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
(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 XFAIL and FAIL.
2014-05-20 Hui Zhu <hui@codesourcery.com>
Yao Qi <yao@codesourcery.com>
PR backtrace/16558
* aarch64-linux-tdep.c (aarch64_linux_sigframe_init): Update comments
and change address of sp and pc.
This commit implements the needed bits for SystemTap SDT probe support
on AArch64 architectures.
First, I started by looking at AArch64 assembly specification and
filling the necessary options on gdbarch's stap machinery in order to
make the generic asm parser (implemented in stap-probe.c) recognize
AArch64's asm.
After my last patch for the SystemTap SDT API, which extends it in order
to accept multiple prefixes and suffixes, this patch became simpler. I
also followed Marcus suggestion and did not shared code between 32- and
64-bit ARM.
Tom asked me in a previous message how I did my tests. I believe I
replied that, but just in case: I ran the tests on
gdb.base/stap-probe.exp by hand. I also managed to run the tests on
real hardware, and they pass without regressions.
2013-12-28 Sergio Durigan Junior <sergiodj@redhat.com>
PR tdep/15653
* NEWS: Mention SystemTap SDT probe support for AArch64 GNU/Linux.
* aarch64-linux-tdep.c: Include necessary headers for parsing of
SystemTap SDT probes.
(aarch64_stap_is_single_operand): New function.
(aarch64_stap_parse_special_token): Likewise.
(aarch64_linux_init_abi): Declare SystemTap SDT probe argument
prefixes and suffixes. Initialize gdbarch with them.
If we are running on a Linux platform we should call linux_init_abi
in order to get all the useful hooks it enables.
gdb/ChangeLog:
2013-10-10 Will Newton <will.newton@linaro.org>
* aarch64-linux-tdep.c (aarch64_linux_init_abi): Call
linux_init_abi.
2013-02-08 Yufeng Zhang <yufeng.zhang@arm.com>
* aarch64-linux-tdep.c (AARCH64_LINUX_SIZEOF_GREGSET): Change the
number of the registers from 36 to 34.
