Merge patch series "riscv: fix ptrace and export VLENB"

Andy Chiu <andy.chiu@sifive.com> says:

We add a vlenb field in Vector context and save it with the
riscv_vstate_save() macro. It should not cause performance regression as
VLENB is a design-time constant and is frequently used by hardware.
Also, adding this field into the __sc_riscv_v_state may benifit us on a
future compatibility issue becuse a hardware may have writable VLENB.

Adding and saving VLENB have an immediate benifit as it gives ptrace a
better view of the Vector extension and makes it possible to reconstruct
Vector register files from the dump without doing an additional csr read.

This patchset also sync the number of note types between us and gdb for
riscv to solve a conflicting note.

This is not an ABI break given that 6.5 has not been released yet.

* b4-shazam-merge:
  RISC-V: vector: export VLENB csr in __sc_riscv_v_state
  RISC-V: Remove ptrace support for vectors

Link: https://lore.kernel.org/r/20230816155450.26200-1-andy.chiu@sifive.com
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>

arch/riscv/include/asm/vector.h

@@ -70,8 +70,9 @@ static __always_inline void __vstate_csr_save(struct __riscv_v_ext_state *dest)
 		"csrr	%1, " __stringify(CSR_VTYPE) "\n\t"
 		"csrr	%2, " __stringify(CSR_VL) "\n\t"
 		"csrr	%3, " __stringify(CSR_VCSR) "\n\t"
+		"csrr	%4, " __stringify(CSR_VLENB) "\n\t"
 		: "=r" (dest->vstart), "=r" (dest->vtype), "=r" (dest->vl),
-		  "=r" (dest->vcsr) : :);
+		  "=r" (dest->vcsr), "=r" (dest->vlenb) : :);
 }
 
 static __always_inline void __vstate_csr_restore(struct __riscv_v_ext_state *src)

arch/riscv/include/uapi/asm/ptrace.h

@@ -97,6 +97,7 @@ struct __riscv_v_ext_state {
 	unsigned long vl;
 	unsigned long vtype;
 	unsigned long vcsr;
+	unsigned long vlenb;
 	void *datap;
 	/*
 	 * In signal handler, datap will be set a correct user stack offset

arch/riscv/kernel/ptrace.c

@@ -25,9 +25,6 @@ enum riscv_regset {
 #ifdef CONFIG_FPU
 	REGSET_F,
 #endif
-#ifdef CONFIG_RISCV_ISA_V
-	REGSET_V,
-#endif
 };
 
 static int riscv_gpr_get(struct task_struct *target,
@@ -84,61 +81,6 @@ static int riscv_fpr_set(struct task_struct *target,
 }
 #endif
 
-#ifdef CONFIG_RISCV_ISA_V
-static int riscv_vr_get(struct task_struct *target,
-			const struct user_regset *regset,
-			struct membuf to)
-{
-	struct __riscv_v_ext_state *vstate = &target->thread.vstate;
-
-	if (!riscv_v_vstate_query(task_pt_regs(target)))
-		return -EINVAL;
-
-	/*
-	 * Ensure the vector registers have been saved to the memory before
-	 * copying them to membuf.
-	 */
-	if (target == current)
-		riscv_v_vstate_save(current, task_pt_regs(current));
-
-	/* Copy vector header from vstate. */
-	membuf_write(&to, vstate, offsetof(struct __riscv_v_ext_state, datap));
-	membuf_zero(&to, sizeof(vstate->datap));
-
-	/* Copy all the vector registers from vstate. */
-	return membuf_write(&to, vstate->datap, riscv_v_vsize);
-}
-
-static int riscv_vr_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, size;
-	struct __riscv_v_ext_state *vstate = &target->thread.vstate;
-
-	if (!riscv_v_vstate_query(task_pt_regs(target)))
-		return -EINVAL;
-
-	/* Copy rest of the vstate except datap */
-	ret = user_regset_copyin(&pos, &count, &kbuf, &ubuf, vstate, 0,
-				 offsetof(struct __riscv_v_ext_state, datap));
-	if (unlikely(ret))
-		return ret;
-
-	/* Skip copy datap. */
-	size = sizeof(vstate->datap);
-	count -= size;
-	ubuf += size;
-
-	/* Copy all the vector registers. */
-	pos = 0;
-	ret = user_regset_copyin(&pos, &count, &kbuf, &ubuf, vstate->datap,
-				 0, riscv_v_vsize);
-	return ret;
-}
-#endif
-
 static const struct user_regset riscv_user_regset[] = {
 	[REGSET_X] = {
 		.core_note_type = NT_PRSTATUS,
@@ -158,17 +100,6 @@ static const struct user_regset riscv_user_regset[] = {
 		.set = riscv_fpr_set,
 	},
 #endif
-#ifdef CONFIG_RISCV_ISA_V
-	[REGSET_V] = {
-		.core_note_type = NT_RISCV_VECTOR,
-		.align = 16,
-		.n = ((32 * RISCV_MAX_VLENB) +
-		      sizeof(struct __riscv_v_ext_state)) / sizeof(__u32),
-		.size = sizeof(__u32),
-		.regset_get = riscv_vr_get,
-		.set = riscv_vr_set,
-	},
-#endif
 };
 
 static const struct user_regset_view riscv_user_native_view = {

include/uapi/linux/elf.h

@@ -443,7 +443,6 @@ typedef struct elf64_shdr {
 #define NT_MIPS_DSP	0x800		/* MIPS DSP ASE registers */
 #define NT_MIPS_FP_MODE	0x801		/* MIPS floating-point mode */
 #define NT_MIPS_MSA	0x802		/* MIPS SIMD registers */
-#define NT_RISCV_VECTOR	0x900		/* RISC-V vector registers */
 #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 */