcore_size;
@@ -608,13 +609,16 @@ static int __init parse_crash_elf64_headers(void)
 
 	/* Read in all elf headers. */
 	elfcorebuf_sz = sizeof(Elf64_Ehdr) + ehdr.e_phnum * sizeof(Elf64_Phdr);
-	elfcorebuf = kmalloc(elfcorebuf_sz, GFP_KERNEL);
+	elfcorebuf_sz_orig = elfcorebuf_sz;
+	elfcorebuf = (void *) __get_free_pages(GFP_KERNEL | __GFP_ZERO,
+					       get_order(elfcorebuf_sz_orig));
 	if (!elfcorebuf)
 		return -ENOMEM;
 	addr = elfcorehdr_addr;
 	rc = read_from_oldmem(elfcorebuf, sizeof(Elf64_Ehdr), &addr, 0);
 	if (rc < 0) {
-		kfree(elfcorebuf);
+		free_pages((unsigned long)elfcorebuf,
+			   get_order(elfcorebuf_sz_orig));
 		return rc;
 	}
 	addr = elfcorehdr_addr + ehdr.e_phoff;
@@ -629,13 +633,15 @@ static int __init parse_crash_elf64_headers(void)
 	/* Merge all PT_NOTE headers into one. */
 	rc = merge_note_headers_elf64(elfcorebuf, &elfcorebuf_sz, &vmcore_list);
 	if (rc) {
-		kfree(elfcorebuf);
+		free_pages((unsigned long)elfcorebuf,
+			   get_order(elfcorebuf_sz_orig));
 		return rc;
 	}
 	rc = process_ptload_program_headers_elf64(elfcorebuf, elfcorebuf_sz,
 							&vmcore_list);
 	if (rc) {
-		kfree(elfcorebuf);
+		free_pages((unsigned long)elfcorebuf,
+			   get_order(elfcorebuf_sz_orig));
 		return rc;
 	}
 	set_vmcore_list_offsets_elf64(elfcorebuf, &vmcore_list);
@@ -671,7 +677,9 @@ static int __init parse_crash_elf32_headers(void)
 
 	/* Read in all elf headers. */
 	elfcorebuf_sz = sizeof(Elf32_Ehdr) + ehdr.e_phnum * sizeof(Elf32_Phdr);
-	elfcorebuf = kmalloc(elfcorebuf_sz, GFP_KERNEL);
+	elfcorebuf_sz_orig = elfcorebuf_sz;
+	elfcorebuf = (void *) __get_free_pages(GFP_KERNEL | __GFP_ZERO,
+					       get_order(elfcorebuf_sz_orig));
 	if (!elfcorebuf)
 		return -ENOMEM;
 	addr = elfcorehdr_addr;
@@ -684,7 +692,8 @@ static int __init parse_crash_elf32_headers(void)
 	rc = read_from_oldmem(elfcorebuf + sizeof(Elf32_Ehdr),
 			      ehdr.e_phnum * sizeof(Elf32_Phdr), &addr, 0);
 	if (rc < 0) {
-		kfree(elfcorebuf);
+		free_pages((unsigned long)elfcorebuf,
+			   get_order(elfcorebuf_sz_orig));
 		return rc;
 	}
 	((Elf32_Ehdr *)elfcorebuf)->e_phoff = sizeof(Elf32_Ehdr);
@@ -692,13 +701,15 @@ static int __init parse_crash_elf32_headers(void)
 	/* Merge all PT_NOTE headers into one. */
 	rc = merge_note_headers_elf32(elfcorebuf, &elfcorebuf_sz, &vmcore_list);
 	if (rc) {
-		kfree(elfcorebuf);
+		free_pages((unsigned long)elfcorebuf,
+			   get_order(elfcorebuf_sz_orig));
 		return rc;
 	}
 	rc = process_ptload_program_headers_elf32(elfcorebuf, elfcorebuf_sz,
 								&vmcore_list);
 	if (rc) {
-		kfree(elfcorebuf);
+		free_pages((unsigned long)elfcorebuf,
+			   get_order(elfcorebuf_sz_orig));
 		return rc;
 	}
 	set_vmcore_list_offsets_elf32(elfcorebuf, &vmcore_list);
@@ -780,7 +791,8 @@ void vmcore_cleanup(void)
 		list_del(&m->list);
 		kfree(m);
 	}
-	kfree(elfcorebuf);
+	free_pages((unsigned long)elfcorebuf,
+		   get_order(elfcorebuf_sz_orig));
 	elfcorebuf = NULL;
 }
 EXPORT_SYMBOL_GPL(vmcore_cleanup);

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