From 03f9360715731f18e4fdae7b30aa34b30dddcd57 Mon Sep 17 00:00:00 2001
From: HATAYAMA Daisuke <d.hatayama@fujitsu.com>
Date: Sat, 26 Mar 2022 21:42:02 +0900
Subject: [PATCH 1/5] x86: Fix failure of collecting vsyscall mapping due to
 change of enum type of vsyscall_mode

vsyscall mapping fails to get collected because the commit
bd49e16e3339 (x86/vsyscall: Add a new vsyscall=xonly mode) merged at
kernel v5.2-rc7 added constant XONLY to the anonymous enumeration type
of variable vsyscall_mode, which made the value of constant NONE
change from 1 to 2.

This commit fixes the issue by checking the value of constant NONE
using gdb's print command and typeof operator since there's no utility
function to handle such anonymous enumeration type currently in crash
utility.

Signed-off-by: HATAYAMA Daisuke <d.hatayama@fujitsu.com>
Signed-off-by: Lianbo Jiang <lijiang@redhat.com>
---
 src/libgcore/gcore_x86.c | 56 ++++++++++++++++++++++++++++++++++++++--
 1 file changed, 54 insertions(+), 2 deletions(-)

diff --git a/src/libgcore/gcore_x86.c b/src/libgcore/gcore_x86.c
index 08e573c741f6..f334a85d4240 100644
--- a/src/libgcore/gcore_x86.c
+++ b/src/libgcore/gcore_x86.c
@@ -41,6 +41,9 @@ struct gcore_x86_table
 static struct gcore_x86_table gcore_x86_table;
 struct gcore_x86_table *gxt = &gcore_x86_table;
 
+static void gdb_run_command(char *cmd, char *buf, size_t size);
+static int get_vsyscall_mode_none(void);
+
 #ifdef X86_64
 static ulong gcore_x86_64_get_old_rsp(int cpu);
 static ulong gcore_x86_64_get_per_cpu__old_rsp(int cpu);
@@ -2367,6 +2370,54 @@ int gcore_is_arch_32bit_emulation(struct task_context *tc)
 	return FALSE;
 }
 
+static void gdb_run_command(char *cmd, char *buf, size_t size)
+{
+	open_tmpfile();
+	if (!gdb_pass_through(cmd,
+			      pc->tmpfile,
+			      GNU_RETURN_ON_ERROR)) {
+		close_tmpfile();
+		error(FATAL, "gdb command failed: %s", cmd);
+	}
+	rewind(pc->tmpfile);
+	fgets(buf, size, pc->tmpfile);
+	close_tmpfile();
+}
+
+static int get_vsyscall_mode_none(void)
+{
+	static int none = -1;
+	char cmd[32], buf[BUFSIZE];
+	int i;
+
+	if (none != -1)
+		return none;
+
+	/*
+	 * Variable vsyscall_mode is of anonymous enumeration
+	 * type. Because there's no utility function in crash utility
+	 * to get value of each constant in specified anonymous
+	 * enumeration type, we have no choice but rely on gdb's print
+	 * command in combination with typeof operator.
+	 */
+	for (i = 0; i < 10; ++i) {
+		snprintf(cmd, sizeof(cmd), "p (typeof(vsyscall_mode))%d", i);
+		gdb_run_command(cmd, buf, sizeof(buf));
+		if (strstr(buf, "NONE"))
+			return none = i;
+	}
+
+	/*
+	 * When the above logic doesn't work as expected, use 2, which
+	 * is the value on the definition where vsyscall_mode was
+	 * first introduced at the commit 3ae36655b97a (x86-64: Rework
+	 * vsyscall emulation and add vsyscall= parameter).
+	 */
+	none = 2;
+
+	return none;
+}
+
 /**
  * Return an address to gate_vma.
  */
@@ -2377,7 +2428,8 @@ ulong gcore_arch_get_gate_vma(void)
 		return 0UL;
 
 	if (symbol_exists("vsyscall_mode")) {
-		enum { ENUMERATE, NONE } vsyscall_mode;
+		int vsyscall_mode;
+		int none = get_vsyscall_mode_none();
 
 		readmem(symbol_value("vsyscall_mode"),
 			KVADDR,
@@ -2386,7 +2438,7 @@ ulong gcore_arch_get_gate_vma(void)
 			"gcore_arch_get_gate_vma: vsyscall_mode",
 			gcore_verbose_error_handle());
 
-		if (vsyscall_mode == NONE)
+		if (vsyscall_mode == none)
 			return 0UL;
 	}
 
-- 
2.37.1