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[ARM/FDPIC v6 06/24] [ARM] FDPIC: Add support for c++ exceptions

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The main difference with existing support is that function addresses
are function descriptor addresses instead. This means that all code
dealing with function pointers now has to cope with function
descriptors instead.

For the same reason, Linux kernel helpers can no longer be called by
dereferencing their address, so we implement wrappers that directly
call the kernel helpers.

When restoring a function address, we also have to restore the FDPIC
register value (r9).

2019-09-10  Christophe Lyon  <christophe.lyon@st.com>
	Mickaël Guêné <mickael.guene@st.com>

	gcc/
	* ginclude/unwind-arm-common.h (unwinder_cache): Add reserved5
	field.

	libgcc/
	* config/arm/linux-atomic.c (__kernel_cmpxchg): Add FDPIC support.
	(__kernel_dmb): Likewise.
	(__fdpic_cmpxchg): New function.
	(__fdpic_dmb): New function.
	* config/arm/unwind-arm.h (FDPIC_REGNUM): New define.
	(gnu_Unwind_Find_got): New function.
	(_Unwind_decode_typeinfo_ptr): Add FDPIC support.
	* unwind-arm-common.inc (UCB_PR_GOT): New.
	(funcdesc_t): New struct.
	(get_eit_entry): Add FDPIC support.
	(unwind_phase2): Likewise.
	(unwind_phase2_forced): Likewise.
	(__gnu_Unwind_RaiseException): Likewise.
	(__gnu_Unwind_Resume): Likewise.
	(__gnu_Unwind_Backtrace): Likewise.
	* unwind-pe.h (read_encoded_value_with_base): Likewise.

	libstdc++/
	* libsupc++/eh_personality.cc (get_ttype_entry): Add FDPIC
	support.


Co-Authored-By: Mickaël Guêné <mickael.guene@st.com>

From-SVN: r275568
This commit is contained in:
Christophe Lyon 2019-09-10 09:47:49 +02:00 committed by Christophe Lyon
parent 11189793b6
commit 5d727a4b20
9 changed files with 236 additions and 5 deletions
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6
gcc/ChangeLog
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@ -1,3 +1,9 @@
2019-09-10 Christophe Lyon <christophe.lyon@st.com>
Mickaël Guêné <mickael.guene@st.com>
* ginclude/unwind-arm-common.h (unwinder_cache): Add reserved5
field.
2019-09-10 Christophe Lyon <christophe.lyon@st.com>
Mickaël Guêné <mickael.guene@st.com>

2
gcc/ginclude/unwind-arm-common.h
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@ -91,7 +91,7 @@ extern "C" {
_uw reserved2; /* Personality routine address */
_uw reserved3; /* Saved callsite address */
_uw reserved4; /* Forced unwind stop arg */
_uw reserved5;
_uw reserved5; /* Personality routine GOT value in FDPIC mode. */
}
unwinder_cache;
/* Propagation barrier cache (valid after phase 1): */

20
libgcc/ChangeLog
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@ -1,3 +1,23 @@
2019-09-10 Christophe Lyon <christophe.lyon@st.com>
Mickaël Guêné <mickael.guene@st.com>
* config/arm/linux-atomic.c (__kernel_cmpxchg): Add FDPIC support.
(__kernel_dmb): Likewise.
(__fdpic_cmpxchg): New function.
(__fdpic_dmb): New function.
* config/arm/unwind-arm.h (FDPIC_REGNUM): New define.
(gnu_Unwind_Find_got): New function.
(_Unwind_decode_typeinfo_ptr): Add FDPIC support.
* unwind-arm-common.inc (UCB_PR_GOT): New.
(funcdesc_t): New struct.
(get_eit_entry): Add FDPIC support.
(unwind_phase2): Likewise.
(unwind_phase2_forced): Likewise.
(__gnu_Unwind_RaiseException): Likewise.
(__gnu_Unwind_Resume): Likewise.
(__gnu_Unwind_Backtrace): Likewise.
* unwind-pe.h (read_encoded_value_with_base): Likewise.
2019-09-10 Christophe Lyon <christophe.lyon@st.com>
Mickaël Guêné <mickael.guene@st.com>

