Support for zisslpcfi in opensbi

PATCH New Deepak Gupta 3 participants 10 messages Dec 12, 2022 – Dec 22, 2022 RISC-V

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Deepak Gupta

author

2022-12-12 03:08 UTC #0 lore raw

cover Support for zisslpcfi in opensbi

Zisslpcfi [1] extension extends risc-v architecture to mitigate against control-flow integrity attacks (ROP/JOP/COP).

Zisslpcfi uses bits (b23-b29) in (m/s/vs) status CSR for enabling cfi in lesser privileged mode and record cfi state. One such state is expected landing pad (ELP). If forward cfi is enabled, indirect call/jmp updates hart's ELP state (1bit) to true. ELP state is cleared only by a landing pad instruction else trap is delivered with ELP state recorded in sstatus CSR.

This two patch series adds following changes to opensbi
- Adds support in opensbi to detect zisslpcfi
- trap redirection updates ELP state accordingly

[1] - https://github.com/riscv/riscv-cfi

Deepak Gupta (2):
include: adding support for zsslpcfi encodings
lib: sbi: zsslpcfi detection and elp cfi state reflect back in status

 include/sbi/riscv_encoding.h |  6 ++++++
 include/sbi/sbi_hart.h       |  2 ++
 lib/sbi/sbi_hart.c           | 21 +++++++++++++++++++++
 lib/sbi/sbi_trap.c           | 18 ++++++++++++++++++
 4 files changed, 47 insertions(+)

Signature · 1 line

2.25.1

Deepak Gupta

author

2022-12-12 03:08 UTC #1 lore raw

PATCH 1/2 include: adding support for zsslpcfi encodings

zsslpcfi extension (see links) introduces b60 (CFI) in menvcfg CSR to enable shadow stack and landing pad for machine and lesser privileged modes. Additionally extension introduces new bits in xstatus for cfi state.

Links:https://github.com/riscv/riscv-cfi

Signed-off-by Deepak Gupta <[email protected]>

---
 include/sbi/riscv_encoding.h | 4 ++++
 include/sbi/sbi_hart.h       | 2 ++
 2 files changed, 6 insertions(+)

include/sbi/riscv_encoding.h +4 -0

index b0f08c8..1fb520f 100644
@@ -210,9 +210,11 @@
 #if __riscv_xlen > 32
 #define ENVCFG_STCE			(_ULL(1) << 63)
 #define ENVCFG_PBMTE			(_ULL(1) << 62)
+#define ENVCFG_CFI			(_ULL(1) << 60)
 #else
 #define ENVCFGH_STCE			(_UL(1) << 31)
 #define ENVCFGH_PBMTE			(_UL(1) << 30)
+#define ENVCFGH_CFI			(_UL(1) << 28)
 #endif
 #define ENVCFG_CBZE			(_UL(1) << 7)
 #define ENVCFG_CBCFE			(_UL(1) << 6)

@@ -229,6 +231,8 @@
 #define CSR_USTATUS			0x000
 #define CSR_UIE				0x004
 #define CSR_UTVEC			0x005
+#define CSR_LPLR			0x006
+#define CSR_SSP				0x020
 
 /* User Trap Handling (N-extension) */
 #define CSR_USCRATCH			0x040

include/sbi/sbi_hart.h +2 -0

index 95b40e7..d25227d 100644
@@ -36,6 +36,8 @@ enum sbi_hart_extensions {
 	SBI_HART_EXT_SMSTATEEN,
 	/** HART has Sstc extension */
 	SBI_HART_EXT_SSTC,
+	/** HART has sslpcfi extension */
+	SBI_HART_EXT_SSLPCFI,
 
 	/** Maximum index of Hart extension */
 	SBI_HART_EXT_MAX,

Signature · 1 line

2.25.1

Bin Meng

2022-12-21 13:39 UTC #2 lore raw

PATCH 1/2 include: adding support for zsslpcfi encodings

Quoted 2 lines · Deepak Gupta

zsslpcfi extension (see links) introduces b60 (CFI) in menvcfg CSR to

The extension name is Zisslpcfi (capital Z)

