[PATCH v3 2/2] sframe: Add support for SFRAME_F_FDE_FUNC_START_PCREL flag
claudiu.zissulescu-ianculescu@oracle.com
claudiu.zissulescu-ianculescu@oracle.com
Thu Jul 17 13:43:28 GMT 2025
From: Claudiu Zissulescu <claudiu.zissulescu-ianculescu@oracle.com>
The Sframe V2 has a new errata which introduces the
SFRAME_F_FDE_FUNC_START_PCREL flag. This flag indicates the encoding
of the SFrame FDE function start address field like this:
- if set, sfde_func_start_address field contains the offset in bytes
to the start PC of the associated function from the field itself.
- if unset, sfde_func_start_address field contains the offset in bytes
to the start PC of the associated function from the start of the
SFrame section.
Signed-off-by: Claudiu Zissulescu <claudiu.zissulescu-ianculescu@oracle.com>
---
sysdeps/generic/sframe-read.c | 128 ++++++++++++++++++++++++++--------
sysdeps/generic/sframe-read.h | 6 ++
sysdeps/generic/sframe.h | 15 +++-
3 files changed, 118 insertions(+), 31 deletions(-)
diff --git a/sysdeps/generic/sframe-read.c b/sysdeps/generic/sframe-read.c
index d536575b2d..a6ebc42d66 100644
--- a/sysdeps/generic/sframe-read.c
+++ b/sysdeps/generic/sframe-read.c
@@ -75,11 +75,10 @@ sframe_get_fde_type (sframe_func_desc_entry *fdep)
static bool
sframe_header_sanity_check_p (sframe_header *hp)
{
- uint8_t all_flags = SFRAME_F_FDE_SORTED | SFRAME_F_FRAME_POINTER;
/* Check preamble is valid. */
if ((hp->sfh_preamble.sfp_magic != SFRAME_MAGIC)
|| (hp->sfh_preamble.sfp_version != SFRAME_VERSION_2)
- || ((hp->sfh_preamble.sfp_flags | all_flags) != all_flags))
+ || (hp->sfh_preamble.sfp_flags & ~SFRAME_V2_F_ALL_FLAGS))
return false;
/* Check offsets are valid. */
@@ -171,25 +170,103 @@ sframe_fre_entry_size (sframe_frame_row_entry *frep, size_t addr_size)
+ sframe_fre_offset_bytes_size (fre_info));
}
-/* Check whether for the given FDEP, the SFrame Frame Row Entry identified via
- the START_IP_OFFSET and the END_IP_OFFSET, provides the stack trace
- information for the PC. */
+/* Get SFrame header from the given decoder context DCTX. */
+
+static inline sframe_header *
+sframe_decoder_get_header (sframe_decoder_ctx *dctx)
+{
+ sframe_header *hp = NULL;
+ if (dctx != NULL)
+ hp = &dctx->sfd_header;
+ return hp;
+}
+
+/* Get the offset of the sfde_func_start_address field (from the start of the
+ on-disk layout of the SFrame section) of the FDE at FUNC_IDX in the decoder
+ context DCTX. */
+
+static uint32_t
+sframe_decoder_get_offsetof_fde_start_addr (sframe_decoder_ctx *dctx,
+ uint32_t func_idx,
+ _Unwind_Reason_Code *errp)
+{
+ sframe_header *dhp;
+
+ dhp = sframe_decoder_get_header (dctx);
+ if (dhp == NULL)
+ {
+ if (errp != NULL)
+ *errp = _URC_END_OF_STACK;
+ return 0;
+ }
+
+ if (func_idx >= dhp->sfh_num_fdes)
+ {
+ if (errp != NULL)
+ *errp = _URC_END_OF_STACK;
+ return 0;
+ }
+ else if (errp != NULL)
+ *errp = _URC_NO_REASON;
+
+ return (sframe_get_hdr_size (dhp)
+ + func_idx * sizeof (sframe_func_desc_entry)
+ + offsetof (sframe_func_desc_entry, sfde_func_start_address));
+}
+
+
+/* Get the offset of the start PC of the SFrame FDE at FUNC_IDX from
+ the start of the SFrame section. If the flag
+ SFRAME_F_FDE_FUNC_START_PCREL is set, sfde_func_start_address is
+ the offset of the start PC of the function from the field itself.
