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Diffstat (limited to 'tools/debug/pdb_scan.c')
| -rw-r--r-- | tools/debug/pdb_scan.c | 234 |
1 files changed, 234 insertions, 0 deletions
diff --git a/tools/debug/pdb_scan.c b/tools/debug/pdb_scan.c new file mode 100644 index 0000000..da7227e --- /dev/null +++ b/tools/debug/pdb_scan.c @@ -0,0 +1,234 @@ +/* + * pdb_scan.c - read-only reverse scan of a QEMU pc.ram backing file for the + * 4-level page-table chain that maps a given VA to a given PA. + * + * Build: + * cc -O2 -Wall -Wextra -o pdb_scan pdb_scan.c + * + * Usage: + * sudo ./pdb_scan /dev/shm/vgpu-guest-ram 0xafef8000 0x4100000 + * + * Arguments: <ramfile> <target_pa> [va] + * - target_pa : physical address the leaf PT entry must point at (page aligned) + * - va : optional VA used to derive the four table indices + * (default 0x4100000: PML4[0], PDPT[0], PD[8], PT[0x100]) + * + * The scan is strictly read-only: the file is mmap()ed PROT_READ/MAP_PRIVATE + * and no writes are issued. It builds two reverse indexes: + * entry[0x000] -> pages (used for PML4[0] and PDPT[0]) + * entry[0x040] -> pages (used for PD[8]) + * then joins them against pages whose entry[0x800] points at target_pa. + */ +#define _GNU_SOURCE +#include <stdio.h> +#include <stdlib.h> +#include <stdint.h> +#include <string.h> +#include <errno.h> +#include <fcntl.h> +#include <unistd.h> +#include <sys/mman.h> +#include <sys/stat.h> + +#define PAGE_SHIFT 12ULL +#define PAGE_SIZE (1ULL << PAGE_SHIFT) +#define PA_MASK 0x000FFFFFFFFFF000ULL + +static uint64_t target_pa; +static uint64_t va; +static uint64_t n_pages; +static const uint8_t *ram; + +static unsigned idx_pml4, idx_pdpt, idx_pd, idx_pt; +static const char *idx_names[4] = {"PML4", "PDPT", "PD", "PT"}; + +static inline uint64_t rd64(uint64_t pa) +{ + uint64_t v; + memcpy(&v, ram + pa, sizeof(v)); + return v; +} + +static inline uint64_t entry_mask(uint64_t e) { return e & PA_MASK; } + +static const char *bits(uint64_t e) +{ + static char b[128]; + snprintf(b, sizeof(b), "P=%d RW=%d US=%d PWT=%d PCD=%d A=%d D=%d PS=%d", + (int)(e & 1), (int)((e >> 1) & 1), (int)((e >> 2) & 1), + (int)((e >> 3) & 1), (int)((e >> 4) & 1), (int)((e >> 5) & 1), + (int)((e >> 6) & 1), (int)((e >> 7) & 1)); + return b; +} + +/* Generic 4-level walk; returns final PA (masked) or UINT64_MAX on break. */ +static uint64_t walk4(uint64_t pml4_pa, uint64_t *raw_out) +{ + uint64_t e[4], pa = pml4_pa; + unsigned idx[4] = {idx_pml4, idx_pdpt, idx_pd, idx_pt}; + int l; + for (l = 0; l < 4; l++) { + if (pa + PAGE_SIZE > (n_pages << PAGE_SHIFT)) + return UINT64_MAX; + e[l] = rd64(pa + (uint64_t)idx[l] * 8); + if (raw_out) raw_out[l] = e[l]; + if (!(e[l] & 1)) + return UINT64_MAX; + if (l == 2 && (e[l] & 0x80)) { /* PS=1: 2 MiB page at PD level */ + uint64_t base = entry_mask(e[l]) & ~((1ULL << 21) - 1); + return base | (va & ((1ULL << 21) - 1)); + } + pa = entry_mask(e[l]); + } + return pa; +} + +int main(int argc, char **argv) +{ + const char *path; + int fd; + struct stat st; + uint64_t i; + int32_t *head0, *next0, *head40, *next40, *pt_list; + uint64_t n_pt = 0; + int have_va = 0; + + if (argc < 3) { + fprintf(stderr, "usage: %s <ramfile> <target_pa> [va]\n", argv[0]); + return 2; + } + path = argv[1]; + target_pa = strtoull(argv[2], NULL, 0) & PA_MASK; + if (argc >= 4) { + va = strtoull(argv[3], NULL, 0); + have_va = 1; + } else { + va = 0x4100000ULL; + } + /* indices: canonical 4-level split */ + idx_pml4 = (unsigned)((va >> 39) & 0x1ff); + idx_pdpt = (unsigned)((va >> 30) & 0x1ff); + idx_pd = (unsigned)((va >> 21) & 0x1ff); + idx_pt = (unsigned)((va >> 12) & 0x1ff); + + fd = open(path, O_RDONLY); + if (fd < 0) { perror("open"); return 1; } + if (fstat(fd, &st) < 0) { perror("fstat"); return 1; } + if (st.st_size == 0) { fprintf(stderr, "empty file\n"); return 1; } + n_pages = (uint64_t)st.st_size >> PAGE_SHIFT; + + ram = mmap(NULL, (size_t)st.st_size, PROT_READ, MAP_PRIVATE, fd, 0); + if (ram == MAP_FAILED) { perror("mmap"); return 1; } + madvise((void *)ram, (size_t)st.st_size, MADV_SEQUENTIAL); + + fprintf(stderr, "ramfile=%s