[X86] Use ptrace(PTRACE_GETREGSET, NT_PRSTATUS) to get registers.

Unlike PTRACE_GETREGS, this new method detects 32-bit processes
reliably, without checking segment register values which
are undocumented and aren't part of any sort of API.
While at it, also fixed x32 detection to use __X32_SYSCALL_BIT,
as it should have been from the beginning.

* defs.h: Declare os_release and KERNEL_VERSION.
* strace.c: Make os_release non-static, remove KERNEL_VERSION define.
* syscall.c: New struct i386_user_regs_struct,
static union x86_regs_union and struct iovec x86_io.
(printcall): Use i386_regs or x86_64_regs depending on x86_io.iov_len.
(get_regs): On x86 and kernels 2.6.30+, use PTRACE_GETREGSET,
on earlier kernels fall back to old method.
(get_scno): [X86] Determine personality based on regset size
on scno & __X32_SYSCALL_BIT.
(syscall_fixup_on_sysenter): Use i386_regs or x86_64_regs depending
on x86_io.iov_len.
(get_syscall_args): Likewise.
(get_error): Likewise.

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

1 files changed, 7 insertions, 4 deletions

diff --git a/defs.h b/defs.h
index ab474cb..8ea1aaa 100644
--- a/defs.h
+++ b/defs.h
@@ -518,10 +518,13 @@ extern bool not_failing_only;
 extern bool show_fd_path;
 extern bool tracing_paths;
 extern bool need_fork_exec_workarounds;
-extern unsigned int xflag;
-extern unsigned int followfork;
-extern unsigned int ptrace_setoptions;
-extern unsigned int max_strlen;
+extern unsigned xflag;
+extern unsigned followfork;
+extern unsigned ptrace_setoptions;
+extern unsigned max_strlen;
+extern unsigned os_release;
+#undef KERNEL_VERSION
+#define KERNEL_VERSION(a,b,c) (((a) << 16) + ((b) << 8) + (c))
 
 enum bitness_t { BITNESS_CURRENT = 0, BITNESS_32 };