With ARMv8.2-LVA architecture extension availability, arm64 hardware
which supports this extension can support upto 52-bit virtual
addresses. It is specially useful for having a 52-bit user-space virtual
address space while the kernel can still retain 48-bit/52-bit virtual
addressing.
Since at the moment we enable the support of this extension in the
kernel via a CONFIG flag (CONFIG_ARM64_VA_BITS_52), so there are
no clear mechanisms in user-space to determine this CONFIG
flag value and use it to determine the kernel-space VA address range
values.
'makedumpfile' can instead use 'TCR_EL1.T1SZ' value from vmcoreinfo
which indicates the size offset of the memory region addressed by
TTBR1_EL1 (and hence can be used for determining the
vabits_actual value).
Using the vmcoreinfo variable exported by kernel commit
bbdbc11804ff ("arm64/crash_core: Export TCR_EL1.T1SZ in vmcoreinfo"),
the user-space can use the following computation for determining whether
an address lies in the linear map range (for newer kernels >= 5.4):
#define __is_lm_address(addr) (!(((u64)addr) & BIT(vabits_actual - 1)))
Note that for the --mem-usage case though we need to calculate
vabits_actual value before the vmcoreinfo read functionality is ready,
so we can instead read the architecture register ID_AA64MMFR2_EL1
directly to see if the underlying hardware supports 52-bit addressing
and accordingly set vabits_actual as:
read_id_aa64mmfr2_el1();
if (hardware supports 52-bit addressing)
vabits_actual = 52;
else
vabits_actual = va_bits value calculated via _stext symbol;
Also make sure that the page_offset, is_linear_addr(addr) and __pa()
calculations work both for older (< 5.4) and newer kernels (>= 5.4).
I have tested several combinations with both kernel categories
[for e.g. with different VA (39, 42, 48 and 52-bit) and PA combinations
(48 and 52-bit)] on at-least 3 different boards.
Unfortunately, this means that we need to call 'populate_kernel_version()'
earlier 'get_page_offset_arm64()' as 'info->kernel_version' remains
uninitialized before its first use otherwise.
This patch is in accordance with ARMv8 Architecture Reference Manual
Cc: Kazuhito Hagio <k-ha...@ab.jp.nec.com>
Cc: John Donnelly <john.p.donne...@oracle.com>
Cc: kexec@lists.infradead.org
Signed-off-by: Bhupesh Sharma <bhsha...@redhat.com>
---
arch/arm64.c | 233 ++++++++++++++++++++++++++++++++++++++++++-------
common.h | 10 +++
makedumpfile.c | 4 +-
makedumpfile.h | 6 +-
4 files changed, 218 insertions(+), 35 deletions(-)
diff --git a/arch/arm64.c b/arch/arm64.c
index 709e0a506916..ccaa8641ca66 100644
--- a/arch/arm64.c
+++ b/arch/arm64.c
@@ -19,10 +19,23 @@
#ifdef __aarch64__
+#include <asm/hwcap.h>
+#include <sys/auxv.h>
#include "../elf_info.h"
#include "../makedumpfile.h"
#include "../print_info.h"
+/* ID_AA64MMFR2_EL1 related helpers: */
+#define ID_AA64MMFR2_LVA_SHIFT 16
+#define ID_AA64MMFR2_LVA_MASK (0xf << ID_AA64MMFR2_LVA_SHIFT)
+
+/* CPU feature ID registers */
+#define get_cpu_ftr(id) ({
\
+ unsigned long __val;
\
+ asm volatile("mrs %0, " __stringify(id) : "=r" (__val));
\
+ __val;
\
+})
+
typedef struct {
unsigned long pgd;
} pgd_t;
@@ -47,6 +60,7 @@ typedef struct {
static int lpa_52_bit_support_available;
static int pgtable_level;
static int va_bits;
+static int vabits_actual;
static unsigned long kimage_voffset;
#define SZ_4K 4096
@@ -58,7 +72,6 @@ static unsigned long kimage_voffset;
#define PAGE_OFFSET_42 ((0xffffffffffffffffUL) << 42)
#define PAGE_OFFSET_47 ((0xffffffffffffffffUL) << 47)
#define PAGE_OFFSET_48 ((0xffffffffffffffffUL) << 48)
-#define PAGE_OFFSET_52 ((0xffffffffffffffffUL) << 52)
#define pgd_val(x) ((x).pgd)
#define pud_val(x) (pgd_val((x).pgd))
@@ -219,13 +232,25 @@ pmd_page_paddr(pmd_t pmd)
#define pte_index(vaddr) (((vaddr) >> PAGESHIFT()) &
(PTRS_PER_PTE - 1))
#define pte_offset(dir, vaddr) (pmd_page_paddr((*dir)) +
pte_index(vaddr) * sizeof(pte_t))
+/*
+ * The linear kernel range starts at the bottom of the virtual address
+ * space. Testing the top bit for the start of the region is a
+ * sufficient check and avoids having to worry about the tag.
