linux-user: Rewrite fixed probe_guest_base
Create a set of subroutines to collect a set of guest addresses, all of which must be mappable on the host. Use this within the renamed pgb_fixed subroutine to validate the user's choice of guest_base specified by the -B command-line option. Reviewed-by: Alex Bennée <alex.bennee@linaro.org> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
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Richard Henderson
parent
0c441aeb39
commit
06f38c6688
@ -2504,6 +2504,157 @@ static abi_ulong create_elf_tables(abi_ulong p, int argc, int envc,
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#endif
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#endif
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/**
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* pgb_try_mmap:
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* @addr: host start address
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* @addr_last: host last address
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* @keep: do not unmap the probe region
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*
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* Return 1 if [@addr, @addr_last] is not mapped in the host,
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* return 0 if it is not available to map, and -1 on mmap error.
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* If @keep, the region is left mapped on success, otherwise unmapped.
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*/
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static int pgb_try_mmap(uintptr_t addr, uintptr_t addr_last, bool keep)
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{
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size_t size = addr_last - addr + 1;
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void *p = mmap((void *)addr, size, PROT_NONE,
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MAP_ANONYMOUS | MAP_PRIVATE |
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MAP_NORESERVE | MAP_FIXED_NOREPLACE, -1, 0);
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int ret;
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if (p == MAP_FAILED) {
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return errno == EEXIST ? 0 : -1;
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}
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ret = p == (void *)addr;
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if (!keep || !ret) {
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munmap(p, size);
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}
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return ret;
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}
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/**
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* pgb_try_mmap_skip_brk(uintptr_t addr, uintptr_t size, uintptr_t brk)
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* @addr: host address
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* @addr_last: host last address
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* @brk: host brk
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*
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* Like pgb_try_mmap, but additionally reserve some memory following brk.
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*/
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static int pgb_try_mmap_skip_brk(uintptr_t addr, uintptr_t addr_last,
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uintptr_t brk, bool keep)
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{
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uintptr_t brk_last = brk + 16 * MiB - 1;
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/* Do not map anything close to the host brk. */
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if (addr <= brk_last && brk <= addr_last) {
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return 0;
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}
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return pgb_try_mmap(addr, addr_last, keep);
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}
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/**
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* pgb_try_mmap_set:
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* @ga: set of guest addrs
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* @base: guest_base
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* @brk: host brk
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*
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* Return true if all @ga can be mapped by the host at @base.
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* On success, retain the mapping at index 0 for reserved_va.
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*/
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typedef struct PGBAddrs {
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uintptr_t bounds[3][2]; /* start/last pairs */
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int nbounds;
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} PGBAddrs;
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static bool pgb_try_mmap_set(const PGBAddrs *ga, uintptr_t base, uintptr_t brk)
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{
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for (int i = ga->nbounds - 1; i >= 0; --i) {
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if (pgb_try_mmap_skip_brk(ga->bounds[i][0] + base,
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ga->bounds[i][1] + base,
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brk, i == 0 && reserved_va) <= 0) {
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return false;
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}
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}
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return true;
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}
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/**
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* pgb_addr_set:
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* @ga: output set of guest addrs
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* @guest_loaddr: guest image low address
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* @guest_loaddr: guest image high address
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* @identity: create for identity mapping
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*
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* Fill in @ga with the image, COMMPAGE and NULL page.
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*/
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static bool pgb_addr_set(PGBAddrs *ga, abi_ulong guest_loaddr,
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abi_ulong guest_hiaddr, bool try_identity)
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{
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int n;
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/*
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* With a low commpage, or a guest mapped very low,
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* we may not be able to use the identity map.