55
libgcc/config/arm/linux-atomic.c
View File

@ -25,11 +25,62 @@ see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
/* Kernel helper for compare-and-exchange. */
typedef int (__kernel_cmpxchg_t) (int oldval, int newval, int *ptr);
#define __kernel_cmpxchg (*(__kernel_cmpxchg_t *) 0xffff0fc0)
#define STR(X) #X
#define XSTR(X) STR(X)
#define KERNEL_CMPXCHG 0xffff0fc0
#if __FDPIC__
/* Non-FDPIC ABIs call __kernel_cmpxchg directly by dereferencing its
address, but under FDPIC we would generate a broken call
sequence. That's why we have to implement __kernel_cmpxchg and
__kernel_dmb here: this way, the FDPIC call sequence works. */
#define __kernel_cmpxchg __fdpic_cmpxchg
#else
#define __kernel_cmpxchg (*(__kernel_cmpxchg_t *) KERNEL_CMPXCHG)
#endif
/* Kernel helper for memory barrier. */
typedef void (__kernel_dmb_t) (void);
#define __kernel_dmb (*(__kernel_dmb_t *) 0xffff0fa0)
#define KERNEL_DMB 0xffff0fa0
#if __FDPIC__
#define __kernel_dmb __fdpic_dmb
#else
#define __kernel_dmb (*(__kernel_dmb_t *) KERNEL_DMB)
#endif
#if __FDPIC__
static int __fdpic_cmpxchg (int oldval, int newval, int *ptr)
{
int result;
asm volatile (
"ldr ip, 1f\n\t"
"bx ip\n\t"
"1:\n\t"
".word " XSTR(KERNEL_CMPXCHG) "\n\t"
: "=r" (result)
: "r" (oldval) , "r" (newval), "r" (ptr)
: "r3", "memory");
/* The result is actually returned by the kernel helper, we need
this to avoid a warning. */
return result;
}
static void __fdpic_dmb (void)
{
asm volatile (
"ldr ip, 1f\n\t"
"bx ip\n\t"
"1:\n\t"
".word " XSTR(KERNEL_DMB) "\n\t"
);
}
#endif
/* Note: we implement byte, short and int versions of atomic operations using
the above kernel helpers; see linux-atomic-64bit.c for "long long" (64-bit)

31
libgcc/config/arm/unwind-arm.h
View File

@ -33,9 +33,33 @@
/* Use IP as a scratch register within the personality routine. */
#define UNWIND_POINTER_REG 12
#define FDPIC_REGNUM 9
#define STR(x) #x
#define XSTR(x) STR(x)
#ifdef __cplusplus
extern "C" {
#endif
_Unwind_Ptr __attribute__((weak)) __gnu_Unwind_Find_got (_Unwind_Ptr);
static inline _Unwind_Ptr gnu_Unwind_Find_got (_Unwind_Ptr ptr)
{
_Unwind_Ptr res;
if (__gnu_Unwind_Find_got)
res = __gnu_Unwind_Find_got (ptr);
else
{
asm volatile ("mov %[result], r" XSTR(FDPIC_REGNUM)
: [result]"=r" (res)
:
:);
}
return res;
}
/* Decode an R_ARM_TARGET2 relocation. */
static inline _Unwind_Word
_Unwind_decode_typeinfo_ptr (_Unwind_Word base __attribute__ ((unused)),
@ -48,7 +72,12 @@ extern "C" {
if (!tmp)
return 0;
#if (defined(linux) && !defined(__uClinux__)) || defined(__NetBSD__) \
#if __FDPIC__
/* For FDPIC, we store the offset of the GOT entry. */
/* So, first get GOT from dynamic linker and then use indirect access. */
tmp += gnu_Unwind_Find_got (ptr);
tmp = *(_Unwind_Word *) tmp;
#elif (defined(linux) && !defined(__uClinux__)) || defined(__NetBSD__) \
|| defined(__FreeBSD__) || defined(__fuchsia__)
/* Pc-relative indirect. */
#define _GLIBCXX_OVERRIDE_TTYPE_ENCODING (DW_EH_PE_pcrel | DW_EH_PE_indirect)

