linux-user: Emulate /proc/self/smaps

/proc/self/smaps is an extension of /proc/self/maps: it provides the
same lines, plus additional information about each range.

GDB uses /proc/self/smaps when available, which means that
generate-core-file tries it first before falling back to
/proc/self/maps. This, in turn, causes it to dump the host mappings,
since /proc/self/smaps is not emulated and is just passed through.

Fix by emulating /proc/self/smaps. Provide true values only for
Size, KernelPageSize, MMUPageSize and VmFlags. Leave all other values
at 0, which is a valid conservative estimate.

Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20230621203627.1808446-4-iii@linux.ibm.com>
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Message-Id: <20230630180423.558337-34-alex.bennee@linaro.org>

linux-user/syscall.c

@@ -8042,7 +8042,36 @@ static int open_self_cmdline(CPUArchState *cpu_env, int fd)
     return 0;
 }
 
-static int open_self_maps(CPUArchState *cpu_env, int fd)
+static void show_smaps(int fd, unsigned long size)
+{
+    unsigned long page_size_kb = TARGET_PAGE_SIZE >> 10;
+    unsigned long size_kb = size >> 10;
+
+    dprintf(fd, "Size:                  %lu kB\n"
+                "KernelPageSize:        %lu kB\n"
+                "MMUPageSize:           %lu kB\n"
+                "Rss:                   0 kB\n"
+                "Pss:                   0 kB\n"
+                "Pss_Dirty:             0 kB\n"
+                "Shared_Clean:          0 kB\n"
+                "Shared_Dirty:          0 kB\n"
+                "Private_Clean:         0 kB\n"
+                "Private_Dirty:         0 kB\n"
+                "Referenced:            0 kB\n"
+                "Anonymous:             0 kB\n"
+                "LazyFree:              0 kB\n"
+                "AnonHugePages:         0 kB\n"
+                "ShmemPmdMapped:        0 kB\n"
+                "FilePmdMapped:         0 kB\n"
+                "Shared_Hugetlb:        0 kB\n"
+                "Private_Hugetlb:       0 kB\n"
+                "Swap:                  0 kB\n"
+                "SwapPss:               0 kB\n"
+                "Locked:                0 kB\n"
+                "THPeligible:    0\n", size_kb, page_size_kb, page_size_kb);
+}
+
+static int open_self_maps_1(CPUArchState *cpu_env, int fd, bool smaps)
 {
     CPUState *cpu = env_cpu(cpu_env);
     TaskState *ts = cpu->opaque;
@@ -8089,6 +8118,18 @@ static int open_self_maps(CPUArchState *cpu_env, int fd)
             } else {
                 dprintf(fd, "\n");
             }
+            if (smaps) {
+                show_smaps(fd, max - min);
+                dprintf(fd, "VmFlags:%s%s%s%s%s%s%s%s\n",
+                        (flags & PAGE_READ) ? " rd" : "",
+                        (flags & PAGE_WRITE_ORG) ? " wr" : "",
+                        (flags & PAGE_EXEC) ? " ex" : "",
+                        e->is_priv ? "" : " sh",
+                        (flags & PAGE_READ) ? " mr" : "",
+                        (flags & PAGE_WRITE_ORG) ? " mw" : "",
+                        (flags & PAGE_EXEC) ? " me" : "",
+                        e->is_priv ? "" : " ms");
+            }
         }
     }
 
@@ -8103,11 +8144,25 @@ static int open_self_maps(CPUArchState *cpu_env, int fd)
                     " --xp 00000000 00:00 0",
                     TARGET_VSYSCALL_PAGE, TARGET_VSYSCALL_PAGE + TARGET_PAGE_SIZE);
     dprintf(fd, "%*s%s\n", 73 - count, "",  "[vsyscall]");
+    if (smaps) {
+        show_smaps(fd, TARGET_PAGE_SIZE);
+        dprintf(fd, "VmFlags: ex\n");
+    }
 #endif
 
     return 0;
 }
 
+static int open_self_maps(CPUArchState *cpu_env, int fd)
+{
+    return open_self_maps_1(cpu_env, fd, false);
+}
+
+static int open_self_smaps(CPUArchState *cpu_env, int fd)
+{
+    return open_self_maps_1(cpu_env, fd, true);
+}
+
 static int open_self_stat(CPUArchState *cpu_env, int fd)
 {
     CPUState *cpu = env_cpu(cpu_env);
@@ -8459,6 +8514,7 @@ int do_guest_openat(CPUArchState *cpu_env, int dirfd, const char *pathname,
     const struct fake_open *fake_open;
     static const struct fake_open fakes[] = {
         { "maps", open_self_maps, is_proc_myself },
+        { "smaps", open_self_smaps, is_proc_myself },
         { "stat", open_self_stat, is_proc_myself },
         { "auxv", open_self_auxv, is_proc_myself },
         { "cmdline", open_self_cmdline, is_proc_myself },