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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: AKASHI Takahiro <takahiro.akashi@linaro.org> Signed-off-by: Will Deacon <will.deacon@arm.com>
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2 changed files with 36 additions and 0 deletions
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@ -551,6 +551,32 @@ static int tls_set(struct task_struct *target, const struct user_regset *regset,
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return ret;
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}
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static int system_call_get(struct task_struct *target,
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const struct user_regset *regset,
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unsigned int pos, unsigned int count,
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void *kbuf, void __user *ubuf)
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{
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int syscallno = task_pt_regs(target)->syscallno;
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return user_regset_copyout(&pos, &count, &kbuf, &ubuf,
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&syscallno, 0, -1);
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}
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static int system_call_set(struct task_struct *target,
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const struct user_regset *regset,
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unsigned int pos, unsigned int count,
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const void *kbuf, const void __user *ubuf)
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{
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int syscallno, ret;
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ret = user_regset_copyin(&pos, &count, &kbuf, &ubuf, &syscallno, 0, -1);
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if (ret)
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return ret;
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task_pt_regs(target)->syscallno = syscallno;
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return ret;
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}
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enum aarch64_regset {
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REGSET_GPR,
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REGSET_FPR,
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@ -559,6 +585,7 @@ enum aarch64_regset {
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REGSET_HW_BREAK,
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REGSET_HW_WATCH,
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#endif
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REGSET_SYSTEM_CALL,
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};
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static const struct user_regset aarch64_regsets[] = {
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@ -608,6 +635,14 @@ static const struct user_regset aarch64_regsets[] = {
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.set = hw_break_set,
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},
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#endif
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[REGSET_SYSTEM_CALL] = {
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.core_note_type = NT_ARM_SYSTEM_CALL,
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.n = 1,
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.size = sizeof(int),
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.align = sizeof(int),
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.get = system_call_get,
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.set = system_call_set,
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},
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};
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static const struct user_regset_view user_aarch64_view = {
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@ -397,6 +397,7 @@ typedef struct elf64_shdr {
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#define NT_ARM_TLS 0x401 /* ARM TLS register */
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#define NT_ARM_HW_BREAK 0x402 /* ARM hardware breakpoint registers */
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#define NT_ARM_HW_WATCH 0x403 /* ARM hardware watchpoint registers */
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#define NT_ARM_SYSTEM_CALL 0x404 /* ARM system call number */
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#define NT_METAG_CBUF 0x500 /* Metag catch buffer registers */
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#define NT_METAG_RPIPE 0x501 /* Metag read pipeline state */
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#define NT_METAG_TLS 0x502 /* Metag TLS pointer */
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