The syscall emulation code previously wasn't interruptible via
cpu_loop_exit(), as this construct relies on a longjmp target that is not
live anymore in the syscall handling code. Consequently, longjmp() would
operate on a (potentially overwritten) stale jump buffer. This patch adds an additional
setjmp and the necessary handling around it to make longjmp() (and by
proxy cpu_loop_exit() safe to call even within a syscall context.
Reviewed-by: Warner Losh <imp@bsdimp.com>
Reviewed-by: Pierrick Bouvier <pierrick.bouvier@linaro.org>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Florian Hofhammer <florian.hofhammer@epfl.ch>
---
linux-user/aarch64/cpu_loop.c | 2 +-
linux-user/alpha/cpu_loop.c | 2 +-
linux-user/arm/cpu_loop.c | 2 +-
linux-user/hexagon/cpu_loop.c | 2 +-
linux-user/hppa/cpu_loop.c | 1 +
linux-user/i386/cpu_loop.c | 8 +++++---
linux-user/include/special-errno.h | 8 ++++++++
linux-user/loongarch64/cpu_loop.c | 5 +++--
linux-user/m68k/cpu_loop.c | 2 +-
linux-user/microblaze/cpu_loop.c | 2 +-
linux-user/mips/cpu_loop.c | 9 ++++++---
linux-user/or1k/cpu_loop.c | 2 +-
linux-user/ppc/cpu_loop.c | 10 +++++++---
linux-user/riscv/cpu_loop.c | 2 +-
linux-user/s390x/cpu_loop.c | 2 +-
linux-user/sh4/cpu_loop.c | 2 +-
linux-user/sparc/cpu_loop.c | 4 +++-
linux-user/syscall.c | 16 ++++++++++++++++
linux-user/xtensa/cpu_loop.c | 1 +
19 files changed, 60 insertions(+), 22 deletions(-)
diff --git a/linux-user/aarch64/cpu_loop.c b/linux-user/aarch64/cpu_loop.c
index 7f66a879ea..e7f643d69d 100644
--- a/linux-user/aarch64/cpu_loop.c
+++ b/linux-user/aarch64/cpu_loop.c
@@ -181,7 +181,7 @@ void cpu_loop(CPUARMState *env)
0, 0);
if (ret == -QEMU_ERESTARTSYS) {
env->pc -= 4;
- } else if (ret != -QEMU_ESIGRETURN) {
+ } else if (ret != -QEMU_ESIGRETURN && ret != -QEMU_ESETPC) {
env->xregs[0] = ret;
}
break;
diff --git a/linux-user/alpha/cpu_loop.c b/linux-user/alpha/cpu_loop.c
index f93597c400..bef196b1f5 100644
--- a/linux-user/alpha/cpu_loop.c
+++ b/linux-user/alpha/cpu_loop.c
@@ -82,7 +82,7 @@ void cpu_loop(CPUAlphaState *env)
env->pc -= 4;
break;
}
- if (sysret == -QEMU_ESIGRETURN) {
+ if (sysret == -QEMU_ESIGRETURN || sysret == -QEMU_ESETPC) {
break;
}
/* Syscall writes 0 to V0 to bypass error check, similar
diff --git a/linux-user/arm/cpu_loop.c b/linux-user/arm/cpu_loop.c
index 40aefc4c1d..19874f4c72 100644
--- a/linux-user/arm/cpu_loop.c
+++ b/linux-user/arm/cpu_loop.c
@@ -399,7 +399,7 @@ void cpu_loop(CPUARMState *env)
0, 0);
if (ret == -QEMU_ERESTARTSYS) {
env->regs[15] -= env->thumb ? 2 : 4;
- } else if (ret != -QEMU_ESIGRETURN) {
+ } else if (ret != -QEMU_ESIGRETURN && ret != -QEMU_ESETPC) {
env->regs[0] = ret;
}
}
diff --git a/linux-user/hexagon/cpu_loop.c b/linux-user/hexagon/cpu_loop.c
