(2013/05/15 0:35), Vivek Goyal wrote:
On Tue, May 14, 2013 at 10:57:35AM +0900, HATAYAMA Daisuke wrote:
The reasons why we don't allocate ELF note segment in the 1st kernel
(old memory) on page boundary is to keep backward compatibility for
old kernels, and that if doing so, we waste not a little memory due to
round-up operation to fit the memory to page boundary since most of
the buffers are in per-cpu area.
ELF notes are per-cpu, so total size of ELF note segments depends on
number of CPUs. The current maximum number of CPUs on x86_64 is 5192,
and there's already system with 4192 CPUs in SGI, where total size
amounts to 1MB. This can be larger in the near future or possibly even
now on another architecture that has larger size of note per a single
cpu. Thus, to avoid the case where memory allocation for large block
fails, we allocate vmcore objects on vmalloc memory.
This patch adds elfnotesegbuf and elfnotesegbuf_sz variables to keep
pointer to the ELF note segment buffer and its size. There's no longer
the vmcore object that corresponds to the ELF note segment in
vmcore_list. Accordingly, read_vmcore() has new case for ELF note
segment and set_vmcore_list_offsets_elf{64,32}() and other helper
functions starts calculating offset from sum of size of ELF headers
and size of ELF note segment.
Signed-off-by: HATAYAMA Daisuke <d.hatayama@xxxxxxxxxxxxxx>
---
fs/proc/vmcore.c | 225 ++++++++++++++++++++++++++++++++++++++++--------------
1 files changed, 165 insertions(+), 60 deletions(-)
diff --git a/fs/proc/vmcore.c b/fs/proc/vmcore.c
index 48886e6..795efd2 100644
--- a/fs/proc/vmcore.c
+++ b/fs/proc/vmcore.c
@@ -34,6 +34,9 @@ static char *elfcorebuf;
static size_t elfcorebuf_sz;
static size_t elfcorebuf_sz_orig;
+static char *elfnotesegbuf;
+static size_t elfnotesegbuf_sz;
How about calling these just elfnotes_buf and elfnotes_sz.
[..]
+/* Merges all the PT_NOTE headers into one. */
+static int __init merge_note_headers_elf64(char *elfptr, size_t *elfsz,
+ char **notesegptr, size_t *notesegsz,
+ struct list_head *vc_list)
+{
+ int i, nr_ptnote=0, rc=0;
+ char *tmp;
+ Elf64_Ehdr *ehdr_ptr;
+ Elf64_Phdr phdr;
+ u64 phdr_sz = 0, note_off;
+ struct vm_struct *vm;
+
+ ehdr_ptr = (Elf64_Ehdr *)elfptr;
+
+ /* The first path calculates the number of PT_NOTE entries and
+ * total size of ELF note segment. */
+ rc = process_note_headers_elf64(ehdr_ptr, &nr_ptnote, &phdr_sz, NULL);
+ if (rc < 0)
+ return rc;
+
+ *notesegsz = roundup(phdr_sz, PAGE_SIZE);
+ *notesegptr = vzalloc(*notesegsz);
+ if (!*notesegptr)
+ return -ENOMEM;
+
+ vm = find_vm_area(*notesegptr);
+ BUG_ON(!vm);
+ vm->flags |= VM_USERMAP;
+
+ /* The second path copies the ELF note segment in the ELF note
+ * segment buffer. */
+ rc = process_note_headers_elf64(ehdr_ptr, NULL, NULL, *notesegptr);
So same function process_note_headers_elf64() is doing two different
things based on parameters passed. Please create two new functions
to do two different things and name these appropriately.
Say
get_elf_note_number_and_size()
copy_elf_notes()
I see. Similar to other functions, 32-bit and 64-bit versions are
needed. So I give them symbols:
get_note_number_and_size_elf64()
copy_notes_elf64()
and elf32 counterpart.
+ if (rc < 0)
+ return rc;
+
/* Prepare merged PT_NOTE program header. */
phdr.p_type = PT_NOTE;
phdr.p_flags = 0;
@@ -304,23 +364,18 @@ static int __init merge_note_headers_elf64(char *elfptr, size_t *elfsz,
return 0;
}
-/* Merges all the PT_NOTE headers into one. */
-static int __init merge_note_headers_elf32(char *elfptr, size_t *elfsz,
- struct list_head *vc_list)
+static int __init process_note_headers_elf32(const Elf32_Ehdr *ehdr_ptr,
+ int *nr_ptnotep, u64 *phdr_szp,
+ char *notesegp)
Can you please describe function parameters at the beginning of function
in a comment. Things are gettting little confusing now.
What does notesegp signify? phdr_szp could be simply *phdr_sz,
nr_ptnotesp could be *nr_notes. Please simplify the naming a bit.
Seems too twisted to me.
I see. I'll reflect that in addition to your other comments.
--
Thanks.
HATAYAMA, Daisuke
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