arm64/crash_core: Export TCR_EL1.T1SZ in vmcoreinfo

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 <[email protected]>
Tested-by: John Donnelly <[email protected]>
Tested-by: Kamlakant Patel <[email protected]>
Tested-by: Amit Daniel Kachhap <[email protected]>
Reviewed-by: James Morse <[email protected]>
Reviewed-by: Amit Daniel Kachhap <[email protected]>
Cc: James Morse <[email protected]>
Cc: Mark Rutland <[email protected]>
Cc: Will Deacon <[email protected]>
Cc: Steve Capper <[email protected]>
Cc: Ard Biesheuvel <[email protected]>
Cc: Dave Anderson <[email protected]>
Cc: Kazuhito Hagio <[email protected]>
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Link: https://lore.kernel.org/r/[email protected]
[[email protected]: removed vabits_actual from the commit log]
Signed-off-by: Catalin Marinas <[email protected]>

Author: Bhupesh Sharma

Documentation/admin-guide/kdump/vmcoreinfo.rst

@@ -404,6 +404,17 @@ KERNELPACMASK
 The mask to extract the Pointer Authentication Code from a kernel virtual
 address.
 
+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
 ===
 

arch/arm64/include/asm/pgtable-hwdef.h

@@ -216,6 +216,7 @@
 #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)

arch/arm64/kernel/crash_core.c

@@ -7,6 +7,14 @@
 #include <linux/crash_core.h>
 #include <asm/cpufeature.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)
 {
@@ -16,6 +24,8 @@ 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());
 	vmcoreinfo_append_str("NUMBER(KERNELPACMASK)=0x%llx\n",
 						system_supports_address_auth() ?