index 5711055aff..9464246e9e 100644
--- a/linux-user/hexagon/cpu_loop.c
+++ b/linux-user/hexagon/cpu_loop.c
@@ -56,7 +56,7 @@ void cpu_loop(CPUHexagonState *env)
0, 0);
if (ret == -QEMU_ERESTARTSYS) {
env->gpr[HEX_REG_PC] -= 4;
- } else if (ret != -QEMU_ESIGRETURN) {
+ } else if (ret != -QEMU_ESIGRETURN && ret != -QEMU_ESETPC) {
env->gpr[0] = ret;
}
break;
diff --git a/linux-user/hppa/cpu_loop.c b/linux-user/hppa/cpu_loop.c
index 972e85c487..4b4b663052 100644
--- a/linux-user/hppa/cpu_loop.c
+++ b/linux-user/hppa/cpu_loop.c
@@ -124,6 +124,7 @@ void cpu_loop(CPUHPPAState *env)
break;
case -QEMU_ERESTARTSYS:
case -QEMU_ESIGRETURN:
+ case -QEMU_ESETPC:
break;
}
break;
diff --git a/linux-user/i386/cpu_loop.c b/linux-user/i386/cpu_loop.c
index f3f58576af..fe922fceb5 100644
--- a/linux-user/i386/cpu_loop.c
+++ b/linux-user/i386/cpu_loop.c
@@ -181,7 +181,9 @@ static void emulate_vsyscall(CPUX86State *env)
if (ret == -TARGET_EFAULT) {
goto sigsegv;
}
- env->regs[R_EAX] = ret;
+ if (ret != -QEMU_ESETPC) {
+ env->regs[R_EAX] = ret;
+ }
/* Emulate a ret instruction to leave the vsyscall page. */
env->eip = caller;
@@ -234,7 +236,7 @@ void cpu_loop(CPUX86State *env)
0, 0);
if (ret == -QEMU_ERESTARTSYS) {
env->eip -= 2;
- } else if (ret != -QEMU_ESIGRETURN) {
+ } else if (ret != -QEMU_ESIGRETURN && ret != -QEMU_ESETPC) {
env->regs[R_EAX] = ret;
}
break;
@@ -253,7 +255,7 @@ void cpu_loop(CPUX86State *env)
0, 0);
if (ret == -QEMU_ERESTARTSYS) {
env->eip -= 2;
- } else if (ret != -QEMU_ESIGRETURN) {
+ } else if (ret != -QEMU_ESIGRETURN && ret != -QEMU_ESETPC) {
env->regs[R_EAX] = ret;
}
break;
diff --git a/linux-user/include/special-errno.h b/linux-user/include/special-errno.h
index 4120455baa..1db757241a 100644
--- a/linux-user/include/special-errno.h
+++ b/linux-user/include/special-errno.h
@@ -29,4 +29,12 @@
*/
#define QEMU_ESIGRETURN 513
+/*
+ * This is returned after a plugin has used the qemu_plugin_set_pc API, to
+ * indicate that the plugin deliberately changed the PC and potentially
+ * modified the register values. The main loop should not touch the guest
+ * registers for this reason.
+ */
+#define QEMU_ESETPC 514
+
#endif /* SPECIAL_ERRNO_H */
diff --git a/linux-user/loongarch64/cpu_loop.c b/linux-user/loongarch64/cpu_loop.c
index 26a5ce3a93..603fcc39c7 100644
--- a/linux-user/loongarch64/cpu_loop.c
+++ b/linux-user/loongarch64/cpu_loop.c
@@ -44,9 +44,10 @@ void cpu_loop(CPULoongArchState *env)
env->pc -= 4;
break;
}
- if (ret == -QEMU_ESIGRETURN) {
+ if (ret == -QEMU_ESIGRETURN || ret == -QEMU_ESETPC) {
/*
- * Returning from a successful sigreturn syscall.
+ * Returning from a successful sigreturn syscall or from
+ * control flow diversion in a plugin callback.
* Avoid clobbering register state.
