diff options
Diffstat (limited to 'bsd-user/main.c')
| -rw-r--r-- | bsd-user/main.c | 43 |
1 files changed, 42 insertions, 1 deletions
diff --git a/bsd-user/main.c b/bsd-user/main.c index 6df4f4f011..48643eeabc 100644 --- a/bsd-user/main.c +++ b/bsd-user/main.c @@ -52,10 +52,47 @@ #include "target_arch_cpu.h" int singlestep; -unsigned long mmap_min_addr; uintptr_t guest_base; bool have_guest_base; +/* + * When running 32-on-64 we should make sure we can fit all of the possible + * guest address space into a contiguous chunk of virtual host memory. + * + * This way we will never overlap with our own libraries or binaries or stack + * or anything else that QEMU maps. + * + * Many cpus reserve the high bit (or more than one for some 64-bit cpus) + * of the address for the kernel. Some cpus rely on this and user space + * uses the high bit(s) for pointer tagging and the like. For them, we + * must preserve the expected address space. + */ +#ifndef MAX_RESERVED_VA +# if HOST_LONG_BITS > TARGET_VIRT_ADDR_SPACE_BITS +# if TARGET_VIRT_ADDR_SPACE_BITS == 32 && \ + (TARGET_LONG_BITS == 32 || defined(TARGET_ABI32)) +/* + * There are a number of places where we assign reserved_va to a variable + * of type abi_ulong and expect it to fit. Avoid the last page. + */ +# define MAX_RESERVED_VA (0xfffffffful & TARGET_PAGE_MASK) +# else +# define MAX_RESERVED_VA (1ul << TARGET_VIRT_ADDR_SPACE_BITS) +# endif +# else +# define MAX_RESERVED_VA 0 +# endif +#endif + +/* + * That said, reserving *too* much vm space via mmap can run into problems + * with rlimits, oom due to page table creation, etc. We will still try it, + * if directed by the command-line option, but not by default. + */ +#if HOST_LONG_BITS == 64 && TARGET_VIRT_ADDR_SPACE_BITS <= 32 +unsigned long reserved_va = MAX_RESERVED_VA; +#else unsigned long reserved_va; +#endif static const char *interp_prefix = CONFIG_QEMU_INTERP_PREFIX; const char *qemu_uname_release; @@ -439,6 +476,10 @@ int main(int argc, char **argv) target_environ = envlist_to_environ(envlist, NULL); envlist_free(envlist); + if (reserved_va) { + mmap_next_start = reserved_va; + } + { Error *err = NULL; if (seed_optarg != NULL) { |