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linux-user: Rewrite target_shmat

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Handle combined host and guest alignment requirements.
Handle host and guest page size differences.
Handle SHM_EXEC.

Resolves: https://gitlab.com/qemu-project/qemu/-/issues/115
Tested-by: Richard Purdie <richard.purdie@linuxfoundation.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
This commit is contained in:
Richard Henderson 2024-02-22 13:24:38 -10:00
parent 9f7c97324c
commit 78bc8ed9a8
1 changed files with 136 additions and 36 deletions
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172
linux-user/mmap.c
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@ -1236,69 +1236,161 @@ static inline abi_ulong target_shmlba(CPUArchState *cpu_env)
}
#endif
#if defined(__arm__) || defined(__mips__) || defined(__sparc__)
#define HOST_FORCE_SHMLBA 1
#else
#define HOST_FORCE_SHMLBA 0
#endif
abi_ulong target_shmat(CPUArchState *cpu_env, int shmid,
abi_ulong shmaddr, int shmflg)
{
CPUState *cpu = env_cpu(cpu_env);
abi_ulong raddr;
struct shmid_ds shm_info;
int ret;
abi_ulong shmlba;
int h_pagesize;
int t_shmlba, h_shmlba, m_shmlba;
size_t t_len, h_len, m_len;
/* shmat pointers are always untagged */
/* find out the length of the shared memory segment */
/*
* Because we can't use host shmat() unless the address is sufficiently
* aligned for the host, we'll need to check both.
* TODO: Could be fixed with softmmu.
*/
t_shmlba = target_shmlba(cpu_env);
h_pagesize = qemu_real_host_page_size();
h_shmlba = (HOST_FORCE_SHMLBA ? SHMLBA : h_pagesize);
m_shmlba = MAX(t_shmlba, h_shmlba);
if (shmaddr) {
if (shmaddr & (m_shmlba - 1)) {
if (shmflg & SHM_RND) {
/*
* The guest is allowing the kernel to round the address.
* Assume that the guest is ok with us rounding to the
* host required alignment too. Anyway if we don't, we'll
* get an error from the kernel.
*/
shmaddr &= ~(m_shmlba - 1);
if (shmaddr == 0 && (shmflg & SHM_REMAP)) {
return -TARGET_EINVAL;
}
} else {
int require = TARGET_PAGE_SIZE;
#ifdef TARGET_FORCE_SHMLBA
require = t_shmlba;
#endif
/*
* Include host required alignment, as otherwise we cannot
* use host shmat at all.
*/
require = MAX(require, h_shmlba);
if (shmaddr & (require - 1)) {
return -TARGET_EINVAL;
}
}
}
} else {
if (shmflg & SHM_REMAP) {
return -TARGET_EINVAL;
}
}
/* All rounding now manually concluded. */
shmflg &= ~SHM_RND;
/* Find out the length of the shared memory segment. */
ret = get_errno(shmctl(shmid, IPC_STAT, &shm_info));
if (is_error(ret)) {
/* can't get length, bail out */
return ret;
}
t_len = TARGET_PAGE_ALIGN(shm_info.shm_segsz);
h_len = ROUND_UP(shm_info.shm_segsz, h_pagesize);
m_len = MAX(t_len, h_len);
shmlba = target_shmlba(cpu_env);
if (shmaddr & (shmlba - 1)) {
if (shmflg & SHM_RND) {
shmaddr &= ~(shmlba - 1);
} else {
return -TARGET_EINVAL;
}
}
if (!guest_range_valid_untagged(shmaddr, shm_info.shm_segsz)) {
if (!guest_range_valid_untagged(shmaddr, m_len)) {
return -TARGET_EINVAL;
}
WITH_MMAP_LOCK_GUARD() {
void *host_raddr;
bool mapped = false;
void *want, *test;
abi_ulong last;
if (shmaddr) {
host_raddr = shmat(shmid, (void *)g2h_untagged(shmaddr), shmflg);
} else {
abi_ulong mmap_start;
/* In order to use the host shmat, we need to honor host SHMLBA. */
mmap_start = mmap_find_vma(0, shm_info.shm_segsz,
MAX(SHMLBA, shmlba));
if (mmap_start == -1) {
if (!shmaddr) {
shmaddr = mmap_find_vma(0, m_len, m_shmlba);
if (shmaddr == -1) {
return -TARGET_ENOMEM;
}
host_raddr = shmat(shmid, g2h_untagged(mmap_start),
shmflg | SHM_REMAP);
mapped = !reserved_va;
} else if (shmflg & SHM_REMAP) {
/*
* If host page size > target page size, the host shmat may map
* more memory than the guest expects. Reject a mapping that
* would replace memory in the unexpected gap.
* TODO: Could be fixed with softmmu.
*/
if (t_len < h_len &&
!page_check_range_empty(shmaddr + t_len,
shmaddr + h_len - 1)) {
return -TARGET_EINVAL;
}
} else {
if (!page_check_range_empty(shmaddr, shmaddr + m_len - 1)) {
return -TARGET_EINVAL;
}
}
if (host_raddr == (void *)-1) {
return get_errno(-1);
}
raddr = h2g(host_raddr);
last = raddr + shm_info.shm_segsz - 1;
/* All placement is now complete. */
want = (void *)g2h_untagged(shmaddr);
page_set_flags(raddr, last,
/*
* Map anonymous pages across the entire range, then remap with
* the shared memory. This is required for a number of corner
* cases for which host and guest page sizes differ.
*/
if (h_len != t_len) {
int mmap_p = PROT_READ | (shmflg & SHM_RDONLY ? 0 : PROT_WRITE);
int mmap_f = MAP_PRIVATE | MAP_ANONYMOUS
| (reserved_va || (shmflg & SHM_REMAP)
? MAP_FIXED : MAP_FIXED_NOREPLACE);
test = mmap(want, m_len, mmap_p, mmap_f, -1, 0);
if (unlikely(test != want)) {
/* shmat returns EINVAL not EEXIST like mmap. */
ret = (test == MAP_FAILED && errno != EEXIST
? get_errno(-1) : -TARGET_EINVAL);
if (mapped) {
do_munmap(want, m_len);
}
return ret;
}
mapped = true;
}
if (reserved_va || mapped) {
shmflg |= SHM_REMAP;
}
test = shmat(shmid, want, shmflg);
if (test == MAP_FAILED) {
ret = get_errno(-1);
if (mapped) {
do_munmap(want, m_len);
}
return ret;
}
assert(test == want);
last = shmaddr + m_len - 1;
page_set_flags(shmaddr, last,
PAGE_VALID | PAGE_RESET | PAGE_READ |
(shmflg & SHM_RDONLY ? 0 : PAGE_WRITE));
(shmflg & SHM_RDONLY ? 0 : PAGE_WRITE) |
(shmflg & SHM_EXEC ? PAGE_EXEC : 0));
shm_region_rm_complete(raddr, last);
shm_region_add(raddr, last);
shm_region_rm_complete(shmaddr, last);
shm_region_add(shmaddr, last);
}
/*
@ -1312,7 +1404,15 @@ abi_ulong target_shmat(CPUArchState *cpu_env, int shmid,
tb_flush(cpu);
}
return raddr;
if (qemu_loglevel_mask(CPU_LOG_PAGE)) {
FILE *f = qemu_log_trylock();
if (f) {
fprintf(f, "page layout changed following shmat\n");
page_dump(f);
qemu_log_unlock(f);
}
}
return shmaddr;
}
abi_long target_shmdt(abi_ulong shmaddr)