Quoted 5 lines

enable shadow stack and landing pad for machine and lesser privileged modes. Additionally extension introduces new bits in xstatus for cfi state.
Links:https://github.com/riscv/riscv-cfi

nits: need a space after :

s/Links/Link

Quoted 37 lines

Signed-off-by Deepak Gupta <[email protected]>

---
 include/sbi/riscv_encoding.h | 4 ++++
 include/sbi/sbi_hart.h       | 2 ++
 2 files changed, 6 insertions(+)

include/sbi/riscv_encoding.h +4 -0

index b0f08c8..1fb520f 100644
@@ -210,9 +210,11 @@
 #if __riscv_xlen > 32
 #define ENVCFG_STCE                    (_ULL(1) << 63)
 #define ENVCFG_PBMTE                   (_ULL(1) << 62)
+#define ENVCFG_CFI                     (_ULL(1) << 60)
 #else
 #define ENVCFGH_STCE                   (_UL(1) << 31)
 #define ENVCFGH_PBMTE                  (_UL(1) << 30)
+#define ENVCFGH_CFI                    (_UL(1) << 28)
 #endif
 #define ENVCFG_CBZE                    (_UL(1) << 7)
 #define ENVCFG_CBCFE                   (_UL(1) << 6)

@@ -229,6 +231,8 @@
 #define CSR_USTATUS                    0x000
 #define CSR_UIE                                0x004
 #define CSR_UTVEC                      0x005
+#define CSR_LPLR                       0x006
+#define CSR_SSP                                0x020
 
 /* User Trap Handling (N-extension) */
 #define CSR_USCRATCH                   0x040

include/sbi/sbi_hart.h +0 -0

index 95b40e7..d25227d 100644

include/sbi/sbi_hart.h enum sbi_hart_extensions { · line 39

Quoted 4 lines

include/sbi/sbi_hart.h +1 -0

@@ -36,6 +36,8 @@ enum sbi_hart_extensions {
        SBI_HART_EXT_SMSTATEEN,
        /** HART has Sstc extension */
        SBI_HART_EXT_SSTC,
+       /** HART has sslpcfi extension */

Zisslpcfi

include/sbi/sbi_hart.h enum sbi_hart_extensions { · line 40

Quoted 1 line

include/sbi/sbi_hart.h +1 -0
+       SBI_HART_EXT_SSLPCFI,

SBI_HART_EXT_ZISSLPCFI

include/sbi/sbi_hart.h enum sbi_hart_extensions {

Quoted 4 lines

include/sbi/sbi_hart.h +0 -1

        /** Maximum index of Hart extension */
        SBI_HART_EXT_MAX,
--

Regards,
Bin

Deepak Gupta

author

2022-12-12 03:08 UTC #3 lore raw

PATCH 2/2 lib: sbi: zsslpcfi detection and elp cfi state reflect back in status

In reply to Deepak Gupta

This patch adds support for zsslpcfi detection in sbi_hart.c If zsslpcfi is detected, this turns on menvcfg.CFI

zsslpcfi records status of cfi state in xstatus csr. Missing landing pad sets MPELP in mstatus. When SBI is redirecting back to S/VS/HS, SPELP is set in sstatus/vsstatus.

Signed-off-by Deepak Gupta <[email protected]>

---
 include/sbi/riscv_encoding.h |  2 ++
 lib/sbi/sbi_hart.c           | 21 +++++++++++++++++++++
 lib/sbi/sbi_trap.c           | 18 ++++++++++++++++++
 3 files changed, 41 insertions(+)

include/sbi/riscv_encoding.h +2 -0

index 1fb520f..d7886e7 100644
@@ -32,6 +32,8 @@
 #define MSTATUS_TVM			_UL(0x00100000)
 #define MSTATUS_TW			_UL(0x00200000)
 #define MSTATUS_TSR			_UL(0x00400000)
+#define MSTATUS_SPELP     		_UL(0x10000000)
+#define MSTATUS_MPELP     		_UL(0x20000000)
 #define MSTATUS32_SD			_UL(0x80000000)
 #if __riscv_xlen == 64
 #define MSTATUS_UXL			_ULL(0x0000000300000000)

lib/sbi/sbi_hart.c +21 -0

index 5447c52..6beae2d 100644
@@ -157,6 +157,16 @@ static void mstatus_init(struct sbi_scratch *scratch)
 #endif
 		}
 