+
+ If FUNC_IDX is not a valid index in the given decoder object, returns 0. */
+
+static int32_t
+sframe_decoder_get_secrel_func_start_addr (sframe_decoder_ctx *dctx,
+ uint32_t func_idx)
+{
+ int32_t func_start_addr;
+ _Unwind_Reason_Code err = 0;
+ int32_t offsetof_fde_in_sec = 0;
+
+ /* Check if we have SFRAME_F_FDE_FUNC_START_PCREL. */
+ sframe_header *sh = &dctx->sfd_header;
+ if ((sh->sfh_preamble.sfp_flags & SFRAME_F_FDE_FUNC_START_PCREL))
+ {
+ offsetof_fde_in_sec =
+ sframe_decoder_get_offsetof_fde_start_addr (dctx, func_idx, &err);
+ /* If func_idx is not a valid index, return 0. */
+ if (err == _URC_END_OF_STACK)
+ return 0;
+ }
+
+ func_start_addr = dctx->sfd_funcdesc[func_idx].sfde_func_start_address;
+
+ return func_start_addr + offsetof_fde_in_sec;
+}
+
+/* Check if the SFrame Frame Row Entry identified via the
+ START_IP_OFFSET and the END_IP_OFFSET (for SFrame FDE at
+ FUNC_IDX). */
static bool
-sframe_fre_check_range_p (sframe_func_desc_entry *fdep,
+sframe_fre_check_range_p (sframe_decoder_ctx *dctx, uint32_t func_idx,
uint32_t start_ip_offset, uint32_t end_ip_offset,
int32_t pc)
{
+ sframe_func_desc_entry *fdep;
int32_t func_start_addr;
uint8_t rep_block_size;
uint32_t fde_type;
uint32_t pc_offset;
bool mask_p;
+ fdep = &dctx->sfd_funcdesc[func_idx];
if (fdep == NULL)
return false;
- func_start_addr = fdep->sfde_func_start_address;
+ func_start_addr = sframe_decoder_get_secrel_func_start_addr (dctx, func_idx);
fde_type = sframe_get_fde_type (fdep);
mask_p = (fde_type == SFRAME_FDE_TYPE_PCMASK);
rep_block_size = fdep->sfde_func_rep_size;
@@ -207,19 +284,6 @@ sframe_fre_check_range_p (sframe_func_desc_entry *fdep,
return (start_ip_offset <= pc_offset) && (end_ip_offset >= pc_offset);
}
-/* The SFrame Decoder. */
-
-/* Get SFrame header from the given decoder context DCTX. */
-
-static inline sframe_header *
-sframe_decoder_get_header (sframe_decoder_ctx *dctx)
-{
- sframe_header *hp = NULL;
- if (dctx != NULL)
- hp = &dctx->sfd_header;
- return hp;
-}
-
/* Get IDX'th offset from FRE. Set ERRP as applicable. */
static int32_t
@@ -298,7 +362,7 @@ sframe_decode_fre_start_address (const char *fre_buf,
static sframe_func_desc_entry *
sframe_get_funcdesc_with_addr_internal (sframe_decoder_ctx *ctx, int32_t addr,
- int *errp)
+ int *errp, uint32_t *func_idx)
{
sframe_header *dhp;
sframe_func_desc_entry *fdp;
@@ -319,19 +383,23 @@ sframe_get_funcdesc_with_addr_internal (sframe_decoder_ctx *ctx, int32_t addr,
/* Do the binary search. */
fdp = (sframe_func_desc_entry *) ctx->sfd_funcdesc;
low = 0;
- high = dhp->sfh_num_fdes;
+ high = dhp->sfh_num_fdes - 1;
while (low <= high)
{
int mid = low + (high - low) / 2;
/* Given sfde_func_start_address <= addr,
addr - sfde_func_start_address must be positive. */
- if (fdp[mid].sfde_func_start_address <= addr
- && ((uint32_t)(addr - fdp[mid].sfde_func_start_address)
+ if (sframe_decoder_get_secrel_func_start_addr (ctx, mid) <= addr
+ && ((uint32_t)(addr - sframe_decoder_get_secrel_func_start_addr (ctx,
+ mid))
< fdp[mid].sfde_func_size))
- return fdp + mid;
+ {
+ *func_idx = mid;
+ return fdp + mid;
+ }
