Re: [PATCH v2] rseq/selftests: fix parametrized test with -fpie

[Shuah Khan]

On 09/27/2018 12:39 PM, Mathieu Desnoyers wrote:
> On x86-64, the parametrized selftest code for rseq crashes with a
> segmentation fault when compiled with -fpie. This happens when the
> param_test binary is loaded at an address beyond 32-bit on x86-64.
> 
> The issue is caused by use of a 32-bit register to hold the address
> of the loop counter variable.
> 
> Fix this by using a 64-bit register to calculate the address of the
> loop counter variables as an offset from rip.
> 
> Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxxxx>
> Acked-by: "Paul E . McKenney" <paulmck@xxxxxxxxxxxxxxxxxx>
> Cc: <stable@xxxxxxxxxxxxxxx> # v4.18
> Cc: Shuah Khan <shuah@xxxxxxxxxx>
> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> Cc: Joel Fernandes <joelaf@xxxxxxxxxx>
> Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
> Cc: Catalin Marinas <catalin.marinas@xxxxxxx>
> Cc: Dave Watson <davejwatson@xxxxxx>
> Cc: Will Deacon <will.deacon@xxxxxxx>
> Cc: Andi Kleen <andi@xxxxxxxxxxxxxx>
> Cc: linux-kselftest@xxxxxxxxxxxxxxx
> Cc: "H . Peter Anvin" <hpa@xxxxxxxxx>
> Cc: Chris Lameter <cl@xxxxxxxxx>
> Cc: Russell King <linux@xxxxxxxxxxxxxxxx>
> Cc: Michael Kerrisk <mtk.manpages@xxxxxxxxx>
> Cc: "Paul E . McKenney" <paulmck@xxxxxxxxxxxxxxxxxx>
> Cc: Paul Turner <pjt@xxxxxxxxxx>
> Cc: Boqun Feng <boqun.feng@xxxxxxxxx>
> Cc: Josh Triplett <josh@xxxxxxxxxxxxxxxx>
> Cc: Steven Rostedt <rostedt@xxxxxxxxxxx>
> Cc: Ben Maurer <bmaurer@xxxxxx>
> Cc: Andy Lutomirski <luto@xxxxxxxxxxxxxx>
> Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
> Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
> ---
> Changes since v1:
> - Update email address for Shuah Khan based on updated MAINTAINERS
>   email address,
> - Rebase on v4.19-rc5.
> ---
>  tools/testing/selftests/rseq/param_test.c | 19 ++++++++++---------
>  1 file changed, 10 insertions(+), 9 deletions(-)
> 
> diff --git a/tools/testing/selftests/rseq/param_test.c b/tools/testing/selftests/rseq/param_test.c
> index 642d4e12abea..eec2663261f2 100644
> --- a/tools/testing/selftests/rseq/param_test.c
> +++ b/tools/testing/selftests/rseq/param_test.c
> @@ -56,15 +56,13 @@ unsigned int yield_mod_cnt, nr_abort;
>  			printf(fmt, ## __VA_ARGS__);	\
>  	} while (0)
>  
> -#if defined(__x86_64__) || defined(__i386__)
> +#ifdef __i386__
>  
>  #define INJECT_ASM_REG	"eax"
>  
>  #define RSEQ_INJECT_CLOBBER \
>  	, INJECT_ASM_REG
>  
> -#ifdef __i386__
> -
>  #define RSEQ_INJECT_ASM(n) \
>  	"mov asm_loop_cnt_" #n ", %%" INJECT_ASM_REG "\n\t" \
>  	"test %%" INJECT_ASM_REG ",%%" INJECT_ASM_REG "\n\t" \
> @@ -76,9 +74,16 @@ unsigned int yield_mod_cnt, nr_abort;
>  
>  #elif defined(__x86_64__)
>  
> +#define INJECT_ASM_REG_P	"rax"
> +#define INJECT_ASM_REG		"eax"
> +
> +#define RSEQ_INJECT_CLOBBER \
> +	, INJECT_ASM_REG_P \
> +	, INJECT_ASM_REG
> +
>  #define RSEQ_INJECT_ASM(n) \
> -	"lea asm_loop_cnt_" #n "(%%rip), %%" INJECT_ASM_REG "\n\t" \
> -	"mov (%%" INJECT_ASM_REG "), %%" INJECT_ASM_REG "\n\t" \
> +	"lea asm_loop_cnt_" #n "(%%rip), %%" INJECT_ASM_REG_P "\n\t" \
> +	"mov (%%" INJECT_ASM_REG_P "), %%" INJECT_ASM_REG "\n\t" \
>  	"test %%" INJECT_ASM_REG ",%%" INJECT_ASM_REG "\n\t" \
>  	"jz 333f\n\t" \
>  	"222:\n\t" \
> @@ -86,10 +91,6 @@ unsigned int yield_mod_cnt, nr_abort;
>  	"jnz 222b\n\t" \
>  	"333:\n\t"
>  
> -#else
> -#error "Unsupported architecture"
> -#endif
> -
>  #elif defined(__s390__)
>  
>  #define RSEQ_INJECT_INPUT \
> 

Applied now to linux-kselftest fixes. I will get this into the next rc

thanks,
-- Shuah