[RFC PATCH 4/4] perf/x86/core: Add tls dump support

[Beau Belgrave]

Now that perf supports TLS dumps, x86-64 can provide the details for how
to get TLS data for user threads.

Enable HAVE_PERF_USER_TLS_DUMP Kconfig only for x86-64. I do not have
access to x86 to validate 32-bit.

Utilize mmap_is_ia32() to determine 32/64 bit threads. Use fsbase for
64-bit and gsbase for 32-bit with appropriate size.

Signed-off-by: Beau Belgrave <beaub@xxxxxxxxxxxxxxxxxxx>
---
 arch/x86/Kconfig                  |  1 +
 arch/x86/events/core.c            | 14 ++++++++++++++
 arch/x86/include/asm/perf_event.h |  5 +++++
 3 files changed, 20 insertions(+)

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 4fff6ed46e90..8d46ec8ded0c 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -263,6 +263,7 @@ config X86
 	select HAVE_PCI
 	select HAVE_PERF_REGS
 	select HAVE_PERF_USER_STACK_DUMP
+	select HAVE_PERF_USER_TLS_DUMP		if X86_64
 	select MMU_GATHER_RCU_TABLE_FREE	if PARAVIRT
 	select MMU_GATHER_MERGE_VMAS
 	select HAVE_POSIX_CPU_TIMERS_TASK_WORK
diff --git a/arch/x86/events/core.c b/arch/x86/events/core.c
index 09050641ce5d..3f851db4c591 100644
--- a/arch/x86/events/core.c
+++ b/arch/x86/events/core.c
@@ -41,6 +41,7 @@
 #include <asm/desc.h>
 #include <asm/ldt.h>
 #include <asm/unwind.h>
+#include <asm/elf.h>
 
 #include "perf_event.h"
 
@@ -3002,3 +3003,16 @@ u64 perf_get_hw_event_config(int hw_event)
 	return 0;
 }
 EXPORT_SYMBOL_GPL(perf_get_hw_event_config);
+
+#ifdef CONFIG_X86_64
+void arch_perf_user_tls_pointer(struct perf_tls *tls)
+{
+	if (!mmap_is_ia32()) {
+		tls->base = current->thread.fsbase;
+		tls->size = sizeof(u64);
+	} else {
+		tls->base = current->thread.gsbase;
+		tls->size = sizeof(u32);
+	}
+}
+#endif
diff --git a/arch/x86/include/asm/perf_event.h b/arch/x86/include/asm/perf_event.h
index 3736b8a46c04..d0f65e572c20 100644
--- a/arch/x86/include/asm/perf_event.h
+++ b/arch/x86/include/asm/perf_event.h
@@ -628,4 +628,9 @@ static __always_inline void perf_lopwr_cb(bool lopwr_in)
 
 #define arch_perf_out_copy_user copy_from_user_nmi
 
+#ifdef CONFIG_HAVE_PERF_USER_TLS_DUMP
+struct perf_tls;
+extern void arch_perf_user_tls_pointer(struct perf_tls *tls);
+#endif
+
 #endif /* _ASM_X86_PERF_EVENT_H */
-- 
2.34.1