Re: [PATCH v9 20/39] arm64/gcs: Ensure that new threads have a GCS

Mark Brown broonie@kernel.org writes:

diff --git a/arch/arm64/mm/gcs.c b/arch/arm64/mm/gcs.c index b0a67efc522b..4a3ce8e3bdfb 100644 --- a/arch/arm64/mm/gcs.c +++ b/arch/arm64/mm/gcs.c @@ -8,6 +8,139 @@ #include <asm/cpufeature.h> #include <asm/page.h> +static unsigned long alloc_gcs(unsigned long addr, unsigned long size,

• 	       unsigned long token_offset, bool set_res_tok)
  

The token_offset and set_res_tok arguments aren't used in this function, so they can be removed.

+{

• int flags = MAP_ANONYMOUS | MAP_PRIVATE;
• struct mm_struct *mm = current->mm;
• unsigned long mapped_addr, unused;
• if (addr)

• flags |= MAP_FIXED_NOREPLACE;
  

• mmap_write_lock(mm);
• mapped_addr = do_mmap(NULL, addr, size, PROT_READ | PROT_WRITE, flags,

• 	      VM_SHADOW_STACK, 0, &unused, NULL);
  

• mmap_write_unlock(mm);
• return mapped_addr;

+}

+static unsigned long gcs_size(unsigned long size) +{

• if (size)

• return PAGE_ALIGN(size);
  

• /* Allocate RLIMIT_STACK/2 with limits of PAGE_SIZE..2G */
• size = PAGE_ALIGN(min_t(unsigned long long,

• 		rlimit(RLIMIT_STACK) / 2, SZ_2G));
  

• return max(PAGE_SIZE, size);

+}

+static bool gcs_consume_token(struct mm_struct *mm, unsigned long user_addr) +{

• u64 expected = GCS_CAP(user_addr);
• u64 val;
• int ret;
• /* This should really be an atomic cpmxchg. It is not. */

s/cpmxchg/cmpxchg/

The same typo is also in arch/x86/kernel/shstk.c, from the "fork: Support shadow stacks in clone3()" patch series.

• ret = access_remote_vm(mm, user_addr, &val, sizeof(val),

• 	       FOLL_FORCE);
  

• if (ret != sizeof(val))

• return false;
  

• if (val != expected)

• return false;
  

• val = 0;
• ret = access_remote_vm(mm, user_addr, &val, sizeof(val),

• 	       FOLL_FORCE | FOLL_WRITE);
  

• if (ret != sizeof(val))

• return false;
  

• return true;

+}