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[Qemu-devel] [PATCH v4 1/4] linux-user/aarch64: Reset btype for syscalls
From: |
Richard Henderson |
Subject: |
[Qemu-devel] [PATCH v4 1/4] linux-user/aarch64: Reset btype for syscalls and signals |
Date: |
Fri, 29 Mar 2019 14:58:57 -1000 |
The value of btype for syscalls is CONSTRAINED UNPREDICTABLE,
so we need to make sure that the value is 0 before clone,
fork, or syscall return.
The value of btype for signals is defined, but it does not make
sense for a SIGILL handler to enter with the btype set as for
the indirect branch that caused the SIGILL.
Signed-off-by: Richard Henderson <address@hidden>
---
v4: Do not clear btype in signal frame.
---
linux-user/aarch64/cpu_loop.c | 7 +++++++
linux-user/aarch64/signal.c | 5 +++--
2 files changed, 10 insertions(+), 2 deletions(-)
diff --git a/linux-user/aarch64/cpu_loop.c b/linux-user/aarch64/cpu_loop.c
index d75fd9d3e2..f5cce4769d 100644
--- a/linux-user/aarch64/cpu_loop.c
+++ b/linux-user/aarch64/cpu_loop.c
@@ -85,6 +85,13 @@ void cpu_loop(CPUARMState *env)
switch (trapnr) {
case EXCP_SWI:
+ /*
+ * The state of BTYPE on syscall entry is CONSTRAINED
+ * UNPREDICTABLE. The real kernel will need to tidy this up
+ * as well. Do this before syscalls so that the value is
+ * correct on return from syscall (especially clone & fork).
+ */
+ env->btype = 0;
ret = do_syscall(env,
env->xregs[8],
env->xregs[0],
diff --git a/linux-user/aarch64/signal.c b/linux-user/aarch64/signal.c
index f84a9cf28a..078873c4a5 100644
--- a/linux-user/aarch64/signal.c
+++ b/linux-user/aarch64/signal.c
@@ -506,10 +506,11 @@ static void target_setup_frame(int usig, struct
target_sigaction *ka,
+ offsetof(struct target_rt_frame_record, tramp);
}
env->xregs[0] = usig;
- env->xregs[31] = frame_addr;
env->xregs[29] = frame_addr + fr_ofs;
- env->pc = ka->_sa_handler;
env->xregs[30] = return_addr;
+ env->xregs[31] = frame_addr;
+ env->pc = ka->_sa_handler;
+ env->btype = 0;
if (info) {
tswap_siginfo(&frame->info, info);
env->xregs[1] = frame_addr + offsetof(struct target_rt_sigframe, info);
--
2.17.1