- if (fdp[mid].sfde_func_start_address < addr)
+ if (sframe_decoder_get_secrel_func_start_addr (ctx, mid) < addr)
low = mid + 1;
else
high = mid - 1;
@@ -510,6 +578,7 @@ __sframe_find_fre (sframe_decoder_ctx *ctx, int32_t pc,
sframe_frame_row_entry *frep)
{
sframe_func_desc_entry *fdep;
+ uint32_t func_idx;
uint32_t fre_type, i;
uint32_t start_ip_offset;
int32_t func_start_addr;
@@ -522,14 +591,14 @@ __sframe_find_fre (sframe_decoder_ctx *ctx, int32_t pc,
return _URC_END_OF_STACK;
/* Find the FDE which contains the PC, then scan its fre entries. */
- fdep = sframe_get_funcdesc_with_addr_internal (ctx, pc, &err);
+ fdep = sframe_get_funcdesc_with_addr_internal (ctx, pc, &err, &func_idx);
if (fdep == NULL || ctx->sfd_fres == NULL)
return _URC_END_OF_STACK;
fre_type = sframe_get_fre_type (fdep);
fres = ctx->sfd_fres + fdep->sfde_func_start_fre_off;
- func_start_addr = fdep->sfde_func_start_address;
+ func_start_addr = sframe_decoder_get_secrel_func_start_addr (ctx, func_idx);
for (i = 0; i < fdep->sfde_func_num_fres; i++)
{
@@ -553,7 +622,8 @@ __sframe_find_fre (sframe_decoder_ctx *ctx, int32_t pc,
if (start_ip_offset > (uint32_t) (pc - func_start_addr))
return _URC_END_OF_STACK;
- if (sframe_fre_check_range_p (fdep, start_ip_offset, end_ip_offset, pc))
+ if (sframe_fre_check_range_p (ctx, func_idx, start_ip_offset,
+ end_ip_offset, pc))
{
/* Decode last FRE bits: offsets size. */
frep->fre_offsets = fres + addr_size + sizeof (frep->fre_info);
diff --git a/sysdeps/generic/sframe-read.h b/sysdeps/generic/sframe-read.h
index 1db1886bce..146142143c 100644
--- a/sysdeps/generic/sframe-read.h
+++ b/sysdeps/generic/sframe-read.h
@@ -99,6 +99,12 @@ __sframe_fre_get_ra_offset (sframe_decoder_ctx *dctx,
sframe_frame_row_entry *fre,
_Unwind_Reason_Code *errp);
+/* Get the offset of the sfde_func_start_address field. */
+
+extern uint32_t
+__sframe_decoder_get_offsetof_fde_start_addr (sframe_decoder_ctx *dctx,
+ uint32_t func_idx,
+ _Unwind_Reason_Code *errp);
#ifdef __cplusplus
}
#endif
diff --git a/sysdeps/generic/sframe.h b/sysdeps/generic/sframe.h
index 3f8ff1c80e..e38adcfe17 100644
--- a/sysdeps/generic/sframe.h
+++ b/sysdeps/generic/sframe.h
@@ -80,9 +80,20 @@ extern "C"
/* Various flags for SFrame. */
/* Function Descriptor Entries are sorted on PC. */
-#define SFRAME_F_FDE_SORTED 0x1
+#define SFRAME_F_FDE_SORTED 0x1
/* Functions preserve frame pointer. */
-#define SFRAME_F_FRAME_POINTER 0x2
+#define SFRAME_F_FRAME_POINTER 0x2
+/* Function start address in SFrame FDE is encoded as the distance from the
+ location of the sfde_func_start_address to the start PC of the function.
+ If absent, the function start address in SFrame FDE is encoded as the
+ distance from the start of the SFrame FDE section to the start PC of the
+ function. */
+#define SFRAME_F_FDE_FUNC_START_PCREL 0x4
+
+/* Set of all defined flags in SFrame V2. */
+#define SFRAME_V2_F_ALL_FLAGS \
+ (SFRAME_F_FDE_SORTED | SFRAME_F_FRAME_POINTER \
+ | SFRAME_F_FDE_FUNC_START_PCREL)
#define SFRAME_CFA_FIXED_FP_INVALID 0
#define SFRAME_CFA_FIXED_RA_INVALID 0
--
2.50.1
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