[PATCH v5 00/10] riscv: Userspace pointer masking and tagged address ABI

[PATCH v5 00/10] riscv: Userspace pointer masking and tagged address ABI

[Samuel Holland]

RISC-V defines three extensions for pointer masking[1]:
 - Smmpm: configured in M-mode, affects M-mode
 - Smnpm: configured in M-mode, affects the next lower mode (S or U-mode)
 - Ssnpm: configured in S-mode, affects the next lower mode (VS, VU, or U-mode)

This series adds support for configuring Smnpm or Ssnpm (depending on
which privilege mode the kernel is running in) to allow pointer masking
in userspace (VU or U-mode), extending the PR_SET_TAGGED_ADDR_CTRL API
from arm64. Unlike arm64 TBI, userspace pointer masking is not enabled
by default on RISC-V. Additionally, the tag width (referred to as PMLEN)
is variable, so userspace needs to ask the kernel for a specific tag
width, which is interpreted as a lower bound on the number of tag bits.

This series also adds support for a tagged address ABI similar to arm64
and x86. Since accesses from the kernel to user memory use the kernel's
pointer masking configuration, not the user's, the kernel must untag
user pointers in software before dereferencing them. And since the tag
width is variable, as with LAM on x86, it must be kept the same across
all threads in a process so untagged_addr_remote() can work.

[1]: https://github.com/riscv/riscv-j-extension/raw/d70011dde6c2/zjpm-spec.pdf
---
This series depends on the per-thread envcfg series in riscv/for-next.

This series can be tested in QEMU by applying a patch set[2].

KASAN_SW_TAGS using pointer masking is an independent patch series[3].

[2]: https://lore.kernel.org/qemu-devel/20240511101053.1875596-1-me@deliversmonkey.space/
[3]: https://lore.kernel.org/linux-riscv/20240814085618.968833-1-samuel.holland@sifive.com/

Changes in v5:
 - Update pointer masking spec version to 1.0 and state to ratified
 - Document how PR_[SG]ET_TAGGED_ADDR_CTRL are used on RISC-V
 - Document that the RISC-V tagged address ABI is the same as AArch64
 - Rename "pm" selftests directory to "abi" to be more generic
 - Fix -Wparentheses warnings
 - Fix order of operations when writing via the tagged pointer
 - Update pointer masking spec version to 1.0 in hwprobe documentation

Changes in v4:
 - Switch IS_ENABLED back to #ifdef to fix riscv32 build
 - Combine __untagged_addr() and __untagged_addr_remote()

Changes in v3:
 - Note in the commit message that the ISA extension spec is frozen
 - Rebase on riscv/for-next (ISA extension list conflicts)
 - Remove RISCV_ISA_EXT_SxPM, which was not used anywhere
 - Use shifts instead of large numbers in ENVCFG_PMM* macro definitions
 - Rename CONFIG_RISCV_ISA_POINTER_MASKING to CONFIG_RISCV_ISA_SUPM,
   since it only controls the userspace part of pointer masking
 - Use IS_ENABLED instead of #ifdef when possible
 - Use an enum for the supported PMLEN values
 - Simplify the logic in set_tagged_addr_ctrl()
 - Use IS_ENABLED instead of #ifdef when possible
 - Implement mm_untag_mask()
 - Remove pmlen from struct thread_info (now only in mm_context_t)

Changes in v2:
 - Drop patch 4 ("riscv: Define is_compat_thread()"), as an equivalent
   patch was already applied
 - Move patch 5 ("riscv: Split per-CPU and per-thread envcfg bits") to a
   different series[3]
 - Update pointer masking specification version reference
 - Provide macros for the extension affecting the kernel and userspace
 - Use the correct name for the hstatus.HUPMM field
 - Rebase on riscv/linux.git for-next
 - Add and use the envcfg_update_bits() helper function
 - Inline flush_tagged_addr_state()
 - Implement untagged_addr_remote()
 - Restrict PMLEN changes once a process is multithreaded
 - Rename "tags" directory to "pm" to avoid .gitignore rules
 - Add .gitignore file to ignore the compiled selftest binary
 - Write to a pipe to force dereferencing the user pointer
 - Handle SIGSEGV in the child process to reduce dmesg noise
 - Export Supm via hwprobe
 - Export Smnpm and Ssnpm to KVM guests

Samuel Holland (10):
  dt-bindings: riscv: Add pointer masking ISA extensions
  riscv: Add ISA extension parsing for pointer masking
  riscv: Add CSR definitions for pointer masking
  riscv: Add support for userspace pointer masking
  riscv: Add support for the tagged address ABI
  riscv: Allow ptrace control of the tagged address ABI
  riscv: selftests: Add a pointer masking test
  riscv: hwprobe: Export the Supm ISA extension
  RISC-V: KVM: Allow Smnpm and Ssnpm extensions for guests
  KVM: riscv: selftests: Add Smnpm and Ssnpm to get-reg-list test

 Documentation/arch/riscv/hwprobe.rst          |   3 +
 Documentation/arch/riscv/uabi.rst             |  16 +
 .../devicetree/bindings/riscv/extensions.yaml |  18 +
 arch/riscv/Kconfig                            |  11 +
 arch/riscv/include/asm/csr.h                  |  16 +
 arch/riscv/include/asm/hwcap.h                |   5 +
 arch/riscv/include/asm/mmu.h                  |   7 +
 arch/riscv/include/asm/mmu_context.h          |  13 +
 arch/riscv/include/asm/processor.h            |   8 +
 arch/riscv/include/asm/switch_to.h            |  11 +
 arch/riscv/include/asm/uaccess.h              |  43 ++-
 arch/riscv/include/uapi/asm/hwprobe.h         |   1 +
 arch/riscv/include/uapi/asm/kvm.h             |   2 +
 arch/riscv/kernel/cpufeature.c                |   3 +
 arch/riscv/kernel/process.c                   | 154 ++++++++
 arch/riscv/kernel/ptrace.c                    |  42 +++
 arch/riscv/kernel/sys_hwprobe.c               |   3 +
 arch/riscv/kvm/vcpu_onereg.c                  |   4 +
 include/uapi/linux/elf.h                      |   1 +
 include/uapi/linux/prctl.h                    |   5 +-
 .../selftests/kvm/riscv/get-reg-list.c        |   8 +
 tools/testing/selftests/riscv/Makefile        |   2 +-
 tools/testing/selftests/riscv/abi/.gitignore  |   1 +
 tools/testing/selftests/riscv/abi/Makefile    |  10 +
 .../selftests/riscv/abi/pointer_masking.c     | 332 ++++++++++++++++++
 25 files changed, 712 insertions(+), 7 deletions(-)
 create mode 100644 tools/testing/selftests/riscv/abi/.gitignore
 create mode 100644 tools/testing/selftests/riscv/abi/Makefile
 create mode 100644 tools/testing/selftests/riscv/abi/pointer_masking.c

-- 
2.45.1

[PATCH v5 01/10] dt-bindings: riscv: Add pointer masking ISA extensions

[Samuel Holland]

The RISC-V Pointer Masking specification defines three extensions:
Smmpm, Smnpm, and Ssnpm. Document the behavior of these extensions as
following the ratified version 1.0 of the specification.

Acked-by: Conor Dooley <conor.dooley@microchip.com>
Reviewed-by: Charlie Jenkins <charlie@rivosinc.com>
Signed-off-by: Samuel Holland <samuel.holland@sifive.com>
---

Changes in v5:
 - Update pointer masking spec version to 1.0 and state to ratified

Changes in v3:
 - Note in the commit message that the ISA extension spec is frozen

Changes in v2:
 - Update pointer masking specification version reference

 .../devicetree/bindings/riscv/extensions.yaml  | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/Documentation/devicetree/bindings/riscv/extensions.yaml b/Documentation/devicetree/bindings/riscv/extensions.yaml
index 2cf2026cff57..28bf1daa1d27 100644
--- a/Documentation/devicetree/bindings/riscv/extensions.yaml
+++ b/Documentation/devicetree/bindings/riscv/extensions.yaml
@@ -128,6 +128,18 @@ properties:
             changes to interrupts as frozen at commit ccbddab ("Merge pull
             request #42 from riscv/jhauser-2023-RC4") of riscv-aia.
 
+        - const: smmpm
+          description: |
+            The standard Smmpm extension for M-mode pointer masking as
+            ratified at commit d70011dde6c2 ("Update to ratified state")
+            of riscv-j-extension.
+
+        - const: smnpm
+          description: |
+            The standard Smnpm extension for next-mode pointer masking as
+            ratified at commit d70011dde6c2 ("Update to ratified state")
+            of riscv-j-extension.
+
         - const: smstateen
           description: |
             The standard Smstateen extension for controlling access to CSRs
@@ -147,6 +159,12 @@ properties:
             and mode-based filtering as ratified at commit 01d1df0 ("Add ability
             to manually trigger workflow. (#2)") of riscv-count-overflow.
 
+        - const: ssnpm
+          description: |
+            The standard Ssnpm extension for next-mode pointer masking as
+            ratified at commit d70011dde6c2 ("Update to ratified state")
+            of riscv-j-extension.
+
         - const: sstc
           description: |
             The standard Sstc supervisor-level extension for time compare as
-- 
2.45.1

[PATCH v5 02/10] riscv: Add ISA extension parsing for pointer masking

[Samuel Holland]

The RISC-V Pointer Masking specification defines three extensions:
Smmpm, Smnpm, and Ssnpm. Add support for parsing each of them. The
specific extension which provides pointer masking support to userspace
(Supm) depends on the kernel's privilege mode, so provide a macro to
abstract this selection.

Smmpm implies the existence of the mseccfg CSR. As it is the only user
of this CSR so far, there is no need for an Xlinuxmseccfg extension.

