| Message ID | 20180711164025.10924-1-laurent@vivier.eu |
|---|---|
| State | New |
| Headers | show |
| Series | [v2] linux-user: fix mmap_find_vma_reserved() | expand |
Le 11/07/2018 à 18:40, Laurent Vivier a écrit : > The value given by mmap_find_vma_reserved() is used with mmap(), > so it is needed to be aligned with the host page size. > > Since commit 18e80c55bb, reserved_va is only aligned to TARGET_PAGE_SIZE, > and it works well if this size is greater or equal to the host page size. > > But ppc64 hosts have 64kB page size and when we start a 4kiB page size > guest (like i386), it fails when it tries to mmap the stack: > > mmap stack: Invalid argument > > Fixes: 18e80c55bb (linux-user: Tidy and enforce reserved_va initialization) > Signed-off-by: Laurent Vivier <laurent@vivier.eu> Richard, I think this fix could be merged into your "linux-user: Fix shmat emulation by honoring host SHMLBA" patch, by adding something like this instead: --- a/linux-user/mmap.c +++ b/linux-user/mmap.c @@ -262,6 +262,8 @@ abi_ulong mmap_find_vma(abi_ulong start, abi_ulong size, abi_ulong align) abi_ulong addr; int wrapped, repeat; + align = MAX(align, qemu_host_page_size); + /* If 'start' == 0, then a default start address is used. */ if (start == 0) { start = mmap_next_start; Thanks, Laurent
On 07/11/2018 09:40 AM, Laurent Vivier wrote: > The value given by mmap_find_vma_reserved() is used with mmap(), > so it is needed to be aligned with the host page size. > > Since commit 18e80c55bb, reserved_va is only aligned to TARGET_PAGE_SIZE, > and it works well if this size is greater or equal to the host page size. > > But ppc64 hosts have 64kB page size and when we start a 4kiB page size > guest (like i386), it fails when it tries to mmap the stack: > > mmap stack: Invalid argument > > Fixes: 18e80c55bb (linux-user: Tidy and enforce reserved_va initialization) > Signed-off-by: Laurent Vivier <laurent@vivier.eu> > --- > > Notes: > v2: > fix typo s/has/as/ > > linux-user/main.c | 5 +++++ > 1 file changed, 5 insertions(+) > > diff --git a/linux-user/main.c b/linux-user/main.c > index 52b5a618fe..15299e9dd7 100644 > --- a/linux-user/main.c > +++ b/linux-user/main.c > @@ -689,6 +689,11 @@ int main(int argc, char **argv, char **envp) > target_environ = envlist_to_environ(envlist, NULL); > envlist_free(envlist); > > + /* reserved_va must be aligned with the host page size > + * as it is used with mmap() > + */ > + reserved_va &= qemu_host_page_mask; > + So... this silently overrides the command-line argument. The current code is only a problem because we assign the default to a global variable, which must be a compile-time constant. I wonder if it's worth add an error message in handle_arg_reserved_va, and moving the default initialization logic from the global variable to here, as if (HOST_LONG_BITS == 64 && TARGET_VIRT_ADDR_SPACE_BITS <= 32 && reserved_va == 0) { reserved_va = MAX_RESERVED_VA & qemu_host_page_mask; } merging your comment with the moved comment from the global variable init. r~
On 07/11/2018 01:27 PM, Laurent Vivier wrote: > Richard, > > I think this fix could be merged into your "linux-user: Fix shmat > emulation by honoring host SHMLBA" patch, by adding something like this > instead: Well, not "instead", but "in addition". Nothing works right when the guest adjustment itself is unaligned, as is the case with reserved_va as you noted, and with (non-reserved) guest_base as I noted in that patch. For v2, I'll split the guest_base fix out to a separate patch. r~
diff --git a/linux-user/main.c b/linux-user/main.c index 52b5a618fe..15299e9dd7 100644 --- a/linux-user/main.c +++ b/linux-user/main.c @@ -689,6 +689,11 @@ int main(int argc, char **argv, char **envp) target_environ = envlist_to_environ(envlist, NULL); envlist_free(envlist); + /* reserved_va must be aligned with the host page size + * as it is used with mmap() + */ + reserved_va &= qemu_host_page_mask; + /* * Now that page sizes are configured in tcg_exec_init() we can do * proper page alignment for guest_base.
The value given by mmap_find_vma_reserved() is used with mmap(), so it is needed to be aligned with the host page size. Since commit 18e80c55bb, reserved_va is only aligned to TARGET_PAGE_SIZE, and it works well if this size is greater or equal to the host page size. But ppc64 hosts have 64kB page size and when we start a 4kiB page size guest (like i386), it fails when it tries to mmap the stack: mmap stack: Invalid argument Fixes: 18e80c55bb (linux-user: Tidy and enforce reserved_va initialization) Signed-off-by: Laurent Vivier <laurent@vivier.eu> --- Notes: v2: fix typo s/has/as/ linux-user/main.c | 5 +++++ 1 file changed, 5 insertions(+)