gsp_sema_service: add content rescue for unmapped push-buffer pool VAs

- Add expected_sem_payload tracking to svc_channel for CE channels
- Implement svc_rescue_push_page() to scan guest RAM for push with
  expected semaphore release when VA translation fails
- Add svc_init_expected_payload() to initialize expected payload from pool
- Add rate-limited logging of distinct stalled VAs (svc_log_stalled_va)
- Advance expected_sem_payload on successful push decode
- Pushes SEMA_MAP_MAX to 65536, SVC_PIN_SLOTS to 32768 for scale

1 files changed, 77 insertions, 0 deletions

diff --git a/tools/guest-diag/scan3.c b/tools/guest-diag/scan3.c
new file mode 100644
index 0000000..94f6a42
--- /dev/null
+++ b/tools/guest-diag/scan3.c
@@ -0,0 +1,77 @@
+/* scan3.c - scan all writable memory of a process for qwords equal to any
+   of the given 64-bit needles; print every hit address.
+   usage: scan3 PID 0xNEEDLE [0xNEEDLE ...] */
+#define _GNU_SOURCE
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <stdint.h>
+#include <fcntl.h>
+#include <unistd.h>
+
+#define MAXR 4096
+#define MAXN 64
+static struct { uint64_t lo, hi; } wr[MAXR];
+static int nwr;
+static uint64_t needle[MAXN];
+static int nn;
+
+static void load_maps(int pid)
+{
+    char path[64], line[1024];
+    snprintf(path, sizeof path, "/proc/%d/maps", pid);
+    FILE *f = fopen(path, "r");
+    if (!f) { perror("maps"); exit(1); }
+    while (fgets(line, sizeof line, f)) {
+        uint64_t lo, hi;
+        char perms[16];
+        if (sscanf(line, "%lx-%lx %15s", &lo, &hi, perms) < 3) continue;
+        if (strchr(perms, 'w') && nwr < MAXR) { wr[nwr].lo = lo; wr[nwr].hi = hi; nwr++; }
+    }
+    fclose(f);
+}
+
+int main(int argc, char **argv)
+{
+    if (argc < 3) { fprintf(stderr, "usage: scan3 PID 0xNEEDLE [...]\n"); return 1; }
+    int pid = atoi(argv[1]);
+    for (int i = 2; i < argc && nn < MAXN; i++)
+        needle[nn++] = strtoull(argv[i], 0, 16);
+    load_maps(pid);
+    printf("writable=%d needles=%d\n", nwr, nn);
+
+    char mp[64];
+    snprintf(mp, sizeof mp, "/proc/%d/mem", pid);
+    int fd = open(mp, O_RDONLY);
+    if (fd < 0) { perror("mem"); return 1; }
+
+    size_t CH = 4 << 20;
+    uint8_t *buf = malloc(CH + 64);
+    int hits = 0;
+    for (int r = 0; r < nwr; r++) {
+        uint64_t a = wr[r].lo;
+        while (a < wr[r].hi) {
+            size_t n = (size_t)((wr[r].hi - a) < CH ? (wr[r].hi - a) : CH);
+            ssize_t got = pread(fd, buf, n, (off_t)a);
+            if (got <= 0) {
+                if (n > (256u << 10)) { n = 256u << 10; continue; }
+                a += 4096; continue;
+            }
+            if ((size_t)got < n) n = got;
+            n -= n % 8;
+            uint64_t *w = (uint64_t *)buf;
+            for (size_t i = 0; i < n / 8; i++) {
+                uint64_t v = w[i];
+                for (int k = 0; k < nn; k++) {
+                    if (v == needle[k]) {
+                        printf("hit 0x%lx = 0x%lx\n", a + i * 8, v);
+                        hits++;
+                    }
+                }
+            }
+            a += n;
+        }
+    }
+    printf("hits=%d\n", hits);
+    return 0;
+}
\ No newline at end of file