+ */
+#define is_linear_addr(addr) ((info->kernel_version < KERNEL_VERSION(5, 4,
0)) ? \
+ (!!((unsigned long)(addr) & (1UL << (vabits_actual - 1)))) : \
+ (!((unsigned long)(addr) & (1UL << (vabits_actual - 1)))))
+
static unsigned long long
__pa(unsigned long vaddr)
{
if (kimage_voffset == NOT_FOUND_NUMBER ||
- (vaddr >= PAGE_OFFSET))
- return (vaddr - PAGE_OFFSET + info->phys_base);
- else
+ is_linear_addr(vaddr)) {
+ if (info->kernel_version < KERNEL_VERSION(5, 4, 0))
+ return ((vaddr & ~PAGE_OFFSET) + info->phys_base);
+ else
+ return (vaddr + info->phys_base - PAGE_OFFSET);
+ } else
return (vaddr - kimage_voffset);
}
@@ -254,6 +279,7 @@ static int calculate_plat_config(void)
(PAGESIZE() == SZ_64K && va_bits == 42)) {
pgtable_level = 2;
} else if ((PAGESIZE() == SZ_64K && va_bits == 48) ||
+ (PAGESIZE() == SZ_64K && va_bits == 52) ||
(PAGESIZE() == SZ_4K && va_bits == 39) ||
(PAGESIZE() == SZ_16K && va_bits == 47)) {
pgtable_level = 3;
@@ -288,8 +314,14 @@ get_phys_base_arm64(void)
return TRUE;
}
+ /* Ignore the 1st PT_LOAD */
if (get_num_pt_loads() && PAGE_OFFSET) {
- for (i = 0;
+ /* Note that the following loop starts with i = 1.
+ * This is required to make sure that the following logic
+ * works both for old and newer kernels (with flipped
+ * VA space, i.e. >= 5.4.0)
+ */
+ for (i = 1;
get_pt_load(i, &phys_start, NULL, &virt_start, NULL);
i++) {
if (virt_start != NOT_KV_ADDR
@@ -346,6 +378,139 @@ get_stext_symbol(void)
return(found ? kallsym : FALSE);
}
+static int
+get_va_bits_from_stext_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. Note that this is a
+ * best case approximation at the moment, as there can be
+ * inconsistencies in this calculation (for e.g., for
+ * 52-bit kernel VA case, the 48th bit is set in
+ * the _stext symbol).
+ *
+ * So, we need to rely on the vabits_actual symbol in the
+ * vmcoreinfo or read via system register for a accurate value
+ * of the virtual addressing supported by the underlying kernel.
+ */
+ if ((_stext & PAGE_OFFSET_48) == PAGE_OFFSET_48) {
+ va_bits = 48;
+ } else if ((_stext & PAGE_OFFSET_47) == PAGE_OFFSET_47) {
+ va_bits = 47;
+ } else if ((_stext & PAGE_OFFSET_42) == PAGE_OFFSET_42) {
+ va_bits = 42;
+ } else if ((_stext & PAGE_OFFSET_39) == PAGE_OFFSET_39) {
+ va_bits = 39;
+ } else if ((_stext & PAGE_OFFSET_36) == PAGE_OFFSET_36) {
+ va_bits = 36;
+ } else {
+ ERRMSG("Cannot find a proper _stext for calculating VA_BITS\n");
+ return FALSE;
+ }
+
+ DEBUG_MSG("va_bits : %d (approximation via _stext)\n", va_bits);
+
+ return TRUE;
+}
+
+/* Note that its important to note that the
+ * ID_AA64MMFR2_EL1 architecture register can be read
+ * only when we give an .arch hint to the gcc/binutils,
+ * so we use the gcc construct '__attribute__ ((target ("arch=armv8.2-a")))'
+ * here which is an .arch directive (see AArch64-Target-selection-directives
+ * documentation from ARM for details). This is required only for
+ * this function to make sure it compiles well with gcc/binutils.
