[Skiboot] [PATCH] Use volatile pointer for constant address asignment

[Nicholas Piggin]

Excerpts from Abhishek Singh Tomar's message of January 17, 2022 11:24 pm:
> use volatile pointer to avoid optimization introduced with gcc-11 on constant address asignment to pointer.
> Resolves : the warray ofset warning during compilation.

Hm. What exactly is the warning, and what is the optimization that's
causing breakage?

Thanks,
Nick

> 
> Signed-off-by: Abhishek Singh Tomar <abhishek at linux.ibm.com>
> ---
>  core/console.c     | 2 +-
>  core/fast-reboot.c | 6 ++++--
>  core/init.c        | 6 +++++-
>  core/opal-dump.c   | 7 ++++---
>  hdata/spira.c      | 2 +-
>  hdata/spira.h      | 2 +-
>  hw/fsp/fsp.c       | 2 +-
>  7 files changed, 17 insertions(+), 10 deletions(-)
> 
> diff --git a/core/console.c b/core/console.c
> index 2a150902..229bc84a 100644
> --- a/core/console.c
> +++ b/core/console.c
> @@ -15,7 +15,7 @@
>  #include <processor.h>
>  #include <cpu.h>
>  
> -static char *con_buf = (char *)INMEM_CON_START;
> +static char *volatile con_buf = (char *)INMEM_CON_START;
>  static size_t con_in;
>  static size_t con_out;
>  static bool con_wrapped;
> diff --git a/core/fast-reboot.c b/core/fast-reboot.c
> index fedfa88c..3e3db68e 100644
> --- a/core/fast-reboot.c
> +++ b/core/fast-reboot.c
> @@ -307,6 +307,8 @@ void __noreturn fast_reboot_entry(void);
>  void __noreturn fast_reboot_entry(void)
>  {
>  	struct cpu_thread *cpu = this_cpu();
> +	void *volatile kerneal_load_base_addr = KERNEL_LOAD_BASE;
> +	void *volatile initramfs_load_base_addr = INITRAMFS_LOAD_BASE;
>  
>  	if (proc_gen == proc_gen_p8) {
>  		/* We reset our ICP first ! Otherwise we might get stray
> @@ -425,8 +427,8 @@ void __noreturn fast_reboot_entry(void)
>  		 * Mambo may have embedded payload here, so don't clear
>  		 * it at all.
>  		 */
> -		memset(KERNEL_LOAD_BASE, 0, KERNEL_LOAD_SIZE);
> -		memset(INITRAMFS_LOAD_BASE, 0, INITRAMFS_LOAD_SIZE);
> +		memset(kerneal_load_base_addr, 0, KERNEL_LOAD_SIZE);
> +		memset(initramfs_load_base_addr, 0, INITRAMFS_LOAD_SIZE);
>  	}
>  
>  	/* Start preloading kernel and ramdisk */
> diff --git a/core/init.c b/core/init.c
> index b4d33518..00f667e1 100644
> --- a/core/init.c
> +++ b/core/init.c
> @@ -869,7 +869,11 @@ void copy_exception_vectors(void)
>  	 * this is the boot flag used by CPUs still potentially entering
>  	 * skiboot.
>  	 */
> -	memcpy((void *)0x100, (void *)(SKIBOOT_BASE + 0x100),
> +	void *volatile exception_vectors_start_addr = (void*)(SKIBOOT_BASE + 0x100);
> +	void *volatile dst = (void*)0x100;
> +
> +
> +	memcpy(dst,exception_vectors_start_addr,
>  			EXCEPTION_VECTORS_END - 0x100);
>  	sync_icache();
>  }
> diff --git a/core/opal-dump.c b/core/opal-dump.c
> index 4f54a3ef..4943fedd 100644
> --- a/core/opal-dump.c
> +++ b/core/opal-dump.c
> @@ -301,6 +301,7 @@ static int64_t opal_mpipl_update(enum opal_mpipl_ops ops,
>  				 u64 src, u64 dest, u64 size)
>  {
>  	int rc;
> +	void *volatile mdrt_table_base_addr =(void*) MDRT_TABLE_BASE;
>  
>  	switch (ops) {
>  	case OPAL_MPIPL_ADD_RANGE:
> @@ -330,7 +331,7 @@ static int64_t opal_mpipl_update(enum opal_mpipl_ops ops,
>  		free(opal_mpipl_cpu_data);
>  		opal_mpipl_cpu_data = NULL;
>  		/* Clear MDRT table */
> -		memset((void *)MDRT_TABLE_BASE, 0, MDRT_TABLE_SIZE);
> +		memset(mdrt_table_base_addr, 0, MDRT_TABLE_SIZE);
>  		/* Set MDRT count to max allocated count */
>  		ntuple_mdrt->act_cnt = cpu_to_be16(MDRT_TABLE_SIZE / sizeof(struct mdrt_table));
>  		rc = OPAL_SUCCESS;
> @@ -529,8 +530,8 @@ bool is_mpipl_enabled(void)
>  
>  void opal_mpipl_init(void)
>  {
> -	void *mdst_base = (void *)MDST_TABLE_BASE;
> -	void *mddt_base = (void *)MDDT_TABLE_BASE;
> +	void *volatile mdst_base = (void *)MDST_TABLE_BASE;
> +	void *volatile mddt_base = (void *)MDDT_TABLE_BASE;
>  	struct dt_node *dump_node;
>  
>  	dump_node = dt_find_by_path(opal_node, "dump");
> diff --git a/hdata/spira.c b/hdata/spira.c
> index 1a351462..3bbec351 100644
> --- a/hdata/spira.c
> +++ b/hdata/spira.c
> @@ -236,7 +236,7 @@ __section(".spirah.data") struct spirah spirah = {
>  };
>  
>  /* The service processor SPIRA-S structure */
> -struct spiras *spiras;
> +struct spiras *volatile spiras;
>  
>  /* Overridden for testing. */
>  #ifndef spira_check_ptr
> diff --git a/hdata/spira.h b/hdata/spira.h
> index 8def23bd..6df3df56 100644
> --- a/hdata/spira.h
> +++ b/hdata/spira.h
> @@ -150,7 +150,7 @@ struct spiras {
>  	u8			reserved[0x180];
>  } __packed __align(0x100);
>  
> -extern struct spiras *spiras;
> +extern struct spiras *volatile spiras;
>  
>  
>  /* This macro can be used to check the validity of a pointer returned
> diff --git a/hw/fsp/fsp.c b/hw/fsp/fsp.c
> index 2c5f9d71..259e83a3 100644
> --- a/hw/fsp/fsp.c
> +++ b/hw/fsp/fsp.c
> @@ -91,7 +91,7 @@ static enum ipl_state ipl_state = ipl_initial;
>  static struct fsp *first_fsp;
>  static struct fsp *active_fsp;
>  static u16 fsp_curseq = 0x8000;
> -static __be64 *fsp_tce_table;
> +static __be64 *volatile fsp_tce_table;
>  
>  #define FSP_INBOUND_SIZE	0x00100000UL
>  static void *fsp_inbound_buf = NULL;
> -- 
> 2.31.1
> 
> _______________________________________________
> Skiboot mailing list
> Skiboot at lists.ozlabs.org
> https://lists.ozlabs.org/listinfo/skiboot
>