On 11/30/2017 05:57 PM, Andy Lutomirski wrote:
__restore_processor_context() had a couple of ordering bugs. It
restored GSBASE after calling load_gs_index(), and the latter can
call into tracing code. It also tried to restore segment registers
before restoring the LDT, which is straight-up wrong.
Reorder the code so that we restore GSBASE, then the descriptor
tables, then the segments.
This fixes two bugs. First, it fixes a regression that broke resume
under certain configurations due to irqflag tracing in
native_load_gs_index(). Second, it fixes resume when the userspace
process that initiated suspect had funny segments. The latter can be
reproduced by compiling this:
// SPDX-License-Identifier: GPL-2.0
/*
* ldt_echo.c - Echo argv[1] while using an LDT segment
*/
int main(int argc, char **argv)
{
int ret;
size_t len;
char *buf;
const struct user_desc desc = {
.entry_number = 0,
.base_addr = 0,
.limit = 0xfffff,
.seg_32bit = 1,
.contents = 0, /* Data, grow-up */
.read_exec_only = 0,
.limit_in_pages = 1,
.seg_not_present = 1,
.useable = 0
};
if (argc != 2)
errx(1, "Usage: %s STRING", argv[0]);
len = asprintf(&buf, "%s\n", argv[1]);
if (len < 0)
errx(1, "Out of memory");
ret = syscall(SYS_modify_ldt, 1, &desc, sizeof(desc));
if (ret < -1)
errno = -ret;
if (ret)
err(1, "modify_ldt");
asm volatile ("movw %0, %%es" :: "rm" ((unsigned short)7));
write(1, buf, len);
return 0;
}
and running ldt_echo >/sys/power/mem
Without the fix, the latter causes a triple fault on resume.
Reported-by: Jarkko Nikula <jarkko.nik...@linux.intel.com>
Fixes: ca37e57bbe0c ("x86/entry/64: Add missing irqflags tracing to
native_load_gs_index()")
Signed-off-by: Andy Lutomirski <l...@kernel.org>
---
Jarkko, can you test this version?
arch/x86/power/cpu.c | 21 +++++++++++++++++----
1 file changed, 17 insertions(+), 4 deletions(-)
It does fix the suspend/resume issue I saw. Patch applied on top of
current head df8ba95c572a and a loop below completed fine on a few
machines where I tested it. All of them had issue with the ca37e57bbe0c.
for ((i=0;i<10;i++)); do rtcwake -s 5 -m mem; echo $i; done
Tested-by: Jarkko Nikula <jarkko.nik...@linux.intel.com>