+ */
+__attribute__ ((target ("arch=armv8.2-a")))
+static unsigned long
+read_id_aa64mmfr2_el1(void)
+{
+ return get_cpu_ftr(ID_AA64MMFR2_EL1);
+}
+
+static int
+get_vabits_actual_from_id_aa64mmfr2_el1(void)
+{
+ int l_vabits_actual;
+ unsigned long val;
+
+ /* Check if ID_AA64MMFR2_EL1 CPU-ID register indicates
+ * ARMv8.2/LVA support:
+ * VARange, bits [19:16]
+ * From ARMv8.2:
+ * Indicates support for a larger virtual address.
+ * Defined values are:
+ * 0b0000 VMSAv8-64 supports 48-bit VAs.
+ * 0b0001 VMSAv8-64 supports 52-bit VAs when using the 64KB
+ * page size. The other translation granules support
+ * 48-bit VAs.
+ *
+ * See ARMv8 ARM for more details.
+ */
+ if (!(getauxval(AT_HWCAP) & HWCAP_CPUID)) {
+ ERRMSG("arm64 CPUID registers unavailable.\n");
+ return ERROR;
+ }
+
+ val = read_id_aa64mmfr2_el1();
+ val = (val & ID_AA64MMFR2_LVA_MASK) > ID_AA64MMFR2_LVA_SHIFT;
+
+ if ((val == 0x1) && (PAGESIZE() == SZ_64K))
+ l_vabits_actual = 52;
+ else
+ l_vabits_actual = 48;
+
+ return l_vabits_actual;
+}
+
+static void
+get_page_offset_arm64(void)
+{
+ /* Check if 'vabits_actual' is initialized yet.
+ * If not, our best bet is to read ID_AA64MMFR2_EL1 CPU-ID
+ * register.
+ */
+ if (!vabits_actual) {
+ vabits_actual = get_vabits_actual_from_id_aa64mmfr2_el1();
+ if ((vabits_actual == ERROR) || (vabits_actual != 52)) {
+ /* If we cannot read ID_AA64MMFR2_EL1 arch
+ * register or if this register does not indicate
+ * support for a larger virtual address, our last
+ * option is to use the VA_BITS to calculate the
+ * PAGE_OFFSET value, i.e. vabits_actual = VA_BITS.
+ */
+ vabits_actual = va_bits;
+ DEBUG_MSG("vabits_actual : %d (approximation via
va_bits)\n",
+ vabits_actual);
+ } else
+ DEBUG_MSG("vabits_actual : %d (via id_aa64mmfr2_el1)\n",
+ vabits_actual);
+ }
+
+ if (!populate_kernel_version()) {
+ ERRMSG("Cannot get information about current kernel\n");
+ return;
+ }
+
+ /* See arch/arm64/include/asm/memory.h for more details of
+ * the PAGE_OFFSET calculation.
+ */
+ if (info->kernel_version < KERNEL_VERSION(5, 4, 0))
+ info->page_offset = ((0xffffffffffffffffUL) -
+ ((1UL) << (vabits_actual - 1)) + 1);
+ else
+ info->page_offset = (-(1UL << vabits_actual));
+
+ DEBUG_MSG("page_offset : %lx (via vabits_actual)\n",
+ info->page_offset);
+}
+
int
get_machdep_info_arm64(void)
{
@@ -360,8 +525,33 @@ get_machdep_info_arm64(void)
/* Check if va_bits is still not initialized. If still 0, call
* get_versiondep_info() to initialize the same.
*/
+ if (NUMBER(VA_BITS) != NOT_FOUND_NUMBER) {
+ va_bits = NUMBER(VA_BITS);
+ DEBUG_MSG("va_bits : %d (vmcoreinfo)\n",
+ va_bits);
+ }
+
+ /* Check if va_bits is still not initialized. If still 0, call
+ * get_versiondep_info() to initialize the same from _stext
+ * symbol.
+ */
if (!va_bits)
- get_versiondep_info_arm64();
+ if (get_va_bits_from_stext_arm64() == FALSE)
+ return FALSE;
+
+ /* See TCR_EL1, Translation Control Register (EL1) register
+ * description in the ARMv8 Architecture Reference Manual.
+ * Basically, we can use the TCR_EL1.T1SZ
+ * value to determine the virtual addressing range supported
+ * in the kernel-space (i.e. vabits_actual).