Reviewed-by: Charlie Jenkins <charlie@rivosinc.com>
Signed-off-by: Samuel Holland <samuel.holland@sifive.com>
---

(no changes since v3)

Changes in v3:
 - Rebase on riscv/for-next (ISA extension list conflicts)
 - Remove RISCV_ISA_EXT_SxPM, which was not used anywhere

Changes in v2:
 - Provide macros for the extension affecting the kernel and userspace

 arch/riscv/include/asm/hwcap.h | 5 +++++
 arch/riscv/kernel/cpufeature.c | 3 +++
 2 files changed, 8 insertions(+)

diff --git a/arch/riscv/include/asm/hwcap.h b/arch/riscv/include/asm/hwcap.h
index 46d9de54179e..8608883da453 100644
--- a/arch/riscv/include/asm/hwcap.h
+++ b/arch/riscv/include/asm/hwcap.h
@@ -93,6 +93,9 @@
 #define RISCV_ISA_EXT_ZCMOP		84
 #define RISCV_ISA_EXT_ZAWRS		85
 #define RISCV_ISA_EXT_SVVPTC		86
+#define RISCV_ISA_EXT_SMMPM		87
+#define RISCV_ISA_EXT_SMNPM		88
+#define RISCV_ISA_EXT_SSNPM		89
 
 #define RISCV_ISA_EXT_XLINUXENVCFG	127
 
@@ -101,8 +104,10 @@
 
 #ifdef CONFIG_RISCV_M_MODE
 #define RISCV_ISA_EXT_SxAIA		RISCV_ISA_EXT_SMAIA
+#define RISCV_ISA_EXT_SUPM		RISCV_ISA_EXT_SMNPM
 #else
 #define RISCV_ISA_EXT_SxAIA		RISCV_ISA_EXT_SSAIA
+#define RISCV_ISA_EXT_SUPM		RISCV_ISA_EXT_SSNPM
 #endif
 
 #endif /* _ASM_RISCV_HWCAP_H */
diff --git a/arch/riscv/kernel/cpufeature.c b/arch/riscv/kernel/cpufeature.c
index b3a057c36996..94596bca464e 100644
--- a/arch/riscv/kernel/cpufeature.c
+++ b/arch/riscv/kernel/cpufeature.c
@@ -377,9 +377,12 @@ const struct riscv_isa_ext_data riscv_isa_ext[] = {
 	__RISCV_ISA_EXT_BUNDLE(zvksg, riscv_zvksg_bundled_exts),
 	__RISCV_ISA_EXT_DATA(zvkt, RISCV_ISA_EXT_ZVKT),
 	__RISCV_ISA_EXT_DATA(smaia, RISCV_ISA_EXT_SMAIA),
+	__RISCV_ISA_EXT_DATA(smmpm, RISCV_ISA_EXT_SMMPM),
+	__RISCV_ISA_EXT_SUPERSET(smnpm, RISCV_ISA_EXT_SMNPM, riscv_xlinuxenvcfg_exts),
 	__RISCV_ISA_EXT_DATA(smstateen, RISCV_ISA_EXT_SMSTATEEN),
 	__RISCV_ISA_EXT_DATA(ssaia, RISCV_ISA_EXT_SSAIA),
 	__RISCV_ISA_EXT_DATA(sscofpmf, RISCV_ISA_EXT_SSCOFPMF),
+	__RISCV_ISA_EXT_SUPERSET(ssnpm, RISCV_ISA_EXT_SSNPM, riscv_xlinuxenvcfg_exts),
 	__RISCV_ISA_EXT_DATA(sstc, RISCV_ISA_EXT_SSTC),
 	__RISCV_ISA_EXT_DATA(svinval, RISCV_ISA_EXT_SVINVAL),
 	__RISCV_ISA_EXT_DATA(svnapot, RISCV_ISA_EXT_SVNAPOT),
-- 
2.45.1

[PATCH v5 03/10] riscv: Add CSR definitions for pointer masking

[Samuel Holland]

Pointer masking is controlled via a two-bit PMM field, which appears in
various CSRs depending on which extensions are implemented. Smmpm adds
the field to mseccfg; Smnpm adds the field to menvcfg; Ssnpm adds the
field to senvcfg. If the H extension is implemented, Ssnpm also defines
henvcfg.PMM and hstatus.HUPMM.

Reviewed-by: Charlie Jenkins <charlie@rivosinc.com>
Signed-off-by: Samuel Holland <samuel.holland@sifive.com>
---

(no changes since v3)

Changes in v3:
 - Use shifts instead of large numbers in ENVCFG_PMM* macro definitions

Changes in v2:
 - Use the correct name for the hstatus.HUPMM field

 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 25966995da04..fe5d4eb9adea 100644
--- a/arch/riscv/include/asm/csr.h
+++ b/arch/riscv/include/asm/csr.h
@@ -119,6 +119,10 @@
 
 /* HSTATUS flags */
 #ifdef CONFIG_64BIT
+#define HSTATUS_HUPMM		_AC(0x3000000000000, UL)
+#define HSTATUS_HUPMM_PMLEN_0	_AC(0x0000000000000, UL)
+#define HSTATUS_HUPMM_PMLEN_7	_AC(0x2000000000000, UL)
+#define HSTATUS_HUPMM_PMLEN_16	_AC(0x3000000000000, UL)
 #define HSTATUS_VSXL		_AC(0x300000000, UL)
 #define HSTATUS_VSXL_SHIFT	32
 #endif
@@ -195,6 +199,10 @@
 /* xENVCFG flags */
 #define ENVCFG_STCE			(_AC(1, ULL) << 63)
 #define ENVCFG_PBMTE			(_AC(1, ULL) << 62)
+#define ENVCFG_PMM			(_AC(0x3, ULL) << 32)
+#define ENVCFG_PMM_PMLEN_0		(_AC(0x0, ULL) << 32)
+#define ENVCFG_PMM_PMLEN_7		(_AC(0x2, ULL) << 32)
+#define ENVCFG_PMM_PMLEN_16		(_AC(0x3, ULL) << 32)
 #define ENVCFG_CBZE			(_AC(1, UL) << 7)
 #define ENVCFG_CBCFE			(_AC(1, UL) << 6)
 #define ENVCFG_CBIE_SHIFT		4
@@ -216,6 +224,12 @@
 #define SMSTATEEN0_SSTATEEN0_SHIFT	63
 #define SMSTATEEN0_SSTATEEN0		(_ULL(1) << SMSTATEEN0_SSTATEEN0_SHIFT)
 
+/* mseccfg bits */
+#define MSECCFG_PMM			ENVCFG_PMM
+#define MSECCFG_PMM_PMLEN_0		ENVCFG_PMM_PMLEN_0
+#define MSECCFG_PMM_PMLEN_7		ENVCFG_PMM_PMLEN_7
+#define MSECCFG_PMM_PMLEN_16		ENVCFG_PMM_PMLEN_16
+
 /* symbolic CSR names: */
 #define CSR_CYCLE		0xc00
 #define CSR_TIME		0xc01
@@ -382,6 +396,8 @@
 #define CSR_MIP			0x344
 #define CSR_PMPCFG0		0x3a0
 #define CSR_PMPADDR0		0x3b0
+#define CSR_MSECCFG		0x747
+#define CSR_MSECCFGH		0x757
 #define CSR_MVENDORID		0xf11
 #define CSR_MARCHID		0xf12
 #define CSR_MIMPID		0xf13
-- 
2.45.1

[PATCH v5 04/10] riscv: Add support for userspace pointer masking

[Samuel Holland]

RISC-V supports pointer masking with a variable number of tag bits
(which is called "PMLEN" in the specification) and which is configured
at the next higher privilege level.

Wire up the PR_SET_TAGGED_ADDR_CTRL and PR_GET_TAGGED_ADDR_CTRL prctls
so userspace can request a lower bound on the number of tag bits and
determine the actual number of tag bits. As with arm64's
PR_TAGGED_ADDR_ENABLE, the pointer masking configuration is
thread-scoped, inherited on clone() and fork() and cleared on execve().

Reviewed-by: Charlie Jenkins <charlie@rivosinc.com>
Tested-by: Charlie Jenkins <charlie@rivosinc.com>
Signed-off-by: Samuel Holland <samuel.holland@sifive.com>
---

Changes in v5:
 - Document how PR_[SG]ET_TAGGED_ADDR_CTRL are used on RISC-V

Changes in v4:
 - Switch IS_ENABLED back to #ifdef to fix riscv32 build

Changes in v3:
 - Rename CONFIG_RISCV_ISA_POINTER_MASKING to CONFIG_RISCV_ISA_SUPM,
   since it only controls the userspace part of pointer masking
 - Use IS_ENABLED instead of #ifdef when possible
 - Use an enum for the supported PMLEN values
 - Simplify the logic in set_tagged_addr_ctrl()

Changes in v2:
 - Rebase on riscv/linux.git for-next
 - Add and use the envcfg_update_bits() helper function
 - Inline flush_tagged_addr_state()

 Documentation/arch/riscv/uabi.rst  | 12 ++++
 arch/riscv/Kconfig                 | 11 ++++
 arch/riscv/include/asm/processor.h |  8 +++
 arch/riscv/include/asm/switch_to.h | 11 ++++
 arch/riscv/kernel/process.c        | 91 ++++++++++++++++++++++++++++++
 include/uapi/linux/prctl.h         |  5 +-
 6 files changed, 137 insertions(+), 1 deletion(-)

diff --git a/Documentation/arch/riscv/uabi.rst b/Documentation/arch/riscv/uabi.rst
index 2b420bab0527..ddb8359a46ed 100644
--- a/Documentation/arch/riscv/uabi.rst
+++ b/Documentation/arch/riscv/uabi.rst
@@ -68,3 +68,15 @@ Misaligned accesses
 Misaligned scalar accesses are supported in userspace, but they may perform
 poorly.  Misaligned vector accesses are only supported if the Zicclsm extension
 is supported.
+
+Pointer masking
+---------------
+
+Support for pointer masking in userspace (the Supm extension) is provided via
+the ``PR_SET_TAGGED_ADDR_CTRL`` and ``PR_GET_TAGGED_ADDR_CTRL`` ``prctl()``
+operations. Pointer masking is disabled by default. To enable it, userspace
+must call ``PR_SET_TAGGED_ADDR_CTRL`` with the ``PR_PMLEN`` field set to the
+number of mask/tag bits needed by the application. ``PR_PMLEN`` is interpreted
+as a lower bound; if the kernel is unable to satisfy the request, the
+``PR_SET_TAGGED_ADDR_CTRL`` operation will fail. The actual number of tag bits
+is returned in ``PR_PMLEN`` by the ``PR_GET_TAGGED_ADDR_CTRL`` operation.
diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index 22dc5ea4196c..0ef449465378 100644
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -531,6 +531,17 @@ config RISCV_ISA_C
 
 	  If you don't know what to do here, say Y.
 