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*/
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if (try_identity) {
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if (LO_COMMPAGE != -1 && LO_COMMPAGE < mmap_min_addr) {
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return false;
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}
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if (guest_loaddr != 0 && guest_loaddr < mmap_min_addr) {
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return false;
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}
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}
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memset(ga, 0, sizeof(*ga));
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n = 0;
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if (reserved_va) {
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ga->bounds[n][0] = try_identity ? mmap_min_addr : 0;
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ga->bounds[n][1] = reserved_va;
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n++;
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/* LO_COMMPAGE and NULL handled by reserving from 0. */
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} else {
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/* Add any LO_COMMPAGE or NULL page. */
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if (LO_COMMPAGE != -1) {
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ga->bounds[n][0] = 0;
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ga->bounds[n][1] = LO_COMMPAGE + TARGET_PAGE_SIZE - 1;
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n++;
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} else if (!try_identity) {
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ga->bounds[n][0] = 0;
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ga->bounds[n][1] = TARGET_PAGE_SIZE - 1;
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n++;
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}
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/* Add the guest image for ET_EXEC. */
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if (guest_loaddr) {
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ga->bounds[n][0] = guest_loaddr;
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ga->bounds[n][1] = guest_hiaddr;
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n++;
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}
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}
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/*
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* Temporarily disable
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* "comparison is always false due to limited range of data type"
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* due to comparison between unsigned and (possible) 0.
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*/
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#pragma GCC diagnostic push
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#pragma GCC diagnostic ignored "-Wtype-limits"
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/* Add any HI_COMMPAGE not covered by reserved_va. */
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if (reserved_va < HI_COMMPAGE) {
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ga->bounds[n][0] = HI_COMMPAGE & qemu_host_page_mask;
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ga->bounds[n][1] = HI_COMMPAGE + TARGET_PAGE_SIZE - 1;
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n++;
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}
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#pragma GCC diagnostic pop
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ga->nbounds = n;
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return true;
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}
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static void pgb_fail_in_use(const char *image_name)
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{
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error_report("%s: requires virtual address space that is in use "
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@ -2512,33 +2663,21 @@ static void pgb_fail_in_use(const char *image_name)
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exit(EXIT_FAILURE);
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}
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static void pgb_have_guest_base(const char *image_name, abi_ulong guest_loaddr,
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abi_ulong guest_hiaddr, long align)
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static void pgb_fixed(const char *image_name, uintptr_t guest_loaddr,
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uintptr_t guest_hiaddr, uintptr_t align)
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{
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const int flags = MAP_ANONYMOUS | MAP_PRIVATE | MAP_NORESERVE;
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void *addr, *test;
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PGBAddrs ga;
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uintptr_t brk = (uintptr_t)sbrk(0);
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if (!QEMU_IS_ALIGNED(guest_base, align)) {
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fprintf(stderr, "Requested guest base %p does not satisfy "
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"host minimum alignment (0x%lx)\n",
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"host minimum alignment (0x%" PRIxPTR ")\n",
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(void *)guest_base, align);
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exit(EXIT_FAILURE);
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}
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/*
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* Expand the allocation to the entire reserved_va.
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* Exclude the mmap_min_addr hole.
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*/
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if (reserved_va) {
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guest_loaddr = (guest_base >= mmap_min_addr ? 0
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: mmap_min_addr - guest_base);
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guest_hiaddr = reserved_va;
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}
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/* Reserve the address space for the binary, or reserved_va. */
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test = g2h_untagged(guest_loaddr);
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addr = mmap(test, guest_hiaddr - guest_loaddr + 1, PROT_NONE, flags, -1, 0);
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if (test != addr) {
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if (!pgb_addr_set(&ga, guest_loaddr, guest_hiaddr, !guest_base)
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|| !pgb_try_mmap_set(&ga, guest_base, brk)) {
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pgb_fail_in_use(image_name);
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}
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}
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@ -2784,7 +2923,7 @@ void probe_guest_base(const char *image_name, abi_ulong guest_loaddr,
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}
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if (have_guest_base) {
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pgb_have_guest_base(image_name, guest_loaddr, guest_hiaddr, align);
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pgb_fixed(image_name, guest_loaddr, guest_hiaddr, align);
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} else if (reserved_va) {
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pgb_reserved_va(image_name, guest_loaddr, guest_hiaddr, align);
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} else if (guest_loaddr) {
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@ -2795,13 +2934,8 @@ void probe_guest_base(const char *image_name, abi_ulong guest_loaddr,
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/* Reserve and initialize the commpage. */
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if (!init_guest_commpage()) {
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/*
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* With have_guest_base, the user has selected the address and
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* we are trying to work with that. Otherwise, we have selected
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* free space and init_guest_commpage must succeeded.
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*/
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assert(have_guest_base);
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pgb_fail_in_use(image_name);
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/* We have already probed for the commpage being free. */
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g_assert_not_reached();
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}
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assert(QEMU_IS_ALIGNED(guest_base, align));
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