[RFC PATCH v1 2/5] unwind_user/sframe: Add support for signal frame indication

[Jens Remus <jremus@linux.ibm.com>]

SFrame V3 represents the assembler directive .cfi_signal_frame using
a SFrame FDE flag.  Note that a SFrame FDE with this particular flag set
may have no SFrame FREs.

Introduce a SFRAME_V3_FDE_SIGNAL_P() helper macro.  Use it in
__find_fre() to populate the signal flag in struct unwind_user_frame,
even if there are no FREs.

Signed-off-by: Jens Remus <jremus@linux.ibm.com>
---
 kernel/unwind/sframe.c | 8 +++++++-
 kernel/unwind/sframe.h | 1 +
 2 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/kernel/unwind/sframe.c b/kernel/unwind/sframe.c
index 21283e3bda42..9fd2fc1572cc 100644
--- a/kernel/unwind/sframe.c
+++ b/kernel/unwind/sframe.c
@@ -446,6 +446,7 @@ static __always_inline int __find_fre(struct sframe_section *sec,
 				      struct unwind_user_frame *frame)
 {
 	unsigned char fde_pctype = SFRAME_V3_FDE_PCTYPE(fde->info);
+	bool signal = SFRAME_V3_FDE_SIGNAL_P(fde->info);
 	struct sframe_fre_internal *fre, *prev_fre = NULL;
 	struct sframe_fre_internal fres[2];
 	unsigned long fre_addr;
@@ -486,8 +487,11 @@ static __always_inline int __find_fre(struct sframe_section *sec,
 		prev_fre = fre;
 	}
 
-	if (!prev_fre)
+	if (!prev_fre) {
+		if (signal)
+			goto signal;
 		return -EINVAL;
+	}
 	fre = prev_fre;
 
 	ret = __read_fre_datawords(sec, fde, fre);
@@ -500,6 +504,8 @@ static __always_inline int __find_fre(struct sframe_section *sec,
 	sframe_init_rule_data(&frame->fp, fre->fp_ctl, fre->fp_off);
 	frame->sp_off  = SFRAME_SP_OFFSET;
 	frame->outermost = SFRAME_V3_FRE_RA_UNDEFINED_P(fre->info);
+signal:
+	frame->signal = signal;
 
 	return 0;
 }
diff --git a/kernel/unwind/sframe.h b/kernel/unwind/sframe.h
index 8a5322e95403..78432857f84c 100644
--- a/kernel/unwind/sframe.h
+++ b/kernel/unwind/sframe.h
@@ -65,6 +65,7 @@ struct sframe_fda_v3 {
 #define SFRAME_V3_FDE_FRE_TYPE(info)		((info) & 0xf)
 #define SFRAME_V3_FDE_PCTYPE(info)		(((info) >> 4) & 0x1)
 #define SFRAME_V3_AARCH64_FDE_PAUTH_KEY(info)	(((info) >> 5) & 0x1)
+#define SFRAME_V3_FDE_SIGNAL_P(info)		(((info) >> 7) & 0x1)
 
 #define SFRAME_FDE_TYPE_REGULAR			0
 #define SFRAME_FDE_TYPE_FLEXIBLE		1
-- 
2.51.0