+config RISCV_ISA_SUPM
+	bool "Supm extension for userspace pointer masking"
+	depends on 64BIT
+	default y
+	help
+	  Add support for pointer masking in userspace (Supm) when the
+	  underlying hardware extension (Smnpm or Ssnpm) is detected at boot.
+
+	  If this option is disabled, userspace will be unable to use
+	  the prctl(PR_{SET,GET}_TAGGED_ADDR_CTRL) API.
+
 config RISCV_ISA_SVNAPOT
 	bool "Svnapot extension support for supervisor mode NAPOT pages"
 	depends on 64BIT && MMU
diff --git a/arch/riscv/include/asm/processor.h b/arch/riscv/include/asm/processor.h
index c1a492508835..5f56eb9d114a 100644
--- a/arch/riscv/include/asm/processor.h
+++ b/arch/riscv/include/asm/processor.h
@@ -178,6 +178,14 @@ extern int set_unalign_ctl(struct task_struct *tsk, unsigned int val);
 #define RISCV_SET_ICACHE_FLUSH_CTX(arg1, arg2)	riscv_set_icache_flush_ctx(arg1, arg2)
 extern int riscv_set_icache_flush_ctx(unsigned long ctx, unsigned long per_thread);
 
+#ifdef CONFIG_RISCV_ISA_SUPM
+/* PR_{SET,GET}_TAGGED_ADDR_CTRL prctl */
+long set_tagged_addr_ctrl(struct task_struct *task, unsigned long arg);
+long get_tagged_addr_ctrl(struct task_struct *task);
+#define SET_TAGGED_ADDR_CTRL(arg)	set_tagged_addr_ctrl(current, arg)
+#define GET_TAGGED_ADDR_CTRL()		get_tagged_addr_ctrl(current)
+#endif
+
 #endif /* __ASSEMBLY__ */
 
 #endif /* _ASM_RISCV_PROCESSOR_H */
diff --git a/arch/riscv/include/asm/switch_to.h b/arch/riscv/include/asm/switch_to.h
index 9685cd85e57c..94e33216b2d9 100644
--- a/arch/riscv/include/asm/switch_to.h
+++ b/arch/riscv/include/asm/switch_to.h
@@ -70,6 +70,17 @@ static __always_inline bool has_fpu(void) { return false; }
 #define __switch_to_fpu(__prev, __next) do { } while (0)
 #endif
 
+static inline void envcfg_update_bits(struct task_struct *task,
+				      unsigned long mask, unsigned long val)
+{
+	unsigned long envcfg;
+
+	envcfg = (task->thread.envcfg & ~mask) | val;
+	task->thread.envcfg = envcfg;
+	if (task == current)
+		csr_write(CSR_ENVCFG, envcfg);
+}
+
 static inline void __switch_to_envcfg(struct task_struct *next)
 {
 	asm volatile (ALTERNATIVE("nop", "csrw " __stringify(CSR_ENVCFG) ", %0",
diff --git a/arch/riscv/kernel/process.c b/arch/riscv/kernel/process.c
index e3142d8a6e28..200d2ed64dfe 100644
--- a/arch/riscv/kernel/process.c
+++ b/arch/riscv/kernel/process.c
@@ -7,6 +7,7 @@
  * Copyright (C) 2017 SiFive
  */
 
+#include <linux/bitfield.h>
 #include <linux/cpu.h>
 #include <linux/kernel.h>
 #include <linux/sched.h>
@@ -180,6 +181,10 @@ void flush_thread(void)
 	memset(&current->thread.vstate, 0, sizeof(struct __riscv_v_ext_state));
 	clear_tsk_thread_flag(current, TIF_RISCV_V_DEFER_RESTORE);
 #endif
+#ifdef CONFIG_RISCV_ISA_SUPM
+	if (riscv_has_extension_unlikely(RISCV_ISA_EXT_SUPM))
+		envcfg_update_bits(current, ENVCFG_PMM, ENVCFG_PMM_PMLEN_0);
+#endif
 }
 
 void arch_release_task_struct(struct task_struct *tsk)
@@ -242,3 +247,89 @@ void __init arch_task_cache_init(void)
 {
 	riscv_v_setup_ctx_cache();
 }
+
+#ifdef CONFIG_RISCV_ISA_SUPM
+enum {
+	PMLEN_0 = 0,
+	PMLEN_7 = 7,
+	PMLEN_16 = 16,
+};
+
+static bool have_user_pmlen_7;
+static bool have_user_pmlen_16;
+
+long set_tagged_addr_ctrl(struct task_struct *task, unsigned long arg)
+{
+	unsigned long valid_mask = PR_PMLEN_MASK;
+	struct thread_info *ti = task_thread_info(task);
+	unsigned long pmm;
+	u8 pmlen;
+
+	if (is_compat_thread(ti))
+		return -EINVAL;
+
+	if (arg & ~valid_mask)
+		return -EINVAL;
+
+	/*
+	 * Prefer the smallest PMLEN that satisfies the user's request,
+	 * in case choosing a larger PMLEN has a performance impact.
+	 */
+	pmlen = FIELD_GET(PR_PMLEN_MASK, arg);
+	if (pmlen == PMLEN_0)
+		pmm = ENVCFG_PMM_PMLEN_0;
+	else if (pmlen <= PMLEN_7 && have_user_pmlen_7)
+		pmm = ENVCFG_PMM_PMLEN_7;
+	else if (pmlen <= PMLEN_16 && have_user_pmlen_16)
+		pmm = ENVCFG_PMM_PMLEN_16;
+	else
+		return -EINVAL;
+
+	envcfg_update_bits(task, ENVCFG_PMM, pmm);
+
+	return 0;
+}
+
+long get_tagged_addr_ctrl(struct task_struct *task)
+{
+	struct thread_info *ti = task_thread_info(task);
+	long ret = 0;
+
+	if (is_compat_thread(ti))
+		return -EINVAL;
+
+	switch (task->thread.envcfg & ENVCFG_PMM) {
+	case ENVCFG_PMM_PMLEN_7:
+		ret = FIELD_PREP(PR_PMLEN_MASK, PMLEN_7);
+		break;
+	case ENVCFG_PMM_PMLEN_16:
+		ret = FIELD_PREP(PR_PMLEN_MASK, PMLEN_16);
+		break;
+	}
+
+	return ret;
+}
+
+static bool try_to_set_pmm(unsigned long value)
+{
+	csr_set(CSR_ENVCFG, value);
+	return (csr_read_clear(CSR_ENVCFG, ENVCFG_PMM) & ENVCFG_PMM) == value;
+}
+
+static int __init tagged_addr_init(void)
+{
+	if (!riscv_has_extension_unlikely(RISCV_ISA_EXT_SUPM))
+		return 0;
+
+	/*
+	 * envcfg.PMM is a WARL field. Detect which values are supported.
+	 * Assume the supported PMLEN values are the same on all harts.
+	 */
+	csr_clear(CSR_ENVCFG, ENVCFG_PMM);
+	have_user_pmlen_7 = try_to_set_pmm(ENVCFG_PMM_PMLEN_7);
+	have_user_pmlen_16 = try_to_set_pmm(ENVCFG_PMM_PMLEN_16);
+
+	return 0;
+}
+core_initcall(tagged_addr_init);
+#endif	/* CONFIG_RISCV_ISA_SUPM */
diff --git a/include/uapi/linux/prctl.h b/include/uapi/linux/prctl.h
index 35791791a879..cefd656ebf43 100644
--- a/include/uapi/linux/prctl.h
+++ b/include/uapi/linux/prctl.h
@@ -230,7 +230,7 @@ struct prctl_mm_map {
 # define PR_PAC_APDBKEY			(1UL << 3)
 # define PR_PAC_APGAKEY			(1UL << 4)
 
-/* Tagged user address controls for arm64 */
+/* Tagged user address controls for arm64 and RISC-V */
 #define PR_SET_TAGGED_ADDR_CTRL		55
 #define PR_GET_TAGGED_ADDR_CTRL		56
 # define PR_TAGGED_ADDR_ENABLE		(1UL << 0)
@@ -244,6 +244,9 @@ struct prctl_mm_map {
 # define PR_MTE_TAG_MASK		(0xffffUL << PR_MTE_TAG_SHIFT)
 /* Unused; kept only for source compatibility */
 # define PR_MTE_TCF_SHIFT		1
+/* RISC-V pointer masking tag length */
+# define PR_PMLEN_SHIFT			24
+# define PR_PMLEN_MASK			(0x7fUL << PR_PMLEN_SHIFT)
 
 /* Control reclaim behavior when allocating memory */
 #define PR_SET_IO_FLUSHER		57
-- 
2.45.1

[PATCH v5 05/10] riscv: Add support for the tagged address ABI

[Samuel Holland]

When pointer masking is enabled for userspace, the kernel can accept
tagged pointers as arguments to some system calls. Allow this by
untagging the pointers in access_ok() and the uaccess routines. The
uaccess routines must peform untagging in software because U-mode and
S-mode have entirely separate pointer masking configurations. In fact,
hardware may not even implement pointer masking for S-mode.

Since the number of tag bits is variable, untagged_addr_remote() needs
to know what PMLEN to use for the remote mm. Therefore, the pointer
masking mode must be the same for all threads sharing an mm. Enforce
this with a lock flag in the mm context, as x86 does for LAM. The flag
gets reset in init_new_context() during fork(), as the new mm is no
longer multithreaded.

