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libsframe: revisit sframe_find_fre API

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Inspite of implementing a rather simple functionality, this function was
relatively difficult to follow, and maintain.  Some changes are done now
to address that - refactor the function and use better names to make it
more readable.

The changes to the implementation do not cause any change in the
contract of the API.

libsframe/
        * sframe.c (sframe_fre_get_end_ip_offset): to here...
        (sframe_find_fre): Refactor some bits from...
This commit is contained in:
Indu Bhagat
2023-05-25 23:44:09 -07:00
parent 812d868850
commit 83c219872b
1 changed files with 51 additions and 36 deletions
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87
libsframe/sframe.c
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@@ -980,6 +980,32 @@ sframe_get_funcdesc_with_addr (sframe_decoder_ctx *ctx,
return sframe_ret_set_errno (errp, SFRAME_ERR_FDE_NOTFOUND);
}
/* Get the end IP offset for the FRE at index i in the FDEP. The buffer FRES
is the starting location for the FRE. */
static uint32_t
sframe_fre_get_end_ip_offset (sframe_func_desc_entry *fdep, unsigned int i,
const char *fres)
{
uint32_t end_ip_offset;
uint32_t fre_type;
fre_type = sframe_get_fre_type (fdep);
/* Get the start address of the next FRE in sequence. */
if (i < fdep->sfde_func_num_fres - 1)
{
sframe_decode_fre_start_address (fres, &end_ip_offset, fre_type);
end_ip_offset -= 1;
}
else
/* The end IP offset for the FRE needs to be deduced from the function
size. */
end_ip_offset = fdep->sfde_func_size - 1;
return end_ip_offset;
}
/* Find the SFrame Row Entry which contains the PC. Returns
SFRAME_ERR if failure. */
@@ -987,14 +1013,15 @@ int
sframe_find_fre (sframe_decoder_ctx *ctx, int32_t pc,
sframe_frame_row_entry *frep)
{
sframe_frame_row_entry cur_fre;
sframe_func_desc_entry *fdep;
uint32_t start_address, i;
sframe_frame_row_entry cur_fre, next_fre;
const char *fres;
unsigned int fre_type, fde_type;
size_t esz;
int err = 0;
uint32_t end_ip_offset, i;
int32_t start_ip, end_ip;
int32_t func_start_addr;
const char *fres;
size_t size = 0;
int err = 0;
/* For regular FDEs (i.e. fde_type SFRAME_FDE_TYPE_PCINC),
where the start address in the FRE is an offset from start pc,
use a bitmask with all bits set so that none of the address bits are
@@ -1022,40 +1049,28 @@ sframe_find_fre (sframe_decoder_ctx *ctx, int32_t pc,
bitmask = 0xff;
fres = ctx->sfd_fres + fdep->sfde_func_start_fre_off;
func_start_addr = fdep->sfde_func_start_address;
for (i = 0; i < fdep->sfde_func_num_fres; i++)
{
err = sframe_decode_fre (fres, &next_fre, fre_type, &esz);
start_address = next_fre.fre_start_addr;
if (((fdep->sfde_func_start_address
+ (int32_t) start_address) & bitmask) <= (pc & bitmask))
{
sframe_frame_row_entry_copy (&cur_fre, &next_fre);
/* Get the next FRE in sequence. */
if (i < fdep->sfde_func_num_fres - 1)
{
sp += esz;
err = sframe_decode_fre (fres, &next_fre, fre_type, &esz);
/* Sanity check the next FRE. */
if (!sframe_fre_sanity_check_p (&next_fre))
return sframe_set_errno (&err, SFRAME_ERR_FRE_INVAL);
size = next_fre.fre_start_addr;
}
else size = fdep->sfde_func_size;
/* If the cur FRE is the one that contains the PC, return it. */
if (((fdep->sfde_func_start_address
+ (int32_t)size) & bitmask) > (pc & bitmask))
{
sframe_frame_row_entry_copy (frep, &cur_fre);
return 0;
}
}
else
err = sframe_decode_fre (fres, &cur_fre, fre_type, &size);
if (err)
return sframe_set_errno (&err, SFRAME_ERR_FRE_INVAL);
start_ip = func_start_addr + cur_fre.fre_start_addr;
end_ip_offset = sframe_fre_get_end_ip_offset (fdep, i, fres + size);
end_ip = func_start_addr + end_ip_offset;
if ((start_ip & bitmask) > (pc & bitmask))
return sframe_set_errno (&err, SFRAME_ERR_FRE_INVAL);
if (((start_ip & bitmask) <= (pc & bitmask))
&& (end_ip & bitmask) >= (pc & bitmask))
{
sframe_frame_row_entry_copy (frep, &cur_fre);
return 0;
}
fres += size;
}
return sframe_set_errno (&err, SFRAME_ERR_FDE_INVAL);
}