[RFC v2 PATCH 1/1] ARM64: KGDB: Add FP/SIMD debug support
Ard Biesheuvel
ard.biesheuvel at linaro.org
Fri Nov 29 03:53:22 EST 2013
On 18 November 2013 13:06, <vijay.kilari at gmail.com> wrote:
> From: Vijaya Kumar K <Vijaya.Kumar at caviumnetworks.com>
>
> Add KGDB debug support for FP/SIMD processor.This support
> only debugging of FP/SIMD in kernel mode.
> With this patch one can view or set FP/SIMD registers in
> kernel context
>
> Signed-off-by: Vijaya Kumar K <Vijaya.Kumar at caviumnetworks.com>
> ---
> arch/arm64/include/asm/fpsimd.h | 1 +
> arch/arm64/kernel/fpsimd.c | 5 ++
> arch/arm64/kernel/kgdb.c | 105 +++++++++++++++++++++++++--------------
> 3 files changed, 73 insertions(+), 38 deletions(-)
>
> diff --git a/arch/arm64/include/asm/fpsimd.h b/arch/arm64/include/asm/fpsimd.h
> index 609bc44..5039d6d 100644
> --- a/arch/arm64/include/asm/fpsimd.h
> +++ b/arch/arm64/include/asm/fpsimd.h
> @@ -60,6 +60,7 @@ extern void fpsimd_load_state(struct fpsimd_state *state);
> extern void fpsimd_thread_switch(struct task_struct *next);
> extern void fpsimd_flush_thread(void);
> extern void fpsimd_reload_fpstate(void);
> +extern int fpsimd_thread_state(void);
>
> #endif
>
> diff --git a/arch/arm64/kernel/fpsimd.c b/arch/arm64/kernel/fpsimd.c
> index 5b13c17..27604c1 100644
> --- a/arch/arm64/kernel/fpsimd.c
> +++ b/arch/arm64/kernel/fpsimd.c
> @@ -124,6 +124,11 @@ void fpsimd_flush_thread(void)
> set_thread_flag(TIF_FOREIGN_FPSTATE);
> }
>
> +int fpsimd_thread_state(void)
Please use a meaningful name for the function. Currently, it returns
true iff 'current' is a non-kernel thread whose FPSIMD state is /not/
present in the FPSIMD register file. You should choose a name that
reflects that purpose.
> +{
> + return (current->mm && test_thread_flag(TIF_FOREIGN_FPSTATE)) ? 1 : 0;
> +}
> +
As Will pointed out, the expression before ? already evaluates to 1 or
0, so appending '? 1 : 0' is redundant.
> void fpsimd_reload_fpstate(void)
> {
> preempt_disable();
> diff --git a/arch/arm64/kernel/kgdb.c b/arch/arm64/kernel/kgdb.c
> index f10f2ba..5e34852 100644
> --- a/arch/arm64/kernel/kgdb.c
> +++ b/arch/arm64/kernel/kgdb.c
> @@ -23,6 +23,14 @@
> #include <linux/kdebug.h>
> #include <linux/kgdb.h>
> #include <asm/traps.h>
> +#include <asm/fpsimd.h>
> +
> +#ifdef CONFIG_KERNEL_MODE_NEON
> +/*
> + * Structure to hold FP/SIMD register contents
> + */
> +struct fpsimd_state kgdb_fpsimd_regs;
'static' if it's local to this source file
> +#endif
>
> struct dbg_reg_def_t dbg_reg_def[DBG_MAX_REG_NUM] = {
> { "x0", 8, offsetof(struct pt_regs, regs[0])},
> @@ -59,40 +67,40 @@ struct dbg_reg_def_t dbg_reg_def[DBG_MAX_REG_NUM] = {
> { "sp", 8, offsetof(struct pt_regs, sp)},
> { "pc", 8, offsetof(struct pt_regs, pc)},
> { "pstate", 4, offsetof(struct pt_regs, pstate)},
> - { "v0", 16, -1 },
> - { "v1", 16, -1 },
> - { "v2", 16, -1 },
> - { "v3", 16, -1 },
> - { "v4", 16, -1 },
> - { "v5", 16, -1 },
> - { "v6", 16, -1 },
> - { "v7", 16, -1 },
> - { "v8", 16, -1 },
> - { "v9", 16, -1 },
> - { "v10", 16, -1 },
> - { "v11", 16, -1 },
> - { "v12", 16, -1 },
> - { "v13", 16, -1 },
> - { "v14", 16, -1 },
> - { "v15", 16, -1 },
> - { "v16", 16, -1 },
> - { "v17", 16, -1 },
> - { "v18", 16, -1 },
> - { "v19", 16, -1 },
> - { "v20", 16, -1 },
> - { "v21", 16, -1 },
> - { "v22", 16, -1 },
> - { "v23", 16, -1 },
> - { "v24", 16, -1 },
> - { "v25", 16, -1 },
> - { "v26", 16, -1 },
> - { "v27", 16, -1 },
> - { "v28", 16, -1 },
> - { "v29", 16, -1 },
> - { "v30", 16, -1 },
> - { "v31", 16, -1 },
> - { "fpsr", 4, -1 },
> - { "fpcr", 4, -1 },
> + { "v0", 16, offsetof(struct fpsimd_state, vregs[0])},
> + { "v1", 16, offsetof(struct fpsimd_state, vregs[1])},
> + { "v2", 16, offsetof(struct fpsimd_state, vregs[2])},
> + { "v3", 16, offsetof(struct fpsimd_state, vregs[3])},
