[Patch v9 20/24] perf/x86: Support SSP sampling using sample_regs_* fields

[Dapeng Mi]

Support sampling of CET SSP register via the sample_regs_* fields.

To sample SSP, the sample_simd_regs_enabled field must be set. This
allows the spare space (reclaimed from the original XMM space) in the
sample_regs_* fields to be used for representing SSP.

Similar to eGPRs sampling, the perf_reg_value() function needs to
check if the PERF_SAMPLE_REGS_ABI_SIMD flag is set first, and then
determine whether to output SSP or legacy XMM registers to userspace.

Additionally, arch-PEBS supports sampling SSP, which is placed into the
GPRs group. Also enables arch-PEBS-based SSP sampling in this patch.

Currently, SSP sampling is only supported on the x86_64 architecture, as
CET is only available on x86_64 platforms.

SSP sampling will be enabled in a subsequent patch that sets
PERF_PMU_CAP_SIMD_REGS.

Co-developed-by: Kan Liang <kan.liang@xxxxxxxxxxxxxxx>
Signed-off-by: Kan Liang <kan.liang@xxxxxxxxxxxxxxx>
Signed-off-by: Dapeng Mi <dapeng1.mi@xxxxxxxxxxxxxxx>
---
 arch/x86/events/core.c                | 11 +++++++++++
 arch/x86/events/intel/ds.c            | 15 +++++++++++++--
 arch/x86/events/perf_event.h          | 16 ++++++++++++++++
 arch/x86/include/asm/perf_event.h     |  1 +
 arch/x86/include/uapi/asm/perf_regs.h |  7 ++++---
 arch/x86/kernel/perf_regs.c           |  5 +++++
 6 files changed, 50 insertions(+), 5 deletions(-)

diff --git a/arch/x86/events/core.c b/arch/x86/events/core.c
index f4f1f80ed6f4..323be08778d6 100644
--- a/arch/x86/events/core.c
+++ b/arch/x86/events/core.c
@@ -725,6 +725,9 @@ int x86_pmu_hw_config(struct perf_event *event)
 			if (event_needs_egprs(event) &&
 			    !(x86_pmu.ext_regs_mask & XFEATURE_MASK_APX))
 				return -EINVAL;
+			if (event_needs_ssp(event) &&
+			    !(x86_pmu.ext_regs_mask & XFEATURE_MASK_CET_USER))
+				return -EINVAL;
 			/* The vector registers set is not supported */
 			if (event_needs_xmm(event) &&
 			    !(x86_pmu.ext_regs_mask & XFEATURE_MASK_SSE))
@@ -1799,11 +1802,13 @@ void x86_pmu_clear_perf_regs(struct pt_regs *regs)
 	perf_regs->h16zmm_regs = NULL;
 	perf_regs->opmask_regs = NULL;
 	perf_regs->egpr_regs = NULL;
+	perf_regs->ssp = NULL;
 }
 
 static void update_perf_regs(struct x86_perf_regs *perf_regs,
 			     struct xregs_state *xsave, u64 bitmap)
 {
+	struct cet_user_state *cet;
 	u64 mask;
 
 	if (!xsave)
@@ -1824,6 +1829,10 @@ static void update_perf_regs(struct x86_perf_regs *perf_regs,
 		perf_regs->opmask = get_xsave_addr(xsave, XFEATURE_OPMASK);
 	if (mask & XFEATURE_MASK_APX)
 		perf_regs->egpr = get_xsave_addr(xsave, XFEATURE_APX);
+	if (mask & XFEATURE_MASK_CET_USER) {
+		cet = get_xsave_addr(xsave, XFEATURE_CET_USER);
+		perf_regs->ssp = cet ? &cet->user_ssp : NULL;
+	}
 }
 
 /*
@@ -2025,6 +2034,8 @@ static void x86_pmu_sample_xregs(struct perf_event *event,
 		mask |= XFEATURE_MASK_OPMASK;
 	if (event_needs_egprs(event))
 		mask |= XFEATURE_MASK_APX;
+	if (event_needs_ssp(event))
+		mask |= XFEATURE_MASK_CET_USER;
 
 	mask &= x86_pmu.ext_regs_mask;
 	if ((sample_type & PERF_SAMPLE_REGS_USER) && data->regs_user.regs) {
diff --git a/arch/x86/events/intel/ds.c b/arch/x86/events/intel/ds.c
index 24bfc3fb6060..54e6f73ffde4 100644
--- a/arch/x86/events/intel/ds.c
+++ b/arch/x86/events/intel/ds.c
@@ -1707,6 +1707,7 @@ static u64 pebs_update_adaptive_cfg(struct perf_event *event)
 	u64 sample_type = attr->sample_type;
 	u64 pebs_data_cfg = 0;
 	bool gprs, tsx_weight;
+	u64 xgprs_mask;
 
 	if (!(sample_type & ~(PERF_SAMPLE_IP|PERF_SAMPLE_TIME)) &&
 	    attr->precise_ip > 1)
@@ -1721,10 +1722,13 @@ static u64 pebs_update_adaptive_cfg(struct perf_event *event)
 	 * + precise_ip < 2 for the non event IP
 	 * + For RTM TSX weight we need GPRs for the abort code.
 	 */
+	xgprs_mask = event->attr.sample_simd_regs_enabled ?
+		     PEBS_GP_REGS | BIT_ULL(PERF_REG_X86_SSP) :
+		     PEBS_GP_REGS;
 	gprs = ((sample_type & PERF_SAMPLE_REGS_INTR) &&
-		(attr->sample_regs_intr & PEBS_GP_REGS)) ||
+		(attr->sample_regs_intr & xgprs_mask)) ||
 	       ((sample_type & PERF_SAMPLE_REGS_USER) &&
-		(attr->sample_regs_user & PEBS_GP_REGS));
+		(attr->sample_regs_user & xgprs_mask));
 
