From: Dmitry V. Levin <ldv@altlinux.org>
Date: Fri, 15 Feb 2019 21:22:30 +0000 (+0000)
Subject: mips o32: fix 7th syscall argument with PTRACE_GET_SYSCALL_INFO API
X-Git-Tag: v5.0~58
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=7a6dbfedfd7ee12b7159f87d0e5294d0b2cfc275;p=strace

mips o32: fix 7th syscall argument with PTRACE_GET_SYSCALL_INFO API

As PTRACE_GET_SYSCALL_INFO API supports 6 syscall arguments,
all architectures that have syscalls with more than 6 arguments
(i.e. mips o32) have to fetch extra arguments manually when using
PTRACE_GET_SYSCALL_INFO API.

* linux/mips/get_syscall_args.c [LINUX_MIPSO32]
(arch_get_syscall_args_extra): New function.
* syscall.c (get_syscall_args) [MAX_ARGS > 6]: Use it.

Fixes: v4.26~49 "Introduce PTRACE_GET_SYSCALL_INFO support"
---

diff --git a/linux/mips/get_syscall_args.c b/linux/mips/get_syscall_args.c
index 522dbae9..48cb103d 100644
--- a/linux/mips/get_syscall_args.c
+++ b/linux/mips/get_syscall_args.c
@@ -38,6 +38,25 @@ arch_get_syscall_args(struct tcb *tcp)
 	return 1;
 }
 
+#ifdef LINUX_MIPSO32
+static void
+arch_get_syscall_args_extra(struct tcb *tcp, const unsigned int n)
+{
+	/* This assumes n >= 4. */
+	if (n_args(tcp) > n
+	    && umoven(tcp, mips_REG_SP + n * sizeof(tcp->u_arg[0]),
+		      (n_args(tcp) - n) * sizeof(tcp->u_arg[0]),
+		      &tcp->u_arg[n]) < 0) {
+		/*
+		 * Let's proceed with the first n arguments
+		 * instead of reporting the failure.
+		 */
+		memset(&tcp->u_arg[n], 0,
+		       (n_args(tcp) - n) * sizeof(tcp->u_arg[0]));
+	}
+}
+#endif
+
 #ifdef SYS_syscall_subcall
 static void
 decode_syscall_subcall(struct tcb *tcp)
diff --git a/syscall.c b/syscall.c
index 1f2fa7a2..d36b8433 100644
--- a/syscall.c
+++ b/syscall.c
@@ -446,6 +446,9 @@ static int arch_get_syscall_args(struct tcb *);
 static void arch_get_error(struct tcb *, bool);
 static int arch_set_error(struct tcb *);
 static int arch_set_success(struct tcb *);
+#if MAX_ARGS > 6
+static void arch_get_syscall_args_extra(struct tcb *, unsigned int);
+#endif
 
 struct inject_opts *inject_vec[SUPPORTED_PERSONALITIES];
 
@@ -1313,13 +1316,23 @@ static int
 get_syscall_args(struct tcb *tcp)
 {
 	if (ptrace_syscall_info_is_valid()) {
-		for (unsigned int i = 0; i < ARRAY_SIZE(tcp->u_arg); ++i)
+		const unsigned int n =
+			MIN(ARRAY_SIZE(tcp->u_arg),
+			    ARRAY_SIZE(ptrace_sci.entry.args));
+		for (unsigned int i = 0; i < n; ++i)
 			tcp->u_arg[i] = ptrace_sci.entry.args[i];
 #if SUPPORTED_PERSONALITIES > 1
 		if (tcp_sysent(tcp)->sys_flags & COMPAT_SYSCALL_TYPES) {
-			for (unsigned int i = 0; i < ARRAY_SIZE(tcp->u_arg); ++i)
+			for (unsigned int i = 0; i < n; ++i)
 				tcp->u_arg[i] = (uint32_t) tcp->u_arg[i];
 		}
+#endif
+		/*
+		 * So far it's just a workaround for mips o32,
+		 * but let's pretend it could be used elsewhere.
+		 */
+#if MAX_ARGS > 6
+		arch_get_syscall_args_extra(tcp, n);
 #endif
 		return 1;
 	}