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libunwind-eh_elf/src/arm/Gstep.c
Tommi Rantala 2aea391d6a ARM: invalidate proc info after non-dwarf unw_step() 
After successfully stepping the cursor on ARM, the proc info is
invalidated only in dwarf_step(). Invalidate the proc info also when
stepping with the non-dwarf based methods. This fixes
unw_get_proc_info() returning stale data.

The core dump unwinder can be used for demonstrating the bug. When
unwinding based only on DWARF data, the proc info is correct:

$ UNW_ARM_UNWIND_METHOD=1 ./test-coredump-unwind core `cat backing_files` 2>/dev/null
    ip=0x000086d8 proc=000086d4-000086dc handler=0x00000000 lsda=0x00000000
    ip=0x000086ef proc=000086dc-000086f2 handler=0x00000000 lsda=0x00000000
    ip=0x000086e7 proc=000086dc-000086f2 handler=0x00000000 lsda=0x00000000
    ip=0x00008597 proc=00008584-0000859a handler=0x00000000 lsda=0x00000000
    ip=0x76e3ac3b proc=76e3aba0-76e3acec handler=0x00000000 lsda=0x00000000

When unwinding based only on the exidx method, we see the proc info
lagging behind:

$ UNW_ARM_UNWIND_METHOD=4 ./test-coredump-unwind core `cat backing_files` 2>/dev/null
    ip=0x000086d8 proc=000086d4-000086db handler=0x00000000 lsda=0x00000000
    ip=0x000086ef proc=000086d4-000086db handler=0x00000000 lsda=0x00000000
    ip=0x000086e7 proc=000086dc-000086f3 handler=0x00000000 lsda=0x00000000
    ip=0x00008597 proc=000086dc-000086f3 handler=0x00000000 lsda=0x00000000
    ip=0x76e3ac3b proc=00008584-0000859b handler=0x00000000 lsda=0x00000000
    ip=0x000085c3 proc=76e3aba0-76e3ae4b handler=0x00000000 lsda=0x00000000

Finally, with this patch applied, we get the desired proc info also with
the exidx unwinder:

$ UNW_ARM_UNWIND_METHOD=4 ./test-coredump-unwind core `cat backing_files` 2>/dev/null
    ip=0x000086d8 proc=000086d4-000086db handler=0x00000000 lsda=0x00000000
    ip=0x000086ef proc=000086dc-000086f3 handler=0x00000000 lsda=0x00000000
    ip=0x000086e7 proc=000086dc-000086f3 handler=0x00000000 lsda=0x00000000
    ip=0x00008597 proc=00008584-0000859b handler=0x00000000 lsda=0x00000000
    ip=0x76e3ac3b proc=76e3aba0-76e3ae4b handler=0x00000000 lsda=0x00000000
    ip=0x000085c3 proc=0000859c-00008613 handler=0x00000000 lsda=0x00000000
2012-09-04 14:58:38 +03:00