 	tsx_weight = (sample_type & PERF_SAMPLE_WEIGHT_TYPE) &&
 		     ((attr->config & INTEL_ARCH_EVENT_MASK) ==
@@ -2674,6 +2678,13 @@ static void setup_arch_pebs_sample_data(struct perf_event *event,
 		__setup_pebs_gpr_group(event, regs,
 				       (struct pebs_gprs *)gprs,
 				       sample_type);
+
+		/* Currently only user space mode enables SSP. */
+		if (user_mode(regs) && (sample_type &
+		    (PERF_SAMPLE_REGS_INTR | PERF_SAMPLE_REGS_USER))) {
+			perf_regs->ssp = &gprs->ssp;
+			ignore_mask |= XFEATURE_MASK_CET_USER;
+		}
 	}
 
 	if (header->aux) {
diff --git a/arch/x86/events/perf_event.h b/arch/x86/events/perf_event.h
index 840ef8a44b52..b1f9d17dddb6 100644
--- a/arch/x86/events/perf_event.h
+++ b/arch/x86/events/perf_event.h
@@ -238,6 +238,22 @@ static inline bool event_needs_egprs(struct perf_event *event)
 	return false;
 }
 
+static inline bool event_needs_ssp(struct perf_event *event)
+{
+	if (!event->attr.sample_simd_regs_enabled)
+		return false;
+
+	if ((event->attr.sample_type & PERF_SAMPLE_REGS_USER) &&
+	    (event->attr.sample_regs_user & BIT_ULL(PERF_REG_X86_SSP)))
+		return true;
+
+	if ((event->attr.sample_type & PERF_SAMPLE_REGS_INTR) &&
+	    (event->attr.sample_regs_intr & BIT_ULL(PERF_REG_X86_SSP)))
+		return true;
+
+	return false;
+}
+
 struct amd_nb {
 	int nb_id;  /* NorthBridge id */
 	int refcnt; /* reference count */
diff --git a/arch/x86/include/asm/perf_event.h b/arch/x86/include/asm/perf_event.h
index bc05f8c17464..4302ef39c42e 100644
--- a/arch/x86/include/asm/perf_event.h
+++ b/arch/x86/include/asm/perf_event.h
@@ -753,6 +753,7 @@ struct x86_perf_regs {
 		u64	*egpr_regs;
 		struct apx_state *egpr;
 	};
+	u64	*ssp;
 };
 
 extern unsigned long perf_arch_instruction_pointer(struct pt_regs *regs);
diff --git a/arch/x86/include/uapi/asm/perf_regs.h b/arch/x86/include/uapi/asm/perf_regs.h
index 977831bd7a9d..faaa82df688d 100644
--- a/arch/x86/include/uapi/asm/perf_regs.h
+++ b/arch/x86/include/uapi/asm/perf_regs.h
@@ -30,10 +30,10 @@ enum perf_event_x86_regs {
 	PERF_REG_X86_R14,
 	PERF_REG_X86_R15,
 	/*
-	 * The eGPRs and XMM have overlaps. Only one can be used
+	 * The eGPRs/SSP and XMM have overlaps. Only one can be used
 	 * at a time. The ABI PERF_SAMPLE_REGS_ABI_SIMD is used to
 	 * distinguish which one is used. If PERF_SAMPLE_REGS_ABI_SIMD
-	 * is set, then eGPRs is used, otherwise, XMM is used.
+	 * is set, then eGPRs/SSP is used, otherwise, XMM is used.
 	 *
 	 * Extended GPRs (eGPRs)
 	 */
@@ -53,10 +53,11 @@ enum perf_event_x86_regs {
 	PERF_REG_X86_R29,
 	PERF_REG_X86_R30,
 	PERF_REG_X86_R31,
+	PERF_REG_X86_SSP,
 	/* These are the limits for the GPRs. */
 	PERF_REG_X86_32_MAX = PERF_REG_X86_GS + 1,
 	PERF_REG_X86_64_MAX = PERF_REG_X86_R15 + 1,
-	PERF_REG_MISC_MAX = PERF_REG_X86_R31 + 1,
+	PERF_REG_MISC_MAX = PERF_REG_X86_SSP + 1,
 
 	/* These all need two bits set because they are 128bit */
 	PERF_REG_X86_XMM0  = 32,
diff --git a/arch/x86/kernel/perf_regs.c b/arch/x86/kernel/perf_regs.c
index b6f75196da02..7a0607b81846 100644
--- a/arch/x86/kernel/perf_regs.c
+++ b/arch/x86/kernel/perf_regs.c
@@ -72,6 +72,11 @@ u64 perf_reg_value(struct pt_regs *regs, int idx)
 					return 0;
 				return perf_regs->egpr_regs[idx - PERF_REG_X86_R16];
 			}
+			if (idx == PERF_REG_X86_SSP) {
+				if (!perf_regs->ssp)
+					return 0;
+				return *perf_regs->ssp;
+			}
 		} else {
 			if (idx >= PERF_REG_X86_XMM0 && idx < PERF_REG_X86_XMM_MAX) {
 				if (!perf_regs->xmm_regs)
-- 
2.34.1