Reviewed-by: Charlie Jenkins <charlie@rivosinc.com>
Tested-by: Charlie Jenkins <charlie@rivosinc.com>
Signed-off-by: Samuel Holland <samuel.holland@sifive.com>
---

Changes in v5:
 - Document that the RISC-V tagged address ABI is the same as AArch64

Changes in v4:
 - Combine __untagged_addr() and __untagged_addr_remote()

Changes in v3:
 - Use IS_ENABLED instead of #ifdef when possible
 - Implement mm_untag_mask()
 - Remove pmlen from struct thread_info (now only in mm_context_t)

Changes in v2:
 - Implement untagged_addr_remote()
 - Restrict PMLEN changes once a process is multithreaded

 Documentation/arch/riscv/uabi.rst    |  4 ++
 arch/riscv/include/asm/mmu.h         |  7 +++
 arch/riscv/include/asm/mmu_context.h | 13 +++++
 arch/riscv/include/asm/uaccess.h     | 43 ++++++++++++++--
 arch/riscv/kernel/process.c          | 73 ++++++++++++++++++++++++++--
 5 files changed, 130 insertions(+), 10 deletions(-)

diff --git a/Documentation/arch/riscv/uabi.rst b/Documentation/arch/riscv/uabi.rst
index ddb8359a46ed..243e40062e34 100644
--- a/Documentation/arch/riscv/uabi.rst
+++ b/Documentation/arch/riscv/uabi.rst
@@ -80,3 +80,7 @@ number of mask/tag bits needed by the application. ``PR_PMLEN`` is interpreted
 as a lower bound; if the kernel is unable to satisfy the request, the
 ``PR_SET_TAGGED_ADDR_CTRL`` operation will fail. The actual number of tag bits
 is returned in ``PR_PMLEN`` by the ``PR_GET_TAGGED_ADDR_CTRL`` operation.
+
+Additionally, when pointer masking is enabled (``PR_PMLEN`` is greater than 0),
+a tagged address ABI is supported, with the same interface and behavior as
+documented for AArch64 (Documentation/arch/arm64/tagged-address-abi.rst).
diff --git a/arch/riscv/include/asm/mmu.h b/arch/riscv/include/asm/mmu.h
index c9e03e9da3dc..1cc90465d75b 100644
--- a/arch/riscv/include/asm/mmu.h
+++ b/arch/riscv/include/asm/mmu.h
@@ -25,9 +25,16 @@ typedef struct {
 #ifdef CONFIG_BINFMT_ELF_FDPIC
 	unsigned long exec_fdpic_loadmap;
 	unsigned long interp_fdpic_loadmap;
+#endif
+	unsigned long flags;
+#ifdef CONFIG_RISCV_ISA_SUPM
+	u8 pmlen;
 #endif
 } mm_context_t;
 
+/* Lock the pointer masking mode because this mm is multithreaded */
+#define MM_CONTEXT_LOCK_PMLEN	0
+
 #define cntx2asid(cntx)		((cntx) & SATP_ASID_MASK)
 #define cntx2version(cntx)	((cntx) & ~SATP_ASID_MASK)
 
diff --git a/arch/riscv/include/asm/mmu_context.h b/arch/riscv/include/asm/mmu_context.h
index 7030837adc1a..8c4bc49a3a0f 100644
--- a/arch/riscv/include/asm/mmu_context.h
+++ b/arch/riscv/include/asm/mmu_context.h
@@ -20,6 +20,9 @@ void switch_mm(struct mm_struct *prev, struct mm_struct *next,
 static inline void activate_mm(struct mm_struct *prev,
 			       struct mm_struct *next)
 {
+#ifdef CONFIG_RISCV_ISA_SUPM
+	next->context.pmlen = 0;
+#endif
 	switch_mm(prev, next, NULL);
 }
 
@@ -30,11 +33,21 @@ static inline int init_new_context(struct task_struct *tsk,
 #ifdef CONFIG_MMU
 	atomic_long_set(&mm->context.id, 0);
 #endif
+	if (IS_ENABLED(CONFIG_RISCV_ISA_SUPM))
+		clear_bit(MM_CONTEXT_LOCK_PMLEN, &mm->context.flags);
 	return 0;
 }
 
 DECLARE_STATIC_KEY_FALSE(use_asid_allocator);
 
+#ifdef CONFIG_RISCV_ISA_SUPM
+#define mm_untag_mask mm_untag_mask
+static inline unsigned long mm_untag_mask(struct mm_struct *mm)
+{
+	return -1UL >> mm->context.pmlen;
+}
+#endif
+
 #include <asm-generic/mmu_context.h>
 
 #endif /* _ASM_RISCV_MMU_CONTEXT_H */
diff --git a/arch/riscv/include/asm/uaccess.h b/arch/riscv/include/asm/uaccess.h
index 72ec1d9bd3f3..fee56b0c8058 100644
--- a/arch/riscv/include/asm/uaccess.h
+++ b/arch/riscv/include/asm/uaccess.h
@@ -9,8 +9,41 @@
 #define _ASM_RISCV_UACCESS_H
 
 #include <asm/asm-extable.h>
+#include <asm/cpufeature.h>
 #include <asm/pgtable.h>		/* for TASK_SIZE */
 
+#ifdef CONFIG_RISCV_ISA_SUPM
+static inline unsigned long __untagged_addr_remote(struct mm_struct *mm, unsigned long addr)
+{
+	if (riscv_has_extension_unlikely(RISCV_ISA_EXT_SUPM)) {
+		u8 pmlen = mm->context.pmlen;
+
+		/* Virtual addresses are sign-extended; physical addresses are zero-extended. */
+		if (IS_ENABLED(CONFIG_MMU))
+			return (long)(addr << pmlen) >> pmlen;
+		else
+			return (addr << pmlen) >> pmlen;
+	}
+
+	return addr;
+}
+
+#define untagged_addr(addr) ({							\
+	unsigned long __addr = (__force unsigned long)(addr);			\
+	(__force __typeof__(addr))__untagged_addr_remote(current->mm, __addr);	\
+})
+
+#define untagged_addr_remote(mm, addr) ({					\
+	unsigned long __addr = (__force unsigned long)(addr);			\
+	mmap_assert_locked(mm);							\
+	(__force __typeof__(addr))__untagged_addr_remote(mm, __addr);		\
+})
+
+#define access_ok(addr, size) likely(__access_ok(untagged_addr(addr), size))
+#else
+#define untagged_addr(addr) (addr)
+#endif
+
 /*
  * User space memory access functions
  */
@@ -130,7 +163,7 @@ do {								\
  */
 #define __get_user(x, ptr)					\
 ({								\
-	const __typeof__(*(ptr)) __user *__gu_ptr = (ptr);	\
+	const __typeof__(*(ptr)) __user *__gu_ptr = untagged_addr(ptr); \
 	long __gu_err = 0;					\
 								\
 	__chk_user_ptr(__gu_ptr);				\
@@ -246,7 +279,7 @@ do {								\
  */
 #define __put_user(x, ptr)					\
 ({								\
-	__typeof__(*(ptr)) __user *__gu_ptr = (ptr);		\
+	__typeof__(*(ptr)) __user *__gu_ptr = untagged_addr(ptr); \
 	__typeof__(*__gu_ptr) __val = (x);			\
 	long __pu_err = 0;					\
 								\
@@ -293,13 +326,13 @@ unsigned long __must_check __asm_copy_from_user(void *to,
 static inline unsigned long
 raw_copy_from_user(void *to, const void __user *from, unsigned long n)
 {
-	return __asm_copy_from_user(to, from, n);
+	return __asm_copy_from_user(to, untagged_addr(from), n);
 }
 
 static inline unsigned long
 raw_copy_to_user(void __user *to, const void *from, unsigned long n)
 {
-	return __asm_copy_to_user(to, from, n);
+	return __asm_copy_to_user(untagged_addr(to), from, n);
 }
 
 extern long strncpy_from_user(char *dest, const char __user *src, long count);
@@ -314,7 +347,7 @@ unsigned long __must_check clear_user(void __user *to, unsigned long n)
 {
 	might_fault();
 	return access_ok(to, n) ?
-		__clear_user(to, n) : n;
+		__clear_user(untagged_addr(to), n) : n;
 }
 
 #define __get_kernel_nofault(dst, src, type, err_label)			\
diff --git a/arch/riscv/kernel/process.c b/arch/riscv/kernel/process.c
index 200d2ed64dfe..58b6482c2bf6 100644
--- a/arch/riscv/kernel/process.c
+++ b/arch/riscv/kernel/process.c
@@ -213,6 +213,10 @@ int copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
 	unsigned long tls = args->tls;
 	struct pt_regs *childregs = task_pt_regs(p);
 
+	/* Ensure all threads in this mm have the same pointer masking mode. */
+	if (IS_ENABLED(CONFIG_RISCV_ISA_SUPM) && p->mm && (clone_flags & CLONE_VM))
+		set_bit(MM_CONTEXT_LOCK_PMLEN, &p->mm->context.flags);
+
 	memset(&p->thread.s, 0, sizeof(p->thread.s));
 
 	/* p->thread holds context to be restored by __switch_to() */
@@ -258,10 +262,16 @@ enum {
 static bool have_user_pmlen_7;
 static bool have_user_pmlen_16;
 
+/*
+ * Control the relaxed ABI allowing tagged user addresses into the kernel.
+ */
+static unsigned int tagged_addr_disabled;
+
 long set_tagged_addr_ctrl(struct task_struct *task, unsigned long arg)
 {
-	unsigned long valid_mask = PR_PMLEN_MASK;
+	unsigned long valid_mask = PR_PMLEN_MASK | PR_TAGGED_ADDR_ENABLE;
 	struct thread_info *ti = task_thread_info(task);
+	struct mm_struct *mm = task->mm;
 	unsigned long pmm;
 	u8 pmlen;
 
@@ -276,16 +286,41 @@ long set_tagged_addr_ctrl(struct task_struct *task, unsigned long arg)
 	 * in case choosing a larger PMLEN has a performance impact.
 	 */
 	pmlen = FIELD_GET(PR_PMLEN_MASK, arg);
-	if (pmlen == PMLEN_0)
+	if (pmlen == PMLEN_0) {
 		pmm = ENVCFG_PMM_PMLEN_0;
-	else if (pmlen <= PMLEN_7 && have_user_pmlen_7)
+	} else if (pmlen <= PMLEN_7 && have_user_pmlen_7) {
+		pmlen = PMLEN_7;
 		pmm = ENVCFG_PMM_PMLEN_7;
-	else if (pmlen <= PMLEN_16 && have_user_pmlen_16)
+	} else if (pmlen <= PMLEN_16 && have_user_pmlen_16) {
+		pmlen = PMLEN_16;
 		pmm = ENVCFG_PMM_PMLEN_16;
-	else
+	} else {
 		return -EINVAL;
+	}
+
+	/*
+	 * Do not allow the enabling of the tagged address ABI if globally
+	 * disabled via sysctl abi.tagged_addr_disabled, if pointer masking
+	 * is disabled for userspace.
+	 */
+	if (arg & PR_TAGGED_ADDR_ENABLE && (tagged_addr_disabled || !pmlen))
+		return -EINVAL;
+
+	if (!(arg & PR_TAGGED_ADDR_ENABLE))
+		pmlen = PMLEN_0;
+
+	if (mmap_write_lock_killable(mm))
+		return -EINTR;
+
+	if (test_bit(MM_CONTEXT_LOCK_PMLEN, &mm->context.flags) && mm->context.pmlen != pmlen) {
+		mmap_write_unlock(mm);
+		return -EBUSY;
+	}
 
 	envcfg_update_bits(task, ENVCFG_PMM, pmm);
+	mm->context.pmlen = pmlen;
+
+	mmap_write_unlock(mm);
 
 	return 0;
 }
@@ -298,6 +333,10 @@ long get_tagged_addr_ctrl(struct task_struct *task)
 	if (is_compat_thread(ti))
 		return -EINVAL;
 
