Re: [Xen-devel] [PATCH v2 01/13] Export hypervisor symbols

[Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>]

On Fri, Sep 20, 2013 at 05:42:00AM -0400, Boris Ostrovsky wrote:

I think the title needs a prefix of say: "xen/platform_op:" or such.

> Export Xen's symbols in format similar to Linux' /proc/kallsyms.

Which is?

I see in Linux:

000000000000bd58 D xen_cr3
...
000000000000e978 d soft_lockup_hrtimer_cnt
..
ffffffff8101cef0 T eager_fpu_init
ffffffff8101d010 t ptrace_triggered

I know that the first column is the EIP (thought some of them seem to be
based on some offset). The last one is pretty obvious too.

But the middle one:
konrad@phenom:~$ cat /proc/kallsyms  | awk '{print $2}' | sort | uniq
b
B
d
D
r
R
t
T
V
W

Could you explain what those mean? And are they part of this?
Or does Xen not carry those?

> 
> Signed-off-by: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
> ---
>  xen/arch/x86/platform_hypercall.c        |  9 +++++
>  xen/arch/x86/x86_64/platform_hypercall.c |  2 +-
>  xen/common/symbols-dummy.c               |  1 +
>  xen/common/symbols.c                     | 58 
> ++++++++++++++++++++++++++++++--
>  xen/include/public/platform.h            | 22 ++++++++++++
>  xen/include/xen/symbols.h                |  4 +++
>  xen/tools/symbols.c                      |  4 +++
>  7 files changed, 97 insertions(+), 3 deletions(-)
> 
> diff --git a/xen/arch/x86/platform_hypercall.c 
> b/xen/arch/x86/platform_hypercall.c
> index 7175a82..39376fe 100644
> --- a/xen/arch/x86/platform_hypercall.c
> +++ b/xen/arch/x86/platform_hypercall.c
> @@ -23,6 +23,7 @@
>  #include <xen/cpu.h>
>  #include <xen/pmstat.h>
>  #include <xen/irq.h>
> +#include <xen/symbols.h>
>  #include <asm/current.h>
>  #include <public/platform.h>
>  #include <acpi/cpufreq/processor_perf.h>
> @@ -597,6 +598,14 @@ ret_t 
> do_platform_op(XEN_GUEST_HANDLE_PARAM(xen_platform_op_t) u_xenpf_op)
>      }
>      break;
>  
> +    case XENPF_get_symbols:
> +    {
> +        ret = xensyms_read(&op->u.symdata);
> +        if ( ret >= 0 && __copy_field_to_guest(u_xenpf_op, op, u.symdata) )
> +            ret = -EFAULT;
> +    }
> +    break;
> + 
>      default:
>          ret = -ENOSYS;
>          break;
> diff --git a/xen/arch/x86/x86_64/platform_hypercall.c 
> b/xen/arch/x86/x86_64/platform_hypercall.c
> index aa2ad54..9ef705a 100644
> --- a/xen/arch/x86/x86_64/platform_hypercall.c
> +++ b/xen/arch/x86/x86_64/platform_hypercall.c
> @@ -35,7 +35,7 @@ CHECK_pf_pcpu_version;
>  #undef xen_pf_pcpu_version
>  
>  #define xenpf_enter_acpi_sleep compat_pf_enter_acpi_sleep
> -
> +#define xenpf_symdata        compat_pf_symdata
>  #define COMPAT
>  #define _XEN_GUEST_HANDLE(t) XEN_GUEST_HANDLE(t)
>  #define _XEN_GUEST_HANDLE_PARAM(t) XEN_GUEST_HANDLE_PARAM(t)
> diff --git a/xen/common/symbols-dummy.c b/xen/common/symbols-dummy.c
> index 5090c3b..52a86c7 100644
> --- a/xen/common/symbols-dummy.c
> +++ b/xen/common/symbols-dummy.c
> @@ -12,6 +12,7 @@ const unsigned int symbols_offsets[1];
>  const unsigned long symbols_addresses[1];
>  #endif
>  const unsigned int symbols_num_syms;
> +const unsigned long symbols_names_bytes;