size=%llu bytes pages=%llu\n", + path, (unsigned long long)st.st_size, (unsigned long long)n_pages); + fprintf(stderr, "target_pa=0x%llx va=0x%llx idx: PML4[%u] PDPT[%u] PD[%u] PT[%u]\n", + (unsigned long long)target_pa, (unsigned long long)va, + idx_pml4, idx_pdpt, idx_pd, idx_pt); + fprintf(stderr, "PT entry offset=0x%x PD entry offset=0x%x\n", + idx_pt * 8, idx_pd * 8); + + head0 = malloc(n_pages * sizeof(int32_t)); + next0 = malloc(n_pages * sizeof(int32_t)); + head40 = malloc(n_pages * sizeof(int32_t)); + next40 = malloc(n_pages * sizeof(int32_t)); + pt_list = malloc(n_pages * sizeof(int32_t)); + if (!head0 || !next0 || !head40 || !next40 || !pt_list) { + fprintf(stderr, "out of memory\n"); return 1; + } + for (i = 0; i < n_pages; i++) { head0[i] = -1; head40[i] = -1; } + + for (i = 0; i < n_pages; i++) { + const uint8_t *p = ram + (i << PAGE_SHIFT); + uint64_t e0, e40, ept, a; + memcpy(&e0, p + 0x000, 8); + memcpy(&e40, p + 0x040, 8); + memcpy(&ept, p + (uint64_t)idx_pt * 8, 8); + + if (entry_mask(ept) == target_pa) + pt_list[n_pt++] = (int32_t)i; + + a = entry_mask(e0); + if (a < (n_pages << PAGE_SHIFT) && (a & (PAGE_SIZE - 1)) == 0) { + uint64_t j = a >> PAGE_SHIFT; + next0[i] = head0[j]; + head0[j] = (int32_t)i; + } + a = entry_mask(e40); + if (a < (n_pages << PAGE_SHIFT) && (a & (PAGE_SIZE - 1)) == 0) { + uint64_t j = a >> PAGE_SHIFT; + next40[i] = head40[j]; + head40[j] = (int32_t)i; + } + } + madvise((void *)ram, (size_t)st.st_size, MADV_RANDOM); + + fprintf(stderr, "pages whose entry[0x%x] == target: %llu\n", + idx_pt * 8, (unsigned long long)n_pt); + + uint64_t n_chain = 0; + for (uint64_t t = 0; t < n_pt; t++) { + int32_t pt = pt_list[t]; + int32_t pd; + for (pd = head40[pt]; pd >= 0; pd = next40[pd]) { + int32_t pdpt; + for (pdpt = head0[pd]; pdpt >= 0; pdpt = next0[pdpt]) { + int32_t pml4; + for (pml4 = head0[pdpt]; pml4 >= 0; pml4 = next0[pml4]) { + uint64_t pa_pml4 = (uint64_t)pml4 << PAGE_SHIFT; + uint64_t pa_pdpt = (uint64_t)pdpt << PAGE_SHIFT; + uint64_t pa_pd = (uint64_t)pd << PAGE_SHIFT; + uint64_t pa_pt = (uint64_t)pt << PAGE_SHIFT; + uint64_t raw[4] = {0}, fin; + fin = walk4(pa_pml4, raw); + n_chain++; + printf("\n=== candidate #%llu ===\n", (unsigned long long)n_chain); + printf("pdb (PML4 PA) = 0x%llx\n", (unsigned long long)pa_pml4); + printf("PML4[%u] @0x%llx+0x%03x = 0x%016llx -> PDPT 0x%llx [%s]\n", + idx_pml4, (unsigned long long)pa_pml4, idx_pml4 * 8, + (unsigned long long)raw[0], (unsigned long long)pa_pdpt, + bits(raw[0])); + printf("PDPT[%u] @0x%llx+0x%03x = 0x%016llx -> PD 0x%llx [%s]\n", + idx_pdpt, (unsigned long long)pa_pdpt, idx_pdpt * 8, + (unsigned long long)raw[1], (unsigned long long)pa_pd, + bits(raw[1])); + printf("PD[%u] @0x%llx+0x%03x = 0x%016llx -> PT 0x%llx [%s]\n", + idx_pd, (unsigned long long)pa_pd, idx_pd * 8, + (unsigned long long)raw[2], (unsigned long long)pa_pt, + bits(raw[2])); + printf("PT[%u] @0x%llx+0x%03x = 0x%016llx -> PA 0x%llx [%s]\n", + idx_pt, (unsigned long long)pa_pt, idx_pt * 8, + (unsigned long long)raw[3], + (unsigned long long)entry_mask(raw[3]), bits(raw[3])); + printf("walk_result = 0x%llx %s\n", + (unsigned long long)fin, + fin == target_pa ? "MATCH" : "MISMATCH"); + } + } + } + } + + /* Reference: the caller-supplied known pdb, if present in the file. */ + if (have_va) { + uint64_t known = 0x11092a000ULL; + if (known < (n_pages << PAGE_SHIFT)) { + uint64_t raw[4] = {0}, fin = walk4(known, raw); + printf("\n=== reference walk from known pdb 0x%llx ===\n", + (unsigned long long)known); + printf("PML4[%u]=0x%016llx PDPT[%u]=0x%016llx PD[%u]=0x%016llx PT[%u]=0x%016llx\n", + idx_pml4, (unsigned long long)raw[0], + idx_pdpt, (unsigned long long)raw[1], + idx_pd, (unsigned long long)raw[2], + idx_pt, (unsigned long long)raw[3]); + printf("walk_result = 0x%llx\n", (unsigned long long)fin); + } + } + + printf("\ntotal candidate chains: %llu\n", (unsigned long long)n_chain); + + munmap((void *)ram, (size_t)st.st_size); + close(fd); + free(head0); free(next0); free(head40); free(next40); free(pt_list); + return 0; +} |