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libgcc: Split FDE search code from PT_GNU_EH_FRAME lookup 

This allows switching to a different implementation for
PT_GNU_EH_FRAME lookup in a subsequent commit.

This moves some of the PT_GNU_EH_FRAME parsing out of the glibc loader
lock that is implied by dl_iterate_phdr.  However, the FDE is already
parsed outside the lock before this change, so this does not introduce
additional crashes in case of a concurrent dlclose.

libgcc/ChangeLog:

	* unwind-dw2-fde-dip.c (struct unw_eh_callback_data): Add hdr.
	Remove func, ret.
	(find_fde_tail): New function.  Split from
	_Unwind_IteratePhdrCallback.  Move the result initialization
	from _Unwind_Find_FDE.
	(_Unwind_Find_FDE): Updated to call find_fde_tail.
This commit is contained in:
Florian Weimer 2021-11-25 18:40:51 +01:00
parent 5bc4cb0412
commit 9488d24206
1 changed files with 50 additions and 42 deletions
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92
libgcc/unwind-dw2-fde-dip.c
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@ -113,8 +113,7 @@ struct unw_eh_callback_data
#if NEED_DBASE_MEMBER
void *dbase;
#endif
void *func;
const fde *ret;
const struct unw_eh_frame_hdr *hdr;
int check_cache;
};
@ -197,10 +196,6 @@ _Unwind_IteratePhdrCallback (struct dl_phdr_info *info, size_t size, void *ptr)
#else
_Unwind_Ptr load_base;
#endif
const unsigned char *p;
const struct unw_eh_frame_hdr *hdr;
_Unwind_Ptr eh_frame;
struct object ob;
_Unwind_Ptr pc_low = 0, pc_high = 0;
struct ext_dl_phdr_info
@ -348,10 +343,8 @@ _Unwind_IteratePhdrCallback (struct dl_phdr_info *info, size_t size, void *ptr)
return 0;
/* Read .eh_frame_hdr header. */
hdr = (const struct unw_eh_frame_hdr *)
data->hdr = (const struct unw_eh_frame_hdr *)
__RELOC_POINTER (p_eh_frame_hdr->p_vaddr, load_base);
if (hdr->version != 1)
return 1;
#ifdef CRT_GET_RFIB_DATA
# if defined __i386__ || defined __nios2__
@ -383,12 +376,30 @@ _Unwind_IteratePhdrCallback (struct dl_phdr_info *info, size_t size, void *ptr)
# endif
#endif
_Unwind_Ptr dbase = unw_eh_callback_data_dbase (data);
return 1;
}
/* Find the FDE for the program counter PC, in a previously located
PT_GNU_EH_FRAME data region. *BASES is updated if an FDE to return is
found. */
static const fde *
find_fde_tail (_Unwind_Ptr pc,
const struct unw_eh_frame_hdr *hdr,
_Unwind_Ptr dbase,
struct dwarf_eh_bases *bases)
{
const unsigned char *p = (const unsigned char *) (hdr + 1);
_Unwind_Ptr eh_frame;
struct object ob;
if (hdr->version != 1)
return NULL;
p = read_encoded_value_with_base (hdr->eh_frame_ptr_enc,
base_from_cb_data (hdr->eh_frame_ptr_enc,
dbase),
(const unsigned char *) (hdr + 1),
&eh_frame);
p, &eh_frame);
/* We require here specific table encoding to speed things up.
Also, DW_EH_PE_datarel here means using PT_GNU_EH_FRAME start
@ -404,7 +415,7 @@ _Unwind_IteratePhdrCallback (struct dl_phdr_info *info, size_t size, void *ptr)
p, &fde_count);
/* Shouldn't happen. */
if (fde_count == 0)
return 1;
return NULL;
if ((((_Unwind_Ptr) p) & 3) == 0)
{
struct fde_table {
@ -419,9 +430,9 @@ _Unwind_IteratePhdrCallback (struct dl_phdr_info *info, size_t size, void *ptr)
_Unwind_Ptr range;
mid = fde_count - 1;
if (data->pc < table[0].initial_loc + data_base)
return 1;
else if (data->pc < table[mid].initial_loc + data_base)
if (pc < table[0].initial_loc + data_base)
return NULL;
else if (pc < table[mid].initial_loc + data_base)
{
lo = 0;
hi = mid;
@ -429,9 +440,9 @@ _Unwind_IteratePhdrCallback (struct dl_phdr_info *info, size_t size, void *ptr)
while (lo < hi)
{
mid = (lo + hi) / 2;
if (data->pc < table[mid].initial_loc + data_base)
if (pc < table[mid].initial_loc + data_base)
hi = mid;
else if (data->pc >= table[mid + 1].initial_loc + data_base)
else if (pc >= table[mid + 1].initial_loc + data_base)
lo = mid + 1;
else
break;
@ -445,10 +456,16 @@ _Unwind_IteratePhdrCallback (struct dl_phdr_info *info, size_t size, void *ptr)
f_enc_size = size_of_encoded_value (f_enc);
read_encoded_value_with_base (f_enc & 0x0f, 0,
&f->pc_begin[f_enc_size], &range);
if (data->pc < table[mid].initial_loc + data_base + range)
data->ret = f;
data->func = (void *) (table[mid].initial_loc + data_base);
return 1;
_Unwind_Ptr func = table[mid].initial_loc + data_base;
if (pc < table[mid].initial_loc + data_base + range)
{
bases->tbase = NULL;
bases->dbase = (void *) dbase;
bases->func = (void *) func;
return f;
}
else
return NULL;
}
}
@ -461,18 +478,20 @@ _Unwind_IteratePhdrCallback (struct dl_phdr_info *info, size_t size, void *ptr)
ob.u.single = (fde *) eh_frame;
ob.s.i = 0;
ob.s.b.mixed_encoding = 1; /* Need to assume worst case. */
data->ret = linear_search_fdes (&ob, (fde *) eh_frame, (void *) data->pc);
if (data->ret != NULL)
const fde *entry = linear_search_fdes (&ob, (fde *) eh_frame, (void *) pc);
if (entry != NULL)
{
_Unwind_Ptr func;
unsigned int encoding = get_fde_encoding (data->ret);
unsigned int encoding = get_fde_encoding (entry);
read_encoded_value_with_base (encoding,
base_from_cb_data (encoding, dbase),
data->ret->pc_begin, &func);
data->func = (void *) func;
entry->pc_begin, &func);
bases->tbase = NULL;
bases->dbase = (void *) dbase;
bases->func = (void *) func;
}
return 1;
return entry;
}
const fde *
@ -489,24 +508,13 @@ _Unwind_Find_FDE (void *pc, struct dwarf_eh_bases *bases)
#if NEED_DBASE_MEMBER
data.dbase = NULL;
#endif
data.func = NULL;
data.ret = NULL;
data.check_cache = 1;
if (dl_iterate_phdr (_Unwind_IteratePhdrCallback, &data) < 0)
if (dl_iterate_phdr (_Unwind_IteratePhdrCallback, &data) <= 0)
return NULL;
if (data.ret)
{
bases->tbase = NULL;
#if NEED_DBASE_MEMBER
bases->dbase = data.dbase;
#else
bases->dbase = NULL;
#endif
bases->func = data.func;
}
return data.ret;
_Unwind_Ptr dbase = unw_eh_callback_data_dbase (&data);
return find_fde_tail ((_Unwind_Ptr) pc, data.hdr, dbase, bases);
}
#else