[PATCHv3] perf bpf: Fix endianness problem when loading parameters in prologue

[PATCHv3] perf bpf: Fix endianness problem when loading parameters in prologue

[Thomas Richter]

Perf BPF prologue generator unconditionally fetches 8 bytes for function
parameters, which causes problem on big endian machine. Thomas gives a
detail analysis for this problem:

 http://lkml.kernel.org/r/968ebda5-abe4-8830-8d69-49f62529d151@linux.vnet.ibm.com

This patch parses the type of each argument and converts data from
memory to expected type.

Now the test runs successfully on 4.13.0-rc5:
[root@s8360046 perf]# ./perf test  bpf
38: BPF filter                                 :
38.1: Basic BPF filtering                      : Ok
38.2: BPF pinning                              : Ok
38.3: BPF prologue generation                  : Ok
38.4: BPF relocation checker                   : Ok
[root@s8360046 perf]#

Signed-off-by: Wang Nan <wangnan0@huawei.com>
Signed-off-by: Thomas Richter <tmricht@linux.vnet.ibm.com>
---
 tools/perf/tests/bpf-script-test-prologue.c |  4 ++-
 tools/perf/util/bpf-prologue.c              | 49 +++++++++++++++++++++++++++--
 2 files changed, 50 insertions(+), 3 deletions(-)

diff --git a/tools/perf/tests/bpf-script-test-prologue.c b/tools/perf/tests/bpf-script-test-prologue.c
index b4ebc75..43f1e16 100644
--- a/tools/perf/tests/bpf-script-test-prologue.c
+++ b/tools/perf/tests/bpf-script-test-prologue.c
@@ -26,9 +26,11 @@ static void (*bpf_trace_printk)(const char *fmt, int fmt_size, ...) =
 	(void *) 6;
 
 SEC("func=null_lseek file->f_mode offset orig")
-int bpf_func__null_lseek(void *ctx, int err, unsigned long f_mode,
+int bpf_func__null_lseek(void *ctx, int err, unsigned long _f_mode,
 			 unsigned long offset, unsigned long orig)
 {
+	fmode_t f_mode = (fmode_t)_f_mode;
+
 	if (err)
 		return 0;
 	if (f_mode & FMODE_WRITE)
diff --git a/tools/perf/util/bpf-prologue.c b/tools/perf/util/bpf-prologue.c
index 1356220..827f914 100644
--- a/tools/perf/util/bpf-prologue.c
+++ b/tools/perf/util/bpf-prologue.c
@@ -58,6 +58,46 @@ check_pos(struct bpf_insn_pos *pos)
 	return 0;
 }
 
+/*
+ * Convert type string (u8/u16/u32/u64/s8/s16/s32/s64 ..., see
+ * Documentation/trace/kprobetrace.txt) to size field of BPF_LDX_MEM
+ * instruction (BPF_{B,H,W,DW}).
+ */
+static int
+argtype_to_ldx_size(const char *type)
+{
+	int arg_size = type ? atoi(&type[1]) : 64;
+
+	switch (arg_size) {
+	case 8:
+		return BPF_B;
+	case 16:
+		return BPF_H;
+	case 32:
+		return BPF_W;
+	case 64:
+	default:
+		return BPF_DW;
+	}
+}
+
+static const char *
+insn_sz_to_str(int insn_sz)
+{
+	switch (insn_sz) {
+	case BPF_B:
+		return "BPF_B";
+	case BPF_H:
+		return "BPF_H";
+	case BPF_W:
+		return "BPF_W";
+	case BPF_DW:
+		return "BPF_DW";
+	default:
+		return "UNKNOWN";
+	}
+}
+
 /* Give it a shorter name */
 #define ins(i, p) append_insn((i), (p))
 
