Messages in this thread | | | Date | Thu, 19 Apr 2012 20:17:56 -0700 | From | David Daney <> | Subject | Re: [PATCH v1 1/5] scripts: Add sortextable to sort the kernel's exception table. |
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On 04/19/2012 06:44 PM, H. Peter Anvin wrote: > I committed this into the tip tree, but I realized something scary on > the way home... this program is broken: it doesn't handle the > relocations that go with the entries. Specifically, it needs to not > just handle __ex_table, it also needs to handle the corresponding > entries in .rel__ex_table. > > On x86-32, in particular, *most*, but not *all*, extable relocations > will have an R_386_32 relocation on it, so the resulting binary will > "mostly work"... but the ELF metadata will be wrong, and pretty much any > user of the try/catch mechanism will be broken, unless your kernel > happens to be located at its preferred address. > > This needs to be addressed, either by adjusting the exception table to > be relative (which would be good for code size on 64-bit platforms) > *and* zero out the .rel__ex_table section or by making the program > actually sort the relocations correctly.
Crap.
I hadn't considered that the image was relocatable. Our MIPS kernels never have relocations.
I am working on a version of this that handles the relocations. It shouldn't be too difficult.
> -hpa > > On 04/19/2012 02:59 PM, David Daney wrote: >> + >> +/* w8rev, w8nat, ...: Handle endianness. */ >> + >> +static uint64_t w8rev(uint64_t const x) >> +{ >> + return ((0xff& (x>> (0 * 8)))<< (7 * 8)) >> + | ((0xff& (x>> (1 * 8)))<< (6 * 8)) >> + | ((0xff& (x>> (2 * 8)))<< (5 * 8)) >> + | ((0xff& (x>> (3 * 8)))<< (4 * 8)) >> + | ((0xff& (x>> (4 * 8)))<< (3 * 8)) >> + | ((0xff& (x>> (5 * 8)))<< (2 * 8)) >> + | ((0xff& (x>> (6 * 8)))<< (1 * 8)) >> + | ((0xff& (x>> (7 * 8)))<< (0 * 8)); >> +} >> + >> +static uint32_t w4rev(uint32_t const x) >> +{ >> + return ((0xff& (x>> (0 * 8)))<< (3 * 8)) >> + | ((0xff& (x>> (1 * 8)))<< (2 * 8)) >> + | ((0xff& (x>> (2 * 8)))<< (1 * 8)) >> + | ((0xff& (x>> (3 * 8)))<< (0 * 8)); >> +} >> + >> +static uint32_t w2rev(uint16_t const x) >> +{ >> + return ((0xff& (x>> (0 * 8)))<< (1 * 8)) >> + | ((0xff& (x>> (1 * 8)))<< (0 * 8)); >> +} >> + >> +static uint64_t w8nat(uint64_t const x) >> +{ >> + return x; >> +} >> + >> +static uint32_t w4nat(uint32_t const x) >> +{ >> + return x; >> +} >> + >> +static uint32_t w2nat(uint16_t const x) >> +{ >> + return x; >> +} >> + >> +static uint64_t (*w8)(uint64_t); >> +static uint32_t (*w)(uint32_t); >> +static uint32_t (*w2)(uint16_t); > Stylistic note: these should use the<tools/*_byteshift.h> headers now.
I will try to use those.
Thanks, David Daney
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