[PATCH 3/9] lib: sbi: Introduce trap context

[Anup Patel]

Club pointers to struct sbi_trap_regs and struct sbi_trap_info a new
struct sbi_trap_context (aka trap context).

To track nested traps, the struct sbi_scratch points to the current
trap context and the trap context has pointer to pervious context of
previous trap.

Signed-off-by: Anup Patel <apatel at ventanamicro.com>
---
 include/sbi/sbi_trap.h | 22 ++++++++++++++++++++++
 lib/sbi/sbi_trap.c     | 35 ++++++++++++++++++++++-------------
 2 files changed, 44 insertions(+), 13 deletions(-)

diff --git a/include/sbi/sbi_trap.h b/include/sbi/sbi_trap.h
index 15ccd0b..513a82e 100644
--- a/include/sbi/sbi_trap.h
+++ b/include/sbi/sbi_trap.h
@@ -117,6 +117,7 @@
 #ifndef __ASSEMBLER__
 
 #include <sbi/sbi_types.h>
+#include <sbi/sbi_scratch.h>
 
 /** Representation of register state at time of trap/interrupt */
 struct sbi_trap_regs {
@@ -208,6 +209,16 @@ struct sbi_trap_info {
 	unsigned long gva;
 };
 
+/** Representation of trap context saved on stack */
+struct sbi_trap_context {
+	/** Pointer to previous trap context */
+	struct sbi_trap_context *prev_context;
+	/** Pointer to register state */
+	struct sbi_trap_regs *regs;
+	/** Pointer to trap details */
+	const struct sbi_trap_info *trap;
+};
+
 static inline unsigned long sbi_regs_gva(const struct sbi_trap_regs *regs)
 {
 	/*
@@ -227,6 +238,17 @@ static inline unsigned long sbi_regs_gva(const struct sbi_trap_regs *regs)
 int sbi_trap_redirect(struct sbi_trap_regs *regs,
 		      const struct sbi_trap_info *trap);
 
+static inline struct sbi_trap_context *sbi_trap_get_context(struct sbi_scratch *scratch)
+{
+	return (scratch) ? (void *)scratch->trap_context : NULL;
+}
+
+static inline void sbi_trap_set_context(struct sbi_scratch *scratch,
+					struct sbi_trap_context *tcntx)
+{
+	scratch->trap_context = (unsigned long)tcntx;
+}
+
 struct sbi_trap_regs *sbi_trap_handler(struct sbi_trap_regs *regs);
 
 #endif
diff --git a/lib/sbi/sbi_trap.c b/lib/sbi/sbi_trap.c
index e514066..dba267c 100644
--- a/lib/sbi/sbi_trap.c
+++ b/lib/sbi/sbi_trap.c
@@ -266,6 +266,8 @@ struct sbi_trap_regs *sbi_trap_handler(struct sbi_trap_regs *regs)
 	const char *msg = "trap handler failed";
 	ulong mcause = csr_read(CSR_MCAUSE);
 	ulong mtval = csr_read(CSR_MTVAL), mtval2 = 0, mtinst = 0;
+	struct sbi_scratch *scratch = sbi_scratch_thishart_ptr();
+	struct sbi_trap_context tcntx;
 	struct sbi_trap_info trap;
 
 	if (misa_extension('H')) {
@@ -273,25 +275,31 @@ struct sbi_trap_regs *sbi_trap_handler(struct sbi_trap_regs *regs)
 		mtinst = csr_read(CSR_MTINST);
 	}
 
+	/* Original trap_info */
+	trap.epc     = regs->mepc;
+	trap.cause   = mcause;
+	trap.tval    = mtval;
+	trap.tval2   = mtval2;
+	trap.tinst   = mtinst;
+	trap.gva     = sbi_regs_gva(regs);
+
+	/* Setup trap context */
+	tcntx.prev_context = sbi_trap_get_context(scratch);
+	tcntx.regs         = regs;
+	tcntx.trap         = &trap;
+
+	/* Update trap context pointer */
+	sbi_trap_set_context(scratch, &tcntx);
+
 	if (mcause & (1UL << (__riscv_xlen - 1))) {
 		if (sbi_hart_has_extension(sbi_scratch_thishart_ptr(),
 					   SBI_HART_EXT_SMAIA))
 			rc = sbi_trap_aia_irq(regs, mcause);
 		else
 			rc = sbi_trap_nonaia_irq(regs, mcause);
-		if (rc) {
-			msg = "unhandled local interrupt";
-			goto trap_error;
-		}
-		return regs;
+		msg = "unhandled local interrupt";
+		goto trap_done;
 	}
-	/* Original trap_info */
-	trap.epc   = regs->mepc;
-	trap.cause = mcause;
-	trap.tval  = mtval;
-	trap.tval2 = mtval2;
-	trap.tinst = mtinst;
-	trap.gva   = sbi_regs_gva(regs);
 
 	switch (mcause) {
 	case CAUSE_ILLEGAL_INSTRUCTION:
@@ -330,8 +338,9 @@ struct sbi_trap_regs *sbi_trap_handler(struct sbi_trap_regs *regs)
 		break;
 	}
 
-trap_error:
+trap_done:
 	if (rc)
 		sbi_trap_error(msg, rc, mcause, mtval, mtval2, mtinst, regs);
+	sbi_trap_set_context(scratch, tcntx.prev_context);
 	return regs;
 }
-- 
2.34.1