+		if (sbi_hart_has_extension(scratch, SBI_HART_EXT_SSLPCFI)) {
+#if __riscv_xlen == 32
+			unsigned long menvcfgh_val;
+			menvcfgh_val = csr_read(CSR_MENVCFGH);
+			menvcfgh_val |= ENVCFGH_CFI;
+			csr_write(CSR_MENVCFGH, menvcfgh_val);
+#else
+			menvcfg_val |= ENVCFG_CFI;
+#endif
+		}
 		csr_write(CSR_MENVCFG, menvcfg_val);
 	}

@@ -555,6 +565,7 @@ static int hart_detect_features(struct sbi_scratch *scratch)
 		sbi_scratch_offset_ptr(scratch, hart_features_offset);
 	unsigned long val, oldval;
 	int rc;
+	int ssp_exist, lplr_exist;
 
 	/* If hart features already detected then do nothing */
 	if (hfeatures->detected)

@@ -693,6 +704,16 @@ __mhpm_skip:
 					SBI_HART_EXT_SMSTATEEN, true);
 	}
 
+	if (hfeatures->priv_version >= SBI_HART_PRIV_VER_1_12) {
+		val = csr_read_allowed(CSR_SSP, (unsigned long)&trap);
+		ssp_exist = trap.cause?0:1;
+		val = csr_read_allowed(CSR_LPLR, (unsigned long)&trap);
+		lplr_exist = trap.cause?0:1;
+		if (lplr_exist & ssp_exist)
+			__sbi_hart_update_extension(hfeatures,
+					SBI_HART_EXT_SSLPCFI, true);
+	}
+
 	/* Let platform populate extensions */
 	rc = sbi_platform_extensions_init(sbi_platform_thishart_ptr(),
 					  hfeatures);

lib/sbi/sbi_trap.c +18 -0

index c875c90..a700041 100644
@@ -87,6 +87,7 @@ int sbi_trap_redirect(struct sbi_trap_regs *regs,
 		      struct sbi_trap_info *trap)
 {
 	ulong hstatus, vsstatus, prev_mode;
+	bool elp = FALSE;
 #if __riscv_xlen == 32
 	bool prev_virt = (regs->mstatusH & MSTATUSH_MPV) ? TRUE : FALSE;
 #else

@@ -100,6 +101,13 @@ int sbi_trap_redirect(struct sbi_trap_regs *regs,
 	if (prev_mode != PRV_S && prev_mode != PRV_U)
 		return SBI_ENOTSUPP;
 
+	/* If extension has support for CFI, clear MPELP because redirecting to VS or (H)S */
+	if (sbi_hart_has_extension(sbi_scratch_thishart_ptr(), SBI_HART_EXT_SSLPCFI)) {
+		elp = (regs->mstatus & MSTATUS_MPELP)? TRUE: FALSE;
+		/* Since redirecting, clear mpelp unconditionally */
+		regs->mstatus &= ~MSTATUS_MPELP;
+	}
+
 	/* If exceptions came from VS/VU-mode, redirect to VS-mode if
 	 * delegated in hedeleg
 	 */

@@ -153,6 +161,11 @@ int sbi_trap_redirect(struct sbi_trap_regs *regs,
 		/* Get VS-mode SSTATUS CSR */
 		vsstatus = csr_read(CSR_VSSTATUS);
 
+		/*if elp was set, set it back in vsstatus */
+		if (elp) {
+			vsstatus |= MSTATUS_SPELP;
+		}
+
 		/* Set SPP for VS-mode */
 		vsstatus &= ~SSTATUS_SPP;
 		if (prev_mode == PRV_S)

@@ -193,6 +206,11 @@ int sbi_trap_redirect(struct sbi_trap_regs *regs,
 
 		/* Clear SIE for S-mode */
 		regs->mstatus &= ~MSTATUS_SIE;
+
+		/* if elp was set, set it back in mstatus */
+		if (elp) {
+			regs->mstatus |= MSTATUS_SPELP;
+		}
 	}
 
 	return 0;