+	/*
+	 * The mm context's pmlen is set only when the tagged address ABI is
+	 * enabled, so the effective PMLEN must be extracted from envcfg.PMM.
+	 */
 	switch (task->thread.envcfg & ENVCFG_PMM) {
 	case ENVCFG_PMM_PMLEN_7:
 		ret = FIELD_PREP(PR_PMLEN_MASK, PMLEN_7);
@@ -307,6 +346,9 @@ long get_tagged_addr_ctrl(struct task_struct *task)
 		break;
 	}
 
+	if (task->mm->context.pmlen)
+		ret |= PR_TAGGED_ADDR_ENABLE;
+
 	return ret;
 }
 
@@ -316,6 +358,24 @@ static bool try_to_set_pmm(unsigned long value)
 	return (csr_read_clear(CSR_ENVCFG, ENVCFG_PMM) & ENVCFG_PMM) == value;
 }
 
+/*
+ * Global sysctl to disable the tagged user addresses support. This control
+ * only prevents the tagged address ABI enabling via prctl() and does not
+ * disable it for tasks that already opted in to the relaxed ABI.
+ */
+
+static struct ctl_table tagged_addr_sysctl_table[] = {
+	{
+		.procname	= "tagged_addr_disabled",
+		.mode		= 0644,
+		.data		= &tagged_addr_disabled,
+		.maxlen		= sizeof(int),
+		.proc_handler	= proc_dointvec_minmax,
+		.extra1		= SYSCTL_ZERO,
+		.extra2		= SYSCTL_ONE,
+	},
+};
+
 static int __init tagged_addr_init(void)
 {
 	if (!riscv_has_extension_unlikely(RISCV_ISA_EXT_SUPM))
@@ -329,6 +389,9 @@ static int __init tagged_addr_init(void)
 	have_user_pmlen_7 = try_to_set_pmm(ENVCFG_PMM_PMLEN_7);
 	have_user_pmlen_16 = try_to_set_pmm(ENVCFG_PMM_PMLEN_16);
 
+	if (!register_sysctl("abi", tagged_addr_sysctl_table))
+		return -EINVAL;
+
 	return 0;
 }
 core_initcall(tagged_addr_init);
-- 
2.45.1

[PATCH v5 06/10] riscv: Allow ptrace control of the tagged address ABI

[Samuel Holland]

This allows a tracer to control the ABI of the tracee, as on arm64.

Signed-off-by: Samuel Holland <samuel.holland@sifive.com>
---

(no changes since v1)

 arch/riscv/kernel/ptrace.c | 42 ++++++++++++++++++++++++++++++++++++++
 include/uapi/linux/elf.h   |  1 +
 2 files changed, 43 insertions(+)

diff --git a/arch/riscv/kernel/ptrace.c b/arch/riscv/kernel/ptrace.c
index 92731ff8c79a..ea67e9fb7a58 100644
--- a/arch/riscv/kernel/ptrace.c
+++ b/arch/riscv/kernel/ptrace.c
@@ -28,6 +28,9 @@ enum riscv_regset {
 #ifdef CONFIG_RISCV_ISA_V
 	REGSET_V,
 #endif
+#ifdef CONFIG_RISCV_ISA_SUPM
+	REGSET_TAGGED_ADDR_CTRL,
+#endif
 };
 
 static int riscv_gpr_get(struct task_struct *target,
@@ -152,6 +155,35 @@ static int riscv_vr_set(struct task_struct *target,
 }
 #endif
 
+#ifdef CONFIG_RISCV_ISA_SUPM
+static int tagged_addr_ctrl_get(struct task_struct *target,
+				const struct user_regset *regset,
+				struct membuf to)
+{
+	long ctrl = get_tagged_addr_ctrl(target);
+
+	if (IS_ERR_VALUE(ctrl))
+		return ctrl;
+
+	return membuf_write(&to, &ctrl, sizeof(ctrl));
+}
+
+static int tagged_addr_ctrl_set(struct task_struct *target,
+				const struct user_regset *regset,
+				unsigned int pos, unsigned int count,
+				const void *kbuf, const void __user *ubuf)
+{
+	int ret;
+	long ctrl;
+
+	ret = user_regset_copyin(&pos, &count, &kbuf, &ubuf, &ctrl, 0, -1);
+	if (ret)
+		return ret;
+
+	return set_tagged_addr_ctrl(target, ctrl);
+}
+#endif
+
 static const struct user_regset riscv_user_regset[] = {
 	[REGSET_X] = {
 		.core_note_type = NT_PRSTATUS,
@@ -182,6 +214,16 @@ static const struct user_regset riscv_user_regset[] = {
 		.set = riscv_vr_set,
 	},
 #endif
+#ifdef CONFIG_RISCV_ISA_SUPM
+	[REGSET_TAGGED_ADDR_CTRL] = {
+		.core_note_type = NT_RISCV_TAGGED_ADDR_CTRL,
+		.n = 1,
+		.size = sizeof(long),
+		.align = sizeof(long),
+		.regset_get = tagged_addr_ctrl_get,
+		.set = tagged_addr_ctrl_set,
+	},
+#endif
 };
 
 static const struct user_regset_view riscv_user_native_view = {
diff --git a/include/uapi/linux/elf.h b/include/uapi/linux/elf.h
index b9935988da5c..a920cf8934dc 100644
--- a/include/uapi/linux/elf.h
+++ b/include/uapi/linux/elf.h
@@ -450,6 +450,7 @@ typedef struct elf64_shdr {
 #define NT_MIPS_MSA	0x802		/* MIPS SIMD registers */
 #define NT_RISCV_CSR	0x900		/* RISC-V Control and Status Registers */
 #define NT_RISCV_VECTOR	0x901		/* RISC-V vector registers */
+#define NT_RISCV_TAGGED_ADDR_CTRL 0x902	/* RISC-V tagged address control (prctl()) */
 #define NT_LOONGARCH_CPUCFG	0xa00	/* LoongArch CPU config registers */
 #define NT_LOONGARCH_CSR	0xa01	/* LoongArch control and status registers */
 #define NT_LOONGARCH_LSX	0xa02	/* LoongArch Loongson SIMD Extension registers */
-- 
2.45.1

[PATCH v5 07/10] riscv: selftests: Add a pointer masking test

[Samuel Holland]

This test covers the behavior of the PR_SET_TAGGED_ADDR_CTRL and
PR_GET_TAGGED_ADDR_CTRL prctl() operations, their effects on the
userspace ABI, and their effects on the system call ABI.

Reviewed-by: Charlie Jenkins <charlie@rivosinc.com>
Tested-by: Charlie Jenkins <charlie@rivosinc.com>
Signed-off-by: Samuel Holland <samuel.holland@sifive.com>
---

Changes in v5:
 - Rename "pm" selftests directory to "abi" to be more generic
 - Fix -Wparentheses warnings
 - Fix order of operations when writing via the tagged pointer

Changes in v2:
 - Rename "tags" directory to "pm" to avoid .gitignore rules
 - Add .gitignore file to ignore the compiled selftest binary
 - Write to a pipe to force dereferencing the user pointer
 - Handle SIGSEGV in the child process to reduce dmesg noise

 tools/testing/selftests/riscv/Makefile        |   2 +-
 tools/testing/selftests/riscv/abi/.gitignore  |   1 +
 tools/testing/selftests/riscv/abi/Makefile    |  10 +
 .../selftests/riscv/abi/pointer_masking.c     | 332 ++++++++++++++++++
 4 files changed, 344 insertions(+), 1 deletion(-)
 create mode 100644 tools/testing/selftests/riscv/abi/.gitignore
 create mode 100644 tools/testing/selftests/riscv/abi/Makefile
 create mode 100644 tools/testing/selftests/riscv/abi/pointer_masking.c

diff --git a/tools/testing/selftests/riscv/Makefile b/tools/testing/selftests/riscv/Makefile
index 7ce03d832b64..099b8c1f46f8 100644
--- a/tools/testing/selftests/riscv/Makefile
+++ b/tools/testing/selftests/riscv/Makefile
@@ -5,7 +5,7 @@
 ARCH ?= $(shell uname -m 2>/dev/null || echo not)
 
