[PATCH 4/4] mips: vmcore_info: export mips arch-specific struct offsets to vmcoreinfo

[Pnina Feder]

Export MIPS architecture-specific struct offsets needed by the
vmcore-tasks tool, including signal frame layouts and register
context structures used to reconstruct user-space register state
from a vmcore dump.

Signed-off-by: Pnina Feder <pnina.feder at mobileye.com>
---
 .../admin-guide/kdump/vmcoreinfo.rst          | 34 +++++++++++++++++++
 arch/mips/kernel/Makefile                     |  1 +
 arch/mips/kernel/signal.c                     |  8 +++++
 arch/mips/kernel/vmcore_info.c                | 22 ++++++++++++
 4 files changed, 65 insertions(+)
 create mode 100644 arch/mips/kernel/vmcore_info.c

diff --git a/Documentation/admin-guide/kdump/vmcoreinfo.rst b/Documentation/admin-guide/kdump/vmcoreinfo.rst
index 3c364434b846..4af32ddf5615 100644
--- a/Documentation/admin-guide/kdump/vmcoreinfo.rst
+++ b/Documentation/admin-guide/kdump/vmcoreinfo.rst
@@ -494,6 +494,40 @@ Used to get the vmalloc_start address from the high_memory symbol.
 
 The maximum number of CPUs.
 
+MIPS
+====
+
+(rt_sigframe, rs_uc)
+--------------------
+
+Offset of the ucontext member within the MIPS rt_sigframe structure.
+Used to locate the signal context within a signal frame on the user
+stack.
+
+(sigcontext, sc_regs)
+---------------------
+
+Offset of the saved register array within struct sigcontext. Used to
+extract user-space register state from signal frames in a vmcore dump.
+
+PAGE_SHIFT
+----------
+
+The base-2 logarithm of the page size. Used for page frame number
+calculations during address translation.
+
+_PFN_MASK|_PAGE_PRESENT|_PAGE_VALID|_PAGE_GLOBAL
+-------------------------------------------------
+
+Page table entry bit masks and flags. Used for walking MIPS page tables
+and translating virtual to physical addresses in a vmcore dump.
+
+PTRS_PER_PGD|PTRS_PER_PMD|PTRS_PER_PTE
+---------------------------------------
+
+Number of entries per page table level. Used for page table walking
+during virtual-to-physical address translation.
+
 powerpc
 =======
 
diff --git a/arch/mips/kernel/Makefile b/arch/mips/kernel/Makefile
index 95a1e674fd67..99f2961f6ee1 100644
--- a/arch/mips/kernel/Makefile
+++ b/arch/mips/kernel/Makefile
@@ -24,6 +24,7 @@ CFLAGS_REMOVE_perf_event_mipsxx.o = $(CC_FLAGS_FTRACE)
 endif
 
 obj-$(CONFIG_CEVT_BCM1480)	+= cevt-bcm1480.o
+obj-$(CONFIG_VMCORE_INFO)	+= vmcore_info.o
 obj-$(CONFIG_CEVT_R4K)		+= cevt-r4k.o
 obj-$(CONFIG_CEVT_DS1287)	+= cevt-ds1287.o
 obj-$(CONFIG_CEVT_GT641XX)	+= cevt-gt641xx.o
diff --git a/arch/mips/kernel/signal.c b/arch/mips/kernel/signal.c
index 4a10f18a8806..f2241f52fa17 100644
--- a/arch/mips/kernel/signal.c
+++ b/arch/mips/kernel/signal.c
@@ -26,6 +26,7 @@
 #include <linux/syscalls.h>
 #include <linux/uaccess.h>
 #include <linux/resume_user_mode.h>
+#include <linux/vmcore_info.h>
 
 #include <asm/abi.h>
 #include <asm/asm.h>
@@ -62,6 +63,13 @@ struct rt_sigframe {
 	struct ucontext rs_uc;
 };
 
+#ifdef CONFIG_VMCORE_INFO
+void mips_rt_signal_frame(void)
+{
+	VMCOREINFO_OFFSET(rt_sigframe, rs_uc);
+}
+#endif
+
 #ifdef CONFIG_MIPS_FP_SUPPORT
 
 /*
diff --git a/arch/mips/kernel/vmcore_info.c b/arch/mips/kernel/vmcore_info.c
new file mode 100644
index 000000000000..5d7fdc662065
--- /dev/null
+++ b/arch/mips/kernel/vmcore_info.c
@@ -0,0 +1,22 @@
+// SPDX-License-Identifier: GPL-2.0-only
+
+#include <linux/vmcore_info.h>
+
+#include <asm/pgtable.h>
+#include <asm/sigcontext.h>
+
+extern void mips_rt_signal_frame(void);
+
+void arch_crash_save_vmcoreinfo(void)
+{
+	mips_rt_signal_frame();
+	VMCOREINFO_OFFSET(sigcontext, sc_regs);
+	VMCOREINFO_NUMBER(PAGE_SHIFT);
+	VMCOREINFO_NUMBER(_PFN_MASK);
+	VMCOREINFO_NUMBER(_PAGE_PRESENT);
+	VMCOREINFO_NUMBER(_PAGE_VALID);
+	VMCOREINFO_NUMBER(_PAGE_GLOBAL);
+	VMCOREINFO_NUMBER(PTRS_PER_PGD);
+	VMCOREINFO_NUMBER(PTRS_PER_PMD);
+	VMCOREINFO_NUMBER(PTRS_PER_PTE);
+}
-- 
2.43.0