>  const u8 symbols_names[1];
>  
>  const u8 symbols_token_table[1];
> diff --git a/xen/common/symbols.c b/xen/common/symbols.c
> index 83b2b58..e74a585 100644
> --- a/xen/common/symbols.c
> +++ b/xen/common/symbols.c
> @@ -17,6 +17,8 @@
>  #include <xen/lib.h>
>  #include <xen/string.h>
>  #include <xen/spinlock.h>
> +#include <public/platform.h>
> +#include <xen/guest_access.h>
>  
>  #ifdef SYMBOLS_ORIGIN
>  extern const unsigned int symbols_offsets[1];
> @@ -26,6 +28,7 @@ extern const unsigned long symbols_addresses[];
>  #define symbols_address(n) symbols_addresses[n]
>  #endif
>  extern const unsigned int symbols_num_syms;
> +extern const unsigned long symbols_names_bytes;
>  extern const u8 symbols_names[];
>  
>  extern const u8 symbols_token_table[];
> @@ -35,7 +38,8 @@ extern const unsigned int symbols_markers[];
>  
>  /* expand a compressed symbol data into the resulting uncompressed string,
>     given the offset to where the symbol is in the compressed stream */
> -static unsigned int symbols_expand_symbol(unsigned int off, char *result)
> +static unsigned int symbols_expand_symbol(unsigned int off, char *result,
> +                                          int maxlen)
>  {
>      int len, skipped_first = 0;
>      const u8 *tptr, *data;
> @@ -49,6 +53,9 @@ static unsigned int symbols_expand_symbol(unsigned int off, 
> char *result)
>       * the compressed stream */
>      off += len + 1;
>  
> +    if (maxlen < len)
> +        len = maxlen;
> +
>      /* for every byte on the compressed symbol data, copy the table
>         entry for that byte */
>      while(len) {
> @@ -129,7 +136,7 @@ const char *symbols_lookup(unsigned long addr,
>          --low;
>  
>          /* Grab name */
> -    symbols_expand_symbol(get_symbol_offset(low), namebuf);
> +    symbols_expand_symbol(get_symbol_offset(low), namebuf, sizeof(namebuf));
>  
>      /* Search for next non-aliased symbol */
>      for (i = low + 1; i < symbols_num_syms; i++) {
> @@ -174,3 +181,50 @@ void __print_symbol(const char *fmt, unsigned long 
> address)
>  
>      spin_unlock_irqrestore(&lock, flags);
>  }
> +
> +/*
> + * Get symbol type information. This is encoded as a single char at the
> + * beginning of the symbol name.
> + */
> +static char symbols_get_symbol_type(unsigned int off)
> +{
> +    /*
> +     * Get just the first code, look it up in the token table,
> +     * and return the first char from this token.
> +     */
> +    return symbols_token_table[symbols_token_index[symbols_names[off + 1]]];
> +}
> +
> +/*
> + * Symbols are most likely accessed sequentially so we remember position from
> + * previous read. This can help us avoid extra call to get_symbol_offset().
> + */
> +static uint64_t next_symbol, next_offset;
> +static DEFINE_SPINLOCK(symbols_mutex);
> +
> +int xensyms_read(struct xenpf_symdata *symdata)
> +{
> +    if ( symdata->xen_symnum > symbols_num_syms )
> +        return -EINVAL;
> +    else if ( symdata->xen_symnum == symbols_num_syms )
> +        return 0;
> +
> +    spin_lock(&symbols_mutex);
> +
> +    if ( symdata->xen_symnum == 0 )
> +        next_offset = next_symbol = 0;