 ifneq (,$(filter $(ARCH),riscv))
-RISCV_SUBTARGETS ?= hwprobe vector mm sigreturn
+RISCV_SUBTARGETS ?= abi hwprobe mm sigreturn vector
 else
 RISCV_SUBTARGETS :=
 endif
diff --git a/tools/testing/selftests/riscv/abi/.gitignore b/tools/testing/selftests/riscv/abi/.gitignore
new file mode 100644
index 000000000000..b38358f91c4d
--- /dev/null
+++ b/tools/testing/selftests/riscv/abi/.gitignore
@@ -0,0 +1 @@
+pointer_masking
diff --git a/tools/testing/selftests/riscv/abi/Makefile b/tools/testing/selftests/riscv/abi/Makefile
new file mode 100644
index 000000000000..ed82ff9c664e
--- /dev/null
+++ b/tools/testing/selftests/riscv/abi/Makefile
@@ -0,0 +1,10 @@
+# SPDX-License-Identifier: GPL-2.0
+
+CFLAGS += -I$(top_srcdir)/tools/include
+
+TEST_GEN_PROGS := pointer_masking
+
+include ../../lib.mk
+
+$(OUTPUT)/pointer_masking: pointer_masking.c
+	$(CC) -static -o$@ $(CFLAGS) $(LDFLAGS) $^
diff --git a/tools/testing/selftests/riscv/abi/pointer_masking.c b/tools/testing/selftests/riscv/abi/pointer_masking.c
new file mode 100644
index 000000000000..dee41b7ee3e3
--- /dev/null
+++ b/tools/testing/selftests/riscv/abi/pointer_masking.c
@@ -0,0 +1,332 @@
+// SPDX-License-Identifier: GPL-2.0-only
+
+#include <errno.h>
+#include <fcntl.h>
+#include <setjmp.h>
+#include <signal.h>
+#include <stdbool.h>
+#include <sys/prctl.h>
+#include <sys/wait.h>
+#include <unistd.h>
+
+#include "../../kselftest.h"
+
+#ifndef PR_PMLEN_SHIFT
+#define PR_PMLEN_SHIFT			24
+#endif
+#ifndef PR_PMLEN_MASK
+#define PR_PMLEN_MASK			(0x7fUL << PR_PMLEN_SHIFT)
+#endif
+
+static int dev_zero;
+
+static int pipefd[2];
+
+static sigjmp_buf jmpbuf;
+
+static void sigsegv_handler(int sig)
+{
+	siglongjmp(jmpbuf, 1);
+}
+
+static int min_pmlen;
+static int max_pmlen;
+
+static inline bool valid_pmlen(int pmlen)
+{
+	return pmlen == 0 || pmlen == 7 || pmlen == 16;
+}
+
+static void test_pmlen(void)
+{
+	ksft_print_msg("Testing available PMLEN values\n");
+
+	for (int request = 0; request <= 16; request++) {
+		int pmlen, ret;
+
+		ret = prctl(PR_SET_TAGGED_ADDR_CTRL, request << PR_PMLEN_SHIFT, 0, 0, 0);
+		if (ret)
+			goto pr_set_error;
+
+		ret = prctl(PR_GET_TAGGED_ADDR_CTRL, 0, 0, 0, 0);
+		ksft_test_result(ret >= 0, "PMLEN=%d PR_GET_TAGGED_ADDR_CTRL\n", request);
+		if (ret < 0)
+			goto pr_get_error;
+
+		pmlen = (ret & PR_PMLEN_MASK) >> PR_PMLEN_SHIFT;
+		ksft_test_result(pmlen >= request, "PMLEN=%d constraint\n", request);
+		ksft_test_result(valid_pmlen(pmlen), "PMLEN=%d validity\n", request);
+
+		if (min_pmlen == 0)
+			min_pmlen = pmlen;
+		if (max_pmlen < pmlen)
+			max_pmlen = pmlen;
+
+		continue;
+
+pr_set_error:
+		ksft_test_result_skip("PMLEN=%d PR_GET_TAGGED_ADDR_CTRL\n", request);
+pr_get_error:
+		ksft_test_result_skip("PMLEN=%d constraint\n", request);
+		ksft_test_result_skip("PMLEN=%d validity\n", request);
+	}
+
+	if (max_pmlen == 0)
+		ksft_exit_fail_msg("Failed to enable pointer masking\n");
+}
+
+static int set_tagged_addr_ctrl(int pmlen, bool tagged_addr_abi)
+{
+	int arg, ret;
+
+	arg = pmlen << PR_PMLEN_SHIFT | tagged_addr_abi;
+	ret = prctl(PR_SET_TAGGED_ADDR_CTRL, arg, 0, 0, 0);
+	if (!ret) {
+		ret = prctl(PR_GET_TAGGED_ADDR_CTRL, 0, 0, 0, 0);
+		if (ret == arg)
+			return 0;
+	}
+
+	return ret < 0 ? -errno : -ENODATA;
+}
+
+static void test_dereference_pmlen(int pmlen)
+{
+	static volatile int i;
+	volatile int *p;
+	int ret;
+
+	ret = set_tagged_addr_ctrl(pmlen, false);
+	if (ret)
+		return ksft_test_result_error("PMLEN=%d setup (%d)\n", pmlen, ret);
+
+	i = pmlen;
+
+	if (pmlen) {
+		p = (volatile int *)((uintptr_t)&i | 1UL << (__riscv_xlen - pmlen));
+
+		/* These dereferences should succeed. */
+		if (sigsetjmp(jmpbuf, 1))
+			return ksft_test_result_fail("PMLEN=%d valid tag\n", pmlen);
+		if (*p != pmlen)
+			return ksft_test_result_fail("PMLEN=%d bad value\n", pmlen);
+		++*p;
+	}
+
+	p = (volatile int *)((uintptr_t)&i | 1UL << (__riscv_xlen - pmlen - 1));
+
+	/* These dereferences should raise SIGSEGV. */
+	if (sigsetjmp(jmpbuf, 1))
+		return ksft_test_result_pass("PMLEN=%d dereference\n", pmlen);
+	++*p;
+	ksft_test_result_fail("PMLEN=%d invalid tag\n", pmlen);
+}
+
+static void test_dereference(void)
+{
+	ksft_print_msg("Testing userspace pointer dereference\n");
+
+	signal(SIGSEGV, sigsegv_handler);
+
+	test_dereference_pmlen(0);
+	test_dereference_pmlen(min_pmlen);
+	test_dereference_pmlen(max_pmlen);
+
+	signal(SIGSEGV, SIG_DFL);
+}
+
+static void execve_child_sigsegv_handler(int sig)
+{
+	exit(42);
+}
+
+static int execve_child(void)
+{
+	static volatile int i;
+	volatile int *p = (volatile int *)((uintptr_t)&i | 1UL << (__riscv_xlen - 7));
+
+	signal(SIGSEGV, execve_child_sigsegv_handler);
+
+	/* This dereference should raise SIGSEGV. */
+	return *p;
+}
+
+static void test_fork_exec(void)
+{
+	int ret, status;
+
+	ksft_print_msg("Testing fork/exec behavior\n");
+
+	ret = set_tagged_addr_ctrl(min_pmlen, false);
+	if (ret)
+		return ksft_test_result_error("setup (%d)\n", ret);
+
+	if (fork()) {
+		wait(&status);
+		ksft_test_result(WIFEXITED(status) && WEXITSTATUS(status) == 42,
+				 "dereference after fork\n");
+	} else {
+		static volatile int i = 42;
+		volatile int *p;
+
+		p = (volatile int *)((uintptr_t)&i | 1UL << (__riscv_xlen - min_pmlen));
+
+		/* This dereference should succeed. */
+		exit(*p);
+	}
+
+	if (fork()) {
+		wait(&status);
+		ksft_test_result(WIFEXITED(status) && WEXITSTATUS(status) == 42,
+				 "dereference after fork+exec\n");
+	} else {
+		/* Will call execve_child(). */
+		execve("/proc/self/exe", (char *const []) { "", NULL }, NULL);
+	}
+}
+
+static void test_tagged_addr_abi_sysctl(void)
+{
+	char value;
+	int fd;
+
+	ksft_print_msg("Testing tagged address ABI sysctl\n");
+
+	fd = open("/proc/sys/abi/tagged_addr_disabled", O_WRONLY);
+	if (fd < 0) {
+		ksft_test_result_skip("failed to open sysctl file\n");
+		ksft_test_result_skip("failed to open sysctl file\n");
+		return;
+	}
+
+	value = '1';
+	pwrite(fd, &value, 1, 0);
+	ksft_test_result(set_tagged_addr_ctrl(min_pmlen, true) == -EINVAL,
+			 "sysctl disabled\n");
+
+	value = '0';
+	pwrite(fd, &value, 1, 0);
+	ksft_test_result(set_tagged_addr_ctrl(min_pmlen, true) == 0,
+			 "sysctl enabled\n");
+
+	set_tagged_addr_ctrl(0, false);
+
+	close(fd);
+}
+
+static void test_tagged_addr_abi_pmlen(int pmlen)
+{
+	int i, *p, ret;
+
+	i = ~pmlen;
+
+	if (pmlen) {
+		p = (int *)((uintptr_t)&i | 1UL << (__riscv_xlen - pmlen));
+
+		ret = set_tagged_addr_ctrl(pmlen, false);
+		if (ret)
+			return ksft_test_result_error("PMLEN=%d ABI disabled setup (%d)\n",
+						      pmlen, ret);
+
+		ret = write(pipefd[1], p, sizeof(*p));
+		if (ret >= 0 || errno != EFAULT)
+			return ksft_test_result_fail("PMLEN=%d ABI disabled write\n", pmlen);
+
+		ret = read(dev_zero, p, sizeof(*p));
+		if (ret >= 0 || errno != EFAULT)
+			return ksft_test_result_fail("PMLEN=%d ABI disabled read\n", pmlen);
+
+		if (i != ~pmlen)
+			return ksft_test_result_fail("PMLEN=%d ABI disabled value\n", pmlen);
+
+		ret = set_tagged_addr_ctrl(pmlen, true);
+		if (ret)
+			return ksft_test_result_error("PMLEN=%d ABI enabled setup (%d)\n",
+						      pmlen, ret);
+
+		ret = write(pipefd[1], p, sizeof(*p));
+		if (ret != sizeof(*p))
+			return ksft_test_result_fail("PMLEN=%d ABI enabled write\n", pmlen);
+
+		ret = read(dev_zero, p, sizeof(*p));
+		if (ret != sizeof(*p))
+			return ksft_test_result_fail("PMLEN=%d ABI enabled read\n", pmlen);
+
+		if (i)
+			return ksft_test_result_fail("PMLEN=%d ABI enabled value\n", pmlen);
+
+		i = ~pmlen;
+	} else {
+		/* The tagged address ABI cannot be enabled when PMLEN == 0. */
+		ret = set_tagged_addr_ctrl(pmlen, true);
+		if (ret != -EINVAL)
+			return ksft_test_result_error("PMLEN=%d ABI setup (%d)\n",
+						      pmlen, ret);
+	}
+
+	p = (int *)((uintptr_t)&i | 1UL << (__riscv_xlen - pmlen - 1));
+
+	ret = write(pipefd[1], p, sizeof(*p));
+	if (ret >= 0 || errno != EFAULT)
+		return ksft_test_result_fail("PMLEN=%d invalid tag write (%d)\n", pmlen, errno);
+
+	ret = read(dev_zero, p, sizeof(*p));
+	if (ret >= 0 || errno != EFAULT)
+		return ksft_test_result_fail("PMLEN=%d invalid tag read\n", pmlen);
+
+	if (i != ~pmlen)
+		return ksft_test_result_fail("PMLEN=%d invalid tag value\n", pmlen);
+
+	ksft_test_result_pass("PMLEN=%d tagged address ABI\n", pmlen);
+}
+
+static void test_tagged_addr_abi(void)
+{
+	ksft_print_msg("Testing tagged address ABI\n");
+
+	test_tagged_addr_abi_pmlen(0);
+	test_tagged_addr_abi_pmlen(min_pmlen);
+	test_tagged_addr_abi_pmlen(max_pmlen);
+}
+
+static struct test_info {
+	unsigned int nr_tests;
+	void (*test_fn)(void);
+} tests[] = {
+	{ .nr_tests = 17 * 3, test_pmlen },
+	{ .nr_tests = 3, test_dereference },
+	{ .nr_tests = 2, test_fork_exec },
+	{ .nr_tests = 2, test_tagged_addr_abi_sysctl },
+	{ .nr_tests = 3, test_tagged_addr_abi },
+};
+
+int main(int argc, char **argv)
+{
+	unsigned int plan = 0;
+	int ret;
+
+	/* Check if this is the child process after execve(). */
+	if (!argv[0][0])
+		return execve_child();
+
+	dev_zero = open("/dev/zero", O_RDWR);
+	if (dev_zero < 0)
+		return 1;
+
+	/* Write to a pipe so the kernel must dereference the buffer pointer. */
+	ret = pipe(pipefd);
+	if (ret)
+		return 1;
+
+	ksft_print_header();
+
+	for (int i = 0; i < ARRAY_SIZE(tests); i++)
+		plan += tests[i].nr_tests;
+
+	ksft_set_plan(plan);
+
+	for (int i = 0; i < ARRAY_SIZE(tests); i++)
+		tests[i].test_fn();
+
+	ksft_finished();
+}
-- 
2.45.1