Signature · 1 line

2.25.1

Bin Meng

2022-12-21 13:43 UTC #4 lore raw

PATCH 2/2 lib: sbi: zsslpcfi detection and elp cfi state reflect back in status

Quoted 50 lines · Deepak Gupta

This patch adds support for zsslpcfi detection in sbi_hart.c If zsslpcfi is detected, this turns on menvcfg.CFI

zsslpcfi records status of cfi state in xstatus csr. Missing landing pad sets MPELP in mstatus. When SBI is redirecting back to S/VS/HS, SPELP is set in sstatus/vsstatus.

Signed-off-by Deepak Gupta <[email protected]>

---
 include/sbi/riscv_encoding.h |  2 ++
 lib/sbi/sbi_hart.c           | 21 +++++++++++++++++++++
 lib/sbi/sbi_trap.c           | 18 ++++++++++++++++++
 3 files changed, 41 insertions(+)

include/sbi/riscv_encoding.h +2 -0

index 1fb520f..d7886e7 100644
@@ -32,6 +32,8 @@
 #define MSTATUS_TVM                    _UL(0x00100000)
 #define MSTATUS_TW                     _UL(0x00200000)
 #define MSTATUS_TSR                    _UL(0x00400000)
+#define MSTATUS_SPELP                  _UL(0x10000000)
+#define MSTATUS_MPELP                  _UL(0x20000000)
 #define MSTATUS32_SD                   _UL(0x80000000)
 #if __riscv_xlen == 64
 #define MSTATUS_UXL                    _ULL(0x0000000300000000)

lib/sbi/sbi_hart.c +10 -0

index 5447c52..6beae2d 100644
@@ -157,6 +157,16 @@ static void mstatus_init(struct sbi_scratch *scratch)
 #endif
                }
 
+               if (sbi_hart_has_extension(scratch, SBI_HART_EXT_SSLPCFI)) {
+#if __riscv_xlen == 32
+                       unsigned long menvcfgh_val;
+                       menvcfgh_val = csr_read(CSR_MENVCFGH);
+                       menvcfgh_val |= ENVCFGH_CFI;
+                       csr_write(CSR_MENVCFGH, menvcfgh_val);
+#else
+                       menvcfg_val |= ENVCFG_CFI;
+#endif
+               }
                csr_write(CSR_MENVCFG, menvcfg_val);
        }

lib/sbi/sbi_hart.c static int hart_detect_features(struct sbi_scratch *scratch) · line 568

Quoted 4 lines

lib/sbi/sbi_hart.c +1 -0

@@ -555,6 +565,7 @@ static int hart_detect_features(struct sbi_scratch *scratch)
                sbi_scratch_offset_ptr(scratch, hart_features_offset);
        unsigned long val, oldval;
        int rc;
+       int ssp_exist, lplr_exist;

Use bool

lib/sbi/sbi_hart.c __mhpm_skip: · line 709

Quoted 10 lines

lib/sbi/sbi_hart.c +3 -0

        /* If hart features already detected then do nothing */
        if (hfeatures->detected)

@@ -693,6 +704,16 @@ __mhpm_skip:
                                        SBI_HART_EXT_SMSTATEEN, true);
        }
 
+       if (hfeatures->priv_version >= SBI_HART_PRIV_VER_1_12) {
+               val = csr_read_allowed(CSR_SSP, (unsigned long)&trap);
+               ssp_exist = trap.cause?0:1;

need space around ? and :

use true/false instead of 1/0

Quoted 15 lines

lib/sbi/sbi_hart.c +7 -0

+               val = csr_read_allowed(CSR_LPLR, (unsigned long)&trap);
+               lplr_exist = trap.cause?0:1;
+               if (lplr_exist & ssp_exist)
+                       __sbi_hart_update_extension(hfeatures,
+                                       SBI_HART_EXT_SSLPCFI, true);
+       }
+
        /* Let platform populate extensions */
        rc = sbi_platform_extensions_init(sbi_platform_thishart_ptr(),
                                          hfeatures);