271 lines
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/* libunwind - a platform-independent unwind library
Copyright (C) 2008 CodeSourcery
Copyright 2011 Linaro Limited
Copyright (C) 2012 Tommi Rantala <tt.rantala@gmail.com>
This file is part of libunwind.
Permission is hereby granted, free of charge, to any person obtaining
a copy of this software and associated documentation files (the
"Software"), to deal in the Software without restriction, including
without limitation the rights to use, copy, modify, merge, publish,
distribute, sublicense, and/or sell copies of the Software, and to
permit persons to whom the Software is furnished to do so, subject to
the following conditions:
The above copyright notice and this permission notice shall be
included in all copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. */
#include "unwind_i.h"
#include "offsets.h"
#include "ex_tables.h"
#include <signal.h>
#define arm_exidx_step UNW_OBJ(arm_exidx_step)
static inline int
arm_exidx_step (struct cursor *c)
{
unw_word_t old_ip, old_cfa;
uint8_t buf[32];
int ret;
old_ip = c->dwarf.ip;
old_cfa = c->dwarf.cfa;
/* mark PC unsaved */
c->dwarf.loc[UNW_ARM_R15] = DWARF_NULL_LOC;
if ((ret = tdep_find_proc_info (&c->dwarf, c->dwarf.ip, 1)) < 0)
return ret;
if (c->dwarf.pi.format != UNW_INFO_FORMAT_ARM_EXIDX)
return -UNW_ENOINFO;
ret = arm_exidx_extract (&c->dwarf, buf);
if (ret == -UNW_ESTOPUNWIND)
return 0;
else if (ret < 0)
return ret;
ret = arm_exidx_decode (buf, ret, &c->dwarf);
if (ret < 0)
return ret;
if (c->dwarf.ip == old_ip && c->dwarf.cfa == old_cfa)
{
Dprintf ("%s: ip and cfa unchanged; stopping here (ip=0x%lx)\n",
__FUNCTION__, (long) c->dwarf.ip);
return -UNW_EBADFRAME;
}
c->dwarf.pi_valid = 0;
return (c->dwarf.ip == 0) ? 0 : 1;
}
PROTECTED int
unw_handle_signal_frame (unw_cursor_t *cursor)
{
struct cursor *c = (struct cursor *) cursor;
int ret;
unw_word_t sc_addr, sp, sp_addr = c->dwarf.cfa;
struct dwarf_loc sp_loc = DWARF_LOC (sp_addr, 0);
if ((ret = dwarf_get (&c->dwarf, sp_loc, &sp)) < 0)
return -UNW_EUNSPEC;
/* Obtain signal frame type (non-RT or RT). */
ret = unw_is_signal_frame (cursor);
/* Save the SP and PC to be able to return execution at this point
later in time (unw_resume). */
c->sigcontext_sp = c->dwarf.cfa;
c->sigcontext_pc = c->dwarf.ip;
/* Since kernel version 2.6.18 the non-RT signal frame starts with a
ucontext while the RT signal frame starts with a siginfo, followed
by a sigframe whose first element is an ucontext.
Prior 2.6.18 the non-RT signal frame starts with a sigcontext while
the RT signal frame starts with two pointers followed by a siginfo
and an ucontext. The first pointer points to the start of the siginfo
structure and the second one to the ucontext structure. */
if (ret == 1)
{
/* Handle non-RT signal frames. Check if the first word on the stack
is the magic number. */
if (sp == 0x5ac3c35a)
{
c->sigcontext_format = ARM_SCF_LINUX_SIGFRAME;
sc_addr = sp_addr + LINUX_UC_MCONTEXT_OFF;
}
else
{
c->sigcontext_format = ARM_SCF_LINUX_OLD_SIGFRAME;
sc_addr = sp_addr;
}
}
else if (ret == 2)
{
/* Handle RT signal frames. Check if the first word on the stack is a
pointer to the siginfo structure. */
if (sp == sp_addr + 8)
{
c->sigcontext_format = ARM_SCF_LINUX_OLD_RT_SIGFRAME;
sc_addr = sp_addr + 8 + sizeof (siginfo_t) + LINUX_UC_MCONTEXT_OFF;
}
else
{
c->sigcontext_format = ARM_SCF_LINUX_RT_SIGFRAME;
sc_addr = sp_addr + sizeof (siginfo_t) + LINUX_UC_MCONTEXT_OFF;
}
}
else
return -UNW_EUNSPEC;
c->sigcontext_addr = sc_addr;
/* Update the dwarf cursor.
Set the location of the registers to the corresponding addresses of the
