svn commit: r347580 - head/sys/amd64/linux

[Edward Tomasz Napierala]

Author: trasz
Date: Tue May 14 20:59:44 2019
New Revision: 347580
URL: https://svnweb.freebsd.org/changeset/base/347580

Log:
  Fix handling of r10 in Linux ptrace(2).  This fixes decoding
  of the 'flags' argument to mmap(2) with Linux strace(1).
  
  Reviewed by:	dchagin
  MFC after:	2 weeks
  Sponsored by:	The FreeBSD Foundation
  Differential Revision:	https://reviews.freebsd.org/D20223

Modified:
  head/sys/amd64/linux/linux_ptrace.c

Modified: head/sys/amd64/linux/linux_ptrace.c
==============================================================================
--- head/sys/amd64/linux/linux_ptrace.c	Tue May 14 20:41:24 2019	(r347579)
+++ head/sys/amd64/linux/linux_ptrace.c	Tue May 14 20:59:44 2019	(r347580)
@@ -338,18 +338,27 @@ linux_ptrace_getregs(struct thread *td, pid_t pid, voi
 
 	map_regs_to_linux(&b_reg, &l_reg);
 
-	/*
-	 * The strace(1) utility depends on RAX being set to -ENOSYS
-	 * on syscall entry.
-	 */
 	error = kern_ptrace(td, PT_LWPINFO, pid, &lwpinfo, sizeof(lwpinfo));
 	if (error != 0) {
 		printf("%s: PT_LWPINFO failed with error %d\n", __func__, error);
 		return (error);
 	}
-	if (lwpinfo.pl_flags & PL_FLAG_SCE)
-		l_reg.rax = -38; // XXX: Don't hardcode?
+	if (lwpinfo.pl_flags & PL_FLAG_SCE) {
+		/*
+		 * The strace(1) utility depends on RAX being set to -ENOSYS
+		 * on syscall entry; otherwise it loops printing those:
+		 *
+		 * [ Process PID=928 runs in 64 bit mode. ]
+		 * [ Process PID=928 runs in x32 mode. ]
+		 */
+		l_reg.rax = -38; /* -ENOSYS */
 
+		/*
+		 * Undo the mangling done in exception.S:fast_syscall_common().
+		 */
+		l_reg.r10 = l_reg.rcx;
+	}
+
 	error = copyout(&l_reg, (void *)data, sizeof(l_reg));
 	return (error);
 }
@@ -399,21 +408,27 @@ linux_ptrace_getregset_prstatus(struct thread *td, pid
 
 	map_regs_to_linux_regset(&b_reg, fsbase, gsbase, &l_regset);
 
-	/*
-	 * The strace(1) utility depends on RAX being set to -ENOSYS
-	 * on syscall entry; otherwise it loops printing those:
-	 *
-	 * [ Process PID=928 runs in 64 bit mode. ]
-	 * [ Process PID=928 runs in x32 mode. ]
-	 */
 	error = kern_ptrace(td, PT_LWPINFO, pid, &lwpinfo, sizeof(lwpinfo));
 	if (error != 0) {
 		printf("%s: PT_LWPINFO failed with error %d\n",
 		    __func__, error);
 		return (error);
 	}
-	if (lwpinfo.pl_flags & PL_FLAG_SCE)
-		l_regset.rax = -38; // XXX: Don't hardcode?
+	if (lwpinfo.pl_flags & PL_FLAG_SCE) {
+		/*
+		 * The strace(1) utility depends on RAX being set to -ENOSYS
+		 * on syscall entry; otherwise it loops printing those:
+		 *
+		 * [ Process PID=928 runs in 64 bit mode. ]
+		 * [ Process PID=928 runs in x32 mode. ]
+		 */
+		l_regset.rax = -38; /* -ENOSYS */
+
+		/*
+		 * Undo the mangling done in exception.S:fast_syscall_common().
+		 */
+		l_regset.r10 = l_regset.rcx;
+	}
 
 	len = MIN(iov.iov_len, sizeof(l_regset));
 	error = copyout(&l_regset, (void *)iov.iov_base, len);