lib/sbi/sbi_trap.c +0 -0

index c875c90..a700041 100644

lib/sbi/sbi_trap.c int sbi_trap_redirect(struct sbi_trap_regs *regs, · line 90

Quoted 4 lines

lib/sbi/sbi_trap.c +1 -0

@@ -87,6 +87,7 @@ int sbi_trap_redirect(struct sbi_trap_regs *regs,
                      struct sbi_trap_info *trap)
 {
        ulong hstatus, vsstatus, prev_mode;
+       bool elp = FALSE;

s/FALSE/false

Quoted 18 lines

lib/sbi/sbi_trap.c +7 -0

 #if __riscv_xlen == 32
        bool prev_virt = (regs->mstatusH & MSTATUSH_MPV) ? TRUE : FALSE;
 #else

@@ -100,6 +101,13 @@ int sbi_trap_redirect(struct sbi_trap_regs *regs,
        if (prev_mode != PRV_S && prev_mode != PRV_U)
                return SBI_ENOTSUPP;
 
+       /* If extension has support for CFI, clear MPELP because redirecting to VS or (H)S */
+       if (sbi_hart_has_extension(sbi_scratch_thishart_ptr(), SBI_HART_EXT_SSLPCFI)) {
+               elp = (regs->mstatus & MSTATUS_MPELP)? TRUE: FALSE;
+               /* Since redirecting, clear mpelp unconditionally */
+               regs->mstatus &= ~MSTATUS_MPELP;
+       }
+
        /* If exceptions came from VS/VU-mode, redirect to VS-mode if
         * delegated in hedeleg
         */

lib/sbi/sbi_trap.c int sbi_trap_redirect(struct sbi_trap_regs *regs, · line 164

Quoted 4 lines

lib/sbi/sbi_trap.c +1 -0

@@ -153,6 +161,11 @@ int sbi_trap_redirect(struct sbi_trap_regs *regs,
                /* Get VS-mode SSTATUS CSR */
                vsstatus = csr_read(CSR_VSSTATUS);
 
+               /*if elp was set, set it back in vsstatus */

need space after /*

Quoted 8 lines

lib/sbi/sbi_trap.c +4 -0

+               if (elp) {
+                       vsstatus |= MSTATUS_SPELP;
+               }
+
                /* Set SPP for VS-mode */
                vsstatus &= ~SSTATUS_SPP;
                if (prev_mode == PRV_S)

lib/sbi/sbi_trap.c int sbi_trap_redirect(struct sbi_trap_regs *regs, · line 215

Quoted 10 lines

lib/sbi/sbi_trap.c +5 -0

@@ -193,6 +206,11 @@ int sbi_trap_redirect(struct sbi_trap_regs *regs,
 
                /* Clear SIE for S-mode */
                regs->mstatus &= ~MSTATUS_SIE;
+
+               /* if elp was set, set it back in mstatus */
+               if (elp) {
+                       regs->mstatus |= MSTATUS_SPELP;
+               }
        }

Regards,
Bin

Andreas Schwab

2022-12-21 13:59 UTC #5 lore raw

PATCH 2/2 lib: sbi: zsslpcfi detection and elp cfi state reflect back in status

Quoted 7 lines · Bin Meng

lib/sbi/sbi_hart.c __mhpm_skip: · line 709

Quoted 7 lines

lib/sbi/sbi_hart.c +3 -0

@@ -693,6 +704,16 @@ __mhpm_skip:
                                        SBI_HART_EXT_SMSTATEEN, true);
        }
 
+       if (hfeatures->priv_version >= SBI_HART_PRIV_VER_1_12) {
+               val = csr_read_allowed(CSR_SSP, (unsigned long)&trap);
+               ssp_exist = trap.cause?0:1;

                   ssp_exist = trap.cause == 0;

Signature · 3 lines

Andreas Schwab, SUSE Labs, schwab at suse.de
GPG Key fingerprint = 0196 BAD8 1CE9 1970 F4BE  1748 E4D4 88E3 0EEA B9D7
"And now for something completely different."