@@ -258,9 +298,14 @@ gen_prologue_slowpath(struct bpf_insn_pos *pos,
 	}
 
 	/* Final pass: read to registers */
-	for (i = 0; i < nargs; i++)
-		ins(BPF_LDX_MEM(BPF_DW, BPF_PROLOGUE_START_ARG_REG + i,
+	for (i = 0; i < nargs; i++) {
+		int insn_sz = (args[i].ref) ? argtype_to_ldx_size(args[i].type) : BPF_DW;
+
+		pr_debug("prologue: load arg %d, insn_sz is %s\n",
+			 i, insn_sz_to_str(insn_sz));
+		ins(BPF_LDX_MEM(insn_sz, BPF_PROLOGUE_START_ARG_REG + i,
 				BPF_REG_FP, -BPF_REG_SIZE * (i + 1)), pos);
+	}
 
 	ins(BPF_JMP_IMM(BPF_JA, BPF_REG_0, 0, JMP_TO_SUCCESS_CODE), pos);
 
-- 
2.9.3

Re: [PATCHv3] perf bpf: Fix endianness problem when loading parameters in prologue

[Arnaldo Carvalho de Melo]

Em Tue, Aug 15, 2017 at 11:21:59AM +0200, Thomas Richter escreveu:

Ok, I'm applying this, the only missing bit was the following line,
right at the start of the patch message body;

From: Wang Nan <wangnan0@huawei.com>

To state that the patch was wrote by Wang, the fact that you
participated in it with some adjustment is implied by having you sign
off the patch, ok?

- Arnaldo

> Perf BPF prologue generator unconditionally fetches 8 bytes for function
> parameters, which causes problem on big endian machine. Thomas gives a
> detail analysis for this problem:
> 
>  http://lkml.kernel.org/r/968ebda5-abe4-8830-8d69-49f62529d151@linux.vnet.ibm.com
> 
> This patch parses the type of each argument and converts data from
> memory to expected type.
> 
> Now the test runs successfully on 4.13.0-rc5:
> [root@s8360046 perf]# ./perf test  bpf
> 38: BPF filter                                 :
> 38.1: Basic BPF filtering                      : Ok
> 38.2: BPF pinning                              : Ok
> 38.3: BPF prologue generation                  : Ok
> 38.4: BPF relocation checker                   : Ok
> [root@s8360046 perf]#
> 
> Signed-off-by: Wang Nan <wangnan0@huawei.com>
> Signed-off-by: Thomas Richter <tmricht@linux.vnet.ibm.com>
> ---
>  tools/perf/tests/bpf-script-test-prologue.c |  4 ++-
>  tools/perf/util/bpf-prologue.c              | 49 +++++++++++++++++++++++++++--
>  2 files changed, 50 insertions(+), 3 deletions(-)
> 
> diff --git a/tools/perf/tests/bpf-script-test-prologue.c b/tools/perf/tests/bpf-script-test-prologue.c
> index b4ebc75..43f1e16 100644
> --- a/tools/perf/tests/bpf-script-test-prologue.c
> +++ b/tools/perf/tests/bpf-script-test-prologue.c
> @@ -26,9 +26,11 @@ static void (*bpf_trace_printk)(const char *fmt, int fmt_size, ...) =
>  	(void *) 6;
>  
>  SEC("func=null_lseek file->f_mode offset orig")
> -int bpf_func__null_lseek(void *ctx, int err, unsigned long f_mode,
> +int bpf_func__null_lseek(void *ctx, int err, unsigned long _f_mode,
>  			 unsigned long offset, unsigned long orig)
>  {
> +	fmode_t f_mode = (fmode_t)_f_mode;
> +
>  	if (err)
>  		return 0;
>  	if (f_mode & FMODE_WRITE)
> diff --git a/tools/perf/util/bpf-prologue.c b/tools/perf/util/bpf-prologue.c
> index 1356220..827f914 100644
> --- a/tools/perf/util/bpf-prologue.c
> +++ b/tools/perf/util/bpf-prologue.c
> @@ -58,6 +58,46 @@ check_pos(struct bpf_insn_pos *pos)
>  	return 0;
>  }
>  
> +/*
> + * Convert type string (u8/u16/u32/u64/s8/s16/s32/s64 ..., see
> + * Documentation/trace/kprobetrace.txt) to size field of BPF_LDX_MEM
> + * instruction (BPF_{B,H,W,DW}).
> + */
> +static int
> +argtype_to_ldx_size(const char *type)
> +{
> +	int arg_size = type ? atoi(&type[1]) : 64;
> +
> +	switch (arg_size) {
> +	case 8:
> +		return BPF_B;
> +	case 16:
> +		return BPF_H;
> +	case 32:
> +		return BPF_W;
> +	case 64:
> +	default:
> +		return BPF_DW;
> +	}
> +}
> +
> +static const char *
> +insn_sz_to_str(int insn_sz)
> +{
> +	switch (insn_sz) {
> +	case BPF_B:
> +		return "BPF_B";
> +	case BPF_H:
> +		return "BPF_H";
> +	case BPF_W:
> +		return "BPF_W";
> +	case BPF_DW:
> +		return "BPF_DW";
> +	default:
> +		return "UNKNOWN";
> +	}
> +}
> +
>  /* Give it a shorter name */
>  #define ins(i, p) append_insn((i), (p))
>  
> @@ -258,9 +298,14 @@ gen_prologue_slowpath(struct bpf_insn_pos *pos,
>  	}
>  
>  	/* Final pass: read to registers */
> -	for (i = 0; i < nargs; i++)
> -		ins(BPF_LDX_MEM(BPF_DW, BPF_PROLOGUE_START_ARG_REG + i,
> +	for (i = 0; i < nargs; i++) {
> +		int insn_sz = (args[i].ref) ? argtype_to_ldx_size(args[i].type) : BPF_DW;
> +
> +		pr_debug("prologue: load arg %d, insn_sz is %s\n",
> +			 i, insn_sz_to_str(insn_sz));
> +		ins(BPF_LDX_MEM(insn_sz, BPF_PROLOGUE_START_ARG_REG + i,
>  				BPF_REG_FP, -BPF_REG_SIZE * (i + 1)), pos);
> +	}
>  
>  	ins(BPF_JMP_IMM(BPF_JA, BPF_REG_0, 0, JMP_TO_SUCCESS_CODE), pos);
>  
> -- 
> 2.9.3

