diff options
| -rw-r--r-- | linux-user/elfload.c | 188 |
1 files changed, 161 insertions, 27 deletions
diff --git a/linux-user/elfload.c b/linux-user/elfload.c index 06d81f83b1..a5f9dd5b31 100644 --- a/linux-user/elfload.c +++ b/linux-user/elfload.c @@ -2504,6 +2504,157 @@ static abi_ulong create_elf_tables(abi_ulong p, int argc, int envc, #endif #endif +/** + * pgb_try_mmap: + * @addr: host start address + * @addr_last: host last address + * @keep: do not unmap the probe region + * + * Return 1 if [@addr, @addr_last] is not mapped in the host, + * return 0 if it is not available to map, and -1 on mmap error. + * If @keep, the region is left mapped on success, otherwise unmapped. + */ +static int pgb_try_mmap(uintptr_t addr, uintptr_t addr_last, bool keep) +{ + size_t size = addr_last - addr + 1; + void *p = mmap((void *)addr, size, PROT_NONE, + MAP_ANONYMOUS | MAP_PRIVATE | + MAP_NORESERVE | MAP_FIXED_NOREPLACE, -1, 0); + int ret; + + if (p == MAP_FAILED) { + return errno == EEXIST ? 0 : -1; + } + ret = p == (void *)addr; + if (!keep || !ret) { + munmap(p, size); + } + return ret; +} + +/** + * pgb_try_mmap_skip_brk(uintptr_t addr, uintptr_t size, uintptr_t brk) + * @addr: host address + * @addr_last: host last address + * @brk: host brk + * + * Like pgb_try_mmap, but additionally reserve some memory following brk. + */ +static int pgb_try_mmap_skip_brk(uintptr_t addr, uintptr_t addr_last, + uintptr_t brk, bool keep) +{ + uintptr_t brk_last = brk + 16 * MiB - 1; + + /* Do not map anything close to the host brk. */ + if (addr <= brk_last && brk <= addr_last) { + return 0; + } + return pgb_try_mmap(addr, addr_last, keep); +} + +/** + * pgb_try_mmap_set: + * @ga: set of guest addrs + * @base: guest_base + * @brk: host brk + * + * Return true if all @ga can be mapped by the host at @base. + * On success, retain the mapping at index 0 for reserved_va. + */ + +typedef struct PGBAddrs { + uintptr_t bounds[3][2]; /* start/last pairs */ + int nbounds; +} PGBAddrs; + +static bool pgb_try_mmap_set(const PGBAddrs *ga, uintptr_t base, uintptr_t brk) +{ + for (int i = ga->nbounds - 1; i >= 0; --i) { + if (pgb_try_mmap_skip_brk(ga->bounds[i][0] + base, + ga->bounds[i][1] + base, + brk, i == 0 && reserved_va) <= 0) { + return false; + } + } + return true; +} + +/** + * pgb_addr_set: + * @ga: output set of guest addrs + * @guest_loaddr: guest image low address + * @guest_loaddr: guest image high address + * @identity: create for identity mapping + * + * Fill in @ga with the image, COMMPAGE and NULL page. + */ +static bool pgb_addr_set(PGBAddrs *ga, abi_ulong guest_loaddr, + abi_ulong guest_hiaddr, bool try_identity) +{ + int n; + + /* + * With a low commpage, or a guest mapped very low, + * we may not be able to use the identity map. + */ + if (try_identity) { + if (LO_COMMPAGE != -1 && LO_COMMPAGE < mmap_min_addr) { + return false; + } + if (guest_loaddr != 0 && guest_loaddr < mmap_min_addr) { + return false; + } + } + + memset(ga, 0, sizeof(*ga)); + n = 0; + + if (reserved_va) { + ga->bounds[n][0] = try_identity ? mmap_min_addr : 0; + ga->bounds[n][1] = reserved_va; + n++; + /* LO_COMMPAGE and NULL handled by reserving from 0. */ + } else { + /* Add any LO_COMMPAGE or NULL page. */ + if (LO_COMMPAGE != -1) { + ga->bounds[n][0] = 0; + ga->bounds[n][1] = LO_COMMPAGE + TARGET_PAGE_SIZE - 1; + n++; + } else if (!try_identity) { + ga->bounds[n][0] = 0; + ga->bounds[n][1] = TARGET_PAGE_SIZE - 1; + n++; + } + + /* Add the guest image for ET_EXEC. */ + if (guest_loaddr) { + ga->bounds[n][0] = guest_loaddr; + ga->bounds[n][1] = guest_hiaddr; + n++; + } + } + + /* + * Temporarily disable + * "comparison is always false due to limited range of data type" + * due to comparison between unsigned and (possible) 0. + */ +#pragma GCC diagnostic push +#pragma GCC diagnostic ignored "-Wtype-limits" + + /* Add any HI_COMMPAGE not covered by reserved_va. */ + if (reserved_va < HI_COMMPAGE) { + ga->bounds[n][0] = HI_COMMPAGE & qemu_host_page_mask; + ga->bounds[n][1] = HI_COMMPAGE + TARGET_PAGE_SIZE - 1; + n++; + } + +#pragma GCC diagnostic pop + + ga->nbounds = n; + return true; +} + static void pgb_fail_in_use(const char *image_name) { error_report("%s: requires virtual address space that is in use " @@ -2512,33 +2663,21 @@ static void pgb_fail_in_use(const char *image_name) exit(EXIT_FAILURE); } -static void pgb_have_guest_base(const char *image_name, abi_ulong guest_loaddr, - abi_ulong guest_hiaddr, long align) +static void pgb_fixed(const char *image_name, uintptr_t guest_loaddr, + uintptr_t guest_hiaddr, uintptr_t align) { - const int flags = MAP_ANONYMOUS | MAP_PRIVATE | MAP_NORESERVE; - void *addr, *test; + PGBAddrs ga; + uintptr_t brk = (uintptr_t)sbrk(0); if (!QEMU_IS_ALIGNED(guest_base, align)) { fprintf(stderr, "Requested guest base %p does not satisfy " - "host minimum alignment (0x%lx)\n", + "host minimum alignment (0x%" PRIxPTR ")\n", (void *)guest_base, align); exit(EXIT_FAILURE); } - /* - * Expand the allocation to the entire reserved_va. - * Exclude the mmap_min_addr hole. - */ - if (reserved_va) { - guest_loaddr = (guest_base >= mmap_min_addr ? 0 - : mmap_min_addr - guest_base); - guest_hiaddr = reserved_va; - } - - /* Reserve the address space for the binary, or reserved_va. */ - test = g2h_untagged(guest_loaddr); - addr = mmap(test, guest_hiaddr - guest_loaddr + 1, PROT_NONE, flags, -1, 0); - if (test != addr) { + if (!pgb_addr_set(&ga, guest_loaddr, guest_hiaddr, !guest_base) + || !pgb_try_mmap_set(&ga, guest_base, brk)) { pgb_fail_in_use(image_name); } } @@ -2784,7 +2923,7 @@ void probe_guest_base(const char *image_name, abi_ulong guest_loaddr, } if (have_guest_base) { - pgb_have_guest_base(image_name, guest_loaddr, guest_hiaddr, align); + pgb_fixed(image_name, guest_loaddr, guest_hiaddr, align); } else if (reserved_va) { pgb_reserved_va(image_name, guest_loaddr, guest_hiaddr, align); } else if (guest_loaddr) { @@ -2795,13 +2934,8 @@ void probe_guest_base(const char *image_name, abi_ulong guest_loaddr, /* Reserve and initialize the commpage. */ if (!init_guest_commpage()) { - /* - * With have_guest_base, the user has selected the address and - * we are trying to work with that. Otherwise, we have selected - * free space and init_guest_commpage must succeeded. - */ - assert(have_guest_base); - pgb_fail_in_use(image_name); + /* We have already probed for the commpage being free. */ + g_assert_not_reached(); } assert(QEMU_IS_ALIGNED(guest_base, align)); |