Attachment 1556716 Details for Bug 1701694 – patch aarch64/Ginit.c to avoid many SIGSEGV

[patch] patch aarch64/Ginit.c to avoid many SIGSEGV

libunwind-aarch64.patch (text/plain), 1.76 KB, created by John Reiser on 2019-04-20 19:39:14 UTC

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Creator: John Reiser

Created: 2019-04-20 19:39:14 UTC

Size: 1.76 KB

patch

obsolete

>--- src/aarch64/Ginit.c.orig	2019-04-20 11:07:52.438612959 -0700
>+++ src/aarch64/Ginit.c	2019-04-20 12:17:55.629682925 -0700
>@@ -82,17 +82,47 @@
>   return 0;
> }
> 
>-static int
>+/* Heurstic to avoid SIGSEGV at bad address.  Assume that a valid 64-bit
>+ * address must have 0x0000 or 0xffff as its most significant 16 bits.
>+ * Sign-extended right shift by 48 produces all 0-bits or all 1-bits,
>+ * and the negative of that will be 0 or 1.
>+ */
>+static unsigned
>+bad_hibits(void const *addr)
>+{
>+  long x = (long)addr;
>+  return 1 < (unsigned long)-(x >> 48);
>+}
>+
>+static int  /* returns 0: OK; -1: addressing error was avoided */
> access_mem (unw_addr_space_t as, unw_word_t addr, unw_word_t *val, int write,
>             void *arg)
> {
>   if (write)
>     {
>+      if (bad_hibits((void const *)addr)) {
>+        Debug (16, "mem[BAD  %lx] <- *%lx\n", addr, val);
>+        return -1;  /* Write into out-of-bounds address */
>+      }
>+      if (bad_hibits((void const *)val)) {
>+        Debug (16, "mem[%lx] <- ZERO  (*BAD %lx)\n", addr, val);
>+        *(unw_word_t *) addr = 0;  /* pretend out-of-bounds is 0 */
>+        return -1;  /* Write from out-of-bounds address */
>+      }
>       Debug (16, "mem[%lx] <- %lx\n", addr, *val);
>       *(unw_word_t *) addr = *val;
>     }
>-  else
>+  else  /* Read */
>     {
>+      if (bad_hibits((void const *)val)) {
>+        Debug (16, "mem[%lx] -> *BAD %lx\n", addr, val);
>+        return -1;  /* Read into out-of-bounds address */
>+      }
>+      if (bad_hibits((void const *)addr)) {
>+        Debug (16, "mem[BAD %lx] -> ZERO (*%lx)\n", addr, *val);
>+        *val = 0;  /* pretend out-of-bounds is 0 */
>+        return -1;  /* Read from out-of-bounds address */
>+      }
>       *val = *(unw_word_t *) addr;
>       Debug (16, "mem[%lx] -> %lx\n", addr, *val);
>     }

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Attachments on bug 1701694: 1556716