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[PATCH]Fix PR backtrace/16558: GDB Aarch64 signal frame unwinder issue
- From: Hui Zhu <hui_zhu at mentor dot com>
- To: gdb-patches ml <gdb-patches at sourceware dot org>
- Date: Wed, 12 Feb 2014 10:15:12 +0800
- Subject: [PATCH]Fix PR backtrace/16558: GDB Aarch64 signal frame unwinder issue
- Authentication-results: sourceware.org; auth=none
The root cause of this issue is unwinder of "#3 <signal handler called>"
doesn't supply right values of registers.
When GDB want to get the previous frame of "#3 <signal handler called>",
it will call cache init function of unwinder "aarch64_linux_sigframe_init".
The address or the value of the registers is get from this function.
So the bug is inside thie function.
I check the asm code of "#3 <signal handler called>":
(gdb) frame 3
#3 <signal handler called>
(gdb) p $pc
$1 = (void (*)()) 0x7f931fa4d0
(gdb) disassemble $pc, +10
Dump of assembler code from 0x7f931fa4d0 to 0x7f931fa4da:
=> 0x0000007f931fa4d0: mov x8, #0x8b // #139
0x0000007f931fa4d4: svc #0x0
0x0000007f931fa4d8: nop
This is the syscall sys_rt_sigreturn, Linux kernel function "restore_sigframe"
will set the frame:
for (i = 0; i < 31; i++)
__get_user_error(regs->regs[i], &sf->uc.uc_mcontext.regs[i],
err);
__get_user_error(regs->sp, &sf->uc.uc_mcontext.sp, err);
__get_user_error(regs->pc, &sf->uc.uc_mcontext.pc, err);
The struct of uc_mcontext is:
struct sigcontext {
__u64 fault_address;
/* AArch64 registers */
__u64 regs[31];
__u64 sp;
__u64 pc;
__u64 pstate;
/* 4K reserved for FP/SIMD state and future expansion */
__u8 __reserved[4096] __attribute__((__aligned__(16)));
};
But in GDB function "aarch64_linux_sigframe_init", the code the get address
of registers is:
for (i = 0; i < 31; i++)
{
trad_frame_set_reg_addr (this_cache,
AARCH64_X0_REGNUM + i,
sigcontext_addr + AARCH64_SIGCONTEXT_XO_OFFSET
+ i * AARCH64_SIGCONTEXT_REG_SIZE);
}
trad_frame_set_reg_addr (this_cache, AARCH64_FP_REGNUM, fp);
trad_frame_set_reg_addr (this_cache, AARCH64_LR_REGNUM, fp + 8);
trad_frame_set_reg_addr (this_cache, AARCH64_PC_REGNUM, fp + 8);
The code that get pc and sp is not right, so I change the code according
to Linux kernel code:
trad_frame_set_reg_addr (this_cache, AARCH64_SP_REGNUM,
sigcontext_addr + AARCH64_SIGCONTEXT_XO_OFFSET
+ 31 * AARCH64_SIGCONTEXT_REG_SIZE);
trad_frame_set_reg_addr (this_cache, AARCH64_PC_REGNUM,
sigcontext_addr + AARCH64_SIGCONTEXT_XO_OFFSET
+ 32 * AARCH64_SIGCONTEXT_REG_SIZE);
The issue was fixed by this change, and I did the regression test. It
also fixed a lot of other FAILs.
Thanks,
Hui
2014-02-12 Hui Zhu <hui@codesourcery.com>
PR backtrace/16558:
* aarch64-linux-tdep.c (aarch64_linux_sigframe_init): Change address
of sp and pc.
--- a/gdb/aarch64-linux-tdep.c
+++ b/gdb/aarch64-linux-tdep.c
@@ -146,7 +146,6 @@ aarch64_linux_sigframe_init (const struc
{
struct gdbarch *gdbarch = get_frame_arch (this_frame);
CORE_ADDR sp = get_frame_register_unsigned (this_frame, AARCH64_SP_REGNUM);
- CORE_ADDR fp = get_frame_register_unsigned (this_frame, AARCH64_FP_REGNUM);
CORE_ADDR sigcontext_addr =
sp
+ AARCH64_RT_SIGFRAME_UCONTEXT_OFFSET
@@ -160,12 +159,14 @@ aarch64_linux_sigframe_init (const struc
sigcontext_addr + AARCH64_SIGCONTEXT_XO_OFFSET
+ i * AARCH64_SIGCONTEXT_REG_SIZE);
}
+ trad_frame_set_reg_addr (this_cache, AARCH64_SP_REGNUM,
+ sigcontext_addr + AARCH64_SIGCONTEXT_XO_OFFSET
+ + 31 * AARCH64_SIGCONTEXT_REG_SIZE);
+ trad_frame_set_reg_addr (this_cache, AARCH64_PC_REGNUM,
+ sigcontext_addr + AARCH64_SIGCONTEXT_XO_OFFSET
+ + 32 * AARCH64_SIGCONTEXT_REG_SIZE);
- trad_frame_set_reg_addr (this_cache, AARCH64_FP_REGNUM, fp);
- trad_frame_set_reg_addr (this_cache, AARCH64_LR_REGNUM, fp + 8);
- trad_frame_set_reg_addr (this_cache, AARCH64_PC_REGNUM, fp + 8);
-
- trad_frame_set_id (this_cache, frame_id_build (fp, func));
+ trad_frame_set_id (this_cache, frame_id_build (sp, func));
}
static const struct tramp_frame aarch64_linux_rt_sigframe =