[PATCH v5 08/10] riscv: hwprobe: Export the Supm ISA extension

[Samuel Holland]

Supm is a virtual ISA extension defined in the RISC-V Pointer Masking
specification, which indicates that pointer masking is available in
U-mode. It can be provided by either Smnpm or Ssnpm, depending on which
mode the kernel runs in. Userspace should not care about this
distinction, so export Supm instead of either underlying extension.

Hide the extension if the kernel was compiled without support for the
pointer masking prctl() interface.

Signed-off-by: Samuel Holland <samuel.holland@sifive.com>
---

Changes in v5:
 - Update pointer masking spec version to 1.0 in hwprobe documentation

Changes in v2:
 - New patch for v2

 Documentation/arch/riscv/hwprobe.rst  | 3 +++
 arch/riscv/include/uapi/asm/hwprobe.h | 1 +
 arch/riscv/kernel/sys_hwprobe.c       | 3 +++
 3 files changed, 7 insertions(+)

diff --git a/Documentation/arch/riscv/hwprobe.rst b/Documentation/arch/riscv/hwprobe.rst
index 85b709257918..b9aec2e5bbd4 100644
--- a/Documentation/arch/riscv/hwprobe.rst
+++ b/Documentation/arch/riscv/hwprobe.rst
@@ -239,6 +239,9 @@ The following keys are defined:
        ratified in commit 98918c844281 ("Merge pull request #1217 from
        riscv/zawrs") of riscv-isa-manual.
 
+  * :c:macro:`RISCV_HWPROBE_EXT_SUPM`: The Supm extension is supported as
+       defined in version 1.0 of the RISC-V Pointer Masking extensions.
+
 * :c:macro:`RISCV_HWPROBE_KEY_CPUPERF_0`: Deprecated.  Returns similar values to
      :c:macro:`RISCV_HWPROBE_KEY_MISALIGNED_SCALAR_PERF`, but the key was
      mistakenly classified as a bitmask rather than a value.
diff --git a/arch/riscv/include/uapi/asm/hwprobe.h b/arch/riscv/include/uapi/asm/hwprobe.h
index 1e153cda57db..868ff41b93d6 100644
--- a/arch/riscv/include/uapi/asm/hwprobe.h
+++ b/arch/riscv/include/uapi/asm/hwprobe.h
@@ -72,6 +72,7 @@ struct riscv_hwprobe {
 #define		RISCV_HWPROBE_EXT_ZCF		(1ULL << 46)
 #define		RISCV_HWPROBE_EXT_ZCMOP		(1ULL << 47)
 #define		RISCV_HWPROBE_EXT_ZAWRS		(1ULL << 48)
+#define		RISCV_HWPROBE_EXT_SUPM		(1ULL << 49)
 #define RISCV_HWPROBE_KEY_CPUPERF_0	5
 #define		RISCV_HWPROBE_MISALIGNED_UNKNOWN	(0 << 0)
 #define		RISCV_HWPROBE_MISALIGNED_EMULATED	(1 << 0)
diff --git a/arch/riscv/kernel/sys_hwprobe.c b/arch/riscv/kernel/sys_hwprobe.c
index cea0ca2bf2a2..0ac78e9f7c94 100644
--- a/arch/riscv/kernel/sys_hwprobe.c
+++ b/arch/riscv/kernel/sys_hwprobe.c
@@ -150,6 +150,9 @@ static void hwprobe_isa_ext0(struct riscv_hwprobe *pair,
 			EXT_KEY(ZFH);
 			EXT_KEY(ZFHMIN);
 		}
+
+		if (IS_ENABLED(CONFIG_RISCV_ISA_SUPM))
+			EXT_KEY(SUPM);
 #undef EXT_KEY
 	}
 
-- 
2.45.1

[PATCH v5 09/10] RISC-V: KVM: Allow Smnpm and Ssnpm extensions for guests

[Samuel Holland]

The interface for controlling pointer masking in VS-mode is henvcfg.PMM,
which is part of the Ssnpm extension, even though pointer masking in
HS-mode is provided by the Smnpm extension. As a result, emulating Smnpm
in the guest requires (only) Ssnpm on the host.

The guest configures Smnpm through the SBI Firmware Features extension,
which KVM does not yet implement, so currently the ISA extension has no
visible effect on the guest, and thus it cannot be disabled. Ssnpm is
configured using the senvcfg CSR within the guest, so that extension
cannot be hidden from the guest without intercepting writes to the CSR.

Signed-off-by: Samuel Holland <samuel.holland@sifive.com>
---

Changes in v5:
 - Do not allow Smnpm to be disabled, as suggested by Anup

Changes in v2:
 - New patch for v2

 arch/riscv/include/uapi/asm/kvm.h | 2 ++
 arch/riscv/kvm/vcpu_onereg.c      | 4 ++++
 2 files changed, 6 insertions(+)

diff --git a/arch/riscv/include/uapi/asm/kvm.h b/arch/riscv/include/uapi/asm/kvm.h
index e97db3296456..4f24201376b1 100644
--- a/arch/riscv/include/uapi/asm/kvm.h
+++ b/arch/riscv/include/uapi/asm/kvm.h
@@ -175,6 +175,8 @@ enum KVM_RISCV_ISA_EXT_ID {
 	KVM_RISCV_ISA_EXT_ZCF,
 	KVM_RISCV_ISA_EXT_ZCMOP,
 	KVM_RISCV_ISA_EXT_ZAWRS,
+	KVM_RISCV_ISA_EXT_SMNPM,
+	KVM_RISCV_ISA_EXT_SSNPM,
 	KVM_RISCV_ISA_EXT_MAX,
 };
 
diff --git a/arch/riscv/kvm/vcpu_onereg.c b/arch/riscv/kvm/vcpu_onereg.c
index b319c4c13c54..5b68490ad9b7 100644
--- a/arch/riscv/kvm/vcpu_onereg.c
+++ b/arch/riscv/kvm/vcpu_onereg.c
@@ -34,9 +34,11 @@ static const unsigned long kvm_isa_ext_arr[] = {
 	[KVM_RISCV_ISA_EXT_M] = RISCV_ISA_EXT_m,
 	[KVM_RISCV_ISA_EXT_V] = RISCV_ISA_EXT_v,
 	/* Multi letter extensions (alphabetically sorted) */
+	[KVM_RISCV_ISA_EXT_SMNPM] = RISCV_ISA_EXT_SSNPM,
 	KVM_ISA_EXT_ARR(SMSTATEEN),
 	KVM_ISA_EXT_ARR(SSAIA),
 	KVM_ISA_EXT_ARR(SSCOFPMF),
+	KVM_ISA_EXT_ARR(SSNPM),
 	KVM_ISA_EXT_ARR(SSTC),
 	KVM_ISA_EXT_ARR(SVINVAL),
 	KVM_ISA_EXT_ARR(SVNAPOT),
@@ -127,8 +129,10 @@ static bool kvm_riscv_vcpu_isa_disable_allowed(unsigned long ext)
 	case KVM_RISCV_ISA_EXT_C:
 	case KVM_RISCV_ISA_EXT_I:
 	case KVM_RISCV_ISA_EXT_M:
+	case KVM_RISCV_ISA_EXT_SMNPM:
 	/* There is not architectural config bit to disable sscofpmf completely */
 	case KVM_RISCV_ISA_EXT_SSCOFPMF:
+	case KVM_RISCV_ISA_EXT_SSNPM:
 	case KVM_RISCV_ISA_EXT_SSTC:
 	case KVM_RISCV_ISA_EXT_SVINVAL:
 	case KVM_RISCV_ISA_EXT_SVNAPOT:
-- 
2.45.1

[PATCH v5 10/10] KVM: riscv: selftests: Add Smnpm and Ssnpm to get-reg-list test

[Samuel Holland]

Add testing for the pointer masking extensions exposed to KVM guests.

