On ARM64 platforms the VA_BITS supported by a linux kernel being run
can be selected by setting 'ARM64_VA_BITS_*' (see 'arch/arm64/Kconfig'
for details).
Now, to determine the 'info->page_offset' in arm64 makedumpfile
context ('arch/arm64.c') we need to determine the VA_BITS which was
selected by the underlying linux kernel.
There can be several ways to determine the VA_BITS, out of which
reading the '_stext' symbol and calculating the 'va_bits' using the
same is the simplest yet portable method.
For reading the kernel symbols like '_stext', we can read the
'/proc/kallsyms' file which contains these symbols and
works even in case of KASLR enabled arm64 kernels, as in those cases,
the '_stext' symbol will end up being randomized and hence
cannot be correctly read from the 'vmlinux' file.
Signed-off-by: Bhupesh Sharma <bhsharma@xxxxxxxxxx>
---
arch/arm64.c | 78 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++----
1 file changed, 74 insertions(+), 4 deletions(-)
diff --git a/arch/arm64.c b/arch/arm64.c
index 25d7a1f4db98..8a71abdabd59 100644
--- a/arch/arm64.c
+++ b/arch/arm64.c
@@ -48,6 +48,12 @@ static unsigned long kimage_voffset;
#define SZ_64K (64 * 1024)
#define SZ_128M (128 * 1024 * 1024)
+#define PAGE_OFFSET_36 ((0xffffffffffffffffUL) << 36)
+#define PAGE_OFFSET_39 ((0xffffffffffffffffUL) << 39)
+#define PAGE_OFFSET_42 ((0xffffffffffffffffUL) << 42)
+#define PAGE_OFFSET_47 ((0xffffffffffffffffUL) << 47)
+#define PAGE_OFFSET_48 ((0xffffffffffffffffUL) << 48)
+
#define pgd_val(x) ((x).pgd)
#define pud_val(x) (pgd_val((x).pgd))
#define pmd_val(x) (pud_val((x).pud))
@@ -140,8 +146,6 @@ pud_offset(pgd_t *pgda, pgd_t *pgdv, unsigned long vaddr)
static int calculate_plat_config(void)
{
- va_bits = NUMBER(VA_BITS);
-
/* derive pgtable_level as per arch/arm64/Kconfig */
if ((PAGESIZE() == SZ_16K && va_bits == 36) ||
(PAGESIZE() == SZ_64K && va_bits == 42)) {
@@ -177,6 +181,45 @@ get_phys_base_arm64(void)
return TRUE;
}
+ulong
+get_stext_symbol(void)
+{
+ int found;
+ FILE *fp;
+ char buf[BUFSIZE];
+ char *kallsyms[MAXARGS];
+ ulong kallsym;
+
+ if (!file_exists("/proc/kallsyms")) {
+ ERRMSG("(%s) does not exist, will not be able to read symbols. %s\n",
+ "/proc/kallsyms", strerror(errno));
+ return FALSE;
+ }
+
+ if ((fp = fopen("/proc/kallsyms", "r")) == NULL) {
+ ERRMSG("Cannot open (%s) to read symbols. %s\n",
+ "/proc/kallsyms", strerror(errno));
+ return FALSE;
+ }
+
+ found = FALSE;
+ kallsym = 0;
+
+ while (!found && fgets(buf, BUFSIZE, fp) &&
+ (parse_line(buf, kallsyms) == 3)) {
+ if (hexadecimal(kallsyms[0], 0) &&
+ STREQ(kallsyms[2], "_stext")) {
+ kallsym = htol(kallsyms[0], RETURN_ON_ERROR,
+ NULL);
+ found = TRUE;
+ break;
+ }
+ }
+ fclose(fp);
+
+ return(found ? kallsym : FALSE);
+}
+
int
get_machdep_info_arm64(void)
{
@@ -188,12 +231,10 @@ get_machdep_info_arm64(void)
kimage_voffset = NUMBER(kimage_voffset);
info->max_physmem_bits = PHYS_MASK_SHIFT;
info->section_size_bits = SECTIONS_SIZE_BITS;
- info->page_offset = 0xffffffffffffffffUL << (va_bits - 1);
DEBUG_MSG("kimage_voffset : %lx\n", kimage_voffset);
DEBUG_MSG("max_physmem_bits : %lx\n", info->max_physmem_bits);
DEBUG_MSG("section_size_bits: %lx\n", info->section_size_bits);
- DEBUG_MSG("page_offset : %lx\n", info->page_offset);
return TRUE;
}
@@ -219,6 +260,35 @@ get_xen_info_arm64(void)
int
get_versiondep_info_arm64(void)
{
+ ulong _stext;
+
+ _stext = get_stext_symbol();
+ if (!_stext) {
+ ERRMSG("Can't get the symbol of _stext.\n");
+ return FALSE;
+ }
+
+ /* Derive va_bits as per arch/arm64/Kconfig */
+ if ((_stext & PAGE_OFFSET_36) == PAGE_OFFSET_36) {
+ va_bits = 36;
+ } else if ((_stext & PAGE_OFFSET_39) == PAGE_OFFSET_39) {
+ va_bits = 39;
+ } else if ((_stext & PAGE_OFFSET_42) == PAGE_OFFSET_42) {
+ va_bits = 42;
+ } else if ((_stext & PAGE_OFFSET_47) == PAGE_OFFSET_47) {
+ va_bits = 47;
+ } else if ((_stext & PAGE_OFFSET_48) == PAGE_OFFSET_48) {
+ va_bits = 48;
+ } else {
+ ERRMSG("Cannot find a proper _stext for calculating VA_BITS\n");
+ return FALSE;
+ }
+
+ info->page_offset = (0xffffffffffffffffUL) << (va_bits - 1);
+
+ DEBUG_MSG("page_offset=%lx, va_bits=%d\n", info->page_offset,
+ va_bits);
+
return TRUE;
}
--
2.7.4
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