94
libgcc/unwind-arm-common.inc
View File

@ -62,6 +62,7 @@ __gnu_Unwind_Find_exidx (_Unwind_Ptr, int *);
#define UCB_PR_ADDR(ucbp) ((ucbp)->unwinder_cache.reserved2)
#define UCB_SAVED_CALLSITE_ADDR(ucbp) ((ucbp)->unwinder_cache.reserved3)
#define UCB_FORCED_STOP_ARG(ucbp) ((ucbp)->unwinder_cache.reserved4)
#define UCB_PR_GOT(ucbp) ((ucbp)->unwinder_cache.reserved5)
/* Unwind descriptors. */
@ -85,6 +86,16 @@ typedef struct __EIT_entry
_uw content;
} __EIT_entry;
#ifdef __FDPIC__
/* Only used in FDPIC case. */
struct funcdesc_t
{
unsigned int ptr;
unsigned int got;
};
#endif
/* Assembly helper functions. */
/* Restore core register state. Never returns. */
@ -259,7 +270,21 @@ get_eit_entry (_Unwind_Control_Block *ucbp, _uw return_address)
{
/* One of the predefined standard routines. */
_uw idx = (*(_uw *) ucbp->pr_cache.ehtp >> 24) & 0xf;
#if __FDPIC__
{
struct funcdesc_t *funcdesc
= (struct funcdesc_t *) __gnu_unwind_get_pr_addr (idx);
if (funcdesc)
{
UCB_PR_ADDR (ucbp) = funcdesc->ptr;
UCB_PR_GOT (ucbp) = funcdesc->got;
}
else
UCB_PR_ADDR (ucbp) = 0;
}
#else
UCB_PR_ADDR (ucbp) = __gnu_unwind_get_pr_addr (idx);
#endif
if (UCB_PR_ADDR (ucbp) == 0)
{
/* Failed */
@ -270,6 +295,10 @@ get_eit_entry (_Unwind_Control_Block *ucbp, _uw return_address)
{
/* Execute region offset to PR */
UCB_PR_ADDR (ucbp) = selfrel_offset31 (ucbp->pr_cache.ehtp);
#if __FDPIC__
UCB_PR_GOT (ucbp)
= (unsigned int) gnu_Unwind_Find_got ((_Unwind_Ptr) UCB_PR_ADDR (ucbp));
#endif
}
return _URC_OK;
}
@ -291,14 +320,29 @@ unwind_phase2 (_Unwind_Control_Block * ucbp, phase2_vrs * vrs)
UCB_SAVED_CALLSITE_ADDR (ucbp) = VRS_PC(vrs);
/* Call the pr to decide what to do. */
#if __FDPIC__
{
volatile struct funcdesc_t funcdesc;
funcdesc.ptr = UCB_PR_ADDR (ucbp);
funcdesc.got = UCB_PR_GOT (ucbp);
pr_result = ((personality_routine) &funcdesc)
(_US_UNWIND_FRAME_STARTING, ucbp, (_Unwind_Context *) vrs);
}
#else
pr_result = ((personality_routine) UCB_PR_ADDR (ucbp))
(_US_UNWIND_FRAME_STARTING, ucbp, (_Unwind_Context *) vrs);
#endif
}
while (pr_result == _URC_CONTINUE_UNWIND);
if (pr_result != _URC_INSTALL_CONTEXT)
abort();
#if __FDPIC__
/* r9 could have been lost due to PLT jump. Restore correct value. */
vrs->core.r[FDPIC_REGNUM] = gnu_Unwind_Find_got (VRS_PC (vrs));
#endif
uw_restore_core_regs (vrs, &vrs->core);
}
@ -346,8 +390,18 @@ unwind_phase2_forced (_Unwind_Control_Block *ucbp, phase2_vrs *entry_vrs,
next_vrs = saved_vrs;
/* Call the pr to decide what to do. */
#if __FDPIC__
{
volatile struct funcdesc_t funcdesc;
funcdesc.ptr = UCB_PR_ADDR (ucbp);
funcdesc.got = UCB_PR_GOT (ucbp);
pr_result = ((personality_routine) &funcdesc)
(action, ucbp, (void *) &next_vrs);
}
#else
pr_result = ((personality_routine) UCB_PR_ADDR (ucbp))
(action, ucbp, (void *) &next_vrs);
#endif
saved_vrs.prev_sp = VRS_SP (&next_vrs);
}
@ -384,6 +438,11 @@ unwind_phase2_forced (_Unwind_Control_Block *ucbp, phase2_vrs *entry_vrs,
return _URC_FAILURE;
}
#if __FDPIC__
/* r9 could have been lost due to PLT jump. Restore correct value. */
saved_vrs.core.r[FDPIC_REGNUM] = gnu_Unwind_Find_got (VRS_PC (&saved_vrs));
#endif
uw_restore_core_regs (&saved_vrs, &saved_vrs.core);
}
@ -429,8 +488,18 @@ __gnu_Unwind_RaiseException (_Unwind_Control_Block * ucbp,
return _URC_FAILURE;
/* Call the pr to decide what to do. */
#if __FDPIC__
{
volatile struct funcdesc_t funcdesc;
funcdesc.ptr = UCB_PR_ADDR (ucbp);
funcdesc.got = UCB_PR_GOT (ucbp);
pr_result = ((personality_routine) &funcdesc)
(_US_VIRTUAL_UNWIND_FRAME, ucbp, (void *) &saved_vrs);
}
#else
pr_result = ((personality_routine) UCB_PR_ADDR (ucbp))
(_US_VIRTUAL_UNWIND_FRAME, ucbp, (void *) &saved_vrs);
#endif
}
while (pr_result == _URC_CONTINUE_UNWIND);
@ -488,13 +557,27 @@ __gnu_Unwind_Resume (_Unwind_Control_Block * ucbp, phase2_vrs * entry_vrs)
}
/* Call the cached PR. */
#if __FDPIC__
{
volatile struct funcdesc_t funcdesc;
funcdesc.ptr = UCB_PR_ADDR (ucbp);
funcdesc.got = UCB_PR_GOT (ucbp);
pr_result = ((personality_routine) &funcdesc)
(_US_UNWIND_FRAME_RESUME, ucbp, (_Unwind_Context *) entry_vrs);
}
#else
pr_result = ((personality_routine) UCB_PR_ADDR (ucbp))
(_US_UNWIND_FRAME_RESUME, ucbp, (_Unwind_Context *) entry_vrs);
#endif
switch (pr_result)
{
case _URC_INSTALL_CONTEXT:
/* Upload the registers to enter the landing pad. */
#if __FDPIC__
/* r9 could have been lost due to PLT jump. Restore correct value. */
entry_vrs->core.r[FDPIC_REGNUM] = gnu_Unwind_Find_got (VRS_PC (entry_vrs));
#endif
uw_restore_core_regs (entry_vrs, &entry_vrs->core);
case _URC_CONTINUE_UNWIND:
@ -586,9 +669,20 @@ __gnu_Unwind_Backtrace(_Unwind_Trace_Fn trace, void * trace_argument,
}
/* Call the pr to decide what to do. */
#if __FDPIC__
{
volatile struct funcdesc_t funcdesc;
funcdesc.ptr = UCB_PR_ADDR (ucbp);
funcdesc.got = UCB_PR_GOT (ucbp);
code = ((personality_routine) &funcdesc)
(_US_VIRTUAL_UNWIND_FRAME | _US_FORCE_UNWIND,
ucbp, (void *) &saved_vrs);
}
#else
code = ((personality_routine) UCB_PR_ADDR (ucbp))
(_US_VIRTUAL_UNWIND_FRAME | _US_FORCE_UNWIND,
ucbp, (void *) &saved_vrs);
#endif
}
while (code != _URC_END_OF_STACK
&& code != _URC_FAILURE);

