Mitigation for "clone on sparc might fail with -EFAULT for no valid reason" (bz 31394)

It seems the kernel can not deal with uncommitted stack space in the area intended
for the register window when executing the clone() system call. So create a nested
frame (proxy for the kernel frame) and flush it from the processor to memory to
force committing pages to the stack before invoking the system call.

Bug: https://www.mail-archive.com/debian-glibc@lists.debian.org/msg62592.html
Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=31394
See-also: https://lore.kernel.org/sparclinux/62f9be9d-a086-4134-9a9f-5df8822708af@mkarcher.dialup.fu-berlin.de/
Signed-off-by: Michael Karcher <sourceware-bugzilla@mkarcher.dialup.fu-berlin.de>
Reviewed-by: DJ Delorie <dj@redhat.com>

diff --git a/sysdeps/unix/sysv/linux/sparc/sparc32/clone.S b/sysdeps/unix/sysv/linux/sparc/sparc32/clone.S
index 748d25fcfed597dc8ae671dcbbe81976976484b3..c9cf9bb055bc0c5cba57d14cbe27d44877e28dd3 100644 (file)
--- a/sysdeps/unix/sysv/linux/sparc/sparc32/clone.S
+++ b/sysdeps/unix/sysv/linux/sparc/sparc32/clone.S
@@ -28,6 +28,9 @@
        .text
 ENTRY (__clone)
        save    %sp,-96,%sp
+       save    %sp,-96,%sp
+       flushw
+       restore
        cfi_def_cfa_register(%fp)
        cfi_window_save
        cfi_register(%o7, %i7)

diff --git a/sysdeps/unix/sysv/linux/sparc/sparc64/clone.S b/sysdeps/unix/sysv/linux/sparc/sparc64/clone.S
index e5ff2cf1a042aeae95514823b2793366512adbea..370d51fda295232efaa985b244059b8adab060fb 100644 (file)
--- a/sysdeps/unix/sysv/linux/sparc/sparc64/clone.S
+++ b/sysdeps/unix/sysv/linux/sparc/sparc64/clone.S
@@ -32,6 +32,9 @@
 
 ENTRY (__clone)
        save    %sp, -192, %sp
+       save    %sp, -192, %sp
+       flushw
+       restore
        cfi_def_cfa_register(%fp)
        cfi_window_save
        cfi_register(%o7, %i7)