Deepak Gupta

author

2022-12-21 20:01 UTC #6 lore raw

PATCH 2/2 lib: sbi: zsslpcfi detection and elp cfi state reflect back in status

Thanks Andreas and Bin for your review comments.
Sent out v2 version of the patch.

-Deepak

Quoted 17 lines · Andreas Schwab

Quoted 7 lines · Bin Meng
lib/sbi/sbi_hart.c __mhpm_skip: · line 709
Quoted 7 lines
lib/sbi/sbi_hart.c +3 -0
@@ -693,6 +704,16 @@ __mhpm_skip:
                                        SBI_HART_EXT_SMSTATEEN, true);
        }
 
+       if (hfeatures->priv_version >= SBI_HART_PRIV_VER_1_12) {
+               val = csr_read_allowed(CSR_SSP, (unsigned long)&trap);
+               ssp_exist = trap.cause?0:1;
                   ssp_exist = trap.cause == 0;
--
Andreas Schwab, SUSE Labs, schwab at suse.de
GPG Key fingerprint = 0196 BAD8 1CE9 1970 F4BE 1748 E4D4 88E3 0EEA B9D7 "And now for something completely different."

Deepak Gupta

author

2022-12-21 18:41 UTC #7 lore raw

PATCH 2/2 lib: sbi: zsslpcfi detection and elp cfi state reflect back in status

In reply to Bin Meng

Quoted 8 lines · Bin Meng

lib/sbi/sbi_trap.c int sbi_trap_redirect(struct sbi_trap_regs *regs, · line 90
Quoted 6 lines
lib/sbi/sbi_trap.c +1 -0
@@ -87,6 +87,7 @@ int sbi_trap_redirect(struct sbi_trap_regs *regs,
                      struct sbi_trap_info *trap)
 {
        ulong hstatus, vsstatus, prev_mode;
+       bool elp = FALSE;
s/FALSE/false

I followed whatever rest of the code is following. In the same function

"
int sbi_trap_redirect(struct sbi_trap_regs *regs,
struct sbi_trap_info *trap)

{
        ulong hstatus, vsstatus, prev_mode;
        bool elp = FALSE;
#if __riscv_xlen == 32
        bool prev_virt = (regs->mstatusH & MSTATUSH_MPV) ? TRUE : FALSE;
#else
        bool prev_virt = (regs->mstatus & MSTATUS_MPV) ? TRUE : FALSE;
#endif
        /* By default, we redirect to HS-mode */
        bool next_virt = FALSE;

"
I can change it to false but it'll look ugly because at other places we're using upper case FALSE.
Let me know what needs to be done.

Quoted 47 lines

Quoted 19 lines

lib/sbi/sbi_trap.c +7 -0

 #if __riscv_xlen == 32
        bool prev_virt = (regs->mstatusH & MSTATUSH_MPV) ? TRUE : FALSE;
 #else

@@ -100,6 +101,13 @@ int sbi_trap_redirect(struct sbi_trap_regs *regs,
        if (prev_mode != PRV_S && prev_mode != PRV_U)
                return SBI_ENOTSUPP;
 
+       /* If extension has support for CFI, clear MPELP because redirecting to VS or (H)S */
+       if (sbi_hart_has_extension(sbi_scratch_thishart_ptr(), SBI_HART_EXT_SSLPCFI)) {
+               elp = (regs->mstatus & MSTATUS_MPELP)? TRUE: FALSE;
+               /* Since redirecting, clear mpelp unconditionally */
+               regs->mstatus &= ~MSTATUS_MPELP;
+       }
+
        /* If exceptions came from VS/VU-mode, redirect to VS-mode if
         * delegated in hedeleg
         */

lib/sbi/sbi_trap.c int sbi_trap_redirect(struct sbi_trap_regs *regs, · line 164

Quoted 4 lines

lib/sbi/sbi_trap.c +1 -0

@@ -153,6 +161,11 @@ int sbi_trap_redirect(struct sbi_trap_regs *regs,
                /* Get VS-mode SSTATUS CSR */
                vsstatus = csr_read(CSR_VSSTATUS);
 