17
libgcc/unwind-pe.h
View File

@ -262,10 +262,27 @@ read_encoded_value_with_base (unsigned char encoding, _Unwind_Ptr base,
if (result != 0)
{
#if __FDPIC__
/* FDPIC relative addresses imply taking the GOT address
into account. */
if ((encoding & DW_EH_PE_pcrel) && (encoding & DW_EH_PE_indirect))
{
result += gnu_Unwind_Find_got ((_Unwind_Ptr) u);
result = *(_Unwind_Internal_Ptr *) result;
}
else
{
result += ((encoding & 0x70) == DW_EH_PE_pcrel
? (_Unwind_Internal_Ptr) u : base);
if (encoding & DW_EH_PE_indirect)
result = *(_Unwind_Internal_Ptr *) result;
}
#else
result += ((encoding & 0x70) == DW_EH_PE_pcrel
? (_Unwind_Internal_Ptr) u : base);
if (encoding & DW_EH_PE_indirect)
result = *(_Unwind_Internal_Ptr *) result;
#endif
}
}

6
libstdc++-v3/ChangeLog
View File

@ -1,3 +1,9 @@
2019-09-10 Christophe Lyon <christophe.lyon@st.com>
Mickaël Guêné <mickael.guene@st.com>
* libsupc++/eh_personality.cc (get_ttype_entry): Add FDPIC
support.
2019-09-10 Jonathan Wakely <jwakely@redhat.com>
PR libstdc++/91711

10
libstdc++-v3/libsupc++/eh_personality.cc
View File

@ -93,7 +93,15 @@ get_ttype_entry (lsda_header_info *info, _uleb128_t i)
_Unwind_Ptr ptr;
i *= size_of_encoded_value (info->ttype_encoding);
read_encoded_value_with_base (info->ttype_encoding, info->ttype_base,
read_encoded_value_with_base (
#if __FDPIC__
/* Force these flags to nake sure to
take the GOT into account. */
(DW_EH_PE_pcrel | DW_EH_PE_indirect),
#else
info->ttype_encoding,
#endif
info->ttype_base,
info->TType - i, &ptr);
return reinterpret_cast<const std::type_info *>(ptr);