[PATCH] um: restore process name

[Johannes Berg]

From: Johannes Berg <johannes.berg at intel.com>

After the execve() to disable ASLR, comm is now "exe",
which is a bit confusing. Use readlink() to get this
to the right name again.

Disable stack frame size warnings on main.o since it's
part of the initial userspace and can use larger stack.

Fixes: 68b9883cc16e ("um: Discover host_task_size from envp")
Signed-off-by: Johannes Berg <johannes.berg at intel.com>
---
 arch/um/os-Linux/Makefile |  2 ++
 arch/um/os-Linux/main.c   | 14 ++++++++++++--
 2 files changed, 14 insertions(+), 2 deletions(-)

diff --git a/arch/um/os-Linux/Makefile b/arch/um/os-Linux/Makefile
index 544e0b344c75..049dfa5bc9c6 100644
--- a/arch/um/os-Linux/Makefile
+++ b/arch/um/os-Linux/Makefile
@@ -12,6 +12,8 @@ obj-y = execvp.o file.o helper.o irq.o main.o mem.o process.o \
 
 CFLAGS_signal.o += -Wframe-larger-than=4096
 
+CFLAGS_main.o += -Wno-frame-larger-than
+
 obj-$(CONFIG_ARCH_REUSE_HOST_VSYSCALL_AREA) += elf_aux.o
 
 USER_OBJS := $(user-objs-y) elf_aux.o execvp.o file.o helper.o irq.o \
diff --git a/arch/um/os-Linux/main.c b/arch/um/os-Linux/main.c
index 8a52c49c5361..31dba0912a19 100644
--- a/arch/um/os-Linux/main.c
+++ b/arch/um/os-Linux/main.c
@@ -10,6 +10,7 @@
 #include <errno.h>
 #include <signal.h>
 #include <string.h>
+#include <limits.h>
 #include <sys/resource.h>
 #include <sys/personality.h>
 #include <as-layout.h>
@@ -112,8 +113,17 @@ int __init main(int argc, char **argv, char **envp)
 	/* Disable randomization and re-exec if it was changed successfully */
 	ret = personality(PER_LINUX | ADDR_NO_RANDOMIZE);
 	if (ret >= 0 && (ret & (PER_LINUX | ADDR_NO_RANDOMIZE)) !=
-			 (PER_LINUX | ADDR_NO_RANDOMIZE))
-		execve("/proc/self/exe", argv, envp);
+			 (PER_LINUX | ADDR_NO_RANDOMIZE)) {
+		char buf[PATH_MAX];
+		ssize_t ret;
+
+		ret = readlink("/proc/self/exe", buf, sizeof(buf));
+		if (ret < 0 || ret >= sizeof(buf)) {
+			perror("readlink failure");
+			exit(1);
+		}
+		execve(buf, argv, envp);
+	}
 
 	set_stklim();
 
-- 
2.47.0