[PATCH 2/3] ARC: dw2 unwind: factor CIE specifics for .eh_frame/.debug_frame

From: Vineet Gupta
Date: Mon Sep 19 2016 - 17:50:00 EST


This paves way for switching to .eh_frame based unwindiing

Signed-off-by: Vineet Gupta <vgupta@xxxxxxxxxxxx>
---
arch/arc/kernel/unwind.c | 25 ++++++++++++++++++-------
1 file changed, 18 insertions(+), 7 deletions(-)

diff --git a/arch/arc/kernel/unwind.c b/arch/arc/kernel/unwind.c
index 0587bf121d11..4e5dbe7617a1 100644
--- a/arch/arc/kernel/unwind.c
+++ b/arch/arc/kernel/unwind.c
@@ -111,6 +111,8 @@ UNW_REGISTER_INFO};
#define DW_EH_PE_indirect 0x80
#define DW_EH_PE_omit 0xff

+#define CIE_ID 0xffffffffUL
+
typedef unsigned long uleb128_t;
typedef signed long sleb128_t;

@@ -232,6 +234,7 @@ void __init arc_unwind_init(void)

static const u32 bad_cie, not_fde;
static const u32 *cie_for_fde(const u32 *fde, const struct unwind_table *);
+static const u32 *__cie_for_fde(const u32 *fde);
static signed fde_pointer_type(const u32 *cie);

struct eh_frame_hdr_table_entry {
@@ -338,10 +341,9 @@ static void init_unwind_hdr(struct unwind_table *table,
for (fde = table->address, tableSize = table->size, n = 0;
tableSize;
tableSize -= sizeof(*fde) + *fde, fde += 1 + *fde / sizeof(*fde)) {
- /* const u32 *cie = fde + 1 - fde[1] / sizeof(*fde); */
- const u32 *cie = (const u32 *)(fde[1]);
+ const u32 *cie = __cie_for_fde(fde);

- if (fde[1] == 0xffffffff)
+ if (fde[1] == CIE_ID)
continue; /* this is a CIE */
ptr = (const u8 *)(fde + 2);
header->table[n].start = read_pointer(&ptr,
@@ -504,6 +506,16 @@ static sleb128_t get_sleb128(const u8 **pcur, const u8 *end)
return value;
}

+static const u32 *__cie_for_fde(const u32 *fde)
+{
+ const u32 *cie;
+
+ /* cie = fde + 1 - fde[1] / sizeof(*fde); */
+ cie = (u32 *) fde[1];
+
+ return cie;
+}
+
static const u32 *cie_for_fde(const u32 *fde, const struct unwind_table *table)
{
const u32 *cie;
@@ -511,19 +523,18 @@ static const u32 *cie_for_fde(const u32 *fde, const struct unwind_table *table)
if (!*fde || (*fde & (sizeof(*fde) - 1)))
return &bad_cie;

- if (fde[1] == 0xffffffff)
+ if (fde[1] == CIE_ID)
return &not_fde; /* this is a CIE */

if ((fde[1] & (sizeof(*fde) - 1)))
/* || fde[1] > (unsigned long)(fde + 1) - (unsigned long)table->address) */
return NULL; /* this is not a valid FDE */

- /* cie = fde + 1 - fde[1] / sizeof(*fde); */
- cie = (u32 *) fde[1];
+ cie = __cie_for_fde(fde);

if (*cie <= sizeof(*cie) + 4 || *cie >= fde[1] - sizeof(*fde)
|| (*cie & (sizeof(*cie) - 1))
- || (cie[1] != 0xffffffff))
+ || (cie[1] != CIE_ID))
return NULL; /* this is not a (valid) CIE */
return cie;
}
--
2.7.4