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[Xen-devel] [PATCH 2/2] xen: Identify panic and reboot/halt functions as noreturn



On an x86 build (GCC Debian 4.7.2-5), this reduces the .text size by exactly
4K, and .init.text by 1751 bytes.

Even in a non-debug build, the generated code uses `call` rather than `jmp` so
there should be no impact on any stack trace generation.

Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
CC: Keir Fraser <keir@xxxxxxx>
CC: Jan Beulich <JBeulich@xxxxxxxx>
CC: Ian Campbell <ian.campbell@xxxxxxxxxx>
CC: Stefano Stabellini <stefano.stabellini@xxxxxxxxxx>
CC: Tim Deegan <tim@xxxxxxx>

---

I believe I have identified each reasonable ARM function which could be tagged
as noreturn, but am not overly familiar with the codebase.

I have compile tested arm32 and arm64
---
 xen/arch/arm/shutdown.c       |    6 +++---
 xen/arch/arm/smpboot.c        |    2 +-
 xen/arch/x86/cpu/mcheck/mce.c |    2 +-
 xen/arch/x86/cpu/mcheck/mce.h |    2 +-
 xen/arch/x86/shutdown.c       |    6 +++---
 xen/common/shutdown.c         |    4 ++--
 xen/drivers/char/console.c    |    2 +-
 xen/include/asm-arm/smp.h     |    2 +-
 xen/include/xen/lib.h         |    2 +-
 xen/include/xen/shutdown.h    |   10 ++++++----
 10 files changed, 20 insertions(+), 18 deletions(-)

diff --git a/xen/arch/arm/shutdown.c b/xen/arch/arm/shutdown.c
index 767cc12..58f1cf1 100644
--- a/xen/arch/arm/shutdown.c
+++ b/xen/arch/arm/shutdown.c
@@ -11,12 +11,12 @@ static void raw_machine_reset(void)
     platform_reset();
 }
 
-static void halt_this_cpu(void *arg)
+static void noreturn halt_this_cpu(void *arg)
 {
     stop_cpu();
 }
 
-void machine_halt(void)
+void noreturn machine_halt(void)
 {
     watchdog_disable();
     console_start_sync();
@@ -25,7 +25,7 @@ void machine_halt(void)
     halt_this_cpu(NULL);
 }
 
-void machine_restart(unsigned int delay_millisecs)
+void noreturn machine_restart(unsigned int delay_millisecs)
 {
     int timeout = 10;
 
diff --git a/xen/arch/arm/smpboot.c b/xen/arch/arm/smpboot.c
index 6c90fa6..7242331 100644
--- a/xen/arch/arm/smpboot.c
+++ b/xen/arch/arm/smpboot.c
@@ -310,7 +310,7 @@ void __cpu_disable(void)
      * scheduler will drop to the idle loop, which will call stop_cpu(). */
 }
 
-void stop_cpu(void)
+void noreturn stop_cpu(void)
 {
     local_irq_disable();
     cpu_is_dead = 1;
diff --git a/xen/arch/x86/cpu/mcheck/mce.c b/xen/arch/x86/cpu/mcheck/mce.c
index 93d7ae1..8a226ca 100644
--- a/xen/arch/x86/cpu/mcheck/mce.c
+++ b/xen/arch/x86/cpu/mcheck/mce.c
@@ -1534,7 +1534,7 @@ static void mc_panic_dump(void)
     dprintk(XENLOG_ERR, "End dump mc_info, %x mcinfo dumped\n", 
mcinfo_dumpped);
 }
 
-void mc_panic(char *s)
+void noreturn mc_panic(char *s)
 {
     is_mc_panic = 1;
     console_force_unlock();
diff --git a/xen/arch/x86/cpu/mcheck/mce.h b/xen/arch/x86/cpu/mcheck/mce.h
index cbd123d..db791ff 100644
--- a/xen/arch/x86/cpu/mcheck/mce.h
+++ b/xen/arch/x86/cpu/mcheck/mce.h
@@ -57,7 +57,7 @@ int mce_available(struct cpuinfo_x86 *c);
 unsigned int mce_firstbank(struct cpuinfo_x86 *c);
 /* Helper functions used for collecting error telemetry */
 struct mc_info *x86_mcinfo_getptr(void);
-void mc_panic(char *s);
+void mc_panic(char *s) noreturn;
 void x86_mc_get_cpu_info(unsigned, uint32_t *, uint16_t *, uint16_t *,
                         uint32_t *, uint32_t *, uint32_t *, uint32_t *);
 
diff --git a/xen/arch/x86/shutdown.c b/xen/arch/x86/shutdown.c
index 6143c40..a99a599 100644
--- a/xen/arch/x86/shutdown.c
+++ b/xen/arch/x86/shutdown.c
@@ -92,7 +92,7 @@ static void noreturn __machine_halt(void *unused)
         halt();
 }
 