Reviewed-by: Anup Patel <anup@brainfault.org>
Signed-off-by: Samuel Holland <samuel.holland@sifive.com>
---

(no changes since v2)

Changes in v2:
 - New patch for v2

 tools/testing/selftests/kvm/riscv/get-reg-list.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/tools/testing/selftests/kvm/riscv/get-reg-list.c b/tools/testing/selftests/kvm/riscv/get-reg-list.c
index 8e34f7fa44e9..54ab484d0000 100644
--- a/tools/testing/selftests/kvm/riscv/get-reg-list.c
+++ b/tools/testing/selftests/kvm/riscv/get-reg-list.c
@@ -41,9 +41,11 @@ bool filter_reg(__u64 reg)
 	case KVM_REG_RISCV_ISA_EXT | KVM_REG_RISCV_ISA_SINGLE | KVM_RISCV_ISA_EXT_I:
 	case KVM_REG_RISCV_ISA_EXT | KVM_REG_RISCV_ISA_SINGLE | KVM_RISCV_ISA_EXT_M:
 	case KVM_REG_RISCV_ISA_EXT | KVM_REG_RISCV_ISA_SINGLE | KVM_RISCV_ISA_EXT_V:
+	case KVM_REG_RISCV_ISA_EXT | KVM_REG_RISCV_ISA_SINGLE | KVM_RISCV_ISA_EXT_SMNPM:
 	case KVM_REG_RISCV_ISA_EXT | KVM_REG_RISCV_ISA_SINGLE | KVM_RISCV_ISA_EXT_SMSTATEEN:
 	case KVM_REG_RISCV_ISA_EXT | KVM_REG_RISCV_ISA_SINGLE | KVM_RISCV_ISA_EXT_SSAIA:
 	case KVM_REG_RISCV_ISA_EXT | KVM_REG_RISCV_ISA_SINGLE | KVM_RISCV_ISA_EXT_SSCOFPMF:
+	case KVM_REG_RISCV_ISA_EXT | KVM_REG_RISCV_ISA_SINGLE | KVM_RISCV_ISA_EXT_SSNPM:
 	case KVM_REG_RISCV_ISA_EXT | KVM_REG_RISCV_ISA_SINGLE | KVM_RISCV_ISA_EXT_SSTC:
 	case KVM_REG_RISCV_ISA_EXT | KVM_REG_RISCV_ISA_SINGLE | KVM_RISCV_ISA_EXT_SVINVAL:
 	case KVM_REG_RISCV_ISA_EXT | KVM_REG_RISCV_ISA_SINGLE | KVM_RISCV_ISA_EXT_SVNAPOT:
@@ -414,9 +416,11 @@ static const char *isa_ext_single_id_to_str(__u64 reg_off)
 		KVM_ISA_EXT_ARR(I),
 		KVM_ISA_EXT_ARR(M),
 		KVM_ISA_EXT_ARR(V),
+		KVM_ISA_EXT_ARR(SMNPM),
 		KVM_ISA_EXT_ARR(SMSTATEEN),
 		KVM_ISA_EXT_ARR(SSAIA),
 		KVM_ISA_EXT_ARR(SSCOFPMF),
+		KVM_ISA_EXT_ARR(SSNPM),
 		KVM_ISA_EXT_ARR(SSTC),
 		KVM_ISA_EXT_ARR(SVINVAL),
 		KVM_ISA_EXT_ARR(SVNAPOT),
@@ -946,8 +950,10 @@ KVM_ISA_EXT_SUBLIST_CONFIG(aia, AIA);
 KVM_ISA_EXT_SUBLIST_CONFIG(fp_f, FP_F);
 KVM_ISA_EXT_SUBLIST_CONFIG(fp_d, FP_D);
 KVM_ISA_EXT_SIMPLE_CONFIG(h, H);
+KVM_ISA_EXT_SIMPLE_CONFIG(smnpm, SMNPM);
 KVM_ISA_EXT_SUBLIST_CONFIG(smstateen, SMSTATEEN);
 KVM_ISA_EXT_SIMPLE_CONFIG(sscofpmf, SSCOFPMF);
+KVM_ISA_EXT_SIMPLE_CONFIG(ssnpm, SSNPM);
 KVM_ISA_EXT_SIMPLE_CONFIG(sstc, SSTC);
 KVM_ISA_EXT_SIMPLE_CONFIG(svinval, SVINVAL);
 KVM_ISA_EXT_SIMPLE_CONFIG(svnapot, SVNAPOT);
@@ -1009,8 +1015,10 @@ struct vcpu_reg_list *vcpu_configs[] = {
 	&config_fp_f,
 	&config_fp_d,
 	&config_h,
+	&config_smnpm,
 	&config_smstateen,
 	&config_sscofpmf,
+	&config_ssnpm,
 	&config_sstc,
 	&config_svinval,
 	&config_svnapot,
-- 
2.45.1

Re: [PATCH v5 09/10] RISC-V: KVM: Allow Smnpm and Ssnpm extensions for guests

[Anup Patel]

On Thu, Oct 17, 2024 at 1:58 AM Samuel Holland
<samuel.holland@sifive.com> wrote:
>
> The interface for controlling pointer masking in VS-mode is henvcfg.PMM,
> which is part of the Ssnpm extension, even though pointer masking in
> HS-mode is provided by the Smnpm extension. As a result, emulating Smnpm
> in the guest requires (only) Ssnpm on the host.
>
> The guest configures Smnpm through the SBI Firmware Features extension,
> which KVM does not yet implement, so currently the ISA extension has no
> visible effect on the guest, and thus it cannot be disabled. Ssnpm is
> configured using the senvcfg CSR within the guest, so that extension
> cannot be hidden from the guest without intercepting writes to the CSR.
>
> Signed-off-by: Samuel Holland <samuel.holland@sifive.com>

LGTM.

Reviewed-by: Anup Patel <anup@brainfault.org>

Regards,
Anup

> ---
>
> Changes in v5:
>  - Do not allow Smnpm to be disabled, as suggested by Anup
>
> Changes in v2:
>  - New patch for v2
>
>  arch/riscv/include/uapi/asm/kvm.h | 2 ++
>  arch/riscv/kvm/vcpu_onereg.c      | 4 ++++
>  2 files changed, 6 insertions(+)
>
> diff --git a/arch/riscv/include/uapi/asm/kvm.h b/arch/riscv/include/uapi/asm/kvm.h
> index e97db3296456..4f24201376b1 100644
> --- a/arch/riscv/include/uapi/asm/kvm.h
> +++ b/arch/riscv/include/uapi/asm/kvm.h
> @@ -175,6 +175,8 @@ enum KVM_RISCV_ISA_EXT_ID {
>         KVM_RISCV_ISA_EXT_ZCF,
>         KVM_RISCV_ISA_EXT_ZCMOP,
>         KVM_RISCV_ISA_EXT_ZAWRS,
> +       KVM_RISCV_ISA_EXT_SMNPM,
> +       KVM_RISCV_ISA_EXT_SSNPM,
>         KVM_RISCV_ISA_EXT_MAX,
>  };
>
> diff --git a/arch/riscv/kvm/vcpu_onereg.c b/arch/riscv/kvm/vcpu_onereg.c
> index b319c4c13c54..5b68490ad9b7 100644
> --- a/arch/riscv/kvm/vcpu_onereg.c
> +++ b/arch/riscv/kvm/vcpu_onereg.c
> @@ -34,9 +34,11 @@ static const unsigned long kvm_isa_ext_arr[] = {
>         [KVM_RISCV_ISA_EXT_M] = RISCV_ISA_EXT_m,
>         [KVM_RISCV_ISA_EXT_V] = RISCV_ISA_EXT_v,
>         /* Multi letter extensions (alphabetically sorted) */
> +       [KVM_RISCV_ISA_EXT_SMNPM] = RISCV_ISA_EXT_SSNPM,
>         KVM_ISA_EXT_ARR(SMSTATEEN),
>         KVM_ISA_EXT_ARR(SSAIA),
>         KVM_ISA_EXT_ARR(SSCOFPMF),
> +       KVM_ISA_EXT_ARR(SSNPM),
>         KVM_ISA_EXT_ARR(SSTC),
>         KVM_ISA_EXT_ARR(SVINVAL),
>         KVM_ISA_EXT_ARR(SVNAPOT),
> @@ -127,8 +129,10 @@ static bool kvm_riscv_vcpu_isa_disable_allowed(unsigned long ext)
>         case KVM_RISCV_ISA_EXT_C:
>         case KVM_RISCV_ISA_EXT_I:
>         case KVM_RISCV_ISA_EXT_M:
> +       case KVM_RISCV_ISA_EXT_SMNPM:
>         /* There is not architectural config bit to disable sscofpmf completely */
>         case KVM_RISCV_ISA_EXT_SSCOFPMF:
> +       case KVM_RISCV_ISA_EXT_SSNPM:
>         case KVM_RISCV_ISA_EXT_SSTC:
>         case KVM_RISCV_ISA_EXT_SVINVAL:
>         case KVM_RISCV_ISA_EXT_SVNAPOT:
> --
> 2.45.1
>

Re: [PATCH v5 00/10] riscv: Userspace pointer masking and tagged address ABI

[patchwork-bot+linux-riscv]

Hello:

This series was applied to riscv/linux.git (for-next)
by Palmer Dabbelt <palmer@rivosinc.com>:

On Wed, 16 Oct 2024 13:27:41 -0700 you wrote:
> RISC-V defines three extensions for pointer masking[1]:
>  - Smmpm: configured in M-mode, affects M-mode
>  - Smnpm: configured in M-mode, affects the next lower mode (S or U-mode)
>  - Ssnpm: configured in S-mode, affects the next lower mode (VS, VU, or U-mode)
> 
> This series adds support for configuring Smnpm or Ssnpm (depending on
> which privilege mode the kernel is running in) to allow pointer masking
> in userspace (VU or U-mode), extending the PR_SET_TAGGED_ADDR_CTRL API
> from arm64. Unlike arm64 TBI, userspace pointer masking is not enabled
> by default on RISC-V. Additionally, the tag width (referred to as PMLEN)
> is variable, so userspace needs to ask the kernel for a specific tag
> width, which is interpreted as a lower bound on the number of tag bits.
> 
> [...]

Here is the summary with links:
  - [v5,01/10] dt-bindings: riscv: Add pointer masking ISA extensions
    https://git.kernel.org/riscv/c/8946ad26c0e2
  - [v5,02/10] riscv: Add ISA extension parsing for pointer masking
    https://git.kernel.org/riscv/c/12749546293e
  - [v5,03/10] riscv: Add CSR definitions for pointer masking
    https://git.kernel.org/riscv/c/1edd6226877b
  - [v5,04/10] riscv: Add support for userspace pointer masking
    https://git.kernel.org/riscv/c/871aba681a0d
  - [v5,05/10] riscv: Add support for the tagged address ABI
    https://git.kernel.org/riscv/c/c4d16116bd11
  - [v5,06/10] riscv: Allow ptrace control of the tagged address ABI
    https://git.kernel.org/riscv/c/cebce87fb04e
  - [v5,07/10] riscv: selftests: Add a pointer masking test
    https://git.kernel.org/riscv/c/5e9f1ee1c523
  - [v5,08/10] riscv: hwprobe: Export the Supm ISA extension
    https://git.kernel.org/riscv/c/d250050aae4f
  - [v5,09/10] RISC-V: KVM: Allow Smnpm and Ssnpm extensions for guests
    https://git.kernel.org/riscv/c/e27f468bcf14
  - [v5,10/10] KVM: riscv: selftests: Add Smnpm and Ssnpm to get-reg-list test
    https://git.kernel.org/riscv/c/814779461d84

You are awesome, thank you!
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