*/
break;
diff --git a/linux-user/m68k/cpu_loop.c b/linux-user/m68k/cpu_loop.c
index 2c9f628241..b98ca8ff7b 100644
--- a/linux-user/m68k/cpu_loop.c
+++ b/linux-user/m68k/cpu_loop.c
@@ -66,7 +66,7 @@ void cpu_loop(CPUM68KState *env)
0, 0);
if (ret == -QEMU_ERESTARTSYS) {
env->pc -= 2;
- } else if (ret != -QEMU_ESIGRETURN) {
+ } else if (ret != -QEMU_ESIGRETURN && ret != -QEMU_ESETPC) {
env->dregs[0] = ret;
}
}
diff --git a/linux-user/microblaze/cpu_loop.c b/linux-user/microblaze/cpu_loop.c
index 78506ab23d..06d92c0b90 100644
--- a/linux-user/microblaze/cpu_loop.c
+++ b/linux-user/microblaze/cpu_loop.c
@@ -54,7 +54,7 @@ void cpu_loop(CPUMBState *env)
if (ret == -QEMU_ERESTARTSYS) {
/* Wind back to before the syscall. */
env->pc -= 4;
- } else if (ret != -QEMU_ESIGRETURN) {
+ } else if (ret != -QEMU_ESIGRETURN && ret != -QEMU_ESETPC) {
env->regs[3] = ret;
}
/* All syscall exits result in guest r14 being equal to the
diff --git a/linux-user/mips/cpu_loop.c b/linux-user/mips/cpu_loop.c
index 2365de1de1..fa264b27ec 100644
--- a/linux-user/mips/cpu_loop.c
+++ b/linux-user/mips/cpu_loop.c
@@ -140,9 +140,12 @@ done_syscall:
env->active_tc.PC -= 4;
break;
}
- if (ret == -QEMU_ESIGRETURN) {
- /* Returning from a successful sigreturn syscall.
- Avoid clobbering register state. */
+ if (ret == -QEMU_ESIGRETURN || ret == -QEMU_ESETPC) {
+ /*
+ * Returning from a successful sigreturn syscall or from
+ * control flow diversion in a plugin callback.
+ * Avoid clobbering register state.
+ */
break;
}
if ((abi_ulong)ret >= (abi_ulong)-1133) {
diff --git a/linux-user/or1k/cpu_loop.c b/linux-user/or1k/cpu_loop.c
index 2167d880d5..e7e9929e6f 100644
--- a/linux-user/or1k/cpu_loop.c
+++ b/linux-user/or1k/cpu_loop.c
@@ -48,7 +48,7 @@ void cpu_loop(CPUOpenRISCState *env)
cpu_get_gpr(env, 8), 0, 0);
if (ret == -QEMU_ERESTARTSYS) {
env->pc -= 4;
- } else if (ret != -QEMU_ESIGRETURN) {
+ } else if (ret != -QEMU_ESIGRETURN && ret != -QEMU_ESETPC) {
cpu_set_gpr(env, 11, ret);
}
break;
diff --git a/linux-user/ppc/cpu_loop.c b/linux-user/ppc/cpu_loop.c
index b0b0cb14b4..1f9ee20bd0 100644
--- a/linux-user/ppc/cpu_loop.c
+++ b/linux-user/ppc/cpu_loop.c
@@ -340,9 +340,13 @@ void cpu_loop(CPUPPCState *env)
env->nip -= 4;
break;
}
- if (ret == (target_ulong)(-QEMU_ESIGRETURN)) {
- /* Returning from a successful sigreturn syscall.
- Avoid corrupting register state. */
+ if (ret == (target_ulong)(-QEMU_ESIGRETURN) ||
+ ret == (target_ulong)(-QEMU_ESETPC)) {
+ /*
+ * Returning from a successful sigreturn syscall or from
+ * control flow diversion in a plugin callback.
+ * Avoid corrupting register state.
