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authorDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-07 18:49:45 +0000
committerDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-07 18:49:45 +0000
commit2c3c1048746a4622d8c89a29670120dc8fab93c4 (patch)
tree848558de17fb3008cdf4d861b01ac7781903ce39 /arch/arm64/kernel/perf_regs.c
parentInitial commit. (diff)
downloadlinux-2c3c1048746a4622d8c89a29670120dc8fab93c4.tar.xz
linux-2c3c1048746a4622d8c89a29670120dc8fab93c4.zip
Adding upstream version 6.1.76.upstream/6.1.76
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'arch/arm64/kernel/perf_regs.c')
-rw-r--r--arch/arm64/kernel/perf_regs.c106
1 files changed, 106 insertions, 0 deletions
diff --git a/arch/arm64/kernel/perf_regs.c b/arch/arm64/kernel/perf_regs.c
new file mode 100644
index 000000000..b4eece3eb
--- /dev/null
+++ b/arch/arm64/kernel/perf_regs.c
@@ -0,0 +1,106 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/compat.h>
+#include <linux/errno.h>
+#include <linux/kernel.h>
+#include <linux/perf_event.h>
+#include <linux/bug.h>
+#include <linux/sched/task_stack.h>
+
+#include <asm/perf_regs.h>
+#include <asm/ptrace.h>
+
+static u64 perf_ext_regs_value(int idx)
+{
+ switch (idx) {
+ case PERF_REG_ARM64_VG:
+ if (WARN_ON_ONCE(!system_supports_sve()))
+ return 0;
+
+ /*
+ * Vector granule is current length in bits of SVE registers
+ * divided by 64.
+ */
+ return (task_get_sve_vl(current) * 8) / 64;
+ default:
+ WARN_ON_ONCE(true);
+ return 0;
+ }
+}
+
+u64 perf_reg_value(struct pt_regs *regs, int idx)
+{
+ if (WARN_ON_ONCE((u32)idx >= PERF_REG_ARM64_EXTENDED_MAX))
+ return 0;
+
+ /*
+ * Our handling of compat tasks (PERF_SAMPLE_REGS_ABI_32) is weird, but
+ * we're stuck with it for ABI compatibility reasons.
+ *
+ * For a 32-bit consumer inspecting a 32-bit task, then it will look at
+ * the first 16 registers (see arch/arm/include/uapi/asm/perf_regs.h).
+ * These correspond directly to a prefix of the registers saved in our
+ * 'struct pt_regs', with the exception of the PC, so we copy that down
+ * (x15 corresponds to SP_hyp in the architecture).
+ *
+ * So far, so good.
+ *
+ * The oddity arises when a 64-bit consumer looks at a 32-bit task and
+ * asks for registers beyond PERF_REG_ARM_MAX. In this case, we return
+ * SP_usr, LR_usr and PC in the positions where the AArch64 SP, LR and
+ * PC registers would normally live. The initial idea was to allow a
+ * 64-bit unwinder to unwind a 32-bit task and, although it's not clear
+ * how well that works in practice, somebody might be relying on it.
+ *
+ * At the time we make a sample, we don't know whether the consumer is
+ * 32-bit or 64-bit, so we have to cater for both possibilities.
+ */
+ if (compat_user_mode(regs)) {
+ if ((u32)idx == PERF_REG_ARM64_SP)
+ return regs->compat_sp;
+ if ((u32)idx == PERF_REG_ARM64_LR)
+ return regs->compat_lr;
+ if (idx == 15)
+ return regs->pc;
+ }
+
+ if ((u32)idx == PERF_REG_ARM64_SP)
+ return regs->sp;
+
+ if ((u32)idx == PERF_REG_ARM64_PC)
+ return regs->pc;
+
+ if ((u32)idx >= PERF_REG_ARM64_MAX)
+ return perf_ext_regs_value(idx);
+
+ return regs->regs[idx];
+}
+
+#define REG_RESERVED (~((1ULL << PERF_REG_ARM64_MAX) - 1))
+
+int perf_reg_validate(u64 mask)
+{
+ u64 reserved_mask = REG_RESERVED;
+
+ if (system_supports_sve())
+ reserved_mask &= ~(1ULL << PERF_REG_ARM64_VG);
+
+ if (!mask || mask & reserved_mask)
+ return -EINVAL;
+
+ return 0;
+}
+
+u64 perf_reg_abi(struct task_struct *task)
+{
+ if (is_compat_thread(task_thread_info(task)))
+ return PERF_SAMPLE_REGS_ABI_32;
+ else
+ return PERF_SAMPLE_REGS_ABI_64;
+}
+
+void perf_get_regs_user(struct perf_regs *regs_user,
+ struct pt_regs *regs)
+{
+ regs_user->regs = task_pt_regs(current);
+ regs_user->abi = perf_reg_abi(current);
+}