+ */
+ if (NUMBER(TCR_EL1_T1SZ) != NOT_FOUND_NUMBER) {
+ vabits_actual = 64 - NUMBER(TCR_EL1_T1SZ);
+ DEBUG_MSG("vabits_actual : %d (vmcoreinfo)\n",
+ vabits_actual);
+ }
+
+ get_page_offset_arm64();
if (!calculate_plat_config()) {
ERRMSG("Can't determine platform config values\n");
@@ -399,34 +589,11 @@ 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);
+ if (!va_bits)
+ if (get_va_bits_from_stext_arm64() == FALSE)
+ return FALSE;
- DEBUG_MSG("va_bits : %d\n", va_bits);
- DEBUG_MSG("page_offset : %lx\n", info->page_offset);
+ get_page_offset_arm64();
return TRUE;
}
diff --git a/common.h b/common.h
index 6e2f657a79c7..1901df195e9d 100644
--- a/common.h
+++ b/common.h
@@ -50,5 +50,15 @@
#define NOT_PADDR (ULONGLONG_MAX)
#define BADADDR ((ulong)(-1))
+/* Indirect stringification. Doing two levels allows the parameter to be a
+ * macro itself. For example, compile with -DFOO=bar, __stringify(FOO)
+ * converts to "bar".
+ *
+ * Copied from linux source: 'include/linux/stringify.h'
+ */
+
+#define __stringify_1(x...) #x
+#define __stringify(x...) __stringify_1(x)
+
#endif /* COMMON_H */
diff --git a/makedumpfile.c b/makedumpfile.c
index 4c4251ea8719..5ab82fd3cf14 100644
--- a/makedumpfile.c
+++ b/makedumpfile.c
@@ -1133,7 +1133,7 @@ fallback_to_current_page_size(void)
return TRUE;
}
-static int populate_kernel_version(void)
+int populate_kernel_version(void)
{
struct utsname utsname;
@@ -2323,6 +2323,7 @@ write_vmcoreinfo_data(void)
WRITE_NUMBER("HUGETLB_PAGE_DTOR", HUGETLB_PAGE_DTOR);
#ifdef __aarch64__
WRITE_NUMBER("VA_BITS", VA_BITS);
+ WRITE_NUMBER_UNSIGNED("TCR_EL1_T1SZ", TCR_EL1_T1SZ);
WRITE_NUMBER_UNSIGNED("PHYS_OFFSET", PHYS_OFFSET);
WRITE_NUMBER_UNSIGNED("kimage_voffset", kimage_voffset);
#endif
@@ -2729,6 +2730,7 @@ read_vmcoreinfo(void)
READ_NUMBER("KERNEL_IMAGE_SIZE", KERNEL_IMAGE_SIZE);
#ifdef __aarch64__
READ_NUMBER("VA_BITS", VA_BITS);
+ READ_NUMBER_UNSIGNED("TCR_EL1_T1SZ", TCR_EL1_T1SZ);
READ_NUMBER_UNSIGNED("PHYS_OFFSET", PHYS_OFFSET);
READ_NUMBER_UNSIGNED("kimage_voffset", kimage_voffset);
#endif
diff --git a/makedumpfile.h b/makedumpfile.h
index 03fb4ce06872..dc65f002bad6 100644
--- a/makedumpfile.h
+++ b/makedumpfile.h
@@ -974,7 +974,9 @@ unsigned long long vaddr_to_paddr_arm64(unsigned long
vaddr);
int get_versiondep_info_arm64(void);
int get_xen_basic_info_arm64(void);
int get_xen_info_arm64(void);
-#define paddr_to_vaddr_arm64(X) (((X) - info->phys_base) | PAGE_OFFSET)
+#define paddr_to_vaddr_arm64(X) ((info->kernel_version < KERNEL_VERSION(5, 4,
0)) ? \
+ ((X) - (info->phys_base - PAGE_OFFSET)) :
\
+ (((X) - info->phys_base) | PAGE_OFFSET))
#define find_vmemmap() stub_false()
#define vaddr_to_paddr(X) vaddr_to_paddr_arm64(X)
@@ -1938,6 +1940,7 @@ struct number_table {
long KERNEL_IMAGE_SIZE;
#ifdef __aarch64__
long VA_BITS;
+ unsigned long TCR_EL1_T1SZ;
unsigned long PHYS_OFFSET;
unsigned long kimage_voffset;
#endif
@@ -2389,5 +2392,6 @@ ulong htol(char *s, int flags);
int hexadecimal(char *s, int count);
int decimal(char *s, int count);
int file_exists(char *file);
+int populate_kernel_version(void);
#endif /* MAKEDUMPFILE_H */
--
2.26.2
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