uc_mcontext / sigcontext structure contents. */
c->dwarf.loc[UNW_ARM_R0] = DWARF_LOC (sc_addr + LINUX_SC_R0_OFF, 0);
c->dwarf.loc[UNW_ARM_R1] = DWARF_LOC (sc_addr + LINUX_SC_R1_OFF, 0);
c->dwarf.loc[UNW_ARM_R2] = DWARF_LOC (sc_addr + LINUX_SC_R2_OFF, 0);
c->dwarf.loc[UNW_ARM_R3] = DWARF_LOC (sc_addr + LINUX_SC_R3_OFF, 0);
c->dwarf.loc[UNW_ARM_R4] = DWARF_LOC (sc_addr + LINUX_SC_R4_OFF, 0);
c->dwarf.loc[UNW_ARM_R5] = DWARF_LOC (sc_addr + LINUX_SC_R5_OFF, 0);
c->dwarf.loc[UNW_ARM_R6] = DWARF_LOC (sc_addr + LINUX_SC_R6_OFF, 0);
c->dwarf.loc[UNW_ARM_R7] = DWARF_LOC (sc_addr + LINUX_SC_R7_OFF, 0);
c->dwarf.loc[UNW_ARM_R8] = DWARF_LOC (sc_addr + LINUX_SC_R8_OFF, 0);
c->dwarf.loc[UNW_ARM_R9] = DWARF_LOC (sc_addr + LINUX_SC_R9_OFF, 0);
c->dwarf.loc[UNW_ARM_R10] = DWARF_LOC (sc_addr + LINUX_SC_R10_OFF, 0);
c->dwarf.loc[UNW_ARM_R11] = DWARF_LOC (sc_addr + LINUX_SC_FP_OFF, 0);
c->dwarf.loc[UNW_ARM_R12] = DWARF_LOC (sc_addr + LINUX_SC_IP_OFF, 0);
c->dwarf.loc[UNW_ARM_R13] = DWARF_LOC (sc_addr + LINUX_SC_SP_OFF, 0);
c->dwarf.loc[UNW_ARM_R14] = DWARF_LOC (sc_addr + LINUX_SC_LR_OFF, 0);
c->dwarf.loc[UNW_ARM_R15] = DWARF_LOC (sc_addr + LINUX_SC_PC_OFF, 0);
/* Set SP/CFA and PC/IP. */
dwarf_get (&c->dwarf, c->dwarf.loc[UNW_ARM_R13], &c->dwarf.cfa);
dwarf_get (&c->dwarf, c->dwarf.loc[UNW_ARM_R15], &c->dwarf.ip);
c->dwarf.pi_valid = 0;
return 1;
}
PROTECTED int
unw_step (unw_cursor_t *cursor)
{
struct cursor *c = (struct cursor *) cursor;
int ret = -UNW_EUNSPEC;
Debug (1, "(cursor=%p)\n", c);
/* Check if this is a signal frame. */
if (unw_is_signal_frame (cursor))
return unw_handle_signal_frame (cursor);
#ifdef CONFIG_DEBUG_FRAME
/* First, try DWARF-based unwinding. */
if (UNW_TRY_METHOD(UNW_ARM_METHOD_DWARF))
{
ret = dwarf_step (&c->dwarf);
Debug(1, "dwarf_step()=%d\n", ret);
if (likely (ret > 0))
return 1;
else if (unlikely (ret == -UNW_ESTOPUNWIND))
return ret;
if (ret < 0 && ret != -UNW_ENOINFO)
{
Debug (2, "returning %d\n", ret);
return ret;
}
}
#endif /* CONFIG_DEBUG_FRAME */
/* Next, try extbl-based unwinding. */
if (UNW_TRY_METHOD (UNW_ARM_METHOD_EXIDX))
{
ret = arm_exidx_step (c);
if (ret > 0)
return 1;
if (ret == -UNW_ESTOPUNWIND || ret == 0)
return ret;
}
/* Fall back on APCS frame parsing.
Note: This won't work in case the ARM EABI is used. */
if (unlikely (ret < 0))
{
if (UNW_TRY_METHOD(UNW_ARM_METHOD_FRAME))
{
ret = UNW_ESUCCESS;
/* DWARF unwinding failed, try to follow APCS/optimized APCS frame chain */
unw_word_t instr, i;
Debug (13, "dwarf_step() failed (ret=%d), trying frame-chain\n", ret);
dwarf_loc_t ip_loc, fp_loc;
unw_word_t frame;
/* Mark all registers unsaved, since we don't know where
they are saved (if at all), except for the EBP and
EIP. */
if (dwarf_get(&c->dwarf, c->dwarf.loc[UNW_ARM_R11], &frame) < 0)
{
return 0;
}
for (i = 0; i < DWARF_NUM_PRESERVED_REGS; ++i) {
c->dwarf.loc[i] = DWARF_NULL_LOC;
}
if (frame)
{
if (dwarf_get(&c->dwarf, DWARF_LOC(frame, 0), &instr) < 0)
{
return 0;
}
instr -= 8;
if (dwarf_get(&c->dwarf, DWARF_LOC(instr, 0), &instr) < 0)
{
return 0;
}
if ((instr & 0xFFFFD800) == 0xE92DD800)
{
/* Standard APCS frame. */
ip_loc = DWARF_LOC(frame - 4, 0);
fp_loc = DWARF_LOC(frame - 12, 0);
}
else
{
/* Codesourcery optimized normal frame. */
ip_loc = DWARF_LOC(frame, 0);
fp_loc = DWARF_LOC(frame - 4, 0);
}
if (dwarf_get(&c->dwarf, ip_loc, &c->dwarf.ip) < 0)
{
return 0;
}
c->dwarf.loc[UNW_ARM_R12] = ip_loc;
c->dwarf.loc[UNW_ARM_R11] = fp_loc;
c->dwarf.pi_valid = 0;
Debug(15, "ip=%lx\n", c->dwarf.ip);
}
else
{
ret = -UNW_ENOINFO;
}
}
}
return ret == -UNW_ENOINFO ? 0 : 1;
}
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