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Commit 766a85d7 authored by AKASHI Takahiro's avatar AKASHI Takahiro Committed by Will Deacon
Browse files

arm64: ptrace: add NT_ARM_SYSTEM_CALL regset 



This regeset is intended to be used to get and set a system call number
while tracing.
There was some discussion about possible approaches to do so:

(1) modify x8 register with ptrace(PTRACE_SETREGSET) indirectly,
    and update regs->syscallno later on in syscall_trace_enter(), or
(2) define a dedicated regset for this purpose as on s390, or
(3) support ptrace(PTRACE_SET_SYSCALL) as on arch/arm

Thinking of the fact that user_pt_regs doesn't expose 'syscallno' to
tracer as well as that secure_computing() expects a changed syscall number,
especially case of -1, to be visible before this function returns in
syscall_trace_enter(), (1) doesn't work well.
We will take (2) since it looks much cleaner.

Signed-off-by: default avatarAKASHI Takahiro <takahiro.akashi@linaro.org>
Signed-off-by: default avatarWill Deacon <will.deacon@arm.com>
parent 034edabe

arch/arm64/kernel/ptrace.c

+35 −0
Original line number Diff line number Diff line
@@ -551,6 +551,32 @@ static int tls_set(struct task_struct *target, const struct user_regset *regset, 
	return ret;

}



static int system_call_get(struct task_struct *target,

			   const struct user_regset *regset,

			   unsigned int pos, unsigned int count,

			   void *kbuf, void __user *ubuf)

{

	int syscallno = task_pt_regs(target)->syscallno;



	return user_regset_copyout(&pos, &count, &kbuf, &ubuf,

				   &syscallno, 0, -1);

}



static int system_call_set(struct task_struct *target,

			   const struct user_regset *regset,

			   unsigned int pos, unsigned int count,

			   const void *kbuf, const void __user *ubuf)

{

	int syscallno, ret;



	ret = user_regset_copyin(&pos, &count, &kbuf, &ubuf, &syscallno, 0, -1);

	if (ret)

		return ret;



	task_pt_regs(target)->syscallno = syscallno;

	return ret;

}



enum aarch64_regset {

	REGSET_GPR,

	REGSET_FPR,
@@ -559,6 +585,7 @@ enum aarch64_regset { 
	REGSET_HW_BREAK,

	REGSET_HW_WATCH,

#endif

	REGSET_SYSTEM_CALL,

};



static const struct user_regset aarch64_regsets[] = {
@@ -608,6 +635,14 @@ static const struct user_regset aarch64_regsets[] = { 
		.set = hw_break_set,

	},

#endif

	[REGSET_SYSTEM_CALL] = {

		.core_note_type = NT_ARM_SYSTEM_CALL,

		.n = 1,

		.size = sizeof(int),

		.align = sizeof(int),

		.get = system_call_get,

		.set = system_call_set,

	},

};



static const struct user_regset_view user_aarch64_view = {

include/uapi/linux/elf.h

+1 −0
Original line number Diff line number Diff line
@@ -397,6 +397,7 @@ typedef struct elf64_shdr { 
#define NT_ARM_TLS	0x401		/* ARM TLS register */

#define NT_ARM_HW_BREAK	0x402		/* ARM hardware breakpoint registers */

#define NT_ARM_HW_WATCH	0x403		/* ARM hardware watchpoint registers */

#define NT_ARM_SYSTEM_CALL	0x404	/* ARM system call number */

#define NT_METAG_CBUF	0x500		/* Metag catch buffer registers */

#define NT_METAG_RPIPE	0x501		/* Metag read pipeline state */

#define NT_METAG_TLS	0x502		/* Metag TLS pointer */