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| author |  Johannes Berg <johannes.berg@intel.com>
| 2023-04-14 15:46:39 +0200 |
|---|---|---|
| committer |  Richard Weinberger <richard@nod.at>
| 2023-04-20 23:08:43 +0200 |
| commit | 6032aca0deb9c138df122192f8ef02de1fdccf25 (patch) | |
| tree | f9acfe2a2c09cfa1b3a86351b8bdf2ccd8fa48ef /arch/um/kernel | |
| parent | um: prevent user code in modules (diff) | |
| download | linux-6032aca0deb9c138df122192f8ef02de1fdccf25.tar.gz linux-6032aca0deb9c138df122192f8ef02de1fdccf25.tar.bz2 linux-6032aca0deb9c138df122192f8ef02de1fdccf25.zip | |
um: make stub data pages size tweakable
There's a lot of code here that hard-codes that the
data is a single page, and right now that seems to
be sufficient, but to make it easier to change this
in the future, add a new STUB_DATA_PAGES constant
and use it throughout the code.
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Richard Weinberger <richard@nod.at>
Diffstat (limited to 'arch/um/kernel')
| -rw-r--r-- | arch/um/kernel/skas/clone.c | 5 | ||||
| -rw-r--r-- | arch/um/kernel/skas/mmu.c | 6 | ||||
| -rw-r--r-- | arch/um/kernel/um_arch.c | 10 |
3 files changed, 13 insertions, 8 deletions
diff --git a/arch/um/kernel/skas/clone.c b/arch/um/kernel/skas/clone.c index ff5061f29167..62435187dda4 100644 --- a/arch/um/kernel/skas/clone.c +++ b/arch/um/kernel/skas/clone.c @@ -24,11 +24,12 @@ void __attribute__ ((__section__ (".__syscall_stub"))) stub_clone_handler(void) { - struct stub_data *data = get_stub_page(); + struct stub_data *data = get_stub_data(); long err; err = stub_syscall2(__NR_clone, CLONE_PARENT | CLONE_FILES | SIGCHLD, - (unsigned long)data + UM_KERN_PAGE_SIZE / 2); + (unsigned long)data + + STUB_DATA_PAGES * UM_KERN_PAGE_SIZE / 2); if (err) { data->parent_err = err; goto done; diff --git a/arch/um/kernel/skas/mmu.c b/arch/um/kernel/skas/mmu.c index 125df465e8ea..656fe16c9b63 100644 --- a/arch/um/kernel/skas/mmu.c +++ b/arch/um/kernel/skas/mmu.c @@ -21,7 +21,7 @@ int init_new_context(struct task_struct *task, struct mm_struct *mm) unsigned long stack = 0; int ret = -ENOMEM; - stack = get_zeroed_page(GFP_KERNEL); + stack = __get_free_pages(GFP_KERNEL | __GFP_ZERO, ilog2(STUB_DATA_PAGES)); if (stack == 0) goto out; @@ -52,7 +52,7 @@ int init_new_context(struct task_struct *task, struct mm_struct *mm) out_free: if (to_mm->id.stack != 0) - free_page(to_mm->id.stack); + free_pages(to_mm->id.stack, ilog2(STUB_DATA_PAGES)); out: return ret; } @@ -74,6 +74,6 @@ void destroy_context(struct mm_struct *mm) } os_kill_ptraced_process(mmu->id.u.pid, 1); - free_page(mmu->id.stack); + free_pages(mmu->id.stack, ilog2(STUB_DATA_PAGES)); free_ldt(mmu); } diff --git a/arch/um/kernel/um_arch.c b/arch/um/kernel/um_arch.c index 8dcda617b8bf..0a23a98d4ca0 100644 --- a/arch/um/kernel/um_arch.c +++ b/arch/um/kernel/um_arch.c @@ -326,9 +326,13 @@ int __init linux_main(int argc, char **argv) add_arg(DEFAULT_COMMAND_LINE_CONSOLE); host_task_size = os_get_top_address(); - /* reserve two pages for the stubs */ - host_task_size -= 2 * PAGE_SIZE; - stub_start = host_task_size; + /* reserve a few pages for the stubs (taking care of data alignment) */ + /* align the data portion */ + BUILD_BUG_ON(!is_power_of_2(STUB_DATA_PAGES)); + stub_start = (host_task_size - 1) & ~(STUB_DATA_PAGES * PAGE_SIZE - 1); + /* another page for the code portion */ + stub_start -= PAGE_SIZE; + host_task_size = stub_start; /* * TASK_SIZE needs to be PGDIR_SIZE aligned or else exit_mmap craps |