Re: [PATCHv3] perf bpf: Fix endianness problem when loading parameters in prologue

[Thomas-Mich Richter]

On 08/15/2017 05:25 PM, Arnaldo Carvalho de Melo wrote:
> Em Tue, Aug 15, 2017 at 11:21:59AM +0200, Thomas Richter escreveu:
> 
> Ok, I'm applying this, the only missing bit was the following line,
> right at the start of the patch message body;
> 
> From: Wang Nan <wangnan0@huawei.com>
> 
> To state that the patch was wrote by Wang, the fact that you
> participated in it with some adjustment is implied by having you sign
> off the patch, ok?
> 
> - Arnaldo


Thanks Arnaldo,

will /hopefully) remember next time.

-- 
Thomas Richter, Dept 3303, IBM LTC Boeblingen Germany
--
Vorsitzende des Aufsichtsrats: Martina Koederitz 
Geschäftsführung: Dirk Wittkopp
Sitz der Gesellschaft: Böblingen / Registergericht: Amtsgericht Stuttgart, HRB 243294

Re: [PATCHv3] perf bpf: Fix endianness problem when loading parameters in prologue

[Arnaldo Carvalho de Melo]

Em Wed, Aug 16, 2017 at 07:56:45AM +0200, Thomas-Mich Richter escreveu:
> On 08/15/2017 05:25 PM, Arnaldo Carvalho de Melo wrote:
> > Ok, I'm applying this, the only missing bit was the following line,
> > right at the start of the patch message body;

> > From: Wang Nan <wangnan0@huawei.com>

> > To state that the patch was wrote by Wang, the fact that you
> > participated in it with some adjustment is implied by having you sign
> > off the patch, ok?

> Thanks Arnaldo,
> 
> will /hopefully) remember next time.

Applied,

- Arnaldo