[PATCH 3/4] riscv: vmcore_info: export riscv arch-specific struct offsets to vmcoreinfo

[Pnina Feder]

Export RISC-V 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@xxxxxxxxxxxx>
---
 .../admin-guide/kdump/vmcoreinfo.rst          | 26 +++++++++++++++++++
 arch/riscv/kernel/signal.c                    |  8 ++++++
 arch/riscv/kernel/vmcore_info.c               | 11 ++++++++
 3 files changed, 45 insertions(+)

diff --git a/Documentation/admin-guide/kdump/vmcoreinfo.rst b/Documentation/admin-guide/kdump/vmcoreinfo.rst
index 36103b3cdc05..3c364434b846 100644
--- a/Documentation/admin-guide/kdump/vmcoreinfo.rst
+++ b/Documentation/admin-guide/kdump/vmcoreinfo.rst
@@ -595,6 +595,32 @@ va_kernel_pa_offset
 Indicates the offset between the kernel virtual and physical mappings.
 Used to translate virtual to physical addresses.
 
+STACK_ALIGN
+-----------
+
+Stack alignment requirement for the architecture. Used to locate signal
+frames 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_PFN_SHIFT
+---------------
+
+The bit shift to extract the PFN from a page table entry. Used for
+virtual-to-physical address translation when walking page tables from
+a vmcore dump.
+
+(rt_sigframe, uc)
+-----------------
+
+Offset of the ucontext member within the RISC-V rt_sigframe structure.
+Used to locate the signal context (and thus saved registers) within a
+signal frame on the user stack.
+
 Task and VMA metadata
 =====================
 
diff --git a/arch/riscv/kernel/signal.c b/arch/riscv/kernel/signal.c
index 59784dc117e4..eb03c0ea6aae 100644
--- a/arch/riscv/kernel/signal.c
+++ b/arch/riscv/kernel/signal.c
@@ -13,6 +13,7 @@
 #include <linux/resume_user_mode.h>
 #include <linux/linkage.h>
 #include <linux/entry-common.h>
+#include <linux/vmcore_info.h>
 
 #include <asm/ucontext.h>
 #include <asm/vdso.h>
@@ -40,6 +41,13 @@ struct rt_sigframe {
 #endif
 };
 
+#ifdef CONFIG_VMCORE_INFO
+void riscv_rt_signal_frame(void)
+{
+	VMCOREINFO_OFFSET(rt_sigframe, uc);
+}
+#endif
+
 #ifdef CONFIG_FPU
 static long restore_fp_state(struct pt_regs *regs,
 			     union __riscv_fp_state __user *sc_fpregs)
diff --git a/arch/riscv/kernel/vmcore_info.c b/arch/riscv/kernel/vmcore_info.c
index c27efceec3cc..dd174042dba3 100644
--- a/arch/riscv/kernel/vmcore_info.c
+++ b/arch/riscv/kernel/vmcore_info.c
@@ -3,6 +3,12 @@
 #include <linux/vmcore_info.h>
 #include <linux/pagemap.h>
 
+#include <asm/processor.h>
+#include <asm/pgtable-bits.h>
+#include <asm/sigcontext.h>
+
+extern void riscv_rt_signal_frame(void);
+
 static inline u64 get_satp_value(void)
 {
 	return csr_read(CSR_SATP);
@@ -28,4 +34,9 @@ void arch_crash_save_vmcoreinfo(void)
 						kernel_map.va_kernel_pa_offset);
 	vmcoreinfo_append_str("KERNELOFFSET=%lx\n", kaslr_offset());
 	vmcoreinfo_append_str("NUMBER(satp)=0x%llx\n", get_satp_value());
+	riscv_rt_signal_frame();
+
+	VMCOREINFO_NUMBER(STACK_ALIGN);
+	VMCOREINFO_OFFSET(sigcontext, sc_regs);
+	VMCOREINFO_NUMBER(_PAGE_PFN_SHIFT);
 }
-- 
2.43.0