+ */
break;
}
if (ret > (target_ulong)(-515)) {
diff --git a/linux-user/riscv/cpu_loop.c b/linux-user/riscv/cpu_loop.c
index ce542540c2..eecc8d1517 100644
--- a/linux-user/riscv/cpu_loop.c
+++ b/linux-user/riscv/cpu_loop.c
@@ -65,7 +65,7 @@ void cpu_loop(CPURISCVState *env)
}
if (ret == -QEMU_ERESTARTSYS) {
env->pc -= 4;
- } else if (ret != -QEMU_ESIGRETURN) {
+ } else if (ret != -QEMU_ESIGRETURN && ret != -QEMU_ESETPC) {
env->gpr[xA0] = ret;
}
if (cs->singlestep_enabled) {
diff --git a/linux-user/s390x/cpu_loop.c b/linux-user/s390x/cpu_loop.c
index 4929b32e1f..67d2a803fb 100644
--- a/linux-user/s390x/cpu_loop.c
+++ b/linux-user/s390x/cpu_loop.c
@@ -83,7 +83,7 @@ void cpu_loop(CPUS390XState *env)
env->regs[6], env->regs[7], 0, 0);
if (ret == -QEMU_ERESTARTSYS) {
env->psw.addr -= env->int_svc_ilen;
- } else if (ret != -QEMU_ESIGRETURN) {
+ } else if (ret != -QEMU_ESIGRETURN && ret != -QEMU_ESETPC) {
env->regs[2] = ret;
}
diff --git a/linux-user/sh4/cpu_loop.c b/linux-user/sh4/cpu_loop.c
index 0c9d7e9c46..ee2958d0d9 100644
--- a/linux-user/sh4/cpu_loop.c
+++ b/linux-user/sh4/cpu_loop.c
@@ -50,7 +50,7 @@ void cpu_loop(CPUSH4State *env)
0, 0);
if (ret == -QEMU_ERESTARTSYS) {
env->pc -= 2;
- } else if (ret != -QEMU_ESIGRETURN) {
+ } else if (ret != -QEMU_ESIGRETURN && ret != -QEMU_ESETPC) {
env->gregs[0] = ret;
}
break;
diff --git a/linux-user/sparc/cpu_loop.c b/linux-user/sparc/cpu_loop.c
index 7391e2add8..ab633eeae3 100644
--- a/linux-user/sparc/cpu_loop.c
+++ b/linux-user/sparc/cpu_loop.c
@@ -229,7 +229,9 @@ void cpu_loop (CPUSPARCState *env)
env->regwptr[2], env->regwptr[3],
env->regwptr[4], env->regwptr[5],
0, 0);
- if (ret == -QEMU_ERESTARTSYS || ret == -QEMU_ESIGRETURN) {
+ if (ret == -QEMU_ERESTARTSYS ||
+ ret == -QEMU_ESIGRETURN ||
+ ret == -QEMU_ESETPC) {
break;
}
if ((abi_ulong)ret >= (abi_ulong)(-515)) {
diff --git a/linux-user/syscall.c b/linux-user/syscall.c
index d466d0e32f..99e1ed97d9 100644
--- a/linux-user/syscall.c
+++ b/linux-user/syscall.c
@@ -43,6 +43,7 @@
#include <linux/capability.h>
#include <sched.h>
#include <sys/timex.h>
+#include <setjmp.h>
#include <sys/socket.h>
#include <linux/sockios.h>
#include <sys/un.h>
@@ -600,6 +601,9 @@ const char *target_strerror(int err)
if (err == QEMU_ESIGRETURN) {
return "Successful exit from sigreturn";
}
+ if (err == QEMU_ESETPC) {
+ return "Successfully redirected control flow";
+ }
return strerror(target_to_host_errno(err));
}
@@ -14410,6 +14414,18 @@ abi_long do_syscall(CPUArchState *cpu_env, int num, abi_long arg1,
return -QEMU_ESIGRETURN;
}
+ /*
+ * Set up a longjmp target here so that we can call cpu_loop_exit to
+ * redirect control flow back to the main loop even from within
+ * syscall-related plugin callbacks.
+ * For other types of callbacks or longjmp call sites, the longjmp target
+ * is set up in the cpu loop itself but in syscalls the target is not live
+ * anymore.
+ */
+ if (unlikely(sigsetjmp(cpu->jmp_env, 0) != 0)) {
+ return -QEMU_ESETPC;
+ }
+
record_syscall_start(cpu, num, arg1,
arg2, arg3, arg4, arg5, arg6, arg7, arg8);
diff --git a/linux-user/xtensa/cpu_loop.c b/linux-user/xtensa/cpu_loop.c
index a0ff10eff8..d2b4ccdfad 100644
--- a/linux-user/xtensa/cpu_loop.c
+++ b/linux-user/xtensa/cpu_loop.c
@@ -186,6 +186,7 @@ void cpu_loop(CPUXtensaState *env)
break;
case -QEMU_ESIGRETURN:
+ case -QEMU_ESETPC:
break;
}
break;
--
2.53.0
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