Re: [PATCH v2] linux-user: Add guest memory layout to exception dump

[Laurent Vivier <laurent@vivier.eu>]

Le 27/09/2022 à 18:58, Helge Deller a écrit :
> When the emulation stops with a hard exception it's very useful for
> debugging purposes to dump the current guest memory layout (for an
> example see /proc/self/maps) beside the CPU registers.
> 
> The open_self_maps() function provides such a memory dump, but since
> it's located in the syscall.c file, various changes (add #includes, make
> this function externally visible, ...) are needed to be able to call it
> from the existing EXCP_DUMP() macro.
> 
> This patch takes another approach by re-defining EXCP_DUMP() to call
> target_exception_dump(), which is in syscall.c, consolidates the log
> print functions and allows to add the call to dump the memory layout.
> 
> Beside a reduced code footprint, this approach keeps the changes across
> the various callers minimal, and keeps EXCP_DUMP() highlighted as
> important macro/function.
> 
> Signed-off-by: Helge Deller <deller@gmx.de>
> 
> ---
> 
> v2:
> Based on feedback by Philippe Mathieu-Daudé, renamed the two functions
> to excp_dump_file() and target_exception_dump(), and #define'ed
> EXCP_DUMP() to target_exception_dump().
> I intentionally did not replace all occurences of EXCP_DUMP() by
> target_exception_dump() as I think it's unneccesary and not beneficial.
> If this is really wished, I will send a v3.
> 
> 
> diff --git a/linux-user/cpu_loop-common.h b/linux-user/cpu_loop-common.h
> index 36ff5b14f2..e644d2ef90 100644
> --- a/linux-user/cpu_loop-common.h
> +++ b/linux-user/cpu_loop-common.h
> @@ -23,18 +23,9 @@
>   #include "exec/log.h"
>   #include "special-errno.h"
> 
> -#define EXCP_DUMP(env, fmt, ...)                                        \
> -do {                                                                    \
> -    CPUState *cs = env_cpu(env);                                        \
> -    fprintf(stderr, fmt , ## __VA_ARGS__);                              \
> -    fprintf(stderr, "Failing executable: %s\n", exec_path);             \
> -    cpu_dump_state(cs, stderr, 0);                                      \
> -    if (qemu_log_separate()) {                                          \
> -        qemu_log(fmt, ## __VA_ARGS__);                                  \
> -        qemu_log("Failing executable: %s\n", exec_path);                \
> -        log_cpu_state(cs, 0);                                           \
> -    }                                                                   \
> -} while (0)
> +void target_exception_dump(CPUArchState *env, const char *fmt, int code);
> +#define EXCP_DUMP(env, fmt, code) \
> +    target_exception_dump(env, fmt, code)
> 
>   void target_cpu_copy_regs(CPUArchState *env, struct target_pt_regs *regs);
>   #endif
> diff --git a/linux-user/syscall.c b/linux-user/syscall.c
> index 2e954d8dbd..7d29c4c396 100644
> --- a/linux-user/syscall.c
> +++ b/linux-user/syscall.c
> @@ -158,6 +158,7 @@
>   #include "qapi/error.h"
>   #include "fd-trans.h"
>   #include "tcg/tcg.h"
> +#include "cpu_loop-common.h"
> 
>   #ifndef CLONE_IO
>   #define CLONE_IO                0x80000000      /* Clone io context */
> @@ -8144,6 +8145,33 @@ static int is_proc_myself(const char *filename, const char *entry)
>       return 0;
>   }
> 
> +static void excp_dump_file(FILE *logfile, CPUArchState *env,
> +                      const char *fmt, int code)
> +{
> +    if (logfile) {
> +        CPUState *cs = env_cpu(env);
> +
> +        fprintf(logfile, fmt, code);
> +        fprintf(logfile, "Failing executable: %s\n", exec_path);
> +        cpu_dump_state(cs, logfile, 0);
> +        open_self_maps(env, fileno(logfile));
> +    }
> +}
> +
> +void target_exception_dump(CPUArchState *env, const char *fmt, int code)
> +{
> +    /* dump to console */
> +    excp_dump_file(stderr, env, fmt, code);
> +
> +    /* dump to log file */
> +    if (qemu_log_separate()) {
> +        FILE *logfile = qemu_log_trylock();
> +
> +        excp_dump_file(logfile, env, fmt, code);
> +        qemu_log_unlock(logfile);
> +    }
> +}
> +
>   #if HOST_BIG_ENDIAN != TARGET_BIG_ENDIAN || \
>       defined(TARGET_SPARC) || defined(TARGET_M68K) || defined(TARGET_HPPA)
>   static int is_proc(const char *filename, const char *entry)
> 

Reviewed-by: Laurent Vivier <laurent@vivier.eu>