> + { "v4", 16, offsetof(struct fpsimd_state, vregs[4])},
> + { "v5", 16, offsetof(struct fpsimd_state, vregs[5])},
> + { "v6", 16, offsetof(struct fpsimd_state, vregs[6])},
> + { "v7", 16, offsetof(struct fpsimd_state, vregs[7])},
> + { "v8", 16, offsetof(struct fpsimd_state, vregs[8])},
> + { "v9", 16, offsetof(struct fpsimd_state, vregs[9])},
> + { "v10", 16, offsetof(struct fpsimd_state, vregs[10])},
> + { "v11", 16, offsetof(struct fpsimd_state, vregs[11])},
> + { "v12", 16, offsetof(struct fpsimd_state, vregs[12])},
> + { "v13", 16, offsetof(struct fpsimd_state, vregs[13])},
> + { "v14", 16, offsetof(struct fpsimd_state, vregs[14])},
> + { "v15", 16, offsetof(struct fpsimd_state, vregs[15])},
> + { "v16", 16, offsetof(struct fpsimd_state, vregs[16])},
> + { "v17", 16, offsetof(struct fpsimd_state, vregs[17])},
> + { "v18", 16, offsetof(struct fpsimd_state, vregs[18])},
> + { "v19", 16, offsetof(struct fpsimd_state, vregs[19])},
> + { "v20", 16, offsetof(struct fpsimd_state, vregs[20])},
> + { "v21", 16, offsetof(struct fpsimd_state, vregs[21])},
> + { "v22", 16, offsetof(struct fpsimd_state, vregs[22])},
> + { "v23", 16, offsetof(struct fpsimd_state, vregs[23])},
> + { "v24", 16, offsetof(struct fpsimd_state, vregs[24])},
> + { "v25", 16, offsetof(struct fpsimd_state, vregs[25])},
> + { "v26", 16, offsetof(struct fpsimd_state, vregs[26])},
> + { "v27", 16, offsetof(struct fpsimd_state, vregs[27])},
> + { "v28", 16, offsetof(struct fpsimd_state, vregs[28])},
> + { "v29", 16, offsetof(struct fpsimd_state, vregs[29])},
> + { "v30", 16, offsetof(struct fpsimd_state, vregs[30])},
> + { "v31", 16, offsetof(struct fpsimd_state, vregs[31])},
> + { "fpsr", 4, offsetof(struct fpsimd_state, fpsr)},
> + { "fpcr", 4, offsetof(struct fpsimd_state, fpcr)},
> };
>
> char *dbg_get_reg(int regno, void *mem, struct pt_regs *regs)
> @@ -100,11 +108,22 @@ char *dbg_get_reg(int regno, void *mem, struct pt_regs *regs)
> if (regno >= DBG_MAX_REG_NUM || regno < 0)
> return NULL;
>
> - if (dbg_reg_def[regno].offset != -1)
> + if (dbg_reg_def[regno].offset != -1 && regno < _GP_REGS)
> memcpy(mem, (void *)regs + dbg_reg_def[regno].offset,
> dbg_reg_def[regno].size);
> - else
> + else {
> +#ifdef CONFIG_KERNEL_MODE_NEON
else if (IS_ENABLED(CONFIG_KERNEL_MODE_NEON)) {
> + if (fpsimd_thread_state()) {
> + fpsimd_save_state(&kgdb_fpsimd_regs);
> + memcpy(mem, (void *)&kgdb_fpsimd_regs +
> + dbg_reg_def[regno].offset,
> + dbg_reg_def[regno].size);
Why do this conditionally? Shouldn't kgdb return whatever is currently
present in the register file, regardless of whether 'current' is a
kernel thread or has had its FPSIMD state swapped out?
Also, one could wonder why this is dependent on KERNEL_MODE_NEON being set
> + } else
> + memset(mem, 0, dbg_reg_def[regno].size);
> +#else
> memset(mem, 0, dbg_reg_def[regno].size);
> +#endif
> + }
> return dbg_reg_def[regno].name;
> }
>
> @@ -113,9 +132,19 @@ int dbg_set_reg(int regno, void *mem, struct pt_regs *regs)
> if (regno >= DBG_MAX_REG_NUM || regno < 0)
> return -EINVAL;
>
> - if (dbg_reg_def[regno].offset != -1)
> + if (dbg_reg_def[regno].offset != -1 && regno < _GP_REGS)
> memcpy((void *)regs + dbg_reg_def[regno].offset, mem,
> - dbg_reg_def[regno].size);
> + dbg_reg_def[regno].size);
> +#ifdef CONFIG_KERNEL_MODE_NEON
> + else {
> + if (fpsimd_thread_state()) {
Again, why the conditional?
> + memcpy((void *)&kgdb_fpsimd_regs +
> + dbg_reg_def[regno].offset,
> + mem, dbg_reg_def[regno].size);
> + fpsimd_load_state(&kgdb_fpsimd_regs);
Are you sure it is safe to clobber all the registers here? Shouldn't
you save the state first, do the memcpy() and then load?
Regards,
Ard.
> + }
> + }
> +#endif
> return 0;
> }
>
> --
> 1.7.9.5
>
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