+               /*if elp was set, set it back in vsstatus */

need space after /*

Quoted 8 lines

lib/sbi/sbi_trap.c +4 -0

+               if (elp) {
+                       vsstatus |= MSTATUS_SPELP;
+               }
+
                /* Set SPP for VS-mode */
                vsstatus &= ~SSTATUS_SPP;
                if (prev_mode == PRV_S)

lib/sbi/sbi_trap.c int sbi_trap_redirect(struct sbi_trap_regs *regs, · line 215

Quoted 10 lines

lib/sbi/sbi_trap.c +5 -0

@@ -193,6 +206,11 @@ int sbi_trap_redirect(struct sbi_trap_regs *regs,
 
                /* Clear SIE for S-mode */
                regs->mstatus &= ~MSTATUS_SIE;
+
+               /* if elp was set, set it back in mstatus */
+               if (elp) {
+                       regs->mstatus |= MSTATUS_SPELP;
+               }
        }

Regards,
Bin

Bin Meng

2022-12-22 01:29 UTC #8 lore raw

PATCH 2/2 lib: sbi: zsslpcfi detection and elp cfi state reflect back in status

Quoted 26 lines · Deepak Gupta

Quoted 8 lines · Bin Meng
lib/sbi/sbi_trap.c int sbi_trap_redirect(struct sbi_trap_regs *regs, · line 90
Quoted 6 lines
lib/sbi/sbi_trap.c +1 -0
@@ -87,6 +87,7 @@ int sbi_trap_redirect(struct sbi_trap_regs *regs,
                      struct sbi_trap_info *trap)
 {
        ulong hstatus, vsstatus, prev_mode;
+       bool elp = FALSE;
s/FALSE/false
I followed whatever rest of the code is following. In the same function
"
int sbi_trap_redirect(struct sbi_trap_regs *regs,
struct sbi_trap_info *trap)
{
        ulong hstatus, vsstatus, prev_mode;
        bool elp = FALSE;
#if __riscv_xlen == 32
        bool prev_virt = (regs->mstatusH & MSTATUSH_MPV) ? TRUE : FALSE;
#else
        bool prev_virt = (regs->mstatus & MSTATUS_MPV) ? TRUE : FALSE;
#endif
        /* By default, we redirect to HS-mode */
        bool next_virt = FALSE;

Quoted 5 lines

"
I can change it to false but it'll look ugly because at other places we're using upper case FALSE.
Let me know what needs to be done.

No need to worry about other places, as I already sent one patch to change all other places.

Regards,
Bin

Deepak Gupta

author

2022-12-12 05:33 UTC #9 lore raw

cover Support for zisslpcfi in opensbi

In reply to Deepak Gupta

I forgot to include URLs to qemu and linux implementation of Zisslpcfi

This is where I am maintaining qemu implementation
https://github.com/deepak0414/qemu/tree/gh_Zisslpcfi-0.1

And kernel implementation here
https://github.com/deepak0414/linux-riscv-cfi/tree/Zisslpcfi-0.1_v6.1-rc2

Quoted 29 lines · Deepak Gupta

Zisslpcfi [1] extension extends risc-v architecture to mitigate against control-flow integrity attacks (ROP/JOP/COP).
Zisslpcfi uses bits (b23-b29) in (m/s/vs) status CSR for enabling cfi in lesser privileged mode and record cfi state. One such state is expected landing pad (ELP). If forward cfi is enabled, indirect call/jmp updates hart's ELP state (1bit) to true. ELP state is cleared only by a landing pad instruction else trap is delivered with ELP state recorded in sstatus CSR.
This two patch series adds following changes to opensbi
- Adds support in opensbi to detect zisslpcfi
- trap redirection updates ELP state accordingly
[1] - https://github.com/riscv/riscv-cfi
Deepak Gupta (2):
include: adding support for zsslpcfi encodings
lib: sbi: zsslpcfi detection and elp cfi state reflect back in status
include/sbi/riscv_encoding.h |  6 ++++++
include/sbi/sbi_hart.h       |  2 ++
lib/sbi/sbi_hart.c           | 21 +++++++++++++++++++++
lib/sbi/sbi_trap.c           | 18 ++++++++++++++++++
4 files changed, 47 insertions(+)
Signature · 1 line
2.25.1