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| author | AKASHI Takahiro <takahiro.akashi@linaro.org> | 2014-11-28 05:26:35 +0000 |
|---|---|---|
| committer | Will Deacon <will.deacon@arm.com> | 2014-11-28 10:24:13 +0000 |
| commit | 1014c81d9a5546b64352c04cdb93494aceb317fc (patch) | |
| tree | e587ed27bb5651cbf6571fd804f479b0618c063c /arch/arm64 | |
| parent | 766a85d7bc5d7f1ddd6de28bdb844eae45ec63b0 (diff) | |
| download | linux-1014c81d9a5546b64352c04cdb93494aceb317fc.tar.bz2 | |
arm64: ptrace: allow tracer to skip a system call
If tracer modifies a syscall number to -1, this traced system call should
be skipped with a return value specified in x0.
This patch implements this semantics.
Please note:
* syscall entry tracing and syscall exit tracing (ftrace tracepoint and
audit) are always executed, if enabled, even when skipping a system call
(that is, -1).
In this way, we can avoid a potential bug where audit_syscall_entry()
might be called without audit_syscall_exit() at the previous system call
being called, that would cause OOPs in audit_syscall_entry().
Signed-off-by: AKASHI Takahiro <takahiro.akashi@linaro.org>
[will: fixed up conflict with blr rework]
Signed-off-by: Will Deacon <will.deacon@arm.com>
Diffstat (limited to 'arch/arm64')
| -rw-r--r-- | arch/arm64/kernel/entry.S | 12 |
1 files changed, 10 insertions, 2 deletions
diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S index 99c8d13fc00d..fd4fa374e5d2 100644 --- a/arch/arm64/kernel/entry.S +++ b/arch/arm64/kernel/entry.S @@ -669,8 +669,15 @@ ENDPROC(el0_svc) * switches, and waiting for our parent to respond. */ __sys_trace: - mov x0, sp + mov w0, #-1 // set default errno for + cmp scno, x0 // user-issued syscall(-1) + b.ne 1f + mov x0, #-ENOSYS + str x0, [sp, #S_X0] +1: mov x0, sp bl syscall_trace_enter + cmp w0, #-1 // skip the syscall? + b.eq __sys_trace_return_skipped uxtw scno, w0 // syscall number (possibly new) mov x1, sp // pointer to regs cmp scno, sc_nr // check upper syscall limit @@ -683,7 +690,8 @@ __sys_trace: blr x16 // call sys_* routine __sys_trace_return: - str x0, [sp] // save returned x0 + str x0, [sp, #S_X0] // save returned x0 +__sys_trace_return_skipped: mov x0, sp bl syscall_trace_exit b ret_to_user |