powerpc/perf: Consolidate perf_callchain_user_[64|32]()

perf_callchain_user_64() and perf_callchain_user_32() are nearly
identical. Consolidate into one function with thin wrappers.

Suggested-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michal Suchanek <msuchanek@suse.de>
[mpe: Adapt to copy_from_user_nofault(), minor formatting]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20200406210022.32265-1-msuchanek@suse.de

1 files changed, 24 insertions, 1 deletions

diff --git a/arch/powerpc/perf/callchain.h b/arch/powerpc/perf/callchain.h
index 7a2cb9e1181a..ae24d4a00da6 100644
--- a/arch/powerpc/perf/callchain.h
+++ b/arch/powerpc/perf/callchain.h
@@ -2,7 +2,7 @@
 #ifndef _POWERPC_PERF_CALLCHAIN_H
 #define _POWERPC_PERF_CALLCHAIN_H
 
-int read_user_stack_slow(void __user *ptr, void *buf, int nb);
+int read_user_stack_slow(const void __user *ptr, void *buf, int nb);
 void perf_callchain_user_64(struct perf_callchain_entry_ctx *entry,
 			    struct pt_regs *regs);
 void perf_callchain_user_32(struct perf_callchain_entry_ctx *entry,
@@ -16,4 +16,27 @@ static inline bool invalid_user_sp(unsigned long sp)
 	return (!sp || (sp & mask) || (sp > top));
 }
 
+/*
+ * On 32-bit we just access the address and let hash_page create a
+ * HPTE if necessary, so there is no need to fall back to reading
+ * the page tables.  Since this is called at interrupt level,
+ * do_page_fault() won't treat a DSI as a page fault.
+ */
+static inline int __read_user_stack(const void __user *ptr, void *ret,
+				    size_t size)
+{
+	unsigned long addr = (unsigned long)ptr;
+	int rc;
+
+	if (addr > TASK_SIZE - size || (addr & (size - 1)))
+		return -EFAULT;
+
+	rc = copy_from_user_nofault(ret, ptr, size);
+
+	if (IS_ENABLED(CONFIG_PPC64) && rc)
+		return read_user_stack_slow(ptr, ret, size);
+
+	return rc;
+}
+
 #endif /* _POWERPC_PERF_CALLCHAIN_H */