On Tue, Nov 07, 2017 at 07:09:20PM +0000, Maciej W. Rozycki wrote:
> Fix a commit 7aeb753b5353 ("MIPS: Implement task_user_regset_view.")
> regression, then activated by commit 6a9c001b7ec3 ("MIPS: Switch ELF
> core dumper to use regsets.)", that caused n32 processes to dump o32
> core files by failing to set the EF_MIPS_ABI2 flag in the ELF core file
> header's `e_flags' member:
>
> $ file tls-core
> tls-core: ELF 32-bit MSB executable, MIPS, N32 MIPS64 rel2 version 1 (SYSV), [...]
> $ ./tls-core
> Aborted (core dumped)
> $ file core
> core: ELF 32-bit MSB core file MIPS, MIPS-I version 1 (SYSV), SVR4-style
> $
>
> Previously the flag was set as the result of a:
>
> #define ELF_CORE_EFLAGS EF_MIPS_ABI2
>
> statement placed in arch/mips/kernel/binfmt_elfn32.c, however in the
> regset case, i.e. when CORE_DUMP_USE_REGSET is set, ELF_CORE_EFLAGS is
> no longer used by `fill_note_info' in fs/binfmt_elf.c, and instead the
> `->e_flags' member of the regset view chosen is. We have the views
> defined in arch/mips/kernel/ptrace.c, however only an o32 and an n64
> one, and the latter is used for n32 as well. Consequently an o32 core
> file is incorrectly dumped from n32 processes (the ELF32 vs ELF64 class
> is chosen elsewhere, and the 32-bit one is correctly selected for n32).
>
> Correct the issue then by defining an n32 regset view and using it as
> appropriate. Issue discovered in GDB testing.
>
> Cc: [email protected] # 3.13+
> Fixes: 7aeb753b5353 ("MIPS: Implement task_user_regset_view.")
> Signed-off-by: Maciej W. Rozycki <[email protected]>
Thanks, queued for 4.15.
Cheers
James
> ---
> arch/mips/kernel/ptrace.c | 17 +++++++++++++++++
> 1 file changed, 17 insertions(+)
>
> linux-mips-regset-view-n32-e-flags-abi2-init.diff
> Index: linux-sfr/arch/mips/kernel/ptrace.c
> ===================================================================
> --- linux-sfr.orig/arch/mips/kernel/ptrace.c 2017-10-27 04:55:34.000000000 +0100
> +++ linux-sfr/arch/mips/kernel/ptrace.c 2017-10-27 20:07:14.933716000 +0100
> @@ -618,6 +618,19 @@ static const struct user_regset_view use
> .n = ARRAY_SIZE(mips64_regsets),
> };
>
> +#ifdef CONFIG_MIPS32_N32
> +
> +static const struct user_regset_view user_mipsn32_view = {
> + .name = "mipsn32",
> + .e_flags = EF_MIPS_ABI2,
> + .e_machine = ELF_ARCH,
> + .ei_osabi = ELF_OSABI,
> + .regsets = mips64_regsets,
> + .n = ARRAY_SIZE(mips64_regsets),
> +};
> +
> +#endif /* CONFIG_MIPS32_N32 */
> +
> #endif /* CONFIG_64BIT */
>
> const struct user_regset_view *task_user_regset_view(struct task_struct *task)
> @@ -629,6 +642,10 @@ const struct user_regset_view *task_user
> if (test_tsk_thread_flag(task, TIF_32BIT_REGS))
> return &user_mips_view;
> #endif
> +#ifdef CONFIG_MIPS32_N32
> + if (test_tsk_thread_flag(task, TIF_32BIT_ADDR))
> + return &user_mipsn32_view;
> +#endif
> return &user_mips64_view;
> #endif
> }