[SRU][Focal][PATCH] arm64/crash_core: Export TCR_EL1.T1SZ in vmcoreinfo

[Ioanna Alifieraki]

From: Bhupesh Sharma <bhsharma at redhat.com>

BugLink: https://bugs.launchpad.net/bugs/1919275

TCR_EL1.TxSZ, which controls the VA space size, is configured by a
single kernel image to support either 48-bit or 52-bit VA space.

If the ARMv8.2-LVA optional feature is present and we are running
with a 64KB page size, then it is possible to use 52-bits of address
space for both userspace and kernel addresses. However, any kernel
binary that supports 52-bit must also be able to fall back to 48-bit
at early boot time if the hardware feature is not present.

Since TCR_EL1.T1SZ indicates the size of the memory region addressed by
TTBR1_EL1, export the same in vmcoreinfo. User-space utilities like
makedumpfile and crash-utility need to read this value from vmcoreinfo
for determining if a virtual address lies in the linear map range.

While at it also add documentation for TCR_EL1.T1SZ variable being
added to vmcoreinfo.

It indicates the size offset of the memory region addressed by
TTBR1_EL1.

Signed-off-by: Bhupesh Sharma <bhsharma at redhat.com>
Tested-by: John Donnelly <john.p.donnelly at oracle.com>
Tested-by: Kamlakant Patel <kamlakantp at marvell.com>
Tested-by: Amit Daniel Kachhap <amit.kachhap at arm.com>
Reviewed-by: James Morse <james.morse at arm.com>
Reviewed-by: Amit Daniel Kachhap <amit.kachhap at arm.com>
Cc: James Morse <james.morse at arm.com>
Cc: Mark Rutland <mark.rutland at arm.com>
Cc: Will Deacon <will at kernel.org>
Cc: Steve Capper <steve.capper at arm.com>
Cc: Ard Biesheuvel <ard.biesheuvel at linaro.org>
Cc: Dave Anderson <anderson at redhat.com>
Cc: Kazuhito Hagio <k-hagio at ab.jp.nec.com>
Cc: linux-arm-kernel at lists.infradead.org
Cc: linux-kernel at vger.kernel.org
Cc: kexec at lists.infradead.org
Link: https://lore.kernel.org/r/1589395957-24628-3-git-send-email-bhsharma@redhat.com
[catalin.marinas at arm.com: removed vabits_actual from the commit log]
Signed-off-by: Catalin Marinas <catalin.marinas at arm.com>
(backported from commit bbdbc11804ff0b4130e7550113b452e96a74d16e)
[hook 1: resolve conflict in documentation]
Signed-off-by: Ioanna Alifieraki <ioanna-maria.alifieraki at canonical.com>
---
 Documentation/admin-guide/kdump/vmcoreinfo.rst | 11 +++++++++++
 arch/arm64/include/asm/pgtable-hwdef.h         |  1 +
 arch/arm64/kernel/crash_core.c                 | 10 ++++++++++
 3 files changed, 22 insertions(+)

diff --git a/Documentation/admin-guide/kdump/vmcoreinfo.rst b/Documentation/admin-guide/kdump/vmcoreinfo.rst
index 007a6b86e0ee..ba1aed57e55d 100644
--- a/Documentation/admin-guide/kdump/vmcoreinfo.rst
+++ b/Documentation/admin-guide/kdump/vmcoreinfo.rst
@@ -393,6 +393,17 @@ KERNELOFFSET
 The kernel randomization offset. Used to compute the page offset. If
 KASLR is disabled, this value is zero.
 
+TCR_EL1.T1SZ
+------------
+
+Indicates the size offset of the memory region addressed by TTBR1_EL1.
+The region size is 2^(64-T1SZ) bytes.
+
+TTBR1_EL1 is the table base address register specified by ARMv8-A
+architecture which is used to lookup the page-tables for the Virtual
+addresses in the higher VA range (refer to ARMv8 ARM document for
+more details).
+
 arm
 ===
 
diff --git a/arch/arm64/include/asm/pgtable-hwdef.h b/arch/arm64/include/asm/pgtable-hwdef.h
index 3df60f97da1f..a0f789fa25f3 100644
--- a/arch/arm64/include/asm/pgtable-hwdef.h
+++ b/arch/arm64/include/asm/pgtable-hwdef.h
@@ -215,6 +215,7 @@
 #define TCR_TxSZ(x)		(TCR_T0SZ(x) | TCR_T1SZ(x))
 #define TCR_TxSZ_WIDTH		6
 #define TCR_T0SZ_MASK		(((UL(1) << TCR_TxSZ_WIDTH) - 1) << TCR_T0SZ_OFFSET)
+#define TCR_T1SZ_MASK		(((UL(1) << TCR_TxSZ_WIDTH) - 1) << TCR_T1SZ_OFFSET)
 
 #define TCR_EPD0_SHIFT		7
 #define TCR_EPD0_MASK		(UL(1) << TCR_EPD0_SHIFT)
diff --git a/arch/arm64/kernel/crash_core.c b/arch/arm64/kernel/crash_core.c
index ca4c3e12d8c5..ec8095bfe23e 100644
--- a/arch/arm64/kernel/crash_core.c
+++ b/arch/arm64/kernel/crash_core.c
@@ -6,6 +6,14 @@
 
 #include <linux/crash_core.h>
 #include <asm/memory.h>
+#include <asm/pgtable-hwdef.h>
+
+static inline u64 get_tcr_el1_t1sz(void);
+
+static inline u64 get_tcr_el1_t1sz(void)
+{
+	return (read_sysreg(tcr_el1) & TCR_T1SZ_MASK) >> TCR_T1SZ_OFFSET;
+}
 
 void arch_crash_save_vmcoreinfo(void)
 {
@@ -15,5 +23,7 @@ void arch_crash_save_vmcoreinfo(void)
 						kimage_voffset);
 	vmcoreinfo_append_str("NUMBER(PHYS_OFFSET)=0x%llx\n",
 						PHYS_OFFSET);
+	vmcoreinfo_append_str("NUMBER(TCR_EL1_T1SZ)=0x%llx\n",
+						get_tcr_el1_t1sz());
 	vmcoreinfo_append_str("KERNELOFFSET=%lx\n", kaslr_offset());
 }
-- 
2.17.1