Define an NT_MIPS_FP_MODE core file note and implement a corresponding regset holding the state handled by PR_SET_FP_MODE and PR_GET_FP_MODE prctl(2) requests. This lets debug software correctly interpret the contents of floating-point general registers both in live debugging and in core files, and also switch floating-point modes of a live process.
Signed-off-by: Maciej W. Rozycki <[email protected]> --- NB due to patch conflicts this change relies on the DSP ASE regset series <https://patchwork.kernel.org/patch/10402171/> to be applied first. --- arch/mips/kernel/ptrace.c | 63 ++++++++++++++++++++++++++++++++++++++++++++++ include/uapi/linux/elf.h | 1 2 files changed, 64 insertions(+) linux-mips-nt-fp-mode.diff Index: linux-jhogan-test/arch/mips/kernel/ptrace.c =================================================================== --- linux-jhogan-test.orig/arch/mips/kernel/ptrace.c 2018-05-09 23:53:34.999776000 +0100 +++ linux-jhogan-test/arch/mips/kernel/ptrace.c 2018-05-09 23:54:22.778128000 +0100 @@ -759,10 +759,57 @@ static int dsp_active(struct task_struct return cpu_has_dsp ? NUM_DSP_REGS + 1 : -ENODEV; } +/* Copy the FP mode setting to the supplied NT_MIPS_FP_MODE buffer. */ +static int fp_mode_get(struct task_struct *target, + const struct user_regset *regset, + unsigned int pos, unsigned int count, + void *kbuf, void __user *ubuf) +{ + int fp_mode; + + fp_mode = mips_get_process_fp_mode(target); + return user_regset_copyout(&pos, &count, &kbuf, &ubuf, &fp_mode, 0, + sizeof(fp_mode)); +} + +/* + * Copy the supplied NT_MIPS_FP_MODE buffer to the FP mode setting. + * + * We optimize for the case where `count % sizeof(int) == 0', which + * is supposed to have been guaranteed by the kernel before calling + * us, e.g. in `ptrace_regset'. We enforce that requirement, so + * that we can safely avoid preinitializing temporaries for partial + * mode writes. + */ +static int fp_mode_set(struct task_struct *target, + const struct user_regset *regset, + unsigned int pos, unsigned int count, + const void *kbuf, const void __user *ubuf) +{ + int fp_mode; + int err; + + BUG_ON(count % sizeof(int)); + + if (pos + count > sizeof(fp_mode)) + return -EIO; + + err = user_regset_copyin(&pos, &count, &kbuf, &ubuf, &fp_mode, 0, + sizeof(fp_mode)); + if (err) + return err; + + if (count > 0) + err = mips_set_process_fp_mode(target, fp_mode); + + return err; +} + enum mips_regset { REGSET_GPR, REGSET_FPR, REGSET_DSP, + REGSET_FP_MODE, }; struct pt_regs_offset { @@ -877,6 +924,14 @@ static const struct user_regset mips_reg .set = dsp32_set, .active = dsp_active, }, + [REGSET_FP_MODE] = { + .core_note_type = NT_MIPS_FP_MODE, + .n = 1, + .size = sizeof(int), + .align = sizeof(int), + .get = fp_mode_get, + .set = fp_mode_set, + }, }; static const struct user_regset_view user_mips_view = { @@ -917,6 +972,14 @@ static const struct user_regset mips64_r .set = dsp64_set, .active = dsp_active, }, + [REGSET_FP_MODE] = { + .core_note_type = NT_MIPS_FP_MODE, + .n = 1, + .size = sizeof(int), + .align = sizeof(int), + .get = fp_mode_get, + .set = fp_mode_set, + }, }; static const struct user_regset_view user_mips64_view = { Index: linux-jhogan-test/include/uapi/linux/elf.h =================================================================== --- linux-jhogan-test.orig/include/uapi/linux/elf.h 2018-05-09 23:53:35.003775000 +0100 +++ linux-jhogan-test/include/uapi/linux/elf.h 2018-05-09 23:54:22.787132000 +0100 @@ -425,6 +425,7 @@ typedef struct elf64_shdr { #define NT_METAG_TLS 0x502 /* Metag TLS pointer */ #define NT_ARC_V2 0x600 /* ARCv2 accumulator/extra registers */ #define NT_MIPS_DSP 0x700 /* MIPS DSP ASE registers */ +#define NT_MIPS_FP_MODE 0x701 /* MIPS floating-point mode */ /* Note header in a PT_NOTE section */ typedef struct elf32_note {
