[Xen-devel] [PATCH v3 3/5] xen: Identify panic and reboot/halt functions as noreturn

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

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

Experimentally, even in a non-debug build, GCC 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>
Acked-by: Tim Deegan <tim@xxxxxxx>

---

Changes in v2:
 * Remove redundant uses with publically declared functions.

I have compile tested arm32 and arm64
---
 xen/arch/arm/shutdown.c         |    2 +-
 xen/arch/x86/cpu/mcheck/mce.h   |    2 +-
 xen/arch/x86/shutdown.c         |    2 +-
 xen/common/shutdown.c           |    2 +-
 xen/include/asm-arm/smp.h       |    2 +-
 xen/include/asm-x86/processor.h |    2 +-
 xen/include/xen/lib.h           |    2 +-
 xen/include/xen/shutdown.h      |    8 +++++---
 8 files changed, 12 insertions(+), 10 deletions(-)

diff --git a/xen/arch/arm/shutdown.c b/xen/arch/arm/shutdown.c
index 767cc12..adc0529 100644
--- a/xen/arch/arm/shutdown.c
+++ b/xen/arch/arm/shutdown.c
@@ -11,7 +11,7 @@ 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();
 }
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..827515d 100644
--- a/xen/arch/x86/shutdown.c
+++ b/xen/arch/x86/shutdown.c
@@ -452,7 +452,7 @@ 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);
 }
diff --git a/xen/common/shutdown.c b/xen/common/shutdown.c
index 9bccd34..fadb69b 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 )
     {
diff --git a/xen/include/asm-arm/smp.h b/xen/include/asm-arm/smp.h
index a1de03c..897d99d 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/asm-x86/processor.h b/xen/include/asm-x86/processor.h
index 9696acc..eeea44a 100644
--- a/xen/include/asm-x86/processor.h
+++ b/xen/include/asm-x86/processor.h
@@ -514,7 +514,7 @@ void show_registers(struct cpu_user_regs *regs);
 void show_execution_state(struct cpu_user_regs *regs);
 #define dump_execution_state() run_in_exception_handler(show_execution_state)
 void show_page_walk(unsigned long addr);
-void fatal_trap(int trapnr, struct cpu_user_regs *regs);
+void fatal_trap(int trapnr, struct cpu_user_regs *regs) noreturn;
 
 void compat_show_guest_stack(struct vcpu *, struct cpu_user_regs *, int lines);
 
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..2b82495 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_restart(unsigned int delay_millisecs) noreturn;
+void machine_halt(void) noreturn;
 void machine_power_off(void);
 
 #endif /* __XEN_SHUTDOWN_H__ */
-- 
1.7.10.4


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