Messages in this thread | | | Date | Wed, 27 Jan 2021 14:53:07 +0000 | From | Dave Martin <> | Subject | Re: [PATCH 2/3] arm64/ptrace: introduce NT_ARM_PRSTATUS to get a full set of registers |
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On Tue, Jan 19, 2021 at 02:06:36PM -0800, Andrei Vagin wrote: > This is an alternative to NT_PRSTATUS that clobbers ip/r12 on AArch32, > x7 on AArch64 when a tracee is stopped in syscall entry or syscall exit > traps. > > Signed-off-by: Andrei Vagin <avagin@gmail.com>
This approach looks like it works, though I still think adding an option for this under PTRACE_SETOPTIONS would be less intrusive.
Adding a shadow regset like this also looks like it would cause the gp regs to be pointlessly be dumped twice in a core dump. Avoiding that might require hacks in the core code...
> --- > arch/arm64/kernel/ptrace.c | 39 ++++++++++++++++++++++++++++++++++++++ > include/uapi/linux/elf.h | 1 + > 2 files changed, 40 insertions(+) > > diff --git a/arch/arm64/kernel/ptrace.c b/arch/arm64/kernel/ptrace.c > index 1863f080cb07..b8e4c2ddf636 100644 > --- a/arch/arm64/kernel/ptrace.c > +++ b/arch/arm64/kernel/ptrace.c > @@ -591,6 +591,15 @@ static int gpr_get(struct task_struct *target, > return ret; > } > > +static int gpr_get_full(struct task_struct *target, > + const struct user_regset *regset, > + struct membuf to) > +{ > + struct user_pt_regs *uregs = &task_pt_regs(target)->user_regs; > + > + return membuf_write(&to, uregs, sizeof(*uregs)); > +} > + > static int gpr_set(struct task_struct *target, const struct user_regset *regset, > unsigned int pos, unsigned int count, > const void *kbuf, const void __user *ubuf) > @@ -1088,6 +1097,7 @@ static int tagged_addr_ctrl_set(struct task_struct *target, const struct > > enum aarch64_regset { > REGSET_GPR, > + REGSET_GPR_FULL,
If we go with this approach, "REGSET_GPR_RAW" might be a preferable name. Both regs represent all the regs ("full"), but REGSET_GPR is mangled by the kernel.
> REGSET_FPR, > REGSET_TLS, > #ifdef CONFIG_HAVE_HW_BREAKPOINT > @@ -1119,6 +1129,14 @@ static const struct user_regset aarch64_regsets[] = { > .regset_get = gpr_get, > .set = gpr_set > }, > + [REGSET_GPR_FULL] = { > + .core_note_type = NT_ARM_PRSTATUS,
Similarly, something like NT_ARM_PRSTATUS_RAW or similar.
> + .n = sizeof(struct user_pt_regs) / sizeof(u64), > + .size = sizeof(u64), > + .align = sizeof(u64), > + .regset_get = gpr_get_full, > + .set = gpr_set > + }, > [REGSET_FPR] = { > .core_note_type = NT_PRFPREG, > .n = sizeof(struct user_fpsimd_state) / sizeof(u32), > @@ -1225,6 +1243,7 @@ static const struct user_regset_view user_aarch64_view = { > #ifdef CONFIG_COMPAT > enum compat_regset { > REGSET_COMPAT_GPR, > + REGSET_COMPAT_GPR_FULL, > REGSET_COMPAT_VFP, > }; > > @@ -1285,6 +1304,18 @@ static int compat_gpr_get(struct task_struct *target, > return 0; > } > > +/* compat_gpr_get_full doesn't overwrite x12 like compat_gpr_get. */ > +static int compat_gpr_get_full(struct task_struct *target, > + const struct user_regset *regset, > + struct membuf to) > +{ > + int i = 0; > + > + while (to.left) > + membuf_store(&to, compat_get_user_reg(target, i++)); > + return 0; > +} > + > static int compat_gpr_set(struct task_struct *target, > const struct user_regset *regset, > unsigned int pos, unsigned int count, > @@ -1435,6 +1466,14 @@ static const struct user_regset aarch32_regsets[] = { > .regset_get = compat_gpr_get, > .set = compat_gpr_set > }, > + [REGSET_COMPAT_GPR_FULL] = { > + .core_note_type = NT_ARM_PRSTATUS, > + .n = COMPAT_ELF_NGREG, > + .size = sizeof(compat_elf_greg_t), > + .align = sizeof(compat_elf_greg_t), > + .regset_get = compat_gpr_get_full, > + .set = compat_gpr_set > + }, > [REGSET_COMPAT_VFP] = { > .core_note_type = NT_ARM_VFP, > .n = VFP_STATE_SIZE / sizeof(compat_ulong_t), > diff --git a/include/uapi/linux/elf.h b/include/uapi/linux/elf.h > index 30f68b42eeb5..a2086d19263a 100644 > --- a/include/uapi/linux/elf.h > +++ b/include/uapi/linux/elf.h > @@ -426,6 +426,7 @@ typedef struct elf64_shdr { > #define NT_ARM_PACA_KEYS 0x407 /* ARM pointer authentication address keys */ > #define NT_ARM_PACG_KEYS 0x408 /* ARM pointer authentication generic key */ > #define NT_ARM_TAGGED_ADDR_CTRL 0x409 /* arm64 tagged address control (prctl()) */
What happened to 0x40a..0x40f?
[...]
Cheers ---Dave
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