> +    else if ( next_symbol != symdata->xen_symnum )
> +        /* Non-sequential access */
> +        next_offset = get_symbol_offset(symdata->xen_symnum);
> +
> +    symdata->type = symbols_get_symbol_type(next_offset);
> +    next_offset = symbols_expand_symbol(next_offset, symdata->name,
> +        sizeof(symdata->name));
> +    symdata->address = symbols_offsets[symdata->xen_symnum] + SYMBOLS_ORIGIN;
> +
> +    next_symbol = symdata->xen_symnum + 1;
> +
> +    spin_unlock(&symbols_mutex);
> +
> +    return strlen(symdata->name);
> +}
> diff --git a/xen/include/public/platform.h b/xen/include/public/platform.h
> index 4341f54..870e14b 100644
> --- a/xen/include/public/platform.h
> +++ b/xen/include/public/platform.h
> @@ -527,6 +527,27 @@ struct xenpf_core_parking {
>  typedef struct xenpf_core_parking xenpf_core_parking_t;
>  DEFINE_XEN_GUEST_HANDLE(xenpf_core_parking_t);
>  
> +#define XENPF_get_symbols  61
> +
> +struct xenpf_symdata {
> +    /* IN variables */
> +    uint64_t xen_symnum;
> +
> +    /* OUT variables */
> +    uint64_t address;
> +    uint64_t type;
> +    /*
> +     * KSYM_NAME_LEN is 128 bytes. However, we cannot be larger than pad in
> +     * xen_platform_op below (which is 128 bytes as well). Since the largest
> +     * symbol is around 50 bytes it's probably more trouble than it's worth
> +     * to try to deal with symbols that are close to 128 bytes in length.
> +     */
> +#define XEN_SYMS_MAX_LEN (128 - 3 * 8)
> +    char name[XEN_SYMS_MAX_LEN];
> +};
> +typedef struct xenpf_symdata xenpf_symdata_t;
> +DEFINE_XEN_GUEST_HANDLE(xenpf_symdata_t);
> +
>  /*
>   * ` enum neg_errnoval
>   * ` HYPERVISOR_platform_op(const struct xen_platform_op*);
> @@ -553,6 +574,7 @@ struct xen_platform_op {
>          struct xenpf_cpu_hotadd        cpu_add;
>          struct xenpf_mem_hotadd        mem_add;
>          struct xenpf_core_parking      core_parking;
> +        struct xenpf_symdata           symdata;
>          uint8_t                        pad[128];
>      } u;
>  };
> diff --git a/xen/include/xen/symbols.h b/xen/include/xen/symbols.h
> index 37cf6bf..c8df28f 100644
> --- a/xen/include/xen/symbols.h
> +++ b/xen/include/xen/symbols.h
> @@ -2,6 +2,8 @@
>  #define _XEN_SYMBOLS_H
>  
>  #include <xen/types.h>
> +#include <public/xen.h>
> +#include <public/platform.h>
>  
>  #define KSYM_NAME_LEN 127
>  
> @@ -34,4 +36,6 @@ do {                                                \
>       __print_symbol(fmt, addr);              \
>  } while(0)
>  
> +extern int xensyms_read(struct xenpf_symdata *symdata);
> +
>  #endif /*_XEN_SYMBOLS_H*/
> diff --git a/xen/tools/symbols.c b/xen/tools/symbols.c
> index f39c906..818204d 100644
> --- a/xen/tools/symbols.c
> +++ b/xen/tools/symbols.c
> @@ -272,6 +272,10 @@ static void write_src(void)
>       }
>       printf("\n");
>  
> +     output_label("symbols_names_bytes");
> +     printf("\t.long\t%d\n", off);
> +     printf("\n");
> +
>       output_label("symbols_markers");
>       for (i = 0; i < ((table_cnt + 255) >> 8); i++)
>               printf("\t.long\t%d\n", markers[i]);
> -- 
> 1.8.1.4
> 
> 
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