linux-kernel - [RFC PATCH 01/12] riscv: zicfiss / zicfilp extension csr and bit definitions

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Date: Mon,  8 Apr 2024 23:10:32 -0700
From: Deepak Gupta <debug@...osinc.com>
To: linux-riscv@...ts.infradead.org,
	linux-kernel@...r.kernel.org,
	llvm@...ts.linux.dev
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Subject: [RFC PATCH 01/12] riscv: zicfiss / zicfilp extension csr and bit definitions

zicfiss and zicfilp extension gets enabled via b3 and b2 in *envcfg CSR.
menvcfg controls enabling for S/HS mode. henvcfg control enabling for VS
while senvcfg controls enabling for U/VU mode.

zicfilp extension extends *status CSR to hold `expected landing pad` bit.
A trap or interrupt can occur between an indirect jmp/call and target
instr. `expected landing pad` bit from CPU is recorded into xstatus CSR so
that when supervisor performs xret, `expected landing pad` state of CPU can
be restored.

zicfiss adds one new CSR
- CSR_SSP: CSR_SSP contains current shadow stack pointer.

Signed-off-by: Deepak Gupta <debug@...osinc.com>
---
 arch/riscv/include/asm/csr.h | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/arch/riscv/include/asm/csr.h b/arch/riscv/include/asm/csr.h
index 2468c55933cd..9f2b2722b67c 100644
--- a/arch/riscv/include/asm/csr.h
+++ b/arch/riscv/include/asm/csr.h
@@ -18,6 +18,15 @@
 #define SR_MPP		_AC(0x00001800, UL) /* Previously Machine */
 #define SR_SUM		_AC(0x00040000, UL) /* Supervisor User Memory Access */
 
+/* zicfilp landing pad status bit */
+#define SR_SPELP	_AC(0x00800000, UL)
+#define SR_MPELP	_AC(0x020000000000, UL)
+#ifdef CONFIG_RISCV_M_MODE
+#define SR_ELP		SR_MPELP
+#else
+#define SR_ELP		SR_SPELP
+#endif
+
 #define SR_FS		_AC(0x00006000, UL) /* Floating-point Status */
 #define SR_FS_OFF	_AC(0x00000000, UL)
 #define SR_FS_INITIAL	_AC(0x00002000, UL)
@@ -196,6 +205,8 @@
 #define ENVCFG_PBMTE			(_AC(1, ULL) << 62)
 #define ENVCFG_CBZE			(_AC(1, UL) << 7)
 #define ENVCFG_CBCFE			(_AC(1, UL) << 6)
+#define ENVCFG_LPE			(_AC(1, UL) << 2)
+#define ENVCFG_SSE			(_AC(1, UL) << 3)
 #define ENVCFG_CBIE_SHIFT		4
 #define ENVCFG_CBIE			(_AC(0x3, UL) << ENVCFG_CBIE_SHIFT)
 #define ENVCFG_CBIE_ILL			_AC(0x0, UL)
@@ -214,6 +225,11 @@
 #define SMSTATEEN0_HSENVCFG		(_ULL(1) << SMSTATEEN0_HSENVCFG_SHIFT)
 #define SMSTATEEN0_SSTATEEN0_SHIFT	63
 #define SMSTATEEN0_SSTATEEN0		(_ULL(1) << SMSTATEEN0_SSTATEEN0_SHIFT)
+/*
+ * zicfiss user mode csr
+ * CSR_SSP holds current shadow stack pointer.
+ */
+#define CSR_SSP                 0x011
 
 /* symbolic CSR names: */
 #define CSR_CYCLE		0xc00
-- 
2.43.2