-void machine_halt(void)
+void noreturn machine_halt(void)
 {
     watchdog_disable();
     console_start_sync();
@@ -452,12 +452,12 @@ static int __init reboot_init(void)
 }
 __initcall(reboot_init);
 
-static void __machine_restart(void *pdelay)
+static void noreturn __machine_restart(void *pdelay)
 {
     machine_restart(*(unsigned int *)pdelay);
 }
 
-void machine_restart(unsigned int delay_millisecs)
+void noreturn machine_restart(unsigned int delay_millisecs)
 {
     unsigned int i, attempt;
     enum reboot_type orig_reboot_type = reboot_type;
diff --git a/xen/common/shutdown.c b/xen/common/shutdown.c
index 9bccd34..87424b1 100644
--- a/xen/common/shutdown.c
+++ b/xen/common/shutdown.c
@@ -17,7 +17,7 @@
 bool_t __read_mostly opt_noreboot;
 boolean_param("noreboot", opt_noreboot);
 
-static void maybe_reboot(void)
+static void noreturn maybe_reboot(void)
 {
     if ( opt_noreboot )
     {
@@ -32,7 +32,7 @@ static void maybe_reboot(void)
     }
 }
 
-void dom0_shutdown(u8 reason)
+void noreturn dom0_shutdown(u8 reason)
 {
     switch ( reason )
     {
diff --git a/xen/drivers/char/console.c b/xen/drivers/char/console.c
index 508f845..7347f96 100644
--- a/xen/drivers/char/console.c
+++ b/xen/drivers/char/console.c
@@ -1038,7 +1038,7 @@ __initcall(debugtrace_init);
  * **************************************************************
  */
 
-void panic(const char *fmt, ...)
+void noreturn panic(const char *fmt, ...)
 {
     va_list args;
     unsigned long flags;
diff --git a/xen/include/asm-arm/smp.h b/xen/include/asm-arm/smp.h
index 1485cc6..0f57c68 100644
--- a/xen/include/asm-arm/smp.h
+++ b/xen/include/asm-arm/smp.h
@@ -15,7 +15,7 @@ DECLARE_PER_CPU(cpumask_var_t, cpu_core_mask);
 
 #define raw_smp_processor_id() (get_processor_id())
 
-extern void stop_cpu(void);
+extern void stop_cpu(void) noreturn;
 
 extern int arch_smp_init(void);
 extern int arch_cpu_init(int cpu, struct dt_device_node *dn);
diff --git a/xen/include/xen/lib.h b/xen/include/xen/lib.h
index 814fcb4..c8b35f1 100644
--- a/xen/include/xen/lib.h
+++ b/xen/include/xen/lib.h
@@ -87,7 +87,7 @@ extern void printk(const char *format, ...)
     __attribute__ ((format (printf, 1, 2)));
 extern void guest_printk(const struct domain *d, const char *format, ...)
     __attribute__ ((format (printf, 2, 3)));
-extern void panic(const char *format, ...)
+extern void panic(const char *format, ...) noreturn
     __attribute__ ((format (printf, 1, 2)));
 extern long vm_assist(struct domain *, unsigned int, unsigned int);
 extern int __printk_ratelimit(int ratelimit_ms, int ratelimit_burst);
diff --git a/xen/include/xen/shutdown.h b/xen/include/xen/shutdown.h
index 2bee748..dfe80d0 100644
--- a/xen/include/xen/shutdown.h
+++ b/xen/include/xen/shutdown.h
@@ -1,13 +1,15 @@
 #ifndef __XEN_SHUTDOWN_H__
 #define __XEN_SHUTDOWN_H__
 
+#include <xen/compiler.h>
+
 /* opt_noreboot: If true, machine will need manual reset on error. */
 extern bool_t opt_noreboot;
 
-void dom0_shutdown(u8 reason);
+void dom0_shutdown(u8 reason) noreturn;
 
-void machine_restart(unsigned int delay_millisecs);
-void machine_halt(void);
-void machine_power_off(void);
+void machine_restart(unsigned int delay_millisecs) noreturn;
+void machine_halt(void) noreturn;
+void machine_power_off(void) noreturn;
 
 #endif /* __XEN_SHUTDOWN_H__ */
-- 
1.7.10.4


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