| Message ID | 20220412173407.13637-4-varad.gautam@suse.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | SMP Support for x86 UEFI Tests | expand |
On Tue, Apr 12, 2022, Varad Gautam wrote: > EFI bootstrapping code configures a call gate in a later commit to jump > from 16-bit to 32-bit code. > > Introduce a set_idt_entry_t() routine which can be used to fill both > an interrupt descriptor and a call gate descriptor on x86. > > Signed-off-by: Varad Gautam <varad.gautam@suse.com> > --- > lib/x86/desc.c | 28 ++++++++++++++++++++++------ > lib/x86/desc.h | 1 + > 2 files changed, 23 insertions(+), 6 deletions(-) > > diff --git a/lib/x86/desc.c b/lib/x86/desc.c > index 087e85c..049adeb 100644 > --- a/lib/x86/desc.c > +++ b/lib/x86/desc.c > @@ -57,22 +57,38 @@ __attribute__((regparm(1))) > #endif > void do_handle_exception(struct ex_regs *regs); > > -void set_idt_entry(int vec, void *addr, int dpl) > +/* > + * Fill an idt_entry_t, clearing e_sz bytes first. > + * > + * This can also be used to set up x86 call gates, since the gate > + * descriptor layout is identical to idt_entry_t, except for the > + * absence of .offset2 and .reserved fields. To do so, pass in e_sz > + * according to the gate descriptor size. > + */ > +void set_idt_entry_t(idt_entry_t *e, size_t e_sz, void *addr, > + u16 sel, u16 type, u16 dpl) The usage in patch 7, "Transition APs from 16-bit to 32-bit mode" is really confusing because it's calling an IDT helper to setup the GDT. Also, the "_t" postfix usually indicates a typedef, not a function Rather than set_idt_entry_t, maybe set_oversized_desc_entry()? That's not very good either, but it's at least not outright confusing. Definitely open to other suggestions... > { > - idt_entry_t *e = &boot_idt[vec]; > - memset(e, 0, sizeof *e); > + memset(e, 0, e_sz); > e->offset0 = (unsigned long)addr; > - e->selector = read_cs(); > + e->selector = sel; > e->ist = 0; > - e->type = 14; > + e->type = type; > e->dpl = dpl; > e->p = 1; > e->offset1 = (unsigned long)addr >> 16; > #ifdef __x86_64__ > - e->offset2 = (unsigned long)addr >> 32; > + if (e_sz == sizeof(*e)) { > + e->offset2 = (unsigned long)addr >> 32; > + } > #endif > } > > +void set_idt_entry(int vec, void *addr, int dpl) > +{ > + idt_entry_t *e = &boot_idt[vec]; > + set_idt_entry_t(e, sizeof *e, addr, read_cs(), 14, dpl); > +} > + > void set_idt_dpl(int vec, u16 dpl) > { > idt_entry_t *e = &boot_idt[vec]; > diff --git a/lib/x86/desc.h b/lib/x86/desc.h > index 3044409..ae0928f 100644 > --- a/lib/x86/desc.h > +++ b/lib/x86/desc.h > @@ -217,6 +217,7 @@ unsigned exception_vector(void); > int write_cr4_checking(unsigned long val); > unsigned exception_error_code(void); > bool exception_rflags_rf(void); > +void set_idt_entry_t(idt_entry_t *e, size_t e_sz, void *addr, u16 sel, u16 type, u16 dpl); > void set_idt_entry(int vec, void *addr, int dpl); > void set_idt_sel(int vec, u16 sel); > void set_idt_dpl(int vec, u16 dpl); > -- > 2.32.0 >
diff --git a/lib/x86/desc.c b/lib/x86/desc.c index 087e85c..049adeb 100644 --- a/lib/x86/desc.c +++ b/lib/x86/desc.c @@ -57,22 +57,38 @@ __attribute__((regparm(1))) #endif void do_handle_exception(struct ex_regs *regs); -void set_idt_entry(int vec, void *addr, int dpl) +/* + * Fill an idt_entry_t, clearing e_sz bytes first. + * + * This can also be used to set up x86 call gates, since the gate + * descriptor layout is identical to idt_entry_t, except for the + * absence of .offset2 and .reserved fields. To do so, pass in e_sz + * according to the gate descriptor size. + */ +void set_idt_entry_t(idt_entry_t *e, size_t e_sz, void *addr, + u16 sel, u16 type, u16 dpl) { - idt_entry_t *e = &boot_idt[vec]; - memset(e, 0, sizeof *e); + memset(e, 0, e_sz); e->offset0 = (unsigned long)addr; - e->selector = read_cs(); + e->selector = sel; e->ist = 0; - e->type = 14; + e->type = type; e->dpl = dpl; e->p = 1; e->offset1 = (unsigned long)addr >> 16; #ifdef __x86_64__ - e->offset2 = (unsigned long)addr >> 32; + if (e_sz == sizeof(*e)) { + e->offset2 = (unsigned long)addr >> 32; + } #endif } +void set_idt_entry(int vec, void *addr, int dpl) +{ + idt_entry_t *e = &boot_idt[vec]; + set_idt_entry_t(e, sizeof *e, addr, read_cs(), 14, dpl); +} + void set_idt_dpl(int vec, u16 dpl) { idt_entry_t *e = &boot_idt[vec]; diff --git a/lib/x86/desc.h b/lib/x86/desc.h index 3044409..ae0928f 100644 --- a/lib/x86/desc.h +++ b/lib/x86/desc.h @@ -217,6 +217,7 @@ unsigned exception_vector(void); int write_cr4_checking(unsigned long val); unsigned exception_error_code(void); bool exception_rflags_rf(void); +void set_idt_entry_t(idt_entry_t *e, size_t e_sz, void *addr, u16 sel, u16 type, u16 dpl); void set_idt_entry(int vec, void *addr, int dpl); void set_idt_sel(int vec, u16 sel); void set_idt_dpl(int vec, u16 dpl);
EFI bootstrapping code configures a call gate in a later commit to jump from 16-bit to 32-bit code. Introduce a set_idt_entry_t() routine which can be used to fill both an interrupt descriptor and a call gate descriptor on x86. Signed-off-by: Varad Gautam <varad.gautam@suse.com> --- lib/x86/desc.c | 28 ++++++++++++++++++++++------ lib/x86/desc.h | 1 + 2 files changed, 23 insertions(+), 6 deletions(-)